World War I, also called the Great War, was fought primarily in Europe and the Middle East between the Allies—Britain, France, Russia, and the United States—and the Central Powers—Germany, Austria-Hungary, and Turkey. It grew out of imperialistic, territorial, and economical rivalries. Unrestricted German submarine warfare against neutral shipping forced the United States to enter the war in 1917 on the side of the Allies, and United States troops tipped the balance of power in their favor. The United States served 4,734,991, with 116,516 killed and 294,902 wounded. The war ended on November 11, 1918, Armistice Day, now honored as Veterans Day.