and pro-German administrators from within the Hungarian Interior Ministry. Round-ups began on 16 April, and from 14 May, four trains of 3,000 Jews per day left Hungary and traveled to the camp at Auschwitz II-Birkenau, arriving along a newly built spur line that terminated a few hundred meters from the gas chambers. Between 10 and 25 percent of the people on each train were chosen as forced laborers; the rest were killed within hours of arrival. Under international pressure, the Hungarian government halted deportations on 6 July 1944, by which time over 437,000 of Hungary's 725,000 Jews had been murdered. Einsatzgruppen The Einsatzgruppen had its origins in the ad hoc Einsatzkommando formed by Heydrich following the Anschluss in Austria in March 1938. Two units of Einsatzgruppen were stationed in the Sudetenland in October 1938. When military action turned out not to be necessary because of the Munich Agreement, the Einsatzgruppen were assigned to confiscate government papers and police documents. They secured government buildings, questioned senior civil servants, and arrested as many as 10,000 Czech communists and German citizens. The Einsatzgruppen also followed Wehrmacht troops and killed potential partisans. Similar groups were used in 1939 for the occupation of Czechoslovakia. Hitler felt that the planned extermination of the Jews was too difficult and important to be entrusted to the military. In 1941 the Einsatzgruppen were sent into the Soviet Union to begin large-scale genocide of Jews, Romani people, and communists. Historian Raul Hilberg estimates that between 1941 and 1945 the Einsatzgruppen and related agencies killed more than two million people, including 1.3 million Jews. The largest mass shooting perpetrated by the Einsatzgruppen was at Babi Yar outside Kiev, where 33,771 Jews were killed in a single operation on 29–30 September 1941. In the Rumbula massacre (November–December 1941), 25,000 victims from the Riga ghetto were killed. Another mass shooting early in 1942 claimed the lives of over 10,000 Jews in Kharkov. The last Einsatzgruppen were disbanded in mid-1944 (although some continued to exist on paper until 1945) due to the German retreat on both fronts and the consequent inability to continue extermination activities. Former Einsatzgruppen members were either assigned duties in the Waffen-SS or concentration camps. Twenty-four Einsatzgruppen commanders were tried for war crimes following the war. SS Court Main Office The SS Court Main Office (Hauptamt SS-Gericht) was an internal legal system for conducting investigations, trials, and punishment of the SS