Alliances in the East
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 November 10, 1918. The Russian withdrawal allowed for the final structure of the alliance, which was based on five Great Powers:
America Joins Allies
On April 2, 1917, President Woodrow Wilson went before a joint session of Congress to request a declaration of war against Germany. Wilson cited Germany’s violation of its pledge to suspend unrestricted submarine warfare in the North Atlantic and the Mediterranean, and its attempts to entice Mexico into an alliance against the United States, as his reasons for declaring war. On April 4, 1917, the U.S. Senate voted in support of the measure to declare war on Germany. The House concurred two days later. The United States later declared war on Austria-Hungary on December 7, 1917.