The Holocaust ended on May 7, 1945, the day the Nazis surrendered to Western forces. The persecution of Jews, Roma and disabled people began in 1933 when the Nazis took over the German government. The victims were moved into concentration camps and forced to work, and large numbers were killed.
The Holocaust did not start with the mass moving of its victims into camps. At first, the Nazis forced people, particularly Jews, into ghettos. These were cramped and restrictive portions of the cities. Near the end of the Holocaust, when the Germans were losing World War II, the remaining concentration camp prisoners were forced to march in order to prevent their being freed by Allied forces.