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The history of the British Isles has witnessed intermittent periods of competition and cooperation between the people that occupy the various parts of Great Britain, Ireland, and the smaller adjacent islands, which together make up the British Isles, as well as with France, Germany, the Low Countries, Denmark, Scandinavia, etc.
The British monarch was head of state of all of the countries of the British Isles from the Union of the Crowns in 1603 until the enactment of the Republic of Ireland Act in 1949, although it's important to note that the term "British Isles" was not yet current in 1603. Additionally, since the independence of Ireland, historians of the region often avoid the term British Isles due to the complexity of relations between the peoples of the archipelago (see: British Isles (terminology)).