WW2 Timeline By Sam Badovinac Sep 3, 1939 War Begins Hitler invades Poland Jul 3, 1940 Germany begins bombing Britain Jun 3, 1941 Germany invades the Soviet Union Dec 3, 1941 Japan bombs Pearl Harbor. The U.S. declares war on Japan. May 3, 1945 Germany surrenders, ending World War II in Europe Aug 1, 1945 Atomic bombs dropped on Hiroshima and Nagasaki. Sep 1, 1945 Japan signs surrender agreement, ending war.