Names of the Second World War

The global conflict that took place between September 1939 and September 1945 is generally referred to as the Second World War or World War II, the latter being commonly used in the United States. Before the attack on Pearl Harbor, the conflict was sometimes called the Second Great War—a reference to the Great War, which was later renamed World War I—and the European War following Germany's invasion of the Soviet Union in June 1941.

Source: Wikipedia — Names of the Second World War (CC BY-SA 4.0)