The Holocaust was the systematic murder of approximately 6 million European Jews and millions of others by the Nazi regime and its collaborators between 1933-1945. Key events included the rise of Hitler and the Nazis to power in Germany in 1933, the establishment of concentration camps starting with Dachau in 1933, and the mass killings of Jews that began in 1941 with mobile killing units in Germany and Poland. By 1945, around two-thirds of the Jewish population in Europe had been murdered in ghettos and extermination camps like Auschwitz.