1930-4-22 London Naval Treaty Signed

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On April 22, 1930, the United States, Britain and Japan signed the London Naval Treaty, which regulated submarine warfare and limited shipbuilding.
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The Treaty for the Limitation and Reduction of Naval Armament, commonly known as the London Naval Treaty, was an agreement between the United Kingdom, the Empire of Japan, France, Italy and the United States, signed on 22 April 1930, which regulated submarine warfare and limited naval shipbuilding. Ratifications were exchanged in London on October 27, 1930, and the treaty went into effect on the same day. It was registered in League of Nations Treaty Series on February 6, 1931.

The terms of the treaty were seen as an extension of the conditions agreed in the Washington Naval Treaty. That treaty had been an effort to prevent a naval arms race after World War I.

The Conference was a revival of the efforts which had gone into the Geneva Naval Conference of 1927. At Geneva, the various negotiators had been unable to reach agreement because of bad feeling between the British Government and that of the United States. This problem may have initially arisen from discussions held between President Herbert Hoover and Prime Minister Ramsay MacDonald at Rapidan Camp in 1929; but a range of factors affected tensions which were exacerbated between the other nations represented at the conference.

Under the Treaty, the standard displacements of submarines was restricted to 2,000 tons with each of the major powers being allowed to keep three submarines up to 2,800 tons, and France being allowed to keep one. Submarine gun caliber was also restricted for the first time to 6.1 inches (155 mm) with one exception, an already constructed French submarine was allowed to retain 8 inch (203 mm) guns. This put an end to the 'big-gun' submarine concept pioneered by the British M class and the French Surcouf.

The Treaty also established a distinction between cruisers armed with guns no greater than 6.1 inches (155mm) ("light cruisers" in unofficial parlance) from those with guns up to 8 inches (203 mm) ("heavy cruisers"). The number of heavy cruisers was limited – *Britain was permitted 15 with a total tonnage of 147,000, the U.S. 18 totalling 180,000, and the Japanese 12 totalling 108,000 tons. For light cruisers, no numbers were specified but tonnage limits were 143,500 tons for the U.S., 192,200 tons for the British, and 100,450 tons for the Japanese.

Destroyer tonnage was also limited, with destroyers being defined as ships of less than 1,850 tons and guns not exceeding 5.1 inches (130 mm). The Americans and British were permitted up to 150,000 tons and Japan 105,500 tons.

Article 22 relating to submarine warfare declared international law applied to them as to surface vessels. Also merchant vessels which demonstrated "persistent refusal to stop" or "active resistance" could be sunk without the ship's crew and passengers being first delivered to a "place of safety".

The next phase of attempted naval arms control was the Second Geneva Naval Conference in 1932; and in that year, Italy "retired" two battleships, twelve cruisers, 25 destroyers, and 12 submarines—in all, 130,000 tons of naval vessels (either scrapped or put in reserve). Active negotiations amongst the other treaty signatories continued during the following years.

This was followed by the Second London Naval Treaty of 1936.
https://en.wikipedia.org/wiki/London_Naval_Treaty
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Prime Minister delivers final message to the press. Treaty document exhibited. Mr Stimson and Mr MacDonald in garden of No 10 Downing Street.