Einsatzgruppen (German: "task forces", "special-ops units") were paramilitary groups formed under the direction of Reinhard Heydrich and operated by the Schutzstaffel (SS) before and during World War II. Their principal task (during the war), according to SS General Erich von dem Bach-Zelewski, at the Nuremberg Trials: "was the annihilation of the Jews, Gypsies, and Soviet political commissars". They were a key component in the implementation of the "Final Solution of the Jewish question" (German: Die Endlösung der Judenfrage) in the conquered territories. These killing units should be viewed in conjunction with the Holocaust.
During the war these units were formed mainly of men from the Ordnungspolizei (Orpo), the Waffen-SS and local volunteers, e.g. militia groups, and led by Gestapo, Kripo, and SD officers. These death squads followed the Wehrmacht as it advanced eastwards through Eastern Europe en route to the Soviet Union. In occupied territory, the Einsatzgruppen also used the local populace for additional security and manpower when needed. The activities of the Einsatzgruppen were spread through a large pool of soldiers from the branches of the SS and the German Reich. Einsatzgruppen were under the control of the Reichssicherheitshauptamt (RSHA) (Reich Main Security Office); i.e., Reinhard Heydrich (until his death) and later his successor Ernst Kaltenbrunner.
The Einsatzgruppen were responsible for the murders of over 1,000,000 people, and they were the first Nazi organizations to commence mass killing of Jews as an organized policy.