The United States entered World War II on the side of the Allies after the Japanese attack on Pearl Harbor on December 7, 1941. This attack led to the U.S. declaring war on Japan, and subsequently on Germany and Italy, who were Axis powers. The attack on Pearl Harbor was a turning point that propelled the United States into World War II, as it prompted a unified response from the American public and government to defend itself and its allies against further attacks.
