<P> The members of the original Triple Entente of 1907 were the French Republic, the British Empire and the Russian Empire . Italy ended its alliance with the Central Powers, arguing that Germany and Austria - Hungary started the war and that the alliance was only defensive in nature; it entered the war on the side of the Entente in 1915 . Japan was another important member . Belgium, Serbia, Greece, Montenegro, and Romania were affiliated members of the Entente . </P> <P> The 1920 Treaty of Sèvres defines the Principal Allied Powers as the British Empire, French Republic, Italy and Japan . The Allied Powers comprised, together with the Principal Allied Powers, Armenia, Belgium, Greece, Hejaz, Poland, Portugal, Romania, Serb - Croat - Slovene state and Czechoslovakia . </P> <P> The U.S. declaration of war on Germany, on 6 April 1917 was on the grounds that Germany had violated its neutrality by attacking international shipping and the Zimmermann Telegram sent to Mexico . It declared war on Austria - Hungary in December 1917 . The U.S. entered the war as an "associated power", rather than as a formal ally of France and the United Kingdom, in order to avoid "foreign entanglements". Although the Ottoman Empire and Bulgaria severed relations with the United States, neither declared war . </P> <P> The Dominions and Crown Colonies of the British Empire made great contributions to the Allied war effort, but did not have independent foreign policies in World War I with the British War Cabinet exercising operational control of British Empire forces . The Dominion governments did control recruiting, and removed personnel from front - line duties as they saw fit . From early 1917, the War Cabinet was superseded by the Imperial War Cabinet, which had Dominion representation . The Australian Corps and Canadian Corps were placed under the command of Australian and Canadian Lieutenant Generals John Monash and Arthur Currie, respectively, who reported in turn to British generals . In April 1918, operational control of all Entente forces on the Western Front passed to the new supreme commander, Ferdinand Foch of France . </P>

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