World War 2 was fought by the United States in the 1900s. The United States tried to stay out of World War 2 but were forced to join the war in 1941 when Japan bombed Pearl Habour. They joined the war on the side of the Allies, ie France, Russia and Great Britain, amongst other countries. The Allies fought again Nazi Germany, Italy and Japan. The Allies were losing the war against the Germans and the tide was turned when the United States and Canada formally joined the Allies.
