Wikipedia
Einsatzgruppen (German for " task forces", "deployment groups"; singular Einsatzgruppe; official full name Einsatzgruppen der Sicherheitspolizei und des SD) were Schutzstaffel (SS) paramilitary death squads of Nazi Germany that were responsible for mass killings, primarily by shooting, during World War II. The Einsatzgruppen were involved in the murder of much of the intelligentsia and cultural elite of Poland, and 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. Almost all of the people they killed were civilians, beginning with the intelligentsia and swiftly progressing to Soviet political commissars, Jews, and Gypsies 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 German armed forces following the invasion of Poland in September 1939 and Operation Barbarossa (the invasion of the Soviet Union) in June 1941. The Einsatzgruppen worked hand-in-hand with the Orpo 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 killed in two days, and the Rumbula massacre (with about 25,000 killed in two days of shooting). As ordered by Nazi leader Adolf Hitler, the Wehrmacht cooperated with the Einsatzgruppen and provided logistical support for their operations. Historian Raul Hilberg estimates that between 1941 and 1945 the Einsatzgruppen and related auxiliary troops killed more than two million people, including 1.3 million Jews. The total number of Jews murdered during the Holocaust is estimated at 5.5 to 6 million people.
After the close of World War II, 24 senior leaders of the Einsatzgruppen were prosecuted in the Einsatzgruppen Trial in 1947–48, charged with crimes against humanity and war crimes. Fourteen death sentences and two life sentences were handed out. Four additional Einsatzgruppe leaders were later tried and executed by other nations.