What were the two sides in World War II known as?

The two sides in World War II were known as the Allies and the Axis powers. The conflict, fought from 1939 to 1945, pitted these opposing coalitions against one another across Europe, Africa, Asia, and the Pacific.

The principal Axis powers were Nazi Germany, Fascist Italy, and Imperial Japan. Other countries cooperated with the Axis to varying degrees, but these three formed its central alliance. Germany's invasion of Poland in September 1939 began the war in Europe, while Japan's attack on Pearl Harbor in December 1941 brought the United States fully into the conflict.

The Allies included the United Kingdom, France, China, the Soviet Union, and the United States, along with many other nations and governments-in-exile. Their membership developed over time; for example, the Soviet Union joined the Allied side after Germany invaded it in June 1941.

A common mix-up is treating the Allies and Axis as two perfectly uniform organizations. They were wartime coalitions with different political systems and competing interests. Their shared objective was defeating the Axis, not creating a permanent unified government.