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The former CB-20 in the Technical Museum, Zagreb
Class overview
Builders	Caproni
Operators	Regia Marina National Republican Navy  Royal Romanian Navy  Kriegsmarine  Soviet Navy  Yugoslav Navy
Preceded by	CA class
Built	1941–1943
In commission	1941–1950s
Planned	72
Completed	21
Preserved	2
General characteristics
Type	Midget submarine
Displacement	35.4 tons surfaced 44.3 tons submerged
Length	15.00 m (49 ft 3 in)
Beam	3.00 m (9 ft 10 in)
Draught	2.05 m (6 ft 9 in)
Propulsion	1 diesel engine, 1 electric motor, 1 shaft
Speed	7.5 knots (13.9 km/h; 8.6 mph) surfaced 7 knots (13 km/h; 8.1 mph) submerged
Complement	4
Armament	2 x 450 mm torpedoes (could be replaced by 2 mines)

The CB class was a group of midget submarines built for the Italian Navy during World War II. However, they were also used by several other navies, seeing action in the Mediterranean and in the Black Sea.

Construction and specifications

The submarines were designed and built by Caproni. They were used as coastal defence units, being a significant improvement of the previous CA class. Each unit had a standard (surfaced) displacement of 35.4 tons and a submerged displacement of 44.3 tons. They measured 15 metres (49 ft 3 in) in length, had a beam of 3 metres (9 ft 10 in) and a draught of 2.05 metres (6 ft 9 in). Power plant consisted of one Isotta Fraschini diesel engine and one Brown Boveri electric motor, both generating a total of 97 kilowatts (130 hp) powering a single shaft, resulting in a surfaced top speed of 7.5 knots (13.9 km/h; 8.6 mph) and a submerged top speed of 7 knots (13 km/h; 8.1 mph). Each boat was armed with two externally-mounted 450-millimetre (18 in) torpedoes, each tube could be reloaded without removing the vessel from water. The two torpedoes could also be replaced by two mines. Each boat had a crew of four, aided in navigation by a small conning tower.

Service

Seventy-two boats were ordered from Caproni in Milan, but only 22 were laid down. Twelve boats were completed before the Italian Armistice and nine afterwards.

Black Sea

The first six boats, completed in 1941, were transferred to the Black Sea by rail, after Nazi Germany asked for Italian naval support on the Eastern Front. They departed on 25 April 1942 and reached the Romanian port of Constanța on 2 May. They formed the 1st Squadriglia Sommergibili CB, under the overall command of Francesco Mimbelli. They fought against the Soviet Black Sea Fleet, CB-5 being sunk at Yalta in June 1942, either by Soviet aircraft or by a torpedo boat. In late 1942, the remaining five submarines were refitted at the Constanța Shipyard in Romania. On 26 August 1943, CB-4 torpedoed and sank the Soviet Shchuka-class submarine Shch-203.

After the Allied armistice with Italy in September 1943, the five Black Sea submarines (CB-1, CB-2, CB-3, CB-4 and CB-6) were transferred to the Royal Romanian Navy. They were all scuttled in the Black Sea in August 1944, after King Michael's Coup.

Four of the Black Sea submarines (CB-1, CB-2, CB-3 and CB-4) were captured by Soviet forces in August 1944 and commissioned on 20 October as TM-4, TM-5, TM-6 and TM-7. They were stricken on 16 February 1945 and subsequently scrapped.

Mediterranean

The first six boats were unsuccessfully employed as submarine hunters near Naples and Salerno, before being transferred to the Black Sea in early 1942. The second squadron (CB-7, CB-8, CB-9, CB-10, CB-11, CB-12) was completed just before the Armistice, in August 1943. All of them, except CB-7 (later cannibalized for spare parts), defected to the Allies. CB-13, CB-14, CB-15 and CB-16 were captured by the Germans, but all except CB-16 were destroyed by Allied air attacks. CB-16 was assigned to the 10th Flotilla of the National Republican Navy, the navy of the Italian Social Republic, but its crew mutinied and surrendered the boat to the British. The last squadron to be completed carried out patrol missions and landed saboteurs. CB-17 was sunk during an air attack, CB-18 was scuttled by her own crew, CB-19 was turned over to the Allies, CB-20 was captured by Yugoslav Partisans, CB-21 was accidentally rammed by a German landing craft and CB-22 was either sunk in an air attack or scuttled by her own crew.

List of submarines

See also

• Italian submarines of World War II

References

1. Walter S. Zapotoczny Jr., Decima Flottiglia MAS: The Best Commandos of the Second World War, Fonthill Media, 2017, Chapter 3 Section 3
2. Robert Gardiner, Conway's All the World's Fighting Ships 1922-1946, Naval Institute Press, 1980, p. 311
3. Walter S. Zapotoczny Jr., Decima Flottiglia MAS: The Best Commandos of the Second World War, Fonthill Media, 2017, Chapter 3 Section 3
4. Robert Gardiner, Conway's All the World's Fighting Ships 1922-1946, Naval Institute Press, 1980, p. 311
5. Jamie Prenatt and Mark Stille, Axis midget submarines pp. 14–15
6. Piero Crociani, Pier Paolo Battistelli, Italian Navy & Air Force Elite Units & Special Forces 1940–45, pp. 21–22
7. Mikhail Monakov, Jurgen Rohwer, Stalin's Ocean-going Fleet: Soviet Naval Strategy and Shipbuilding Programs 1935-1953, p. 266
8. Jack Greene, Alessandro Massignani, The Black Prince and the Sea Devils: The Story of Valerio Borghese and the elite units of the Decima Mas, p. 42
9. Robert Gardiner, Conway's All the World's Fighting Ships 1922-1946, Naval Institute Press, 1980, pp. 311 and 361
10. W.M. Thornton, Submarine Insignia and Submarine Services of the World, Pen and Sword Publishing, 1996, p. 100
11. Paul Kemp, Midget Submarines of the Second World War, Chatham, 1999, p. 65
12. Bryan Perrett, Ian V. Hogg, Encyclopedia of the Second World War, Longman, 1989, p. 279
13. Maurizio Brescia, Mussolini’s Navy: A Reference Guide to the Regia Marina 1930-1945, Seaforth Publishing, 2012
14. Mikhail Monakov, Jurgen Rohwer, Stalin's Ocean-going Fleet: Soviet Naval Strategy and Shipbuilding Programs 1935-1953, p. 275
15. Piero Crociani, Pier Paolo Battistelli, Italian Navy & Air Force Elite Units & Special Forces 1940–45, pp. 21–22
16. Jamie Prenatt and Mark Stille, Axis midget submarines p. 15

Further reading

• Chesneau, Roger, ed. (1997). Conway's All the World's Fighting Ships 1922–46. Conway Maritime Press Ltd. ISBN 978-0851771465.
• Kemp, Paul (1996). Underwater Warriors. Cassell. ISBN 978-0304354542.

External links

• Classe CB Marina Militare website

• Italy
• Engineering

• Submarine classes
• Submarines of the Regia Marina
• Midget submarines
• World War II submarines of Italy
• Caproni
• Ships built in Italy
• World War II submarines of Romania