World War II officially started when Germany invaded Poland on Sept. 1, 1939, and the war ended on Sept. 2, 1945, when the Japanese formally surrendered aboard the USS Missouri. The war in Europe ended when Germany surrendered to the Allies on May 7, 1945.
Germany took over Austria and Czechoslovakia in 1938 and 1939, respectively. Reluctant to get into another war, the other European countries did nothing, but after the invasion of Poland, Great Britain and France both declared war on Germany on Sept. 3, 1939. World War II pitted the Axis countries of Germany, Japan and Italy against the Allies of the United States, Great Britain and the Soviet Union. The war eventually spread over six continents and led to approximately 50 million military and civilian deaths.