Treaty battleship

A treaty battleship was a battleship built in the 1920s or 1930s under the terms of one of a number of international treaties governing warship construction. Many of these ships played an active role in the Second World War, but few survived long after it.

In the Washington Naval Treaty of 1922, the world's five naval powers agreed to abide by strict restrictions on the construction of battleships and battlecruisers, in order to prevent an arms race in naval construction such as preceded the Great War. The Treaty limited the number of capital ships possessed by each signatory, and also the total tonnage of each navy's battleships. New ships could only be constructed to replace the surviving ships as they retired after 20 years' service. Furthermore, any new ship would be limited to guns of 16-inch caliber and a displacement of 35,000 tons.

The Washington Treaty limits were extended and modified by the London Naval Treaty of 1930 and the Second London Naval Treaty of 1936. During the 1930s, however, the effectiveness of these agreements broke down, as some signatory powers (in particular Japan) withdrew from the treaty arrangements and others only paid lip service to them. By 1938, Britain and the USA had both invoked an 'escalator clause' in the Second London Treaty which allowed battleships of up to 45,000 tons displacement, and the Treaty was effectively defunct.

The strict limits on displacement forced the designers of battleships to make compromises which they might have wished to avoid given the choice. The 1920s and 1930s saw a number of innovations in battleship design, particularly in engines, underwater protection, and aircraft.

The Washington Naval Treaty was signed in 1922 by Britain, France, the United States, Japan and Italy, as the five powers which had any significant numbers of modern dreadnought battleships and battlecruisers. The Treaty was aimed at preventing an expensive arms race, principally between Britain, the USA and Japan. The Treaty established a definition of a capital ship, which was any ship with a displacement of 10,000 tons or more, or with guns above 8 in (203 mm) calibre, apart from an aircraft carrier. Carriers were specifically constrained from having guns above 8 in calibre, in order to prevent confusion between the two types. Each signatory agreed to limit its total number of capital ships, and its total tonnage of capital ships. These measures meant that several classes of battleships and battlecruisers which were planned, or had even been begun, were scrapped or cancelled.

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