Following the Nazi invasion of the Soviet Union on June 22, 1941, the Germans turned from forced emigration of Jews to mass murder. Special action squads, or Einsatzgruppen, moved on the heels of the advancing German army with orders to kill any Jews they could find. Some residents of the occupied regions - mostly Ukrainians, Latvians and Lithuanians - aided the killing squads by serving as auxiliary police.
The units acted swiftly, taking the Jewish population by surprise - they would enter a town and round up all the Jews as well as many Communist party leaders and Roma Gypsies. Victims were forced to surrender valuables and remove their clothing; then the killing squad members marched their victims to open fields, forests or ravines where they shot or gassed the victims before dumping the bodies into mass graves.
The killing squads murdered more than a million Jews and hundreds of thousands of other innocent people.