The main opponents of the World War were The Axis, which was formed by Germany, Italy, and the Empire of Japan and the Allies, which was initially formed by Great Britain and France.
The United States entered the side of the Allies.
The Bombing of Pearl Harbor on December 7th, 1941.
Starting in the late 1920s, Joseph Stalin launched a series of five-year plans intended to transform the Soviet Union from a peasant society into an industrial superpower.