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{{short description|Explosive weapon that utilizes nuclear reactions}}
] of the ] ], rose some 18 km (11 mi) above the ].]]
{{Redirect-multi|3|Atom bomb|A-bomb|Nuke}}
A '''nuclear weapon''' is a ] that derives its energy from the nuclear reactions of fission and/or fusion. Even the smallest nuclear weapons are more powerful than all but the largest conventional explosives such as the ]. A ten-megaton weapon can destroy an entire city. A hundred-megaton weapon (although judged impractical) would set wooden houses and forests afire in a circle 60-100 miles (100-160 km) in diameter{{fn|1}}. Nuclear weapons have been delivered twice in the history of warfare – both in the ending days of ]; the first such bombing was on the morning of ] ], when the ] dropped a uranium gun-type device code-named "]" on the ]ese city of ], and the last nuclear bombing occurred three days later; this second bomb was a plutonium implosion-type device code- named "]", dropped on the city of ].
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]s at the ]. '''Clockwise from top left:''' ], ], ], ], ], ],
LGM-30A/B/F Minuteman I or II, ]]]
{{Nuclear weapons}}
{{Weapons of mass destruction}}
A '''nuclear weapon'''{{efn|also known as an '''atom bomb''', '''atomic bomb''', '''nuclear bomb''', or '''nuclear warhead''', and colloquially as an '''A-bomb''' or '''nuke'''}} is an ] that derives its destructive force from ]s, either ] (fission bomb) or a combination of fission and ] reactions (]), producing a ]. Both bomb types release large quantities of ] from relatively small amounts of ].


The ] of a fission ("atomic") bomb released an amount of energy approximately equal to {{convert|20,000|tonTNT|TJ|lk=on}}.<ref name="Magazines1945">{{cite magazine|title=Atomic Power for War and Peace|magazine=Popular Mechanics|url=https://books.google.com/books?id=hN8DAAAAMBAJ&pg=PA18|date=October 1945|pages=18–19|publisher=Hearst Magazines}}</ref> The first thermonuclear ("hydrogen") bomb ] released energy approximately equal to {{convert|10|e6tonTNT|PJ}}. Nuclear bombs have had ]s between 10 tons TNT (the ]) and 50 megatons for the ] (see ]). A thermonuclear weapon weighing as little as {{convert|600|lb|kg|sigfig=2}} can release energy equal to more than {{convert|1.2|MtTNT}}.<ref name=nukearc>{{cite web |first=Carey |last=Sublette |url=http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html |title=Complete List of All U.S. Nuclear Weapons |website=Nuclear weapon archive |date=12 June 2020 |access-date=2021-03-18}}</ref>
] accounts for the rest of more than two thousand nuclear detonations, chiefly by the following seven states: the ], ], ], ], ], ] and ].


A nuclear device no larger than a ] can devastate an entire city by blast, fire, and ]. Since they are ], the ] is a focus of ] policy. Nuclear weapons have been deployed twice in ], both by the United States ] in 1945 during ].
The declared nuclear powers are the United States, ], the United Kingdom, France, the People's Republic of China, India, and Pakistan. In addition, ] has modern aerial delivery systems and there is evidence of an extensive nuclear program, though such has never been publicly admitted (see: ]). ] has stated recently that it has nuclear capabilities; ] may possess an obsolete Soviet nuclear stockpile due to a post-] ]. ] and others may be attempting to develop indigenous nuclear capabilities. See the ] for more details.


== Testing and deployment ==
Non-weaponized ]s have been proposed for various non-military uses.
Nuclear weapons have only twice been used in warfare, both times by the ] against ] at the end of ]. On August 6, 1945, the ] (USAAF) detonated a ] gun-type ] nicknamed "]" over the Japanese city of ]; three days later, on August 9, the USAAF<ref>{{Cite web |title=The U S Army Air Forces in World War II |url=https://www.afhistory.af.mil/FAQs/Fact-Sheets/Article/458967/the-u-s-army-air-forces-in-world-war-ii/https://www.afhistory.af.mil/FAQs/Fact-Sheets/Article/458967/the-u-s-army-air-forces-in-world-war-ii/ |access-date=2023-11-27 |website=Air Force Historical Support Division |language=en-US }}{{Dead link|date=April 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> detonated a ] implosion-type fission bomb nicknamed "]" over the Japanese city of ]. These bombings caused injuries that resulted in the deaths of approximately 200,000 ]s and ].<ref>{{cite web |url=http://www.rerf.or.jp/general/qa_e/qa1.html |title=Frequently Asked Questions #1 |publisher=] |quote=total number of deaths is not known precisely ... acute (within two to four months) deaths ... Hiroshima ... 90,000–166,000 ... Nagasaki ... 60,000–80,000 |access-date=September 18, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070919143939/http://www.rerf.or.jp/general/qa_e/qa1.html |archive-date=September 19, 2007 }}</ref> The ethics of these bombings and their role in ] are to this day, still ].


Since the ], nuclear weapons have been detonated over 2,000 times for ] and demonstration. Only ] possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the ], the ] (succeeded as a nuclear power by ]), the ], ], ], ], ], and ]. ] is believed to possess nuclear weapons, though, in a ], it does not acknowledge having them. ], ], ], ], the ], and ] are ] states.<ref name="nuclearweapons1">{{cite web |url=https://fas.org/programs/ssp/nukes/nuclearweapons/nukestatus.html |title=Federation of American Scientists: Status of World Nuclear Forces |publisher=Fas.org |access-date=December 29, 2012 |url-status=live |archive-url=https://web.archive.org/web/20130102173724/http://www.fas.org/programs/ssp/nukes/nuclearweapons/nukestatus.html |archive-date=January 2, 2013}}</ref><ref>{{cite web |url=https://fas.org/nuke/guide/israel/nuke/index.html |title=Nuclear Weapons – Israel |publisher=Fas.org |date=January 8, 2007 |access-date=December 15, 2010 |url-status=live |archive-url=https://web.archive.org/web/20101207122117/http://www.fas.org/nuke/guide/israel/nuke/index.html |archive-date=December 7, 2010}}</ref>{{efn|See also ]}} ] is the only country to have ] and then ] its nuclear weapons.<ref name="Nuclear Threat Initiatives, South Africa (NTI South Africa)">{{cite web|last=Executive release|title=South African nuclear bomb|url=http://www.nti.org/country-profiles/south-africa/nuclear/|website=Nuclear Threat Initiatives|publisher=Nuclear Threat Initiatives, South Africa (NTI South Africa)|access-date=March 13, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120928185925/http://www.nti.org/country-profiles/south-africa/nuclear/|archive-date=September 28, 2012}}</ref>
==Types of nuclear weapons==
]
{{see details|Nuclear weapon design}}


The ] aims to reduce the spread of nuclear weapons, but there are different views of its effectiveness.<ref>Ian Lowe, "Three minutes to midnight", '']'', March 2016, p. 49.</ref>
The simplest nuclear weapons derive their energy from ]. A mass of ] material is rapidly assembled into a ], in which a ] begins and ], releasing tremendous amounts of energy. This is accomplished either by shooting one piece of subcritical material into another, or compressing a subcritical mass into a state of ]. A major challenge in all nuclear weapon designs is ensuring that a significant fraction of the fuel is consumed before the weapon destroys itself. These are colloquially known as '''atomic bombs'''.


== Types ==
More advanced nuclear weapons take advantage of ] to derive more energy. In such a weapon, the ] thermal radiation from a nuclear fission explosion is used to heat and compress a capsule of ], ], or ], in which fusion occurs, releasing even more energy. These weapons, colloquially known as '''hydrogen bombs''', can be many hundreds of times more powerful than fission weapons. The so-called "]" is thought to be responsible for megaton range thermonuclear weapons.
{{Main|Nuclear weapon design}}
] of the ] was the first detonation of a nuclear weapon, which led ] to recall verses from the ] scripture '']'': "If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one&nbsp;"... "I am become Death, the destroyer of worlds".{{sfn|Jungk|1958|p=201}}]]


], principal leader of the ], often referred to as the "father of the atomic bomb".]]
More exotic nuclear weapons also exist, designed for special purposes. The detonation of a nuclear weapon is accompanied by a blast of ]. Surrounding a nuclear weapon with suitable materials (such as ] or ]) can result in the production of exceptionally large quantities of ]. A nuclear weapon may also be designed to permit as many neutrons as possible to escape; such a weapon is called a ]. Hypothetical ]s, which would use matter-] reactions, would not technically be nuclear weapons (as they would not be using energy derived from either nuclear fission or fusion), but bear noting due to a potentially higher potential energy by weight than conventional or nuclear explosives.


There are two basic types of nuclear weapons: those that derive the majority of their energy from ] reactions alone, and those that use fission reactions to begin ] reactions that produce a large amount of the total energy output.<ref name="Inc.1954">{{cite journal|author=Educational Foundation for Nuclear Science, Inc.|title=Bulletin of the Atomic Scientists|journal=Bulletin of the Atomic Scientists: Science and Public Affairs |url=https://books.google.com/books?id=rw0AAAAAMBAJ&pg=PA61|date=February 1954|publisher=Educational Foundation for Nuclear Science, Inc.|pages=61–|issn=0096-3402 |url-status=live |archive-url=https://web.archive.org/web/20170331041028/https://books.google.com/books?id=rw0AAAAAMBAJ&pg=PA61|archive-date=March 31, 2017}}</ref>
== Effects of a nuclear explosion ==
{{see details|Nuclear explosion}}
]
The energy released from a nuclear weapon comes in four primary categories:
*Blast&#8212;40-60% of total energy
*Thermal radiation&#8212;30-50% of total energy
*Ionizing radiation&#8212;5% of total energy
*Residual radiation (fallout)&#8212;5-10% of total energy
The amount of energy released in each form depends on the design of the weapon, and the environment in which it is detonated. The residual radiation of ] is a delayed release of energy, while the other three forms of energy release are immediate.


=== Fission weapons ===
The energy released by nuclear weapons is generally measured in its equivalence to ]s and ]s&mdash;thousands and millions of tons, respectively&mdash;of ]. The first fission weapons had yields measurable in the tens of kilotons, while the largest practical hydrogen bombs had yields around 10 megatons. In practice, nuclear weapon yields can be highly variable, from the sub-kiloton power of the man-portable ] warheads developed by the United States, to the impractical 54 megaton ] created by the Soviet Union as a display of political power.
] weapon designs]]
All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as '''atomic bombs''' or '''atom bombs''' (abbreviated as '''A-bombs'''). This has long been noted as something of a ], as their energy comes from the ] of the atom, just as it does with fusion weapons.


In fission weapons, a mass of ] (] or ]) is forced into ]—allowing an ] of ]s—either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled ]es. The latter approach, the "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former.
The dominant effects of a nuclear weapon (the blast and thermal radiation) are the same physical damage mechanisms as conventional ]. The primary difference is that nuclear weapons are capable of releasing much larger amounts of energy at once. Most of the damage caused by a nuclear weapon is not directly related to the nuclear process of energy release, but would be present for any explosion of the same magnitude. If a weapon is set off in the upper atmosphere, it can also generate an ] which can disable radio communications as well as damage certain types of electrical instruments.


A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 ]s) of ] ({{convert|1|to|5E5|tTNT|sigfig=2|disp=out}}).<ref name="Hansen">Hansen, Chuck. ''U.S. Nuclear Weapons: The Secret History.'' San Antonio, TX: Aerofax, 1988; and the more-updated Hansen, Chuck, " {{webarchive |url=https://web.archive.org/web/20161230020259/http://www.uscoldwar.com/ |date=December 30, 2016}}" (CD-ROM & download available). PDF. 2,600 pages, Sunnyvale, California, Chuklea Publications, 1995, 2007. {{ISBN|978-0-9791915-0-3}} (2nd Ed.)</ref>
The damage done by each of the three initial forms of energy release differs with the size of the weapon. Thermal radiation drops off the slowest with distance, so the larger the weapon the more important this effect becomes. Ionizing radiation is strongly absorbed by air, so it is only dangerous by itself for smaller weapons. Blast damage falls off more quickly than thermal radiation but more slowly than ionizing radiation.

All fission reactions generate ], the remains of the split atomic nuclei. Many fission products are either highly ] (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of ]. Fission products are the principal radioactive component of ]. Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in the surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive.

The most commonly used fissile materials for nuclear weapons applications have been ] and ]. Less commonly used has been ]. ] and some isotopes of ] may be usable for nuclear explosives as well, but it is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute.<ref>{{cite web |last1=Albright |first1=David |author-link=David Albright |last2=Kramer |first2=Kimberly |date=August 22, 2005 |title=Neptunium 237 and Americium: World Inventories and Proliferation Concerns |url=http://isis-online.org/uploads/isis-reports/documents/np_237_and_americium.pdf |publisher=] |access-date=October 13, 2011 |url-status=live |archive-url=https://web.archive.org/web/20120103234833/http://isis-online.org/uploads/isis-reports/documents/np_237_and_americium.pdf |archive-date=January 3, 2012}}</ref>

=== Fusion weapons ===
{{Main|Thermonuclear weapon}}
] for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.]]

The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as ''']s''' or more colloquially as '''hydrogen bombs''' (abbreviated as '''H-bombs'''), as they rely on fusion reactions between isotopes of ] (] and ]). All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions.<ref>Carey Sublette, {{webarchive |url=https://web.archive.org/web/20160303170957/http://nuclearweaponarchive.org/Nwfaq/Nfaq4-5.html |date=March 3, 2016}}, accessed May 10, 2011.</ref>

Only six countries—the ], ], the ], ], ], and ]—have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged ] is controversial.<ref>On India's alleged hydrogen bomb test, see Carey Sublette, {{webarchive |url=https://web.archive.org/web/20110927013551/http://nuclearweaponarchive.org/India/IndiaRealYields.html |date=September 27, 2011}}.</ref> ] claims to have tested a fusion weapon {{as of|2016|January|lc=y}}, though this claim is disputed.<ref>{{cite web|last1=McKirdy|first1=Euan|title=North Korea announces it conducted nuclear test |url=http://www.cnn.com/2016/01/05/asia/north-korea-seismic-event/|website=CNN|date=January 6, 2016|access-date=January 7, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160107193043/http://www.cnn.com/2016/01/05/asia/north-korea-seismic-event/|archive-date=January 7, 2016}}</ref> Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight.<ref>{{Cite web |url=https://www.armscontrol.org/factsheets/Nuclear-Testing-and-Comprehensive-Test-Ban-Treaty-CTBT-Timeline|title=Nuclear Testing and Comprehensive Test Ban Treaty (CTBT) Timeline |website=Arms control association |url-status=dead |archive-url=https://web.archive.org/web/20200421174531/https://www.armscontrol.org/factsheets/Nuclear-Testing-and-Comprehensive-Test-Ban-Treaty-CTBT-Timeline|archive-date=April 21, 2020}}</ref>

Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. In the ], which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel (], ], or ]) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, ]s and ]s emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed ]s, which can then induce fission in materials not normally prone to it, such as ]. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of the yield comes from the final fissioning of depleted uranium.<ref name="Hansen" />

Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to ] danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated, the ] of the USSR, which released an energy equivalent of over {{convert|50|MtonTNT}}, was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements.<ref name="Sublette">{{cite web |url=http://nuclearweaponarchive.org/ |last=Sublette |first=Carey |title=The Nuclear Weapon Archive |access-date=March 7, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070301105632/http://nuclearweaponarchive.org/ |archive-date=March 1, 2007}}</ref> In the early 1950s the ] in the United States had plans for the testing of two massive bombs, Gnomon and ], 1 gigaton of TNT and 10 gigatons of TNT respectively.<ref>{{Cite web |last=Simha |first=Rakesh Krishnan |date=2016-01-05 |title=Nuclear overkill: The quest for the 10 gigaton bomb |url=https://www.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351 |access-date=2023-10-08 |website=Russia Beyond |language=en-US |archive-date=November 29, 2023 |archive-url=https://web.archive.org/web/20231129191303/https://www.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351 |url-status=live }}</ref><ref>{{Cite web |last=Wellerstein |first=Alex |author-link=Alex Wellerstein |date=2021-10-29 |title=The untold story of the world's biggest nuclear bomb |url=https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/ |access-date=2023-10-08 |website=Bulletin of the Atomic Scientists |language=en-US |archive-date=August 27, 2023 |archive-url=https://web.archive.org/web/20230827130626/https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/ |url-status=live }}</ref>
], often referred to as the "father of the hydrogen bomb"]]

Fusion reactions do not create fission products, and thus contribute far less to the creation of ] than fission reactions, but because all ]s contain at least one ] stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past the ] into the ], where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion.

=== Other types ===
{{Main|Boosted fission weapon|Neutron bomb|Radiological warfare|Induced gamma emission|Antimatter weapon}}
There are other types of nuclear weapons as well. For example, a ] is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of the fission bomb core. The external method of boosting enabled the ] to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles.

The detonation of any nuclear weapon is accompanied by a blast of ]. Surrounding a nuclear weapon with suitable materials (such as ] or ]) creates a weapon known as a ]. This device can produce exceptionally large quantities of long-lived ]. It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct.

In connection with the ], research into the ] was conducted under the DOD program ] but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target.

During the ] high-altitude nuclear test in 1962, an unexpected effect was produced which is called a ]. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling a nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area.<ref>{{Cite web |date=2021-07-15 |title=Why the U.S. once set off a nuclear bomb in space |url=https://www.nationalgeographic.com/premium/article/why-the-us-once-set-off-a-nuclear-bomb-in-space-called-starfish-prime |access-date=2023-11-27 |website=Premium |language=en |archive-date=November 29, 2023 |archive-url=https://web.archive.org/web/20231129191301/https://www.nationalgeographic.com/premium/article/why-the-us-once-set-off-a-nuclear-bomb-in-space-called-starfish-prime |url-status=live }}</ref>

Research has been done into the possibility of ]: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the ] divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment".<ref>U.S. Department of Energy, {{webarchive |url=https://web.archive.org/web/20150924140708/http://www.fas.org/sgp/othergov/doe/rdd-8.pdf |date=September 24, 2015}} (January 1, 2002), accessed November 20, 2011.</ref>

] provide a possible pathway to fissionless fusion bombs. These are naturally occurring ] (] being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in the ]) have been proposed as possible triggers for conventional thermonuclear reactions.

], which consists of ] resembling ordinary ] particles in most of their properties but having opposite ], has been considered as a trigger mechanism for nuclear weapons.<ref name="arxiv.org">{{cite arXiv|eprint=physics/0510071 |last1=Gsponer |first1=Andre |title=Fourth Generation Nuclear Weapons: Military effectiveness and collateral effects |year=2005}}</ref><ref>{{cite web |url=http://www.nextbigfuture.com/2015/09/details-on-antimatter-triggered-fusion.html|title=Details on antimatter triggered fusion bombs |website=NextBigFuture.com|date=September 22, 2015 |url-status=live |archive-url=https://web.archive.org/web/20170422125419/http://www.nextbigfuture.com/2015/09/details-on-antimatter-triggered-fusion.html|archive-date=April 22, 2017}}</ref><ref>{{cite web |url=http://cui.unige.ch/isi/sscr/phys/anti-BPP-3.html |title=Page discussing the possibility of using antimatter as a trigger for a thermonuclear explosion |publisher=Cui.unige.ch |access-date=May 30, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130424174413/http://cui.unige.ch/isi/sscr/phys/anti-BPP-3.html |archive-date=April 24, 2013}}</ref> A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it is feasible beyond the military domain.<ref>{{Cite book |arxiv=physics/0507114 |last1=Gsponer |first1=Andre |last2=Hurni |first2=Jean-Pierre |chapter=The physics of antimatter induced fusion and thermonuclear explosions |editor1-first=G. |editor1-last=Velarde |editor2-first=E. |editor2-last=Minguez |title=Proceedings of the 4th International Conference on Emerging Nuclear Energy Systems, Madrid, June 30/July 4, 1986 |publisher=World Scientific, Singapore |year=1987 |pages=166–169}}</ref> However, the US Air Force funded studies of the physics of antimatter in the ], and began considering its possible use in weapons, not just as a trigger, but as the explosive itself.<ref>{{cite news |author1=Keay Davidson |author2=Chronicle Science Writer |url=http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/04/MNGM393GPK1.DTL |title=Air Force pursuing antimatter weapons: Program was touted publicly, then came official gag order |publisher=Sfgate.com |date=October 4, 2004 |access-date=May 30, 2013 |url-status=live |archive-url=https://web.archive.org/web/20120609101650/http://www.sfgate.com/cgi-bin/article.cgi?file=%2Fc%2Fa%2F2004%2F10%2F04%2FMNGM393GPK1.DTL |archive-date=June 9, 2012}}</ref> A fourth generation nuclear weapon design<ref name="arxiv.org" /> is related to, and relies upon, the same principle as ].<ref>{{cite web |url=http://nuclearweaponarchive.org/News/INESAPTR1.html|title=Fourth Generation Nuclear Weapons|access-date=October 24, 2014 |url-status=live |archive-url=https://web.archive.org/web/20160323010905/http://nuclearweaponarchive.org/News/INESAPTR1.html|archive-date=March 23, 2016}}</ref>

Most variation in ] is for the purpose of achieving ], and in manipulating design elements to attempt to minimize weapon size,<ref name="Hansen" /> ] or requirements for special materials, especially fissile fuel or tritium.

====Tactical nuclear weapons====
] missile. Capable of firing a 100-kiloton nuclear warhead a distance of 185 km]]
Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as ]s.

The ] purportedly conceived by ] is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron ]. Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in the 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200&nbsp;mm ] and 155&nbsp;mm ]) and ] forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable.{{citation needed|date=May 2022}}

A type of nuclear explosive most suitable for use by ground special forces was the ], or SADM, sometimes popularly known as a ]. This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment.{{citation needed|date=May 2022}}

Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include the USAF ], the ] and US Army ]. Missile interceptors such as the ] and the ] also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads.{{citation needed|date=May 2022}}

Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as ] weapons. These included nuclear ] or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities.{{citation needed|date=May 2022}}


== Weapons delivery == == Weapons delivery ==
{{See also|Nuclear weapons delivery|Nuclear triad|Strategic bomber|Intercontinental ballistic missile|Submarine-launched ballistic missile}}
]s, such as this "]" weapon dropped on ], Japan. They were large and could only be delivered by ] aircraft]]
] of the Russian ] R-36 ]; also known by the NATO reporting name: ]. Upon its first fielding in the late 1960s, the SS-18 remains the single highest ] missile delivery system ever built.]]


The system used to ] a nuclear weapon to its target is an important factor affecting both ] and ]. The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940.<ref>Stephen I. Schwartz, ed., ''Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940.'' Washington, D.C.: Brookings Institution Press, 1998. See also , an excerpt from the book. {{webarchive |url=https://web.archive.org/web/20081121144318/http://www.brook.edu/fp/projects/nucwcost/figure1.htm |date=November 21, 2008}}</ref>
The term ''strategic nuclear weapons'' is generally used to denote large weapons which would be used to destroy large targets, such as cities. ''Tactical nuclear weapons'' are smaller weapons used to destroy specific military, communications, or infrastructure targets. By modern standards, the bombs that destroyed ] in ] may perhaps be considered tactical weapons (with yields between 13 and 22 kilotons (54 to 92 TJ)), although modern tactical weapons are considerably lighter and more compact.


The simplest method for delivering a nuclear weapon is a ] dropped from ]; this was the method used by the ] in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both ]s and tactical ]s. This method is the primary means of nuclear weapons delivery; the majority of US nuclear warheads, for example, are free-fall gravity bombs, namely the ], which is being improved upon to this day.<ref name="Hansen" /><ref>{{Cite web |last=Mehta |first=Aaron |date=2023-10-27 |title=US to introduce new nuclear gravity bomb design: B61-13 |url=https://breakingdefense.sites.breakingmedia.com/2023/10/us-to-introduce-new-nuclear-gravity-bomb-design-b61-13/ |access-date=2023-11-27 |website=Breaking Defense |language=en-US |archive-date=December 17, 2023 |archive-url=https://web.archive.org/web/20231217083734/https://breakingdefense.com/2023/10/us-to-introduce-new-nuclear-gravity-bomb-design-b61-13/ |url-status=live }}</ref>
Basic methods of delivery for nuclear weapons are:


] ] (submarine launched ballistic missile), from submerged to the ], or re-entry phase, of the ]s]]
=== Gravity bombs ===
]" device, were large and cumbersome ]s.]]


Preferable from a strategic point of view is a nuclear weapon mounted on a ], which can use a ] trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for a faster and less vulnerable attack, the development of long-range ]s (ICBMs) and ]s (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success.
No nuclear weapon qualifies as a "wooden bomb" &mdash; US military slang for a bomb that is trouble-free, maintenance-free, and danger-free under all conditions. Gravity bombs are designed to be dropped from planes, which requires that the weapon can withstand vibrations and changes in air temperature and pressure during the course of a flight. Early weapons often had a removable core for safety, installed by the air crew during flight. They had to meet safety conditions, to prevent accidental detonation or dropping. A variety of types also had to have a fuse to initiate detonation. US nuclear weapons that met these criteria are designated by the letter "B" followed, without a hyphen, by the sequential number of the "]" it contains. The "]", for example, was the primary bomb in the US arsenal for decades.


More advanced systems, such as ]s (MIRVs), can launch multiple warheads at different targets from one missile, reducing the chance of a successful ]. Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult.<ref name="Hansen" />
Various air-dropping techniques exist, including ], ]-retarded delivery, and ] modes, intended to give the dropping aircraft time to escape the ensuing blast.


] have involved the most variety of delivery types, including not only gravity bombs and missiles but also ] shells, ], and ]s and ] for ]. An atomic ] has been tested by the United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as ]s), such as the ], have been developed, although the difficulty of combining sufficient yield with portability limits their military utility.<ref name="Hansen" />
The first gravity nuclear bombs could only be carried by the ]. The next generation of weapons were still so big and heavy that they could only be carried by ]s such as the ] and ]s, but by the mid-] smaller weapons had been developed that could be carried and deployed by simple ]s.


== Nuclear strategy ==
===Ballistic missile warheads===
{{Main|Nuclear strategy|Deterrence theory}}
]ed missile (such as the ]) can hold multiple nuclear warheads on one missile bus.]]
{{See also|Pre-emptive nuclear strike|Nuclear peace|Essentials of Post–Cold War Deterrence|Single Integrated Operational Plan|Nuclear warfare|On Thermonuclear War}}
Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by a nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of ]. The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for ] status (the ability to destroy an enemy's nuclear forces before they could retaliate). During the Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed ] models that could lead to stable deterrence conditions.<ref name="Handel2012">{{cite book|author=Michael I. Handel|title=War, Strategy and Intelligence |url=https://books.google.com/books?id=Gp0rBgAAQBAJ&pg=PA85|date=November 12, 2012|publisher=Routledge|isbn=978-1-136-28624-7|pages=85– |url-status=live |archive-url=https://web.archive.org/web/20170331214605/https://books.google.com/books?id=Gp0rBgAAQBAJ&pg=PA85|archive-date=March 31, 2017}}</ref>


] was an ] developed to replace the ] in the late 1980s. Each missile, like the ] Russian ], could contain up to ten nuclear warheads (shown in red), each of which could be aimed at a different target. A factor in the development of ]s was to make complete ] difficult for an enemy country.]]
]s using a ] trajectory usually deliver a ] over the horizon. Some ]s may have a range of tens to hundreds of kilometers, while larger ]s or ]s may use suborbital or partial orbital trajectories for intercontinental range. Early ballistic missiles carried a single warhead, often of ]-range yield. Due to accuracy considerations, this kind of high yield was considered necessary in order to ensure a particular target's destruction.


Different forms of ] (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against the weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on ]s or land mobile ]s whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened ] bunkers. Other components of nuclear strategies included using missile defenses to destroy the missiles before they land or implementing ] measures using early-warning systems to evacuate citizens to safe areas before an attack.
Since the ] modern ballistic weapons have seen the development of far more accurate targeting technologies. This set the stage for the use of "Multiple Independently-targettable Re-entry Vehicles" (]s) with up to a dozen independently targetable ]s, usually in the hundreds-of-]s-range yield, on one ballistic platform. This allows for a number of advantages over a missile with a single warhead. It allows a single missile to strike a variety of apparently unrelated targets, or it can inflict maximum damage on a single target by encircling the target with warheads, as well as providing such an onslaught of warheads in conjunction with other tactical weapons that any form of defensive technology would be rendered useless. Soviet plans in the '70s were said to entail dropping one MIRV based warhead every ninety seconds to three minutes on major US targets for up to an hour.


Weapons designed to threaten large populations or to deter attacks are known as ''].'' Nuclear weapons for use on a ]field in military situations are called ''].''
Missile warheads in the American arsenal are indicated by the letter "W"; for example, the W61 missile warhead would have the same ] as the B61 gravity bomb described above, but it would have different environmental requirements, and different safety requirements since it would not be crew-tended after launch and remain atop a missile for a great length of time.


Critics of nuclear war strategy often suggest that a nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in ]. This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism.
===Cruise missile warheads===
]s have a shorter range than ]s, but would be harder for an enemy to detect or intercept.]]


Critics from the peace movement and within the military establishment{{citation needed|date=June 2013}} have questioned the usefulness of such weapons in the current military climate. According to an ] issued by the ] in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if the survival of the state were at stake.
A ] or ]-propelled ] that flies at low altitude using an automated guidance system (usually ], sometimes supplemented by either ] or ] from friendly forces) to make them harder to detect or intercept could carry a nuclear warhead. ]s have shorter range and smaller payloads than ballistic missiles, so their warheads are smaller and less powerful. Rather than multiple warheads, which would have to be dropped separately as though the cruise missile were itself a bomber, each cruise missile carries its own warhead, although the ] bomber was designed to carry in its bomb-bay a rotating fixture for cruise missiles which resembles a set of MIRV warheads. Conventional cruise missiles sometimes use ] payloads, though. Cruise missiles may be launched from mobile launchers on the ground, from naval ships, or from aircraft.


]s have been of great strategic importance for the United States, Russia, and other nuclear powers since they entered service in the ], as they can hide from ]s and fire their nuclear weapons with virtual impunity.]]
There is no letter change in the US arsenal to distinguish the warheads of cruise missiles from those for ballistic missiles.
Another ] position is that ] can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the ] between the US and the ].<ref>{{cite book |last1=Creveld |first1=Martin Van |title=The Oxford History of Modern War |chapter=Technology and War II:Postmodern War? |editor=Charles Townshend |publisher=Oxford University Press |year=2000 |location=New York |page= |isbn=978-0-19-285373-8 |chapter-url=https://archive.org/details/oxfordhistoryofm00town |url=https://archive.org/details/oxfordhistoryofm00town/page/349}}</ref> In the late 1950s and early 1960s, Gen. ] of France, an adviser to ], argued in books like ''The Balance of Terror: Strategy for the Nuclear Age'' (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase ]. Some prominent ] scholars, such as ] and ], have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of ], especially in troubled regions of the world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation,<ref>{{Cite journal |last=Mearsheimer |first=John |year=2006 |title=Conversations in International Relations: Interview with John J. Mearsheimer (Part I) |url=http://jonmearsheimer.uchicago.edu/pdfs/A0020.pdf |url-status=dead |journal=International Relations |volume=20 |issue=1 |pages=105–123 |doi=10.1177/0047117806060939 |s2cid=220788933 |archive-url=https://web.archive.org/web/20130501181414/http://johnmearsheimer.uchicago.edu/pdfs/A0020.pdf |archive-date=May 1, 2013 |accessdate=November 23, 2020 |issn = 0047-1178 }} See page 116</ref> and Waltz, who was somewhat more non-].<ref>Kenneth Waltz, "More May Be Better", in Scott Sagan and Kenneth Waltz, eds., ''The Spread of Nuclear Weapons'' (New York: Norton, 1995).</ref><ref name=waltz>Kenneth Waltz, , {{webarchive |url=https://web.archive.org/web/20101201053554/http://www.mtholyoke.edu/acad/intrel/waltz1.htm |date=December 1, 2010}} ''Adelphi Papers'', no. 171 (London: International Institute for Strategic Studies, 1981).</ref> Interest in proliferation and the ] that it generates continues to this day, with ongoing debate about indigenous Japanese and ]n nuclear deterrent against ].<ref>{{cite web |url=http://www.strategicstudiesinstitute.army.mil/pubs/display.cfm?pubID=1327|title=Should We Let the Bomb Spread? Edited by Mr. Henry D. Sokolski. Strategic studies institute. November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161123214604/http://www.strategicstudiesinstitute.army.mil/pubs/display.cfm?pubID=1327|archive-date=November 23, 2016}}</ref>


The threat of potentially suicidal terrorists possessing nuclear weapons (a form of ]) complicates the decision process. The prospect of ] might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless ] instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the ], that this complication calls for a new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War.<ref name="feldman">See, for example: Feldman, Noah. " {{webarchive |url=https://web.archive.org/web/20160219172015/http://www.nytimes.com/2006/10/29/magazine/29islam.html |date=February 19, 2016}}", ''New York Times Magazine'' (October 29, 2006).</ref> Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with ].<ref>Daniel Plesch & Stephen Young, "Senseless policy", '' {{webarchive |url=https://web.archive.org/web/20150919025137/https://books.google.com/books?id=sgsAAAAAMBAJ&printsec=frontcover |date=September 19, 2015}}'', November/December 1998, page 4. Fetched from URL on April 18, 2011.</ref>
===Other delivery systems===


] ICBM test launch from ], United States. ] land-based ]s are considered destabilizing because they tend to put a premium on ].]]
] artillery shell was the smallest nuclear weapon developed by the USA.]]


] argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider a policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.".<ref>{{cite journal|last=Gallucci|first=Robert|s2cid=68857650|title=Averting Nuclear Catastrophe: Contemplating Extreme Responses to U.S. Vulnerability|journal=Annals of the American Academy of Political and Social Science|date=September 2006|volume=607|pages=51–58|doi=10.1177/0002716206290457}}</ref>
Other potential delivery methods include ] shells, mines such as ], and nuclear ]s and torpedoes for ]. An atomic mortar was also tested. In the ] the U.S. developed small nuclear warheads for air defense use, such as the ]. Further developments of this concept, some with much larger warheads, showed promise as ]. Most of the United States' nuclear air-defense weapons were out of service by the end of the ], and nuclear depth bombs were taken out of service by ]. However, the USSR (and later Russia) continues to maintain anti-ballistic missiles with nuclear warheads. Small, two-man portable tactical weapons (erroneously referred to as ]s), such as the ], have been developed, although the difficulty of balancing yield and portability limits their military utility.


] makes a similar case, arguing that the key to expanded deterrence is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, ] cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin."<ref name="Allison">{{cite news|last=Allison|first=Graham|title=How to Keep the Bomb From Terrorist s|url=http://www.thedailybeast.com/newsweek/2009/03/13/how-to-keep-the-bomb-from-terrorists.html|access-date=January 28, 2013|newspaper=Newsweek|date=March 13, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20130513111324/http://www.thedailybeast.com/newsweek/2009/03/13/how-to-keep-the-bomb-from-terrorists.html|archive-date=May 13, 2013}}</ref> The process is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials."<ref name="Allison" />
See ] for a list of the designs of nuclear weapons fielded by the various nuclear powers.


According to the Pentagon's June 2019 "]" of the Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation."<ref>{{cite news |title=The Pentagon Revealed Its Nuclear War Strategy and It's Terrifying |url=https://www.vice.com/en_ca/article/mb84db/the-pentagon-revealed-its-nuclear-war-strategy-and-its-terrifying |work=] |date=June 21, 2019 |access-date=October 9, 2019 |archive-date=December 7, 2019 |archive-url=https://web.archive.org/web/20191207063100/https://www.vice.com/en_ca/article/mb84db/the-pentagon-revealed-its-nuclear-war-strategy-and-its-terrifying |url-status=live }}</ref><ref>{{cite news |title=Nuclear weapons: experts alarmed by new Pentagon 'war-fighting' doctrine |url=https://www.theguardian.com/world/2019/jun/19/nuclear-weapons-pentagon-us-military-doctrine |work=The Guardian |date=June 19, 2019 |access-date=October 9, 2019 |archive-date=June 19, 2019 |archive-url=https://web.archive.org/web/20190619222056/https://www.theguardian.com/world/2019/jun/19/nuclear-weapons-pentagon-us-military-doctrine |url-status=live }}</ref>
== History ==
{{see details|History of nuclear weapons}}
].]]
The first nuclear weapons were created by the ], with assistance from the ], during ] as part of the top-secret ]. While the first weapons were developed primarily out of fear that ] would first develop them, they were eventually used against the Japanese cities of ] in August 1945. The ] developed and tested their first nuclear weapon in ], based partially on espionage obtained from spies in the USA, and both the USA and USSR developed fusion weapons by the mid-1950s. With the invention of reliable ] during the 1960s, it became possible for nuclear weapons to be delivered anywhere in the world on a very short notice, and the two ] superpowers adopted a strategy of ] to maintain a shaky peace.


== Governance, control, and law ==
Nuclear weapons were symbols of military and national power, and ] was often used both to test new designs as well as to send political messages. Other nations also developed nuclear weapons during this time, including the United Kingdom, ], and ]. These five members of the "nuclear club" agreed to attempt to limit the spread of ] to other nations, though at least three other countries (], ], ], and most likely ]) developed nuclear arms during this time. At the end of the Cold War in the early 1990s, the ] inherited the weapons of the former USSR, and along with the USA pledged to reduce their stockpile for increased international safety. Nuclear proliferation has continued, though, with ] testing their first weapons in 1998, and the state of ] claiming to have developed nuclear weapons in 2004. Nuclear weapons have been at the heart of many national and international political disputes, and have played a major part in ] since their dramatic public debut in the 1940s, and have usually symbolized the ultimate ability of mankind to utilize the strength of nature for destruction.
{{Main|Treaty on the Non-Proliferation of Nuclear Weapons|Strategic Arms Limitation Talks|Intermediate-Range Nuclear Forces Treaty|START I|START II|Strategic Offensive Reductions Treaty|Comprehensive Nuclear-Test-Ban Treaty|Lahore Declaration|New START|Treaty on the Prohibition of Nuclear Weapons}}
{{See also|Anti-nuclear movement}}
] was created in 1957 to encourage peaceful development of nuclear technology while providing international safeguards against nuclear proliferation.]]


Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by the ] or ].{{efn|In the United States, the President and the Secretary of Defense, acting as the ], must ''jointly'' authorize the use of nuclear weapons.}} Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage".<ref>], {{Webarchive|url=https://web.archive.org/web/20160101090600/http://bos.sagepub.com/content/71/6/11.full |date=January 1, 2016 }}, '']'', November/December 2015, vol. 71 no. 6, 11–17.</ref>
There have been (at least) four major false alarms, the most recent in 1995, that almost resulted in the US or Russia launching its weapons in retaliation for a supposed attack.


In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The ] was issued in ] on July 9, 1955, by ] in the midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including ], who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist ] offered to sponsor a conference—called for in the manifesto—in ], Eaton's birthplace. This conference was to be the first of the ], held in July 1957.
==Media==
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{{multi-video item|filename=Enewetak atomic detonations.ogg|title= Eniwetok nuclear detonation tests|description= Video clips of three test nuclear explosions in Eniwetok, Marshall Islands.|format=]}}
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By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of ]. The ] (1963) restricted all nuclear testing to ], to prevent contamination from nuclear fallout, whereas the ] (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military ] to member countries without fear of proliferation.
== Related topics==

{{WMD}}
] on July 7, 2017<br />{{Leftlegend|#008cff|Yes}} {{Leftlegend|#ff0000|No}}{{Leftlegend|#c0c0c0|Did not vote}}]]
*More technical details
In 1957, the ] (IAEA) was established under the mandate of the ] to encourage development of peaceful applications of nuclear technology, provide international safeguards against its misuse, and facilitate the application of safety measures in its use. In 1996, many nations signed the ],<ref name=status /> which prohibits all testing of nuclear weapons. A testing ban imposes a significant hindrance to nuclear arms development by any complying country.<ref name="Richelson">Richelson, Jeffrey. ''Spying on the bomb: American nuclear intelligence from Nazi Germany to Iran and North Korea.'' New York: Norton, 2006.</ref> The Treaty requires the ratification by 44 specific states before it can go into force; {{as of|2012|lc=y}}, the ratification of eight of these states is still required.<ref name=status>Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (2010). " {{webarchive |url=https://web.archive.org/web/20110406151906/http://www.ctbto.org/the-treaty/status-of-signature-and-ratification/ |date=April 6, 2011}}". Accessed May 27, 2010. Of the "Annex 2" states whose ratification of the CTBT is required before it enters into force, China, Egypt, Iran, Israel, and the United States have signed but not ratified the Treaty. India, North Korea, and Pakistan have not signed the Treaty.</ref>
**]

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Additional treaties and agreements have governed nuclear weapons stockpiles between the countries with the two largest stockpiles, the United States and the Soviet Union, and later between the United States and Russia. These include treaties such as ] (never ratified), ] (expired), ], ] (never in effect), ], and ], as well as non-binding agreements such as ] and the Presidential Nuclear Initiatives<ref> {{webarchive |url=https://web.archive.org/web/20110119164340/http://www.armscontrol.org/factsheets/pniglance |date=January 19, 2011}}, Fact Sheet, Arms Control Association.</ref> of 1991. Even when they did not enter into force, these agreements helped limit and later reduce the numbers and types of nuclear weapons between the United States and the Soviet Union/Russia.
*History

**]
Nuclear weapons have also been opposed by agreements between countries. Many nations have been declared ]s, areas where nuclear weapons production and deployment are prohibited, through the use of treaties. The ] (1967) prohibited any production or deployment of nuclear weapons in ] and the ], and the ] (1964) prohibits nuclear weapons in many African countries. As recently as 2006 a ] was established among the former Soviet republics of Central Asia prohibiting nuclear weapons. ].]]
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In 1996, the ], the highest court of the United Nations, issued an Advisory Opinion concerned with the "]". The court ruled that the use or threat of use of nuclear weapons would violate various articles of ], including the ], the ], the ], and the ]. Given the unique, destructive characteristics of nuclear weapons, the ] calls on States to ensure that these weapons are never used, irrespective of whether they consider them lawful or not.<ref> {{webarchive |url=https://web.archive.org/web/20100421062555/http://www.icrc.org/web/eng/siteeng0.nsf/htmlall/section_ihl_nuclear_weapons |date=April 21, 2010}} International Committee of the Red Cross</ref>
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Additionally, there have been other, specific actions meant to discourage countries from developing nuclear arms. In the wake of the tests by India and Pakistan in 1998, economic sanctions were (temporarily) levied against both countries, though neither were signatories with the Nuclear Non-Proliferation Treaty. One of the stated '']'' for the initiation of the 2003 ] was an accusation by the United States that Iraq was actively pursuing nuclear arms (though this was soon discovered ] as the program had been discontinued). In 1981, Israel had ] being constructed in ], ], in what it called an attempt to halt Iraq's previous nuclear arms ambitions; in 2007, Israel ] being constructed in ].
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In 2013, ] said that governments of France, India, North Korea, Pakistan, UK, and South Africa have used nuclear power or research reactors to assist nuclear weapons development or to contribute to their supplies of nuclear explosives from military reactors.<ref name=diesrev>{{cite web |url=http://www.ies.unsw.edu.au/sites/all/files/MD%20BookReview_EnergyPolicy2013.pdf |title=Book review: Contesting the future of nuclear power |author=Mark Diesendorf |year=2013 |website=Energy Policy |url-status=dead |archive-url=https://web.archive.org/web/20130927163154/http://www.ies.unsw.edu.au/sites/all/files/MD%20BookReview_EnergyPolicy2013.pdf |archive-date=September 27, 2013 |author-link=Mark Diesendorf |access-date=July 9, 2013}}{{dubious|date=July 2013}}</ref> In 2017, 122 countries mainly in the ] voted in favor of adopting the ], which eventually entered into force in 2021.<ref>{{Cite web |title=History of the TPNW |url=https://www.icanw.org/history_of_the_tpnw |access-date=2023-06-05 |website=ICAN |language=en |archive-date=June 5, 2023 |archive-url=https://web.archive.org/web/20230605172312/https://www.icanw.org/history_of_the_tpnw |url-status=live }}</ref>
**]

**] (including nuclear weapons accidents)
The ] measures the likelihood of a human-made ] and is published annually by the ]. The two years with the highest likelihood had previously been 1953, when the Clock was set to two minutes until midnight after the US and the Soviet Union began testing hydrogen bombs, and 2018, following the failure of world leaders to address tensions relating to nuclear weapons and climate change issues.<ref>{{cite news|url=https://www.cnn.com/2018/01/25/politics/doomsday-clock-closer-nuclear-midnight/index.html|title='Doomsday clock' ticks closer to apocalyptic midnight|last=Koran|first=Laura|work=]|date=January 25, 2018|access-date=November 3, 2019|archive-date=November 3, 2019|archive-url=https://web.archive.org/web/20191103111015/https://www.cnn.com/2018/01/25/politics/doomsday-clock-closer-nuclear-midnight/index.html|url-status=live}}</ref> In 2023, following the ] during the ], the doomsday clock was set to 90 seconds, the highest likelihood of global catastrophe since the existence of the Doomsday Clock.<ref>{{Cite web |last=Spinazze |first=Gayle |date=2023-01-24 |title=PRESS RELEASE: Doomsday Clock set at 90 seconds to midnight |url=https://thebulletin.org/2023/01/press-release-doomsday-clock-set-at-90-seconds-to-midnight/ |access-date=2023-06-05 |website=Bulletin of the Atomic Scientists |language=en-US |archive-date=January 24, 2023 |archive-url=https://web.archive.org/web/20230124152126/https://thebulletin.org/2023/01/press-release-doomsday-clock-set-at-90-seconds-to-midnight/ |url-status=live }}</ref>
*Related technology and science

**]
As of 2024, Russia has intensified nuclear threats in Ukraine and is reportedly planning to place nuclear weapons in orbit, breaching the 1967 Outer Space Treaty. China is significantly expanding its nuclear arsenal, with projections of over 1,000 warheads by 2030 and up to 1,500 by 2035. North Korea is progressing in intercontinental ballistic missile tests and has a mutual-defense treaty with Russia, exchanging artillery for possible missile technology. Iran is currently viewed as a nuclear "threshold" state.<ref>{{Cite news |date=12 August 2024 |title=America prepares for a new nuclear-arms race |url=https://www.economist.com/united-states/2024/08/12/america-prepares-for-a-new-nuclear-arms-race |access-date=2024-08-13 |work=The Economist |issn=0013-0613}}</ref>
**]

**]
=== Disarmament ===
**]
**] {{Main|Nuclear disarmament}}
{{for|statistics on possession and deployment|List of states with nuclear weapons}}
*]
] and United States nuclear weapon stockpiles throughout the ] until 2015, with a precipitous drop in total numbers following the end of the Cold War in 1991.]]
**]

**]
Nuclear disarmament refers to both the act of reducing or eliminating nuclear weapons and to the end state of a nuclear-free world, in which nuclear weapons are eliminated.
**]

**]
Beginning with the 1963 ] and continuing through the 1996 ], there have been many treaties to limit or reduce nuclear weapons testing and stockpiles. The 1968 ] has as one of its explicit conditions that all signatories must "pursue negotiations in good faith" towards the long-term goal of "complete disarmament". The nuclear-weapon states have largely treated that aspect of the agreement as "decorative" and without force.<ref>Gusterson, Hugh, " {{webarchive |url=https://web.archive.org/web/20080917225812/http://www.thebulletin.org/web-edition/columnists/hugh-gusterson/finding-article-vi |date=September 17, 2008}}" ''Bulletin of the Atomic Scientists'' (January 8, 2007).</ref>
*Proliferation and politics

**]
Only one country—South Africa—has ever fully renounced nuclear weapons they had independently developed. The former Soviet republics of ], ], and ] returned Soviet nuclear arms stationed in their countries to Russia after the ].
**]

**]
Proponents of nuclear disarmament say that it would lessen the probability of nuclear war, especially accidentally. Critics of nuclear disarmament say that it would undermine the present ] and deterrence and would lead to increased global instability. Various American elder statesmen,<ref>{{cite news |url=https://www.washingtonpost.com/opinions/nuclear-energy-after-fukushima/2011/10/05/gIQAbxIFRL_story.html |title=Nuclear energy after Fukushima |author=Jim Hoagland |date=October 6, 2011 |newspaper=] |url-status=live |archive-url=https://web.archive.org/web/20131001011125/http://articles.washingtonpost.com/2011-10-06/opinions/35279184_1_nuclear-weapons-nuclear-power-nuclear-energy |archive-date=October 1, 2013 |access-date=September 6, 2017 }}</ref> who were in office during the ] period, have been advocating the elimination of nuclear weapons. These officials include ], ], ], and ]. In January 2010, ] stated that "no issue carries more importance to the long-term health and security of humanity than the effort to reduce, and perhaps one day, rid the world of nuclear weapons".<ref>Lawrence M. Krauss. The Doomsday Clock Still Ticks, ''Scientific American'', January 2010, p. 26.</ref>
**]

**]
] workers use equipment provided by the US ] to dismantle a Soviet-era missile silo. After the end of the Cold War, Ukraine and the other non-Russian, post-Soviet republics relinquished Soviet nuclear stockpiles to Russia.]]
**]

**]
In January 1986, Soviet leader ] publicly proposed a three-stage program for abolishing the world's nuclear weapons by the end of the 20th century.<ref>{{cite book |first=William |last=Taubman |year=2017 |title=Gorbachev: His Life and Times |location=New York City |publisher=Simon and Schuster |isbn=978-1-4711-4796-8 |page=291}}</ref> In the years after the end of the Cold War, there have been numerous campaigns to urge the abolition of nuclear weapons, such as that organized by the ] movement, and the goal of a "world without nuclear weapons" was advocated by United States President ] in an April 2009 speech in ].<ref>{{cite news |url=https://www.huffingtonpost.com/2009/04/05/obama-prague-speech-on-nu_n_183219.html |title=Obama Prague Speech On Nuclear Weapons |publisher=Huffingtonpost.com |date=April 5, 2009 |access-date=May 30, 2013 |first=Nick |last=Graham |url-status=live |archive-url=https://web.archive.org/web/20130509130409/http://www.huffingtonpost.com/2009/04/05/obama-prague-speech-on-nu_n_183219.html |archive-date=May 9, 2013}}</ref> A ] poll from April 2010 indicated that the American public was nearly evenly split on the issue.<ref>{{cite news |url=http://politicalticker.blogs.cnn.com/2010/04/12/cnn-poll-public-divided-on-eliminating-all-nuclear-weapons/ |title=CNN Poll: Public divided on eliminating all nuclear weapons |publisher=Politicalticker.blogs.cnn.com |date=April 12, 2010 |access-date=May 30, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130721061030/http://politicalticker.blogs.cnn.com/2010/04/12/cnn-poll-public-divided-on-eliminating-all-nuclear-weapons/ |archive-date=July 21, 2013 }}</ref>
*Popular culture

**]
Some analysts have argued that nuclear weapons have made the world relatively safer, with peace through ] and through the ], including in south Asia.<ref>{{cite web|url=http://www.stimson.org/images/uploads/research-pdfs/ESCCONTROLCHAPTER1.pdf|title=The Stability-Instability Paradox, Misperception, and Escalation Control in South Asia|first=Michael|last=Krepon|website=Stimson|access-date=November 20, 2015|url-status=dead|archive-url=https://web.archive.org/web/20150924110533/http://www.stimson.org/images/uploads/research-pdfs/ESCCONTROLCHAPTER1.pdf|archive-date=September 24, 2015}}</ref><ref>{{cite web|url=http://krepon.armscontrolwonk.com/archive/2911/the-stability-instability-paradox|title=Michael Krepon • The Stability-Instability Paradox|access-date=October 24, 2014|url-status=dead|archive-url=https://web.archive.org/web/20150112223352/http://krepon.armscontrolwonk.com/archive/2911/the-stability-instability-paradox|archive-date=January 12, 2015}}</ref> ] has argued that nuclear weapons have helped keep an uneasy peace, and further nuclear weapon proliferation might even help avoid the large scale conventional wars that were so common before their invention at the end of ].<ref name=waltz /> But former Secretary ] says there is a new danger, which cannot be addressed by deterrence: "The classical notion of deterrence was that there was some consequences before which aggressors and evildoers would recoil. In a world of suicide bombers, that calculation doesn't operate in any comparable way".<ref>{{cite web |url=https://thehill.com/opinion/columnists/ben-goddard/59952-cold-warriors-say-no-nukes/ |title=Cold Warriors say no nukes |author=Ben Goddard |date=January 27, 2010 |website=The Hill |url-status=live |archive-url=https://web.archive.org/web/20140213100710/http://thehill.com/opinion/columnists/ben-goddard/78391-cold-warriors-say-no-nukes |archive-date=February 13, 2014}}</ref> ] has said, "If you think of the people who are doing suicide attacks, and people like that get a nuclear weapon, they are almost by definition not deterrable".<ref>{{cite web |url=http://thebulletin.org/new-abolitionists |title=The new abolitionists |author=Hugh Gusterson |date=March 30, 2012 |website=] |url-status=dead |archive-url=https://web.archive.org/web/20140217074609/http://thebulletin.org/new-abolitionists |archive-date=February 17, 2014 |author-link=Hugh Gusterson |access-date=February 2, 2014 }}</ref>

As of early 2019, more than 90% of world's 13,865 nuclear weapons were owned by Russia and the United States.<ref>{{cite news |first=Kelsey |last=Reichmann |title=Here's how many nuclear warheads exist, and which countries own them |url=https://www.defensenews.com/global/2019/06/16/heres-how-many-nuclear-warheads-exist-and-which-countries-own-them/ |work=] |date=June 16, 2019 |access-date=July 23, 2019 |archive-date=July 28, 2020 |archive-url=https://web.archive.org/web/20200728104810/https://www.defensenews.com/global/2019/06/16/heres-how-many-nuclear-warheads-exist-and-which-countries-own-them/ |url-status=live }}</ref><ref>{{cite news |title=Global Nuclear Arsenal Declines, But Future Cuts Uncertain Amid U.S.-Russia Tensions |url=https://www.rferl.org/a/nuclear-weapons-russia-start-inf-warheads/30003088.html |work=] (RFE/RL) |date=June 17, 2019 |access-date=July 23, 2019 |archive-date=July 2, 2019 |archive-url=https://web.archive.org/web/20190702194556/https://www.rferl.org/a/nuclear-weapons-russia-start-inf-warheads/30003088.html |url-status=live }}</ref>

=== United Nations ===
{{Main|United Nations Office for Disarmament Affairs}}
The UN Office for Disarmament Affairs (UNODA) is a department of the ] established in January 1998 as part of the ] ]'s plan to reform the UN as presented in his report to the ] in July 1997.<ref>{{cite web |author=Kofi Annan |url=https://undocs.org/A/51/950 |title=Renewing the United Nations: A Program for Reform |id=A/51/950 |publisher=United Nations |date=July 14, 1997 |access-date=March 17, 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170318000952/http://undocs.org/A/51/950 |archive-date=March 18, 2017}}</ref>

Its goal is to promote nuclear disarmament and ] and the strengthening of the disarmament regimes in respect to other weapons of mass destruction, ] and ]. It also promotes disarmament efforts in the area of ]s, especially ]s and ], which are often the weapons of choice in contemporary conflicts.

== Controversy ==
{{See also|Nuclear weapons debate|History of the anti-nuclear movement}}

=== Ethics ===
{{Main|Nuclear ethics}}
] protest march in Oxford, 1980]]
Even before the first nuclear weapons had been developed, scientists involved with the ] were divided over the use of the weapon. The role of the two atomic bombings of the country in ] and the US's ] justification for them has been the subject of scholarly and popular debate for decades. The question of whether nations should have nuclear weapons, or test them, has been continually and nearly universally controversial.<ref name="brown">Jerry Brown and ] (1997). ''Profiles in Power: The Anti-nuclear Movement and the Dawn of the Solar Age'', Twayne Publishers, pp. 191–192.</ref>

=== Notable nuclear weapons accidents ===
{{Main|Nuclear and radiation accidents and incidents|List of military nuclear accidents}}
{{See also|List of nuclear close calls}}
* August 21, 1945: While conducting experiments on a plutonium-gallium core at ], physicist ] received a lethal dose of radiation when an error caused it to enter ]. He died 25 days later, on September 15, 1945, from ].<ref>{{Cite web |title=Atomic Accidents – Nuclear Museum |url=https://ahf.nuclearmuseum.org/ahf/history/atomic-accidents/ |access-date=2023-11-28 |website=ahf.nuclearmuseum.org/ |language=en-US |archive-date=October 12, 2023 |archive-url=https://web.archive.org/web/20231012072140/https://ahf.nuclearmuseum.org/ahf/history/atomic-accidents/ |url-status=live }}</ref>
* May 21, 1946: While conducting further experiments on the same core at Los Alamos National Laboratory, physicist ] accidentally caused the core to become briefly ]. He received a lethal dose of ] and ], and died nine days later on May 30, 1946. After the death of Daghlian and Slotin, the mass became known as the "]". It was ultimately used to construct a bomb for use on the Nevada Test Range.<ref>{{cite web|url=https://www.atlasobscura.com/articles/demon-core-that-killed-two-scientists|title=The Nuclear 'Demon Core' That Killed Two Scientists|date=April 23, 2018|access-date=April 23, 2018|archive-date=April 24, 2018|archive-url=https://web.archive.org/web/20180424024624/https://www.atlasobscura.com/articles/demon-core-that-killed-two-scientists|url-status=live}}</ref>
* February 13, 1950: a ] in northern ] after jettisoning a ] atomic bomb. This was the first such ] in history. The accident was designated a "]"—an accident involving a nuclear weapon, but which does not present a risk of war. Experts believe that up to 50 nuclear weapons were lost during the Cold War.<ref>{{cite news |title=The Cold War's Missing Atom Bombs |url=https://www.spiegel.de/international/world/a-nuclear-needle-in-a-haystack-the-cold-war-s-missing-atom-bombs-a-590513.html |work=Der Spiegel |date=November 14, 2008 |access-date=August 20, 2019 |archive-url=https://web.archive.org/web/20190627105727/https://www.spiegel.de/international/world/a-nuclear-needle-in-a-haystack-the-cold-war-s-missing-atom-bombs-a-590513.html |archive-date=June 27, 2019 |url-status=live}}</ref>
* May 22, 1957: a {{convert|42,000|lb|adj=on}} ] accidentally fell from a bomber near Albuquerque, New Mexico. The detonation of the device's conventional explosives destroyed it on impact and formed a crater {{convert|25|ft}} in diameter on land owned by the ]. According to a researcher at the Natural Resources Defense Council, it was one of the most powerful bombs made to date.<ref>{{cite news|title=Accident Revealed After 29 Years: H-Bomb Fell Near Albuquerque in 1957 |url=https://www.latimes.com/archives/la-xpm-1986-08-27-mn-14421-story.html|access-date=August 31, 2014|agency=Associated Press|newspaper=Los Angeles Times|date=August 27, 1986 |url-status=live |archive-url=https://web.archive.org/web/20140910195156/http://articles.latimes.com/1986-08-27/news/mn-14421_1_hydrogen-bomb|archive-date=September 10, 2014}}</ref>
* June 7, 1960: the ] destroyed a ] nuclear missile and shelter and contaminated the ] in New Jersey.
* January 24, 1961: the ] occurred near ]. A ] carrying two ]s broke up in mid-air, dropping its nuclear payload in the process.<ref name="BOAS">{{cite magazine |url=https://books.google.com/books?id=dQsAAAAAMBAJ|page=28|magazine=]|date=May 1975|title=Big Bangs from Little Bombs|author=Barry Schneider|access-date=July 13, 2009}}</ref>
* ], where a ] attack aircraft with a nuclear weapon fell into the sea.<ref name=CruiseReport>{{cite web|title=Ticonderoga Cruise Reports |url=http://www.history.navy.mil/download/cv-deploy-vietnam.htm |archive-url=https://web.archive.org/web/20040907220034/http://www.history.navy.mil/download/cv-deploy-vietnam.htm |url-status=dead |archive-date=September 7, 2004 |format=Navy.mil weblist of Aug 2003 compilation from cruise reports |access-date=April 20, 2012 |quote=The National Archives hold'''' deck logs for aircraft carriers for the Vietnam Conflict.}}</ref> The pilot, the aircraft, and the ] were never recovered.<ref> {{webarchive |url=https://web.archive.org/web/20130901064320/http://www.atomicarchive.com/Almanac/Brokenarrows_static.shtml |date=September 1, 2013}} at www.atomicarchive.com. Accessed August 24, 2007.</ref> It was not until 1989 that ] revealed the loss of the one-megaton bomb.<ref>{{Cite news |date=May 9, 1989 |title=U.S. Confirms '65 Loss of H-Bomb Near Japanese Islands |newspaper=] |agency=] |page=A–27}}</ref>
* January 17, 1966: the ] occurred when a ] of the ] collided with a ] during ] off the coast of ]. The KC-135 was completely destroyed when its fuel load ignited, killing all four crew members. The B-52G broke apart, killing three of the seven crew members aboard.<ref name="hayes">{{cite news |last=Hayes |first=Ron |date=January 17, 2007 |title=H-bomb incident crippled pilot's career |newspaper=Palm Beach Post |url=http://www.palmbeachpost.com/localnews/content/local_news/epaper/2007/01/17/m1a_Hbomb_0117.html?cxtype=rss&cxsvc=7&cxcat=17 |archive-url=https://web.archive.org/web/20110616223334/http://www.palmbeachpost.com/localnews/content/local_news/epaper/2007/01/17/m1a_Hbomb_0117.html?cxtype=rss&cxsvc=7&cxcat=17 |archive-date=June 16, 2011 |access-date=May 24, 2006 |url-status=dead }}</ref> Of the four ] type ] the B-52G carried,<ref>{{Cite book|first=Randall C. |last=Maydew |title=America's Lost H-Bomb: Palomares, Spain, 1966 |publisher=Sunflower University Press |isbn=978-0-89745-214-4 |year=1997}}</ref> three were found on land near ], Spain. The non-nuclear explosives in two of the weapons detonated upon impact with the ground, resulting in the contamination of a {{convert|2|km2|acre|sp=us|adj=on}} (0.78 square mile) area by ] ]. The fourth, which fell into the ], was recovered intact after a 2{{frac|1|2}}-month-long search.<ref name=long>{{Cite news |last=Long |first=Tony |date=January 17, 2008 |url=https://www.wired.com/science/discoveries/news/2008/01/dayintech_0117 |title=Jan. 17, 1966: H-Bombs Rain Down on a Spanish Fishing Village |publisher=WIRED |access-date=February 16, 2008 |url-status=live |archive-url=https://web.archive.org/web/20081203112702/http://www.wired.com/science/discoveries/news/2008/01/dayintech_0117 |archive-date=December 3, 2008}}</ref>
* January 21, 1968: the ] involved a ] (USAF) ]. The aircraft was carrying four ]s when a cabin fire forced the crew to abandon the aircraft. Six crew members ejected safely, but one who did not have an ] was killed while trying to bail out. The bomber crashed onto ] in ], causing the nuclear payload to rupture and disperse, which resulted in widespread ].<ref>{{cite news |title=The Cold War's Missing Atom Bombs |url=https://www.spiegel.de/international/world/a-nuclear-needle-in-a-haystack-the-cold-war-s-missing-atom-bombs-a-590513.html |work=Der Spiegel |date=November 14, 2008 |access-date=August 20, 2019 |archive-date=June 27, 2019 |archive-url=https://web.archive.org/web/20190627105727/https://www.spiegel.de/international/world/a-nuclear-needle-in-a-haystack-the-cold-war-s-missing-atom-bombs-a-590513.html |url-status=live }}</ref> One of the bombs remains lost.<ref>{{cite news |title=US left nuclear weapon under ice in Greenland |url=https://www.telegraph.co.uk/news/worldnews/europe/greenland/3439318/US-left-nuclear-weapon-under-ice-in-Greenland.html |archive-url=https://ghostarchive.org/archive/20220110/https://www.telegraph.co.uk/news/worldnews/europe/greenland/3439318/US-left-nuclear-weapon-under-ice-in-Greenland.html |archive-date=January 10, 2022 |url-access=subscription |url-status=live |work=The Daily Telegraph |date=November 11, 2008}}{{cbignore}}</ref>
* September 18–19, 1980: the ] occurred in Damascus, Arkansas, where a ] equipped with a nuclear warhead exploded. The accident was caused by a maintenance man who dropped a socket from a socket wrench down an {{convert|80|ft|adj=on}} shaft, puncturing a fuel tank on the rocket. Leaking fuel resulted in a ] fuel explosion, jettisoning the ] beyond the launch site.<ref>{{Cite book |last1=Schlosser |first1=Eric |title=Physics Today |date=2013 |isbn=978-1-59420-227-8 |volume=67 |pages= |chapter=Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety |bibcode=2014PhT....67d..48W |doi=10.1063/PT.3.2350 |chapter-url=https://archive.org/details/commandcontrol00eric/page/48 |issue=4}}</ref><ref>{{cite web |last1=Christ |first1=Mark K. |title=Titan II Missile Explosion |url=http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543 |url-status=live |archive-url=https://web.archive.org/web/20140912135526/http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543 |archive-date=September 12, 2014 |access-date=August 31, 2014 |website=The Encyclopedia of Arkansas History & Culture |publisher=Arkansas Historic Preservation Program}}</ref><ref>{{cite book |last1=Stumpf |first1=David K. |title="We Can Neither Confirm Nor Deny" Sentinels of History: Refelections on Arkansas Properties on the National Register of Historic Places |date=2000 |publisher=University of Arkansas Press |editor1-last=Christ |editor1-first=Mark K. |location=Fayetteville, Arkansas |editor2-last=Slater |editor2-first=Cathryn H.}}</ref>

=== Nuclear testing and fallout ===
{{Main|Nuclear fallout}} {{See also|Downwinders}}
].]]
] shows a ] in the background. Scenes such as this were typical during the 1950s. From 1951 to 1962 the government conducted 100 atmospheric tests at the nearby ].]]

Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980. ] from nuclear weapons testing was first drawn to public attention in 1954 when the ] hydrogen bomb test at the ] contaminated the crew and catch of the Japanese fishing boat '']''.<ref name=rudig2 /> One of the fishermen died in Japan seven months later, and the fear of contaminated ] led to a temporary boycotting of the popular staple in Japan. The incident caused widespread concern around the world, especially regarding the effects of nuclear fallout and atmospheric ], and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries".<ref name=rudig2>{{cite book |last=Rudig |first=Wolfgang |date=1990 |title=Anti-nuclear Movements: A World Survey of Opposition to Nuclear Energy |url=https://books.google.com/books?id=ZXwfAQAAIAAJ |publisher=Longman |pages=54–55 |isbn=978-0582902695}}</ref>

As public awareness and concern mounted over the possible health hazards associated with exposure to the nuclear fallout, various studies were done to assess the extent of the hazard. A ]/ ] study claims that fallout from atmospheric nuclear tests would lead to perhaps 11,000 excess deaths among people alive during atmospheric testing in the United States from all forms of cancer, including leukemia, from 1951 to well into the 21st century.<ref>{{cite web|title=Report on the Health Consequences to the American Population from Nuclear Weapons Tests Conducted by the United States and Other Nations |url=https://www.cdc.gov/nceh/radiation/fallout/|publisher=CDC|access-date=December 7, 2013 |url-status=live |archive-url=https://web.archive.org/web/20131204164348/http://www.cdc.gov/nceh/radiation/fallout/|archive-date=December 4, 2013}}</ref><ref>{{cite book |url=http://books.nap.edu/catalog.php?record_id=10621|title=Exposure of the American Population to Radioactive Fallout from Nuclear Weapons Tests|author=Committee to Review the CDC-NCI Feasibility Study of the Health Consequences Nuclear Weapons Tests, National Research Council|access-date=October 24, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140907210530/http://books.nap.edu/catalog.php?record_id=10621|archive-date=September 7, 2014 |doi=10.17226/10621|pmid=25057651|year=2003|isbn=978-0-309-08713-1}}</ref>
{{as of|2009|March}}, the US is the only nation that compensates nuclear test victims. Since the ] of 1990, more than $1.38&nbsp;billion in compensation has been approved. The money is going to people who took part in the tests, notably at the ], and to others exposed to the radiation.<ref name=compo>{{cite web|url=https://abcnews.go.com/International/wireStory?id=7159303|title=What governments offer to victims of nuclear tests|website=ABC News|access-date=October 24, 2014|archive-date=January 18, 2023|archive-url=https://web.archive.org/web/20230118174820/https://abcnews.go.com/International/wireStory?id=7159303|url-status=live}}</ref><ref>{{cite web |url=http://www.usdoj.gov/civil/omp/omi/Tre_SysClaimsToDateSum.pdf|title=Radiation Exposure Compensation System: Claims to Date Summary of Claims Received by 06/11/2009 |url-status=live |archive-url=https://web.archive.org/web/20090907192321/http://www.usdoj.gov/civil/omp/omi/Tre_SysClaimsToDateSum.pdf|archive-date=September 7, 2009}}</ref>

In addition, leakage of byproducts of nuclear weapon production into groundwater has been an ongoing issue, particularly at the ].<ref name="Hanford Ref">{{cite web|last1=Coghlan|first1=Andy|title=US nuclear dump is leaking toxic waste |url=https://www.newscientist.com/article/dn23214-us-nuclear-dump-is-leaking-toxic-waste/|website=New Scientist|access-date=March 12, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160413045211/https://www.newscientist.com/article/dn23214-us-nuclear-dump-is-leaking-toxic-waste/|archive-date=April 13, 2016}}</ref>

== Effects of nuclear explosions ==
{{Main|Effects of nuclear explosions}}

=== Effects of nuclear explosions on human health ===
{{Main|Effects of nuclear explosions on human health}}
]'s back injuries taken in January 1946 by a US Marine photographer]]
Some scientists estimate that a nuclear war with 100 Hiroshima-size nuclear explosions on cities could cost the lives of tens of millions of people from long-term climatic effects alone. The climatology hypothesis is that ''if'' each city ]s, a great deal of soot could be thrown up into the atmosphere which could blanket the earth, cutting out sunlight for years on end, causing the disruption of food chains, in what is termed a ].<ref>Philip Yam. Nuclear Exchange, ''Scientific American'', June 2010, p. 24.</ref><ref>Alan Robock and Owen Brian Toon. Local Nuclear War, Global Suffering, ''Scientific American'', January 2010, pp. 74–81.</ref>

People near the Hiroshima explosion and who managed to survive the explosion subsequently suffered a variety of horrible medical effects. Some of these effects are still present to this day:<ref>{{Cite web |url=https://k1project.columbia.edu/news/hiroshima-and-nagasaki|title=Hiroshima and Nagasaki: The Long Term Health Effects {{!}} K=1 Project|website=k1project.columbia.edu|language=en|access-date=September 7, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170620041039/https://k1project.columbia.edu/news/hiroshima-and-nagasaki |archive-date=June 20, 2017}}</ref>
* Initial stage—the first 1–9 weeks, in which are the greatest number of deaths, with 90% due to thermal injury or blast effects and 10% due to super-lethal ] exposure.
* Intermediate stage—from 10 to 12 weeks. The deaths in this period are from ] in the median lethal range – ]
* Late period—lasting from 13 to 20 weeks. This period has some improvement in survivors' condition.
* Delayed period—from 20+ weeks. Characterized by numerous complications, mostly related to healing of thermal and mechanical injuries, and if the individual was exposed to a few hundred to a thousand ]s of radiation, it is coupled with infertility, sub-fertility and blood disorders. Furthermore, ionizing radiation above a dose of around 50–100 millisievert exposure has been shown to statistically begin increasing one's chance of dying of cancer sometime in their lifetime over the normal unexposed rate of ~25%, in the long term, a heightened rate of cancer, proportional to the dose received, would begin to be observed after ~5+ years, with lesser problems such as eye ]s and other more minor effects in other organs and tissue also being observed over the long term.

Fallout exposure—depending on if further afield individuals ] or evacuate perpendicular to the direction of the wind, and therefore avoid contact with the fallout plume, and stay there for the days and weeks after the nuclear explosion, their exposure to fallout, and therefore their total dose, will vary. With those who do shelter in place, and or evacuate, experiencing a total dose that would be negligible in comparison to someone who just went about their life as normal.<ref>{{cite web |url-status=live |quote=7 hour rule: At 7 hours after detonation the fission product activity will have decreased to about 1/10 (10%) of its amount at 1 hour. At about 2 days (49 hours-7X7) the activity will have decreased to 1% of the 1-hour value |url=http://www.falloutradiation.com/johnwayne7 |website=Fallout Radiation.com |title=Decay Information |archive-url=https://web.archive.org/web/20110831072351/http://www.falloutradiation.com/johnwayne7 |archive-date=August 31, 2011}}</ref><ref>{{cite web|url=http://www3.nd.edu/~nsl/Lectures/phys205/pdf/Nuclear_Warfare_9.pdf|title=Nuclear Warfare|page=22|url-status=dead|archive-url=https://web.archive.org/web/20131126220402/http://www3.nd.edu/~nsl/Lectures/phys205/pdf/Nuclear_Warfare_9.pdf|archive-date=November 26, 2013|access-date=May 21, 2016}}</ref>

Staying indoors until after the most hazardous fallout ], ] decays away to 0.1% of its initial quantity after ten ]s—which is represented by 80 days in ]s case, would make the difference between likely contracting ] or escaping completely from this substance depending on the actions of the individual.<ref>{{cite web|title=Public Health Assessment – Iodine-131 Releases |url=http://www.atsdr.cdc.gov/HAC/PHA/OakRidgeI131_022508/I%20131%20Final_02_25_08_508.pdf |date=March 2008 |website=Agency for Toxic Substances and Disease Registry |publisher=U.S. Center for Disease Control|access-date=May 21, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160511014537/http://www.atsdr.cdc.gov/HAC/pha/oakridgeI131_022508/I%20131%20Final_02_25_08_508.pdf |archive-date=May 11, 2016}}</ref>

=== Effects of nuclear war ===
{{See also|Nuclear holocaust|Doomsday Clock|Doomsday device|World War III|Nuclear famine}}
], the largest nuclear weapon detonated by the US, in 1954]]
Nuclear war could yield unprecedented human death tolls and ]. Detonating large numbers of nuclear weapons would have an immediate, short term and long-term effects on the climate, potentially causing cold weather known as a "]".<ref>{{Cite news |last=Meyer |first=Robinson |date=April 29, 2016 |title=You're More Likely to Die in a Human Extinction Event Than a Car Crash |work=The Atlantic |url=https://www.theatlantic.com/technology/archive/2016/04/a-human-extinction-isnt-that-unlikely/480444/ |access-date=April 19, 2020 |archive-date=May 1, 2016 |archive-url=https://web.archive.org/web/20160501051000/http://www.theatlantic.com/technology/archive/2016/04/a-human-extinction-isnt-that-unlikely/480444/ |url-status=live }}</ref><ref name="newstudy-2022">{{cite news |last1=Diaz-Maurin |first1=François |title=Nowhere to hide: How a nuclear war would kill you — and almost everyone else |url=https://thebulletin.org/2022/10/nowhere-to-hide-how-a-nuclear-war-would-kill-you-and-almost-everyone-else/ |work=] |date=20 October 2022 |access-date=October 26, 2022 |archive-date=October 26, 2022 |archive-url=https://web.archive.org/web/20221026154805/https://thebulletin.org/2022/10/nowhere-to-hide-how-a-nuclear-war-would-kill-you-and-almost-everyone-else/ |url-status=live }}</ref> In 1982, ] estimated that a ] might kill 400–450&nbsp;million directly, mostly in the United States, Europe and Russia, and maybe several hundred million more through follow-up consequences in those same areas.<ref>{{Cite journal |last=Martin |first=Brian |date=1982 |title=Critique of nuclear extinction |url=http://www.bmartin.cc/pubs/82jpr.html |journal=Journal of Peace Research |volume=19 |issue=4 |pages=287–300 |doi=10.1177/002234338201900401 |access-date=October 25, 2014 |s2cid=110974484 |archive-date=April 4, 2020 |archive-url=https://web.archive.org/web/20200404000718/https://www.bmartin.cc/pubs/82jpr.html |url-status=live }}</ref> Many scholars have posited that a global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to the ].<ref>{{cite journal |author=Tonn, Bruce |author2=MacGregor, Donald |name-list-style=amp |doi=10.1016/j.futures.2009.07.009 |title=A singular chain of events |journal=Futures |volume=41 |issue=10 |year=2009 |pages=706–714|s2cid=144553194 }}</ref> The ''International Physicians for the Prevention of Nuclear War'' believe that nuclear war could indirectly contribute to human extinction via secondary effects, including environmental consequences, ], and economic collapse. It has been estimated that a relatively small-scale nuclear exchange between ] involving 100 ] yield (15 kilotons) weapons, could cause a nuclear winter and kill more than a billion people.<ref>{{cite web |last1=Helfand |first1=Ira |title=Nuclear Famine: Two Billion People at Risk? |url=http://www.ippnw.org/pdf/nuclear-famine-two-billion-at-risk-2013.pdf |website=] |access-date=13 February 2016 |archive-date=April 5, 2016 |archive-url=https://web.archive.org/web/20160405015355/http://www.ippnw.org/pdf/nuclear-famine-two-billion-at-risk-2013.pdf |url-status=live }}</ref>

According to a peer-reviewed study published in the journal '']'' in August 2022, a full-scale nuclear war between the US and Russia would directly kill 360 million people and more than 5 billion people would die from ]. More than 2 billion people could die from a smaller-scale nuclear war between India and Pakistan.<ref name="newstudy-2022"/><ref>{{cite news |title=World Nuclear war between the U.S. and Russia would kill more than 5 billion people – just from starvation, study finds |url=https://www.cbsnews.com/news/nuclear-war-5-billion-people-starvation-deaths-study/ |work=CBS News |date=16 August 2022 |access-date=October 26, 2022 |archive-date=October 26, 2022 |archive-url=https://web.archive.org/web/20221026190805/https://www.cbsnews.com/news/nuclear-war-5-billion-people-starvation-deaths-study/ |url-status=live }}</ref><ref>{{cite journal |title=Global food insecurity and famine from reduced crop, marine fishery and livestock production due to climate disruption from nuclear war soot injection |journal=] |date=15 August 2022 |doi=10.1038/s43016-022-00573-0 |last1=Xia |first1=Lili |last2=Robock |first2=Alan |last3=Scherrer |first3=Kim |last4=Harrison |first4=Cheryl S. |last5=Bodirsky |first5=Benjamin Leon |last6=Weindl |first6=Isabelle |last7=Jägermeyr |first7=Jonas |last8=Bardeen |first8=Charles G. |last9=Toon |first9=Owen B. |last10=Heneghan |first10=Ryan |volume=3 |issue=8 |pages=586–596 |pmid=37118594 |s2cid=251601831 |doi-access=free |hdl=11250/3039288 |hdl-access=free }}</ref>

=== Public opposition ===
{{See also|Nuclear disarmament|International Day against Nuclear Tests}}
] between the US/NATO and the Warsaw Pact, 1981]]
], France, in the 1980s]]

Peace movements emerged in Japan and in 1954 they converged to form a unified "]." Japanese opposition to nuclear weapons tests in the Pacific Ocean was widespread, and "an estimated 35 million signatures were collected on petitions calling for bans on nuclear weapons".<ref name=falkj>Jim Falk (1982). ''Global Fission: The Battle Over Nuclear Power'', Oxford University Press, pp. 96–97.</ref>

In the United Kingdom, the ] organised by the ] (CND) took place at ] 1958, when, according to the CND, several thousand people marched for four days from ], London, to the ] close to ] in ], England, to demonstrate their opposition to nuclear weapons.<ref name=CND>{{cite web |url=http://www.cnduk.org/pages/binfo/hist.html |title=A brief history of CND |publisher=Cnduk.org |access-date=May 30, 2013 |url-status=live |archive-url=https://web.archive.org/web/20040617103503/http://www.cnduk.org/pages/binfo/hist.html |archive-date=June 17, 2004}}</ref><ref name=GuardianUnlimited:1958>{{cite news |work=] |title=Early defections in march to Aldermaston |date=April 5, 1958 |url=http://century.guardian.co.uk/1950-1959/Story/0,,105488,00.html |location=London |url-status=live |archive-url=https://web.archive.org/web/20061008112515/http://century.guardian.co.uk/1950-1959/Story/0,,105488,00.html |archive-date=October 8, 2006}}</ref> The Aldermaston marches continued into the late 1960s when tens of thousands of people took part in the four-day marches.<ref name=falkj />

In 1959, a letter in the ''Bulletin of the Atomic Scientists'' was the start of a successful campaign to stop the ] dumping ] in the sea 19 kilometres from ].<ref>Jim Falk (1982). ''Global Fission: The Battle Over Nuclear Power'', Oxford University Press, p. 93.</ref> In 1962, ] won the ] for his work to stop the atmospheric testing of nuclear weapons, and the "Ban the Bomb" movement spread.<ref name="brown" />

In 1963, many countries ratified the ] prohibiting atmospheric nuclear testing. Radioactive fallout became less of an issue and the anti-nuclear weapons movement went into decline for some years.<ref name=rudig2 /><ref>Jim Falk (1982). ''Global Fission: The Battle Over Nuclear Power'', Oxford University Press, p. 98.</ref> A resurgence of interest occurred amid European and American ] in the 1980s.<ref>Spencer Weart, ''Nuclear Fear: A History of Images'' (Cambridge, Massachusetts: Harvard University Press, 1988), chapters 16 and 19.</ref>

== Costs and technology spin-offs ==
{{See also|Global Positioning System|Nuclear weapons delivery|History of computing hardware|ENIAC|Swords to ploughshares}}
According to an audit by the ], between 1940 and 1996, the US spent ${{Format price|{{Inflation|US|5821000000000|1996|r=3}}}} in present-day terms{{Inflation-fn|US}} on nuclear weapons programs. 57% of which was spent on building ] systems. 6.3% of the total$, {{Format price|{{Inflation|US|365000000000|1996|r=3}}}} in present-day terms, was spent on ] and ], for example cleaning up the ], and 7% of the total$, {{Format price|{{Inflation|US|409000000000|1996|r=3}}}} was spent on making nuclear weapons themselves.<ref>{{cite web |url=http://www.brookings.edu/fp/projects/nucwcost/figure1.htm|website=Brookings Institution|title=Estimated Minimum Incurred Costs of U.S. Nuclear Weapons Programs, 1940–1996 |access-date=November 20, 2015 |archive-url=https://web.archive.org/web/20040305101238/http://www.brookings.edu/fp/projects/nucwcost/figure1.htm |archive-date=March 5, 2004}}</ref>

== Non-weapons uses ==
{{Main|Peaceful nuclear explosion}}
Peaceful nuclear explosions are ]s conducted for non-military purposes, such as activities related to ] including the creation of ]s. During the 1960s and 1970s, both the United States and the Soviet Union conducted a number of PNEs.<ref>{{Cite web |url=https://scienceandglobalsecurity.org/archive/sgs07nordyke.pdf |title=Archived copy |access-date=May 14, 2024 |archive-date=May 14, 2024 |archive-url=https://web.archive.org/web/20240514144116/https://scienceandglobalsecurity.org/archive/sgs07nordyke.pdf |url-status=live }}</ref> The United States created plans for several uses of PNEs, including ].<ref>{{Cite web |url=https://www.osti.gov/opennet/reports/plowshar.pdf |title=Archived copy |access-date=May 14, 2024 |archive-date=April 3, 2024 |archive-url=https://web.archive.org/web/20240403165317/https://www.osti.gov/opennet/reports/plowshar.pdf |url-status=live }}</ref> Six of the explosions by the Soviet Union are considered to have been of an applied nature, not just tests.

The United States and the Soviet Union later halted their programs. Definitions and limits are covered in the Peaceful Nuclear Explosions Treaty of 1976.<ref>{{cite web |url=http://www.fordlibrarymuseum.gov/library/document/0248/whpr19760527-013.pdf |date=May 28, 1976 |title=Announcement of Treaty on Underground Nuclear Explosions Peaceful Purposes (PNE Treaty) |publisher=Gerald R. Ford Museum and Library |url-status=dead |archive-url=https://web.archive.org/web/20160305223640/https://www.fordlibrarymuseum.gov/library/document/0248/whpr19760527-013.pdf |archive-date=March 5, 2016 |access-date=February 22, 2016}}</ref><ref>{{cite web |url=http://www.presidency.ucsb.edu/ws/?pid=6245 |title=Gerald R. Ford: "Message to the Senate Transmitting United States-Soviet Treaty and Protocol on the Limitation of Underground Nuclear Explosions", July 29, 1976 |last1=Peters |first1=Gerhard |last2=Woolley |first2=John T |publisher=University of California – Santa Barbara |website=The American Presidency Project |url-status=dead |archive-url=https://web.archive.org/web/20160303170850/http://www.presidency.ucsb.edu/ws/?pid=6245 |archive-date=March 3, 2016 |access-date=February 22, 2016 }}</ref> The stalled ] of 1996 would prohibit all nuclear explosions, regardless of whether they are for peaceful purposes or not.<ref>{{cite web|title=Status of Signature and Ratification |url=https://www.ctbto.org/the-treaty/status-of-signature-and-ratification/|website=ctbto dot org|publisher=CTBT Organization Preparatory Commission |access-date=December 29, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20161228205543/http://ctbto.org/the-treaty/status-of-signature-and-ratification |archive-date=December 28, 2016}}</ref>

== History of development ==
{{Main|History of nuclear weapons}}
{{See also|Soviet atomic bomb project|Manhattan Project|Cold War|History of the Teller–Ulam design}}
{{Excerpt|History of nuclear weapons|Background|paragraphs=1, 4-6, 9-13}}

== See also ==
{{div col}}
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ] (Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean)
* ] of Japan
{{div col end}}


== References == == References ==
=== Notes ===
*{{fnb|1}} p. 54. ]. ''The Road from Los Alamos''. Simon and Schuster, New York. (] ISBN 0-671-74012-1)
;Explanatory Notes
*Glasstone, Samuel and Dolan, Philip J., '''', U.S. Government Printing Office, 1977.
{{Notelist}}
*'''', Departments of the Army, Navy, and Air Force, Washington, D.C., 1996.

*Hansen, Chuck. ''U.S. Nuclear Weapons: The Secret History'', Arlington, TX: Aerofax, 1988.
;Citations
*Hansen, Chuck. ''The Swords of Armageddon: U.S. nuclear weapons development since 1945'', Sunnyvale, CA: Chukelea Publications, 1995 .
{{Reflist}}
*]. '''', Princeton University Press, 1945. (The first declassified report by the US government on nuclear weapons) (])

*'''', Office of Technology Assessment (May 1979).
===Bibliography===
*Rhodes, Richard. ''Dark Sun: The Making of the Hydrogen Bomb''. Simon and Schuster, New York, (] ISBN 0684824140)
{{See also|List of books about nuclear issues}}
*Rhodes, Richard. ''The Making of the Atomic Bomb''. Simon and Schuster, New York, (] ISBN 0684813785)
{{refbegin|30em}}
*Weart, Spencer R. ''Nuclear Fear: A History of Images''. Cambridge, Mass.: Harvard University Press, 1988.
* ]. ''The Road from Los Alamos''. New York: Simon and Schuster, 1991. {{ISBN|0-671-74012-1}}
==External links==
* DeVolpi, Alexander, Minkov, Vladimir E., Simonenko, Vadim A., and Stanford, George S. ''Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry''. Fidlar Doubleday, 2004 (Two volumes, both accessible on Google Book Search) (Content of both volumes is now available in the 2009 trilogy by Alexander DeVolpi: ''Nuclear Insights: The Cold War Legacy'')
*
* Glasstone, Samuel and Dolan, Philip J. '''' Washington, D.C.: U.S. Government Printing Office, 1977.
* is a reliable source of information and has links to other sources and an informative .
* ''''. {{Webarchive|url=https://web.archive.org/web/20150408021307/http://fas.org/nuke/guide/usa/doctrine/dod/fm8-9/1toc.htm |date=April 8, 2015 }}. Departments of the Army, Navy, and Air Force: Washington, D.C., 1996
*
* ]. ''U.S. Nuclear Weapons: The Secret History.'' Arlington, TX: Aerofax, 1988
*
* Hansen, Chuck, "" (CD-ROM & download available). {{Webarchive|url=https://web.archive.org/web/20161230020259/http://www.uscoldwar.com/ |date=December 30, 2016 }}. PDF. 2,600 pages, Sunnyvale, California, Chucklea Publications, 1995, 2007. {{ISBN|978-0-9791915-0-3}} (2nd Ed.)
*
* Holloway, David. ''Stalin and the Bomb''. New Haven: Yale University Press, 1994. {{ISBN|0-300-06056-4}}
*The provide solid information on weapons of mass destruction, including and their
* The Manhattan Engineer District, "" (1946), {{Webarchive|url=https://web.archive.org/web/20120204055504/http://www.atomicarchive.com/Docs/MED/index.shtml |date=February 4, 2012 }}
*The is a public domain text and is an excellent source on how to survive a nuclear attack.
* {{in lang|fr}} Jean-Hugues Oppel, ''Réveillez le président'', Éditions Payot et rivages, 2007 ({{ISBN|978-2-7436-1630-4}}). The book is a fiction about the ] of France; the book also contains about ten chapters on true historical incidents involving nuclear weapons and strategy.
* - click on the ''Next >>'' button at the bottom of each slide.
* ]. '''' {{Webarchive|url=https://web.archive.org/web/20170421015824/http://www.atomicarchive.com/Docs/SmythReport/index.shtml |date=April 21, 2017 }}. Princeton, NJ: Princeton University Press, 1945. (]{{spaced ndash}}the first declassified report by the US government on nuclear weapons)
*
* ''''. Office of Technology Assessment, May 1979.
*
* ]. ''Dark Sun: The Making of the Hydrogen Bomb''. New York: Simon and Schuster, 1995. {{ISBN|0-684-82414-0}}
*
* Rhodes, Richard. '']''. New York: Simon and Schuster, 1986 {{ISBN|0-684-81378-5}}
* reports the program which makes the picture of the importance of the terrible disaster of atomic bomb and peace.
* ] and Goodby, James E. ''The War that Must Never be Fought'', Hoover Press, 2015, {{ISBN|978-0-8179-1845-3}}.
* Nobel Peace Prize-winning organization with information about the medical consequences of nuclear weapons, war and militarization.
* ] ''Nuclear Fear: A History of Images''. Cambridge, Massachusetts: Harvard University Press, 1988. {{ISBN|0-674-62836-5}}
* Weart, Spencer R. ''The Rise of Nuclear Fear''. Cambridge, Massachusetts: Harvard University Press, 2012. {{ISBN|0-674-05233-1}}
{{refend}}

== Further reading ==
{{Library resources box}}
{{refbegin|30em}}

* ] and David Wright, "Broken Shield: Missiles designed to destroy incoming nuclear warheads fail frequently in tests and could increase global risk of mass destruction", '']'', vol. 320, no. no. 6 (June 2019), pp.&nbsp;62–67. "Current U.S. ] plans are being driven largely by ], ] and ]. Missile defenses will not allow us to escape our vulnerability to nuclear weapons. Instead large-scale developments will create barriers to taking real steps toward ]—by blocking further cuts in nuclear arsenals and potentially spurring new deployments." (p.&nbsp;67.)
* ], "Missile Mania: The death of the Treaty]] has escalated the arms race", '']'', vol. 309, no. 6 (September 23, 2019), p.&nbsp;4.
* ], and ], "The Return of Doomsday: The New Nuclear Arms Race – and How Washington and Moscow Can Stop It", '']'', vol. 98, no. 5 (September / October 2019), pp.&nbsp;150–161. Former ] ] and former ] ] write that "the old equilibrium" between the United States and Russia has been "destabilized" by "clashing national interests, insufficient dialogue, eroding arms control structures, advanced missile systems, and new ]s... Unless Washington and Moscow confront these problems now, a major international conflict or nuclear escalation is disturbingly plausible—perhaps even likely." (p.&nbsp;161.)
* ], "The Nuclear Worrier" (review of ], ''The Doomsday Machine: Confessions of a ] Planner'', New York, Bloomsbury, 2017, {{ISBN|9781608196708}}, 420 pp.), '']'', vol. LXV, no. 1 (January 18, 2018), pp.&nbsp;13–15.
* ], '']'', ], 2013, {{ISBN|1594202273}}. The book became the basis for a 2-hour 2017 ] ] episode, likewise titled "Command and Control". Nuclear weapons continue to be equally hazardous to their owners as to their potential targets. Under the 1970 ], ] are obliged to work toward the elimination of nuclear weapons.
* Tom Stevenson, "A Tiny Sun" (review of ], ''The Bomb: Presidents, Generals, and the Secret History of Nuclear War'', Simon and Schuster, 2021, 384 pp.; and Keir A. Lieber and Daryl G. Press, ''The Myth of the Nuclear Revolution: Power Politics in the Atomic Age'', Cornell, 2020, 180 pp.), '']'', vol. 44, no. 4 (24 February 2022), pp.&nbsp;29–32. "Nuclear strategists systematically underestimate the chances of nuclear accident... here have been too many close calls for accidental use to be discounted." (p.&nbsp;32.)
* David Wright and Cameron Tracy, "Over-hyped: Physics dictates that ]s cannot live up to the grand promises made on their behalf", '']'', vol. 325, no. 2 (August 2021), pp.&nbsp;64–71. "Failure to fully assess is a recipe for wasteful spending and increased global risk." (p.&nbsp;71.)
{{refend}}


== External links ==
{{Wikiquote}}
{{wikinews category|Nuclear proliferation}}
{{Wikibooks|The Atomic Age}}
{{Spoken Misplaced Pages|Nuclear Weapon.ogg|date=December 1, 2005}}
*{{Commons-inline|Nuclear weapons}}
* : reliable source, has links to other sources and an informative .
* The {{Webarchive|url=https://web.archive.org/web/19961018095317/https://fas.org/ |date=October 18, 1996 }} provide information on weapons of mass destruction, including and their
* {{Webarchive|url=https://web.archive.org/web/20010302000827/http://alsos.wlu.edu/ |date=March 2, 2001 }} – contains resources related to nuclear weapons, including a historical and technical overview and searchable bibliography of web and print resources
* Video archive of at
* {{Webarchive|url=https://web.archive.org/web/20210327181530/http://www.nuclearmuseum.org/ |date=March 27, 2021 }} – located in New Mexico; a Smithsonian Affiliate Museum
* {{Webarchive|url=https://web.archive.org/web/20210515170516/http://www.ibiblio.org/rcip/nuclear.html |date=May 15, 2021 }}
* at AtomicArchive.com
* {{Webarchive|url=https://web.archive.org/web/20090115230637/http://www.lanl.gov/history/ |date=January 15, 2009 }} (US nuclear history)
* {{Webarchive|url=https://web.archive.org/web/20161110215743/https://www.pbs.org/wgbh/amex/bomb/ |date=November 10, 2016 }}, PBS website on the history of the H-bomb
*
* or NPIHP is a global network of individuals and institutions engaged in the study of international nuclear history through archival documents, oral history interviews and other empirical sources.
* {{Webarchive|url=https://web.archive.org/web/20150828053318/http://nuclearsecrecy.com/nukemap/ |date=August 28, 2015 }} – a 3D nuclear weapons effects simulator powered by Google Maps.


{{United States nuclear devices}}
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{{Nuclear technology}}
{{Nuclear and radiation accidents and incidents}}
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Latest revision as of 03:27, 11 December 2024

Explosive weapon that utilizes nuclear reactions "Atom bomb", "A-bomb", and "Nuke" redirect here. For other uses, see Atom bomb (disambiguation), A-bomb (disambiguation), and Nuke (disambiguation).

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An assortment of American nuclear intercontinental ballistic missiles at the National Museum of the United States Air Force. Clockwise from top left: PGM-17 Thor, LGM-25C Titan II, HGM-25A Titan I, Thor-Agena, LGM-30G Minuteman III, LGM-118 Peacekeeper, LGM-30A/B/F Minuteman I or II, PGM-19 Jupiter
Nuclear weapons
Photograph of a mock-up of the Little Boy nuclear weapon dropped on Hiroshima, Japan, in August 1945.
Background
Nuclear-armed states
NPT recognized
United States
Russia
United Kingdom
France
China
Others
India
Israel (undeclared)
Pakistan
North Korea
Former
South Africa
Belarus
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A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter.

The first test of a fission ("atomic") bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ). The first thermonuclear ("hydrogen") bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). Nuclear bombs have had yields between 10 tons TNT (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ).

A nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been deployed twice in war, both by the United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II.

Testing and deployment

Nuclear weapons have only twice been used in warfare, both times by the United States against Japan at the end of World War II. On August 6, 1945, the United States Army Air Forces (USAAF) detonated a uranium gun-type fission bomb nicknamed "Little Boy" over the Japanese city of Hiroshima; three days later, on August 9, the USAAF detonated a plutonium implosion-type fission bomb nicknamed "Fat Man" over the Japanese city of Nagasaki. These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel. The ethics of these bombings and their role in Japan's surrender are to this day, still subjects of debate.

Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over 2,000 times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Italy, Turkey, Belgium, the Netherlands, and Belarus are nuclear weapons sharing states. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons.

The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but there are different views of its effectiveness.

Types

Main article: Nuclear weapon design
The Trinity test of the Manhattan Project was the first detonation of a nuclear weapon, which led J. Robert Oppenheimer to recall verses from the Hindu scripture Bhagavad Gita: "If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one "... "I am become Death, the destroyer of worlds".
J. Robert Oppenheimer, principal leader of the Manhattan Project, often referred to as the "father of the atomic bomb".

There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, and those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output.

Fission weapons

The two basic fission weapon designs

All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs). This has long been noted as something of a misnomer, as their energy comes from the nucleus of the atom, just as it does with fusion weapons.

In fission weapons, a mass of fissile material (enriched uranium or plutonium) is forced into supercriticality—allowing an exponential growth of nuclear chain reactions—either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled explosive lenses. The latter approach, the "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former.

A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 kilotons) of TNT (4.2 to 2.1×10 GJ).

All fission reactions generate fission products, the remains of the split atomic nuclei. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of radioactive contamination. Fission products are the principal radioactive component of nuclear fallout. Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in the surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive.

The most commonly used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239. Less commonly used has been uranium-233. Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute.

Fusion weapons

Main article: Thermonuclear weapon
The basics of the Teller–Ulam design for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.

The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs), as they rely on fusion reactions between isotopes of hydrogen (deuterium and tritium). All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions.

Only six countries—the United States, Russia, the United Kingdom, China, France, and India—have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial. North Korea claims to have tested a fusion weapon as of January 2016, though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight.

Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. In the Teller-Ulam design, which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel (tritium, deuterium, or lithium deuteride) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, gamma rays and X-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed neutrons, which can then induce fission in materials not normally prone to it, such as depleted uranium. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of the yield comes from the final fissioning of depleted uranium.

Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to criticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated, the Tsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210 PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements. In the early 1950s the Livermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon and Sundial, 1 gigaton of TNT and 10 gigatons of TNT respectively.

Edward Teller, often referred to as the "father of the hydrogen bomb"

Fusion reactions do not create fission products, and thus contribute far less to the creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past the tropopause into the stratosphere, where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion.

Other types

Main articles: Boosted fission weapon, Neutron bomb, Radiological warfare, Induced gamma emission, and Antimatter weapon

There are other types of nuclear weapons as well. For example, a boosted fission weapon is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of the fission bomb core. The external method of boosting enabled the USSR to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles.

The detonation of any nuclear weapon is accompanied by a blast of neutron radiation. Surrounding a nuclear weapon with suitable materials (such as cobalt or gold) creates a weapon known as a salted bomb. This device can produce exceptionally large quantities of long-lived radioactive contamination. It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct.

In connection with the Strategic Defense Initiative, research into the nuclear pumped laser was conducted under the DOD program Project Excalibur but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target.

During the Starfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called a nuclear electromagnetic pulse. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling a nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area.

Research has been done into the possibility of pure fusion bombs: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the United States Department of Energy divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment".

Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurring isotopes (Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in the hafnium controversy) have been proposed as possible triggers for conventional thermonuclear reactions.

Antimatter, which consists of particles resembling ordinary matter particles in most of their properties but having opposite electric charge, has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it is feasible beyond the military domain. However, the US Air Force funded studies of the physics of antimatter in the Cold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion.

Most variation in nuclear weapon design is for the purpose of achieving different yields for different situations, and in manipulating design elements to attempt to minimize weapon size, radiation hardness or requirements for special materials, especially fissile fuel or tritium.

Tactical nuclear weapons

Soviet OTR-21 Tochka missile. Capable of firing a 100-kiloton nuclear warhead a distance of 185 km

Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as tactical nuclear weapons.

The neutron bomb purportedly conceived by Sam Cohen is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron radiation. Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in the 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200 mm W79 and 155 mm W82) and short range missile forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable.

A type of nuclear explosive most suitable for use by ground special forces was the Special Atomic Demolition Munition, or SADM, sometimes popularly known as a suitcase nuke. This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment.

Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include the USAF AIR-2 Genie, the AIM-26 Falcon and US Army Nike Hercules. Missile interceptors such as the Sprint and the Spartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads.

Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as antisubmarine weapons. These included nuclear depth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities.

Weapons delivery

See also: Nuclear weapons delivery, Nuclear triad, Strategic bomber, Intercontinental ballistic missile, and Submarine-launched ballistic missile
The first nuclear weapons were gravity bombs, such as this "Fat Man" weapon dropped on Nagasaki, Japan. They were large and could only be delivered by heavy bomber aircraft
A demilitarized, commercial launch of the Russian Strategic Rocket Forces R-36 ICBM; also known by the NATO reporting name: SS-18 Satan. Upon its first fielding in the late 1960s, the SS-18 remains the single highest throw weight missile delivery system ever built.

The system used to deliver a nuclear weapon to its target is an important factor affecting both nuclear weapon design and nuclear strategy. The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940.

The simplest method for delivering a nuclear weapon is a gravity bomb dropped from aircraft; this was the method used by the United States against Japan in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both strategic bombers and tactical fighter-bombers. This method is the primary means of nuclear weapons delivery; the majority of US nuclear warheads, for example, are free-fall gravity bombs, namely the B61, which is being improved upon to this day.

Montage of an inert test of a United States Trident SLBM (submarine launched ballistic missile), from submerged to the terminal, or re-entry phase, of the multiple independently targetable reentry vehicles

Preferable from a strategic point of view is a nuclear weapon mounted on a missile, which can use a ballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for a faster and less vulnerable attack, the development of long-range intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success.

More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing the chance of a successful missile defense. Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult.

Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines, and nuclear depth charges and torpedoes for anti-submarine warfare. An atomic mortar has been tested by the United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs), such as the Special Atomic Demolition Munition, have been developed, although the difficulty of combining sufficient yield with portability limits their military utility.

Nuclear strategy

Main articles: Nuclear strategy and Deterrence theory See also: Pre-emptive nuclear strike, Nuclear peace, Essentials of Post–Cold War Deterrence, Single Integrated Operational Plan, Nuclear warfare, and On Thermonuclear War

Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by a nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of nuclear deterrence. The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for first strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During the Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions.

The now decommissioned United States' Peacekeeper missile was an ICBM developed to replace the Minuteman missile in the late 1980s. Each missile, like the heavier lift Russian SS-18 Satan, could contain up to ten nuclear warheads (shown in red), each of which could be aimed at a different target. A factor in the development of MIRVs was to make complete missile defense difficult for an enemy country.

Different forms of nuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against the weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on submarines or land mobile transporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened missile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy the missiles before they land or implementing civil defense measures using early-warning systems to evacuate citizens to safe areas before an attack.

Weapons designed to threaten large populations or to deter attacks are known as strategic weapons. Nuclear weapons for use on a battlefield in military situations are called tactical weapons.

Critics of nuclear war strategy often suggest that a nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction. This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism.

Critics from the peace movement and within the military establishment have questioned the usefulness of such weapons in the current military climate. According to an advisory opinion issued by the International Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if the survival of the state were at stake.

Ballistic missile submarines have been of great strategic importance for the United States, Russia, and other nuclear powers since they entered service in the Cold War, as they can hide from reconnaissance satellites and fire their nuclear weapons with virtual impunity.

Another deterrence position is that nuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the Cold War between the US and the Soviet Union. In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle, argued in books like The Balance of Terror: Strategy for the Nuclear Age (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase international stability. Some prominent neo-realist scholars, such as Kenneth Waltz and John Mearsheimer, have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of total war, especially in troubled regions of the world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation, and Waltz, who was somewhat more non-interventionist. Interest in proliferation and the stability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese and South Korean nuclear deterrent against North Korea.

The threat of potentially suicidal terrorists possessing nuclear weapons (a form of nuclear terrorism) complicates the decision process. The prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless terrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the September 11, 2001, attacks, that this complication calls for a new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War. Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction.

A Minuteman III ICBM test launch from Vandenberg Air Force Base, United States. MIRVed land-based ICBMs are considered destabilizing because they tend to put a premium on striking first.

Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider a policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.".

Graham Allison makes a similar case, arguing that the key to expanded deterrence is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin." The process is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials."

According to the Pentagon's June 2019 "Doctrine for Joint Nuclear Operations" of the Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation."

Governance, control, and law

Main articles: Treaty on the Non-Proliferation of Nuclear Weapons, Strategic Arms Limitation Talks, Intermediate-Range Nuclear Forces Treaty, START I, START II, Strategic Offensive Reductions Treaty, Comprehensive Nuclear-Test-Ban Treaty, Lahore Declaration, New START, and Treaty on the Prohibition of Nuclear Weapons See also: Anti-nuclear movement
The International Atomic Energy Agency was created in 1957 to encourage peaceful development of nuclear technology while providing international safeguards against nuclear proliferation.

Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by the head of government or head of state. Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage".

In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The Russell–Einstein Manifesto was issued in London on July 9, 1955, by Bertrand Russell in the midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein, who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor a conference—called for in the manifesto—in Pugwash, Nova Scotia, Eaton's birthplace. This conference was to be the first of the Pugwash Conferences on Science and World Affairs, held in July 1957.

By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of nuclear testing. The Partial Nuclear Test Ban Treaty (1963) restricted all nuclear testing to underground nuclear testing, to prevent contamination from nuclear fallout, whereas the Treaty on the Non-Proliferation of Nuclear Weapons (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military nuclear technology to member countries without fear of proliferation.

UN vote on adoption of the Treaty on the Prohibition of Nuclear Weapons on July 7, 2017
  Yes   No  Did not vote

In 1957, the International Atomic Energy Agency (IAEA) was established under the mandate of the United Nations to encourage development of peaceful applications of nuclear technology, provide international safeguards against its misuse, and facilitate the application of safety measures in its use. In 1996, many nations signed the Comprehensive Nuclear-Test-Ban Treaty, which prohibits all testing of nuclear weapons. A testing ban imposes a significant hindrance to nuclear arms development by any complying country. The Treaty requires the ratification by 44 specific states before it can go into force; as of 2012, the ratification of eight of these states is still required.

Additional treaties and agreements have governed nuclear weapons stockpiles between the countries with the two largest stockpiles, the United States and the Soviet Union, and later between the United States and Russia. These include treaties such as SALT II (never ratified), START I (expired), INF, START II (never in effect), SORT, and New START, as well as non-binding agreements such as SALT I and the Presidential Nuclear Initiatives of 1991. Even when they did not enter into force, these agreements helped limit and later reduce the numbers and types of nuclear weapons between the United States and the Soviet Union/Russia.

Nuclear weapons have also been opposed by agreements between countries. Many nations have been declared Nuclear-Weapon-Free Zones, areas where nuclear weapons production and deployment are prohibited, through the use of treaties. The Treaty of Tlatelolco (1967) prohibited any production or deployment of nuclear weapons in Latin America and the Caribbean, and the Treaty of Pelindaba (1964) prohibits nuclear weapons in many African countries. As recently as 2006 a Central Asian Nuclear Weapon Free Zone was established among the former Soviet republics of Central Asia prohibiting nuclear weapons.

The number of nuclear warheads by country in 2024, based on an estimation by the Federation of American Scientists.

In 1996, the International Court of Justice, the highest court of the United Nations, issued an Advisory Opinion concerned with the "Legality of the Threat or Use of Nuclear Weapons". The court ruled that the use or threat of use of nuclear weapons would violate various articles of international law, including the Geneva Conventions, the Hague Conventions, the UN Charter, and the Universal Declaration of Human Rights. Given the unique, destructive characteristics of nuclear weapons, the International Committee of the Red Cross calls on States to ensure that these weapons are never used, irrespective of whether they consider them lawful or not.

Additionally, there have been other, specific actions meant to discourage countries from developing nuclear arms. In the wake of the tests by India and Pakistan in 1998, economic sanctions were (temporarily) levied against both countries, though neither were signatories with the Nuclear Non-Proliferation Treaty. One of the stated casus belli for the initiation of the 2003 Iraq War was an accusation by the United States that Iraq was actively pursuing nuclear arms (though this was soon discovered not to be the case as the program had been discontinued). In 1981, Israel had bombed a nuclear reactor being constructed in Osirak, Iraq, in what it called an attempt to halt Iraq's previous nuclear arms ambitions; in 2007, Israel bombed another reactor being constructed in Syria.

In 2013, Mark Diesendorf said that governments of France, India, North Korea, Pakistan, UK, and South Africa have used nuclear power or research reactors to assist nuclear weapons development or to contribute to their supplies of nuclear explosives from military reactors. In 2017, 122 countries mainly in the Global South voted in favor of adopting the Treaty on the Prohibition of Nuclear Weapons, which eventually entered into force in 2021.

The Doomsday Clock measures the likelihood of a human-made global catastrophe and is published annually by the Bulletin of the Atomic Scientists. The two years with the highest likelihood had previously been 1953, when the Clock was set to two minutes until midnight after the US and the Soviet Union began testing hydrogen bombs, and 2018, following the failure of world leaders to address tensions relating to nuclear weapons and climate change issues. In 2023, following the escalation of nuclear threats during the Russian invasion of Ukraine, the doomsday clock was set to 90 seconds, the highest likelihood of global catastrophe since the existence of the Doomsday Clock.

As of 2024, Russia has intensified nuclear threats in Ukraine and is reportedly planning to place nuclear weapons in orbit, breaching the 1967 Outer Space Treaty. China is significantly expanding its nuclear arsenal, with projections of over 1,000 warheads by 2030 and up to 1,500 by 2035. North Korea is progressing in intercontinental ballistic missile tests and has a mutual-defense treaty with Russia, exchanging artillery for possible missile technology. Iran is currently viewed as a nuclear "threshold" state.

Disarmament

Main article: Nuclear disarmament For statistics on possession and deployment, see List of states with nuclear weapons.
The USSR and United States nuclear weapon stockpiles throughout the Cold War until 2015, with a precipitous drop in total numbers following the end of the Cold War in 1991.

Nuclear disarmament refers to both the act of reducing or eliminating nuclear weapons and to the end state of a nuclear-free world, in which nuclear weapons are eliminated.

Beginning with the 1963 Partial Test Ban Treaty and continuing through the 1996 Comprehensive Nuclear-Test-Ban Treaty, there have been many treaties to limit or reduce nuclear weapons testing and stockpiles. The 1968 Nuclear Non-Proliferation Treaty has as one of its explicit conditions that all signatories must "pursue negotiations in good faith" towards the long-term goal of "complete disarmament". The nuclear-weapon states have largely treated that aspect of the agreement as "decorative" and without force.

Only one country—South Africa—has ever fully renounced nuclear weapons they had independently developed. The former Soviet republics of Belarus, Kazakhstan, and Ukraine returned Soviet nuclear arms stationed in their countries to Russia after the collapse of the USSR.

Proponents of nuclear disarmament say that it would lessen the probability of nuclear war, especially accidentally. Critics of nuclear disarmament say that it would undermine the present nuclear peace and deterrence and would lead to increased global instability. Various American elder statesmen, who were in office during the Cold War period, have been advocating the elimination of nuclear weapons. These officials include Henry Kissinger, George Shultz, Sam Nunn, and William Perry. In January 2010, Lawrence M. Krauss stated that "no issue carries more importance to the long-term health and security of humanity than the effort to reduce, and perhaps one day, rid the world of nuclear weapons".

Ukrainian workers use equipment provided by the US Defense Threat Reduction Agency to dismantle a Soviet-era missile silo. After the end of the Cold War, Ukraine and the other non-Russian, post-Soviet republics relinquished Soviet nuclear stockpiles to Russia.

In January 1986, Soviet leader Mikhail Gorbachev publicly proposed a three-stage program for abolishing the world's nuclear weapons by the end of the 20th century. In the years after the end of the Cold War, there have been numerous campaigns to urge the abolition of nuclear weapons, such as that organized by the Global Zero movement, and the goal of a "world without nuclear weapons" was advocated by United States President Barack Obama in an April 2009 speech in Prague. A CNN poll from April 2010 indicated that the American public was nearly evenly split on the issue.

Some analysts have argued that nuclear weapons have made the world relatively safer, with peace through deterrence and through the stability–instability paradox, including in south Asia. Kenneth Waltz has argued that nuclear weapons have helped keep an uneasy peace, and further nuclear weapon proliferation might even help avoid the large scale conventional wars that were so common before their invention at the end of World War II. But former Secretary Henry Kissinger says there is a new danger, which cannot be addressed by deterrence: "The classical notion of deterrence was that there was some consequences before which aggressors and evildoers would recoil. In a world of suicide bombers, that calculation doesn't operate in any comparable way". George Shultz has said, "If you think of the people who are doing suicide attacks, and people like that get a nuclear weapon, they are almost by definition not deterrable".

As of early 2019, more than 90% of world's 13,865 nuclear weapons were owned by Russia and the United States.

United Nations

Main article: United Nations Office for Disarmament Affairs

The UN Office for Disarmament Affairs (UNODA) is a department of the United Nations Secretariat established in January 1998 as part of the United Nations Secretary-General Kofi Annan's plan to reform the UN as presented in his report to the General Assembly in July 1997.

Its goal is to promote nuclear disarmament and non-proliferation and the strengthening of the disarmament regimes in respect to other weapons of mass destruction, chemical and biological weapons. It also promotes disarmament efforts in the area of conventional weapons, especially land mines and small arms, which are often the weapons of choice in contemporary conflicts.

Controversy

See also: Nuclear weapons debate and History of the anti-nuclear movement

Ethics

Main article: Nuclear ethics
Anti-nuclear weapons protest march in Oxford, 1980

Even before the first nuclear weapons had been developed, scientists involved with the Manhattan Project were divided over the use of the weapon. The role of the two atomic bombings of the country in Japan's surrender and the US's ethical justification for them has been the subject of scholarly and popular debate for decades. The question of whether nations should have nuclear weapons, or test them, has been continually and nearly universally controversial.

Notable nuclear weapons accidents

Main articles: Nuclear and radiation accidents and incidents and List of military nuclear accidents See also: List of nuclear close calls

Nuclear testing and fallout

Main article: Nuclear fallout See also: Downwinders
Over 2,000 nuclear explosions have been conducted in over a dozen different sites around the world. Red Russia/Soviet Union, blue France, light blue United States, violet Britain, yellow China, orange India, brown Pakistan, green North Korea and light green (territories exposed to nuclear bombs). The black dot indicates the location of the Vela incident.
This view of downtown Las Vegas shows a mushroom cloud in the background. Scenes such as this were typical during the 1950s. From 1951 to 1962 the government conducted 100 atmospheric tests at the nearby Nevada Test Site.

Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980. Radioactive fallout from nuclear weapons testing was first drawn to public attention in 1954 when the Castle Bravo hydrogen bomb test at the Pacific Proving Grounds contaminated the crew and catch of the Japanese fishing boat Lucky Dragon. One of the fishermen died in Japan seven months later, and the fear of contaminated tuna led to a temporary boycotting of the popular staple in Japan. The incident caused widespread concern around the world, especially regarding the effects of nuclear fallout and atmospheric nuclear testing, and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries".

As public awareness and concern mounted over the possible health hazards associated with exposure to the nuclear fallout, various studies were done to assess the extent of the hazard. A Centers for Disease Control and Prevention/ National Cancer Institute study claims that fallout from atmospheric nuclear tests would lead to perhaps 11,000 excess deaths among people alive during atmospheric testing in the United States from all forms of cancer, including leukemia, from 1951 to well into the 21st century. As of March 2009, the US is the only nation that compensates nuclear test victims. Since the Radiation Exposure Compensation Act of 1990, more than $1.38 billion in compensation has been approved. The money is going to people who took part in the tests, notably at the Nevada Test Site, and to others exposed to the radiation.

In addition, leakage of byproducts of nuclear weapon production into groundwater has been an ongoing issue, particularly at the Hanford site.

Effects of nuclear explosions

Main article: Effects of nuclear explosions

Effects of nuclear explosions on human health

Main article: Effects of nuclear explosions on human health
A photograph of Sumiteru Taniguchi's back injuries taken in January 1946 by a US Marine photographer

Some scientists estimate that a nuclear war with 100 Hiroshima-size nuclear explosions on cities could cost the lives of tens of millions of people from long-term climatic effects alone. The climatology hypothesis is that if each city firestorms, a great deal of soot could be thrown up into the atmosphere which could blanket the earth, cutting out sunlight for years on end, causing the disruption of food chains, in what is termed a nuclear winter.

People near the Hiroshima explosion and who managed to survive the explosion subsequently suffered a variety of horrible medical effects. Some of these effects are still present to this day:

  • Initial stage—the first 1–9 weeks, in which are the greatest number of deaths, with 90% due to thermal injury or blast effects and 10% due to super-lethal radiation exposure.
  • Intermediate stage—from 10 to 12 weeks. The deaths in this period are from ionizing radiation in the median lethal range – LD50
  • Late period—lasting from 13 to 20 weeks. This period has some improvement in survivors' condition.
  • Delayed period—from 20+ weeks. Characterized by numerous complications, mostly related to healing of thermal and mechanical injuries, and if the individual was exposed to a few hundred to a thousand millisieverts of radiation, it is coupled with infertility, sub-fertility and blood disorders. Furthermore, ionizing radiation above a dose of around 50–100 millisievert exposure has been shown to statistically begin increasing one's chance of dying of cancer sometime in their lifetime over the normal unexposed rate of ~25%, in the long term, a heightened rate of cancer, proportional to the dose received, would begin to be observed after ~5+ years, with lesser problems such as eye cataracts and other more minor effects in other organs and tissue also being observed over the long term.

Fallout exposure—depending on if further afield individuals shelter in place or evacuate perpendicular to the direction of the wind, and therefore avoid contact with the fallout plume, and stay there for the days and weeks after the nuclear explosion, their exposure to fallout, and therefore their total dose, will vary. With those who do shelter in place, and or evacuate, experiencing a total dose that would be negligible in comparison to someone who just went about their life as normal.

Staying indoors until after the most hazardous fallout isotope, I-131 decays away to 0.1% of its initial quantity after ten half-lifes—which is represented by 80 days in I-131s case, would make the difference between likely contracting Thyroid cancer or escaping completely from this substance depending on the actions of the individual.

Effects of nuclear war

See also: Nuclear holocaust, Doomsday Clock, Doomsday device, World War III, and Nuclear famine
Mushroom cloud from the explosion of Castle Bravo, the largest nuclear weapon detonated by the US, in 1954

Nuclear war could yield unprecedented human death tolls and habitat destruction. Detonating large numbers of nuclear weapons would have an immediate, short term and long-term effects on the climate, potentially causing cold weather known as a "nuclear winter". In 1982, Brian Martin estimated that a US–Soviet nuclear exchange might kill 400–450 million directly, mostly in the United States, Europe and Russia, and maybe several hundred million more through follow-up consequences in those same areas. Many scholars have posited that a global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to the extinction of the human race. The International Physicians for the Prevention of Nuclear War believe that nuclear war could indirectly contribute to human extinction via secondary effects, including environmental consequences, societal breakdown, and economic collapse. It has been estimated that a relatively small-scale nuclear exchange between India and Pakistan involving 100 Hiroshima yield (15 kilotons) weapons, could cause a nuclear winter and kill more than a billion people.

According to a peer-reviewed study published in the journal Nature Food in August 2022, a full-scale nuclear war between the US and Russia would directly kill 360 million people and more than 5 billion people would die from starvation. More than 2 billion people could die from a smaller-scale nuclear war between India and Pakistan.

Public opposition

See also: Nuclear disarmament and International Day against Nuclear Tests
Protest in Bonn against the nuclear arms race between the US/NATO and the Warsaw Pact, 1981
Demonstration against nuclear testing in Lyon, France, in the 1980s

Peace movements emerged in Japan and in 1954 they converged to form a unified "Japan Council against Atomic and Hydrogen Bombs." Japanese opposition to nuclear weapons tests in the Pacific Ocean was widespread, and "an estimated 35 million signatures were collected on petitions calling for bans on nuclear weapons".

In the United Kingdom, the Aldermaston Marches organised by the Campaign for Nuclear Disarmament (CND) took place at Easter 1958, when, according to the CND, several thousand people marched for four days from Trafalgar Square, London, to the Atomic Weapons Research Establishment close to Aldermaston in Berkshire, England, to demonstrate their opposition to nuclear weapons. The Aldermaston marches continued into the late 1960s when tens of thousands of people took part in the four-day marches.

In 1959, a letter in the Bulletin of the Atomic Scientists was the start of a successful campaign to stop the Atomic Energy Commission dumping radioactive waste in the sea 19 kilometres from Boston. In 1962, Linus Pauling won the Nobel Peace Prize for his work to stop the atmospheric testing of nuclear weapons, and the "Ban the Bomb" movement spread.

In 1963, many countries ratified the Partial Test Ban Treaty prohibiting atmospheric nuclear testing. Radioactive fallout became less of an issue and the anti-nuclear weapons movement went into decline for some years. A resurgence of interest occurred amid European and American fears of nuclear war in the 1980s.

Costs and technology spin-offs

See also: Global Positioning System, Nuclear weapons delivery, History of computing hardware, ENIAC, and Swords to ploughshares

According to an audit by the Brookings Institution, between 1940 and 1996, the US spent $11.3 trillion in present-day terms on nuclear weapons programs. 57% of which was spent on building nuclear weapons delivery systems. 6.3% of the total$, 709 billion in present-day terms, was spent on environmental remediation and nuclear waste management, for example cleaning up the Hanford site, and 7% of the total$, 795 billion was spent on making nuclear weapons themselves.

Non-weapons uses

Main article: Peaceful nuclear explosion

Peaceful nuclear explosions are nuclear explosions conducted for non-military purposes, such as activities related to economic development including the creation of canals. During the 1960s and 1970s, both the United States and the Soviet Union conducted a number of PNEs. The United States created plans for several uses of PNEs, including Operation Plowshare. Six of the explosions by the Soviet Union are considered to have been of an applied nature, not just tests.

The United States and the Soviet Union later halted their programs. Definitions and limits are covered in the Peaceful Nuclear Explosions Treaty of 1976. The stalled Comprehensive Nuclear-Test-Ban Treaty of 1996 would prohibit all nuclear explosions, regardless of whether they are for peaceful purposes or not.

History of development

Main article: History of nuclear weapons See also: Soviet atomic bomb project, Manhattan Project, Cold War, and History of the Teller–Ulam design This section is an excerpt from History of nuclear weapons § Background.
In nuclear fission, the nucleus of a fissile atom (in this case, enriched uranium) absorbs a thermal neutron, becomes unstable and splits into two new atoms, releasing some energy and between one and three new neutrons, which can perpetuate the process.

In the first decades of the 20th century, physics was revolutionized with developments in the understanding of the nature of atoms including the discoveries in atomic theory by John Dalton. Around the turn of the 20th century, it was discovered by Hans Geiger and Ernest Marsden and then Ernest Rutherford, that atoms had a highly dense, very small, charged central core called an atomic nucleus. In 1898, Pierre and Marie Curie discovered that pitchblende, an ore of uranium, contained a substance—which they named radium—that emitted large amounts of radiation. Ernest Rutherford and Frederick Soddy identified that atoms were breaking down and turning into different elements. Hopes were raised among scientists and laymen that the elements around us could contain tremendous amounts of unseen energy, waiting to be harnessed.

In Paris in 1934, Irène and Frédéric Joliot-Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles; in Italy Enrico Fermi reported similar results when bombarding uranium with neutrons.

In December 1938, Otto Hahn and Fritz Strassmann reported that they had detected the element barium after bombarding uranium with neutrons. Lise Meitner and Otto Robert Frisch correctly interpreted these results as being due to the splitting of the uranium atom. Frisch confirmed this experimentally on January 13, 1939. They gave the process the name "fission" because of its similarity to the splitting of a cell into two new cells. Even before it was published, news of Meitner's and Frisch's interpretation crossed the Atlantic. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction.

Leo Szilard, pictured in about 1960, invented the electron microscope, linear accelerator, cyclotron, nuclear chain reaction and patented the nuclear reactor

After learning about the German fission in 1939, Leo Szilard concluded that uranium would be the element which can realize his 1933 idea about nuclear chain reaction.

Uranium appears in nature primarily in two isotopes: uranium-238 and uranium-235. When the nucleus of uranium-235 absorbs a neutron, it undergoes nuclear fission, releasing energy and, on average, 2.5 neutrons. Because uranium-235 releases more neutrons than it absorbs, it can support a chain reaction and so is described as fissile. Uranium-238, on the other hand, is not fissile as it does not normally undergo fission when it absorbs a neutron.

By the start of the war in September 1939, many scientists likely to be persecuted by the Nazis had already escaped. Physicists on both sides were well aware of the possibility of utilizing nuclear fission as a weapon, but no one was quite sure how it could be engineered. In August 1939, concerned that Germany might have its own project to develop fission-based weapons, Albert Einstein signed a letter to U.S. President Franklin D. Roosevelt warning him of the threat.

Roosevelt responded by setting up the Uranium Committee under Lyman James Briggs but, with little initial funding ($6,000), progress was slow. It was not until the U.S. entered the war in December 1941 that Washington decided to commit the necessary resources to a top-secret high priority bomb project.

Organized research first began in Britain and Canada as part of the Tube Alloys project: the world's first nuclear weapons project. The Maud Committee was set up following the work of Frisch and Rudolf Peierls who calculated uranium-235's critical mass and found it to be much smaller than previously thought which meant that a deliverable bomb should be possible. In the February 1940 Frisch–Peierls memorandum they stated that: "The energy liberated in the explosion of such a super-bomb...will, for an instant, produce a temperature comparable to that of the interior of the sun. The blast from such an explosion would destroy life in a wide area. The size of this area is difficult to estimate, but it will probably cover the centre of a big city."

Edgar Sengier, a director of Shinkolobwe Mine in the Congo which produced by far the highest quality uranium ore in the world, had become aware of uranium's possible use in a bomb. In late 1940, fearing that it might be seized by the Germans, he shipped the mine's entire stockpile of ore to a warehouse in New York.

The final iteration of the Gadget nuclear device prior to its successful test on July 16, 1945, the culmination of the United States' 3-year Manhattan Project's research and development of nuclear weapons

See also

References

Notes

Explanatory Notes
  1. also known as an atom bomb, atomic bomb, nuclear bomb, or nuclear warhead, and colloquially as an A-bomb or nuke
  2. See also Mordechai Vanunu
  3. In the United States, the President and the Secretary of Defense, acting as the National Command Authority, must jointly authorize the use of nuclear weapons.
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Bibliography

See also: List of books about nuclear issues

Further reading

Library resources about
Nuclear weapon
  • Laura Grego and David Wright, "Broken Shield: Missiles designed to destroy incoming nuclear warheads fail frequently in tests and could increase global risk of mass destruction", Scientific American, vol. 320, no. no. 6 (June 2019), pp. 62–67. "Current U.S. missile defense plans are being driven largely by technology, politics and fear. Missile defenses will not allow us to escape our vulnerability to nuclear weapons. Instead large-scale developments will create barriers to taking real steps toward reducing nuclear risks—by blocking further cuts in nuclear arsenals and potentially spurring new deployments." (p. 67.)
  • Michael T. Klare, "Missile Mania: The death of the INF Treaty has escalated the arms race", The Nation, vol. 309, no. 6 (September 23, 2019), p. 4.
  • Moniz, Ernest J., and Sam Nunn, "The Return of Doomsday: The New Nuclear Arms Race – and How Washington and Moscow Can Stop It", Foreign Affairs, vol. 98, no. 5 (September / October 2019), pp. 150–161. Former U.S. Secretary of Energy Ernest Moniz and former U.S. Senator Sam Nunn write that "the old equilibrium" between the United States and Russia has been "destabilized" by "clashing national interests, insufficient dialogue, eroding arms control structures, advanced missile systems, and new cyberweapons... Unless Washington and Moscow confront these problems now, a major international conflict or nuclear escalation is disturbingly plausible—perhaps even likely." (p. 161.)
  • Thomas Powers, "The Nuclear Worrier" (review of Daniel Ellsberg, The Doomsday Machine: Confessions of a Nuclear War Planner, New York, Bloomsbury, 2017, ISBN 9781608196708, 420 pp.), The New York Review of Books, vol. LXV, no. 1 (January 18, 2018), pp. 13–15.
  • Eric Schlosser, Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety, Penguin Press, 2013, ISBN 1594202273. The book became the basis for a 2-hour 2017 PBS American Experience episode, likewise titled "Command and Control". Nuclear weapons continue to be equally hazardous to their owners as to their potential targets. Under the 1970 Treaty on the Non-Proliferation of Nuclear Weapons, nuclear-weapon states are obliged to work toward the elimination of nuclear weapons.
  • Tom Stevenson, "A Tiny Sun" (review of Fred Kaplan, The Bomb: Presidents, Generals, and the Secret History of Nuclear War, Simon and Schuster, 2021, 384 pp.; and Keir A. Lieber and Daryl G. Press, The Myth of the Nuclear Revolution: Power Politics in the Atomic Age, Cornell, 2020, 180 pp.), London Review of Books, vol. 44, no. 4 (24 February 2022), pp. 29–32. "Nuclear strategists systematically underestimate the chances of nuclear accident... here have been too many close calls for accidental use to be discounted." (p. 32.)
  • David Wright and Cameron Tracy, "Over-hyped: Physics dictates that hypersonic weapons cannot live up to the grand promises made on their behalf", Scientific American, vol. 325, no. 2 (August 2021), pp. 64–71. "Failure to fully assess is a recipe for wasteful spending and increased global risk." (p. 71.)

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