The Washington Naval Treaty, also known as the Five-Power Treaty, was a treaty signed during 1922 among the major Allies of World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Naval Conference in Washington, D.C. from November 1921 to February 1922 and signed by the governments of the British Empire (including the United Kingdom, Canada, Australia, New Zealand, South Africa and India), United States, France, Italy, and Japan. It limited the construction of battleships, battlecruisers and aircraft carriers by the signatories. The numbers of other categories of warships, including cruisers, destroyers, and submarines, were not limited by the treaty, but those ships were limited to 10,000 tons displacement each.
The treaty was concluded on February 6, 1922. Ratifications of that treaty were exchanged in Washington on August 17, 1923, and it was registered in the League of Nations Treaty Series on April 16, 1924.
Later naval arms limitation conferences sought additional limitations of warship building. The terms of the Washington Naval Treaty were modified by the London Naval Treaty of 1930 and the Second London Naval Treaty of 1936. By the mid-1930s, Japan and Italy renounced the treaties, while Germany renounced the Treaty of Versailles which had limited its navy. Naval arms limitation became increasingly difficult for the other signatories.
Background
Immediately after World War I, Britain still had the world's largest and most powerful navy, followed by the United States and more distantly by Japan, France and Italy. The British Royal Navy had interned the defeated German High Seas Fleet. The Allies had differing opinions concerning the final disposition of the Imperial German Navy, with the French and Italians wanting the German fleet divided between the victorious powers and the Americans and British wanting the ships destroyed. The negotiations became mostly moot after the German crews had scuttled most of their ships.
News of the scuttling angered the French and the Italians, with the French particularly unimpressed with British explanations that the fleet guarding the Germans had then been away on exercises. Nevertheless, the British joined their allies in condemning the German actions, and no credible evidence emerged to suggest that the British had collaborated actively with the Germans with respect to the scuttling. The Treaty of Versailles, signed a week later, imposed strict limits on the size and the number of warships that the newly-installed German government was allowed to build and maintain.
The Americans, the British, the French, the Italians, and the Japanese had been allies during World War I, but with the German threat seemingly finished, a naval arms race between the erstwhile allies seemed likely for the next few years. US President Woodrow Wilson's administration had already announced successive plans for the expansion of the US Navy from 1916 to 1919 that would have resulted in a massive fleet of 50 modern battleships.
In response, the Japanese Diet finally authorised construction of warships to enable the Japanese Navy to attain its goal of an "eight-eight" fleet programme, with eight modern battleships and eight battlecruisers. The Japanese started work on four battleships and four battlecruisers, all of which were much larger and more powerful than those of the classes that they were replacing.
The 1921 British Naval Estimates planned four battleships and four battlecruisers, with another four battleships to follow the subsequent year.
The new arms race was unwelcome to the American public. The US Congress disapproved of Wilson's 1919 naval expansion plan, and the 1920 presidential election campaign caused politics to resume the non-interventionalism of the prewar era, with little enthusiasm for continued naval expansion. Britain also could ill afford any resumption of battleship construction, given the exorbitant cost.
In late 1921, the US became aware that Britain was planning a conference to discuss the strategic situation in the Pacific and Far East regions. To forestall the conference and to satisfy domestic demands for a global disarmament conference, Warren Harding's administration called the Washington Naval Conference in November 1921.
The Conference agreed to the Five-Power Naval Treaty as well as a Four-Power Treaty on Japan and a Nine-Power Treaty on China.