The Washington Naval Treaty (also known as the Five-Power Treaty) was signed at the end of the Washington Naval Conference, held from November 12, 1921, to February 6, 1922. It set limits to the capital fleets–the largest ships, including battleships and aircraft carriers–of the five leading post–World War I naval powers: the United States, Great Britain, Japan, France, and Italy. The United States and Great Britain were recognized as the world’s leading naval powers, with the leading allotments for ship construction. Japan was third, while France and Italy received the smallest allotments. Britain, the United States, and Japan also agreed to limit the fortification of their possessions in the Pacific. Not on the list of conference invitees were Germany, whose military was limited by the treaty that ended World War I; Russia, which was diplomatically isolated as a result of its civil war and implementation of Communism; and smaller naval powers such as Spain and Brazil. The British delegation also represented members of the British Commonwealth–among them Canada, Australia, New Zealand, South Africa, and India.

The Washington Naval Treaty (also known as the Five-Power Treaty) was signed at the end of the Washington Naval Conference, held from November 12, 1921, to February 6, 1922. It set limits to the capital fleets–the largest ships, including battleships and aircraft carriers–of the five leading post–World War I naval powers: the United States, Great Britain, Japan, France, and Italy. The United States and Great Britain were recognized as the world’s leading naval powers, with the leading allotments for ship construction. Japan was third, while France and Italy received the smallest allotments. Britain, the United States, and Japan also agreed to limit the fortification of their possessions in the Pacific. Not on the list of conference invitees were Germany, whose military was limited by the treaty that ended World War I; Russia, which was diplomatically isolated as a result of its civil war and implementation of Communism; and smaller naval powers such as Spain and Brazil. The British delegation also represented members of the British Commonwealth–among them Canada, Australia, New Zealand, South Africa, and India.

The horrors of World War I resulted in a renewed interest in arms control and international peace. Many blamed an “arms race”–especially the naval arms race between Britain and Germany–for the outbreak of the war. A post–World War I arms race would not only have threatened peace but also, given the immense cost of modern warships, strained the budgets of countries struggling financially in the wake of the war.

The circumstances of World War I eliminated two naval competitors–Germany, because of the strict limits placed on its fleet by the Treaty of Versailles, and Russia (soon to be renamed the Soviet Union), as a result of the damage to its fleet suffered during the war, the Russian Revolution, and its subsequent civil war. After World War I, the United States and Japan emerged as the world’s rising naval powers and potential rivals to one another in the Pacific and in China. The United States had been attempting to increase its naval presence since its victory in the Spanish-American War in 1898 and the circumnavigation of the globe by the “Great White Fleet” from 1907 to 1909, begun under American president and naval aficionado Theodore Roosevelt. During World War I, the United States focused on building its Navy, with the slogan of “a fleet second to none.” Japan’s naval power, demonstrated in its crushing victory over Russia in the Russo-Japanese War (1904–5), had been enhanced by its annexation of former German possessions, and potential bases, in the Pacific. Also, Japan had adopted an aggressive position in China, leading to conflict with the United States’ “Open Door” policy in that country, which called for keeping China open to trade with all countries equally.

Tensions between Japan and the United States were also heightened by American treatment of Japanese immigrants. Both the American and Japanese navies had been planning for a possible war between the two countries since the early twentieth century, and the limited cooperation between the two powers as allies in World War I had not ended their mutual mistrust. Managing the rivalry of the Pacific powers was a major consideration in global diplomacy. The rise of the United States and, to a lesser extent, Japan as world powers also threatened Great Britain’s long-standing naval hegemony.

The Washington Naval Treaty attempts to regulate and limit naval competition by establishing a fixed hierarchy of world navies based on graduated size limits. The new naval hierarchy established parity for the first time, at least on paper, between the United States Navy and Britain’s Royal Navy, which had been the world’s premier naval force since the late seventeenth century. The treaty also allots an Asian-based power, Japan, the third largest navy, ahead of such European powers as France and Italy.

The document focuses on limiting the overall tonnage of the largest ships, known as “capital ships” (battleships and aircraft carriers), and does not set limits on the overall tonnage of smaller ships, such as cruisers. (“Tonnage” is a naval term referring to the tons of water a ship displaces while afloat.) However, the treaty limits the size and gunnery of the smaller ships. The treaty mostly ignores submarines, which the Germans had used to devastating effect in World War I. The new weapon treated in the most detail is the aircraft carrier, which played only a minor role in war, but attracted a great deal of attention from the naval conference. The treaty is quite detailed, both specifying which ships are to be retained and which scrapped for each signatory and anticipating ships under construction. It even carefully outlines the procedure for scrapping a vessel, in order to prevent signatories from inflicting only superficial, easily repaired damage to a vessel and reporting it as scrapped.

Efforts at demilitarization focus on the Pacific, the only area where the world’s three major navies confronted each other directly. The treaty seeks to demilitarize the Pacific by limiting the fortification of American, Japanese, and British islands that are potential naval bases. As a provision of the treaty, the United States gives up the right to fortify Guam and the Philippines, while reserving the right to fortify the Hawaiian Islands. Japan abandons–reluctantly–any new fortifications of its numerous insular possessions, including some, such as the Kuril Islands, quite close to Japan itself. By depriving both the United States and Japan of fortified forward bases, the treaty intends to decrease the likelihood of war in the Pacific between the United States and Japan.

Although the treaty did prevent a naval arms race in capital ships and aircraft carriers in the 1920s, its lack of limitation on the total tonnage of smaller ships, such as cruisers and submarines, left the door open for a limited naval arms race. Subsequent naval conferences, the Geneva Naval Conference of 1927 and the London Naval Conferences of the 1930s, attempted to close this loophole.

The Washington Naval Treaty’s emphasis on aircraft carriers was prescient, as aircraft carriers became the dominant vessels of World War II and postwar navies. However, the correlation of forces established in this treaty proved ephemeral because of subsequent military and political developments. Germany and the Soviet Union reemerged as major military powers. The ratification of the treaty ended the Anglo-Japanese Alliance, signed in 1902, and Japan, frustrated with its consignment to a position of inferiority relative to the United States and Britain, sought revision to raise their ratio to American forces from sixty to seventy percent, eventually renouncing the treaty entirely in 1936. Fascist Italy also largely ignored the treaty. Britain maintained parity with or even a slight edge over the United States for most of the 1920s and 1930s, but, with its declining industrial base, it was unable to keep up with the enormous productivity of the United States in the long run. The American Navy’s supremacy has persisted and intensified to the present day, when it occupies a position far above that of any rival.

Despite the eventual outbreak of war between the United States and Japan, provoked militarily by the Japanese attack on Pearl Harbor on December 7, 1941, the Washington Naval Treaty has often been considered a success in the short term and even been put forth as a model of a successful arms limitation agreement. Even during the Cold War, the United States and its major rival, the Soviet Union, signed such agreements as the Strategic Arms Limitation Talks I and II (SALT I and SALT II), treaties intended to limit weapons development; however, as bilateral treaties between enemies, these treaties differed from the Washington Naval Treaty, which was an agreement between ostensible allies. Though mixed, the effects of the Washington Naval Treaty can still be felt, as the idea of limiting arms development and arms races through mutual agreement persists.

• Asada, Sadao.From Mahan to Pearl Harbor: The Imperial Japanese Navy and the United States. Annapolis: Naval Inst., 2006. Print.
• Braisted, William Reynolds.The United States Navy in the Pacific, 1909–1922. Annapolis: Naval Inst., 2008. Print.
• Jordan, John.Warships after Washington: The Development of the Five Major Fleets, 1922–1930. Annapolis: Naval Inst., 2011. Print.