Einsatzgruppen (ˈaɪnzatsˌɡʁʊpm̩, deployment groups; also 'task forces') were Schutzstaffel (SS) paramilitary death squads of Nazi Germany that were responsible for mass murder, primarily by shooting, during World War II (1939–1945) in German-occupied Europe. The Einsatzgruppen had an integral role in the implementation of the so-called "Final Solution to the Jewish question" (Die Endlösung der Judenfrage) in territories conquered by Nazi Germany, and were involved in the murder of much of the intelligentsia and cultural elite of Poland, including members of the Catholic priesthood. Almost all of the people they murdered were civilians, beginning with the intelligentsia and swiftly progressing to Soviet political commissars, Jews, and Romani people, as well as actual or alleged partisans throughout Eastern Europe.
Under the direction of Reichsführer-SS Heinrich Himmler and the supervision of SS-Obergruppenführer Reinhard Heydrich, the Einsatzgruppen operated in territories occupied by the Wehrmacht (German armed forces) following the invasion of Poland in September 1939 and the invasion of the Soviet Union in June 1941. The Einsatzgruppen worked hand-in-hand with the Order Police battalions on the Eastern Front to carry out operations ranging from the murder of a few people to operations which lasted over two or more days, such as the massacre at Babi Yar with 33,771 Jews murdered in two days, and the Rumbula massacre (with about 25,000 Jews murdered in two days of shooting). As ordered by Nazi leader Adolf Hitler, the Wehrmacht cooperated with the Einsatzgruppen, providing logistical support for their operations, and participated in the mass murders. Historian Raul Hilberg estimates that between 1941 and 1945 the Einsatzgruppen, related agencies, and foreign auxiliary personnel murdered more than two million people, including 1.3 million of the 5.5 to 6 million Jews murdered during the Holocaust.
After the close of World War II, 24 officers, including multiple commanding officers, of the Einsatzgruppen were prosecuted in the Einsatzgruppen trial in 1947–48, charged with crimes against humanity and war crimes.