The Holocaust was the systematic, bureaucratic annihilation of six million Jews by the Nazi regime and their collaborators as a central act of state during World War II. In 1933 approximately nine million Jews lived in the 21 countries of Europe that would be occupied by Germany during the war. By 1945 two out of every three European Jews had been killed. Although Jews were the primary victims, hundreds of thousands of Roma (Gypsies) and at least 250,000 mentally or physically disabled persons were also victims of Nazi genocide. As Nazi tyranny spread across Europe from 1933 to 1945, millions of other innocent people were persecuted and murdered. M