1 Sep 1939—2 Sep 1945: World War II (WWII) This war spanned 6 years and 1 day. It began when Germany invaded Poland. The United States entered the war on 7 Dec 1941 when the Japanese attacked Pearl Harbor. Japan formally surrendered 2 Sep 1945.
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1941
7 Dec 1941—2 Sep 1945: USA enters WWII The United States entered WWII when Japan attacked Pearl Harbor. The war ended with the surrender of Japan on 2 Sep 1945.
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