The Allies or the Entente was an international military coalition of countries led by the French Republic, the United Kingdom, the Russian Empire, the United States, the Kingdom of Italy, and the Empire of Japan against the Central Powers of the German Empire, Austria-Hungary, the Ottoman Empire, and the Kingdom of Bulgaria in World War I (1914–1918).
By the end of the first decade of the 20th century, the major European powers were divided between the Triple Entente and the Triple Alliance. The Triple Entente was made up of the United Kingdom, France, and Russia. The Triple Alliance was originally composed of Germany, Austria–Hungary, and Italy, but Italy remained neutral in 1914. As the war progressed, each coalition added new members. Japan joined the Entente in 1914 and, despite proclaiming its neutrality at the beginning of the war, Italy also joined the Entente in 1915. The term "Allies" became more widely used than "Entente", although the United Kingdom, France, Russia, and Italy were also referred to as the Quadruple Entente and, together with Japan, as the Quintuple Entente. The five British Dominions (Australia, Canada, New Zealand, Newfoundland, and the Union of South Africa) all fought alongside the British. The colonies of Allied countries, such as the American Philippines, Belgian Congo, British India, French Algeria, and Japanese Korea, were also used as a source of manpower by the colonial powers.
The United States joined near the end of the war in 1917 (the same year in which Russia withdrew from the conflict) as an "associated power" rather than an official ally. Primary reasons for why the United States joined the war include the unrestricted submarine warfare waged by Germany in the Atlantic, the revelation of the Zimmermann telegram, and strong economic and political ties with the Allies. Other "associated members" of the Allies included Serbia, Belgium, Montenegro, Asir, Nejd and Hasa, Portugal, Romania, Hejaz, Panama, Cuba, Greece, China, Siam, Brazil, Armenia, Luxembourg, Guatemala, Nicaragua, Costa Rica, Haiti, Liberia, and Honduras. The treaties signed at the Paris Peace Conference recognized the British Empire, France, Italy, Japan, and the United States as "the Principal Allied and Associated Powers"; France, the UK, Italy, and the US were also referred as the "Big Four" top powers of the war.