Nazi Germany invades the Soviet Union in "Operation Barbarossa." German mobile units called the Einsatzgruppen follow the frontline troops into the Soviet Union. Their job is to identify, round up, and kill all Jews, Soviet officials, and other persons deemed potentially hostile to German rule. The Einsatzgruppen squads begin to carry out mass shootings during the last week of June 1941.
German troops crossing the Soviet border during Operation Barbarossa, June 22 1941. (Wikimedia Commons)