World War II began on 1st September 1939 with the German invasion of Poland. Initially limited to Europe, it became a world war when the USSR, Japan and the US became involved in 1941. The human and material cost was disastrous with over 50 million dead, including the victims of war crimes (genocide). It ended in Europe on 8th May 1945 with the surrender of the 3rd Reich, and finally in Japan on 2nd September when Japan surrendered. The two main winners, the United States and the USSR were promoted to the rank of superpower.