The London Naval Treaty was an agreement between the United Kingdom, the Empire of Japan, France, Italy and the United States, signed on April 22, 1930, which regulated submarine warfare and limited naval shipbuilding. 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.
The terms of the treaty were seen as an extension of the conditions agreed in the Washington Naval Treaty. The agreement is officially termed the Treaty for the Limitation and Reduction of Naval Armament.
Article 22 relating to submarine warfare declared that international law applied to them as to surface vessels. Also merchant vessels which did demonstrate "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. Active negotiations amongst the other treaty signatories continued during the following years. This was followed by the Second London Naval Treaty of 1936.
- Steiner, Zara S. (2005). The Lights that Failed: European International History 1919-1933, pp. 587-591.
- "Naval Men See Hull on the London Talks; Admiral Leigh and Commander Wilkinson Will Sail Today to Act as Advisers," New York Times. June 9, 1934.
- Treaty for the Limitation and Reduction of Naval Armaments, (Part IV, Art. 22, relating to submarine warfare). London, 22 April 1930.