<P> 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) launched from occupied Poland 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 . </P> <P> 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 . </P> <P> The Einsatzgruppen were formed under the direction of SS - Obergruppenführer Reinhard Heydrich and operated by the Schutzstaffel (SS) before and during World War II . The Einsatzgruppen had its origins in the ad hoc Einsatzkommando formed by Heydrich to secure government buildings and documents following the Anschluss in Austria in March 1938 . Originally part of the Sicherheitspolizei (Security Police; SiPo), two units of Einsatzgruppen were stationed in the Sudetenland in October 1938 . When military action turned out not to be necessary due to the Munich Agreement, the Einsatzgruppen were assigned to confiscate government papers and police documents . They also secured government buildings, questioned senior civil servants, and arrested as many as 10,000 Czech communists and German citizens . From September 1939, the Reichssicherheitshauptamt (Reich Main Security Office; RSHA) had overall command of the Einsatzgruppen . </P> <P> As part of the drive to remove so - called "undesirable" elements from the German population, from September to December 1939 the Einsatzgruppen and others took part in Action T4, a programme of systematic murder of the physically and mentally handicapped and psychiatric hospital patients undertaken by the Nazi regime . Action T4 mainly took place from 1939 to 1941, but the killings continued until the end of the war . Initially the victims were shot by the Einsatzgruppen and others, but gas chambers were put into use by spring 1940 . </P>

What was the 3 main functions of the einsatzgruppen
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