World War II was a global war from 1939 to 1945 that involved most of the world's countries forming two military alliances: the Allies and Axis powers. Adolf Hitler was the dictator of Germany from 1933 until his death in 1945. He rose to power as the leader of the Nazi Party and initiated World War II in Europe by invading Poland in 1939. Hitler was closely involved in military operations and central to the Holocaust, which resulted in the genocide of about six million Jews and millions of others. The total casualties of World War II were estimated at 50-55 million civilian deaths and 21-25 million military deaths.