Allied Entente

The Allies of World War I, or Entente Powers, were the countries that opposed the Central Powers in the First World War.

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.

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, the Serb-Croat-Slovene state and Czechoslovakia.

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 Zimmerman 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.

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 From early 1917, the War Cabinet was superseded by the Imperial War Cabinet, which had Dominion representation.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 Frontpassed to the new supreme commander, Ferdinand Foch of France.

The original alignment opposed to the Central Powers was the Triple Entente, which was formed by three Great European Powers: The war began with the Austrian attack invasion of Serbia on 28 July 1914, in response to the assassination of Archduke Franz Ferdinand. The Austrian Empire followed with an attack on the Serbian ally Montenegro on 8 August. On the Western Front, the two neutral States of Belgium and Luxembourg were immediately occupied by German troops as part of the German Schlieffen Plan.
 * British Empire
 * French Republic
 * Russian Empire

Of the two Low Countries involved in the war, Luxembourg chose to capitulate, and was viewed as a collaborationist state by the Entente powers: Luxembourg never became part of the Allies, and only narrowly avoided Belgium's efforts of annexation, at the conclusion of hostilities in 1919. On 23 August Japan joined the Entente, which then counted seven members. The entrance of the British Empire brought Nepal into the war.

On 23 May 1915, Italy entered the war on the Entente side and declared war on Austria; previously, Italy had been a member of the Triple Alliance but had remained neutral since the beginning of the conflict. In 1916, Montenegro capitulated and left the Entente, and two nations joined, Portugal and Romania.

On 6 April 1917, the United States entered the war. Liberia, Siam and Greece also became allies. After the October Revolution, Russia left the alliance and ended formal involvement in the war, by the signing of the treaty of Brest Litovsk in November effectively creating a separate peace with the Central Powers. This was followed by Romanian cessation of hostilities, however the Balkan State declared war on Central Powers again on 10 November 1918. The Russian withdrawal allowed for the final structure of the alliance, which was based on five Great Powers: Following the Versailles conference, Britain, France, Italy and Japan became the permanent members of the League of Nations council. The United States, meant to be the fifth permanent member, left because the US Senate voted on 19 March 1920 against the ratification of the Treaty of Versailles, thus preventing American participation in the League.
 * French Republic
 * British Empire
 * United States
 * Italy
 * Japan