Answer:
World War II was the biggest and deadliest war in history, involving more than 30 countries. Sparked by the 1939 Nazi invasion of Poland, the war dragged on for six bloody years until the Allies defeated Nazi Germany and Japan in 1945.The causes of World War II included the aggressive actions of Germany, Japan, and Italy and the harsh terms of the Treaty of Versailles, which led many Germans to resent the victors of World War I. ... One major effect of World War II was the development and use of nuclear weapons, which would later lead to the Cold War.
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