Hitler felt that the planned extermination of the Jews was too difficult and important to be entrusted to the military.[287] In 1941 the Einsatzgruppen were sent into the Soviet Union to begin large-scale genocide of Jews, Romani people, and communists.[288] 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.[289] 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.[290] In the Rumbula massacre (November–December 1941), 25,000 victims from the Riga ghetto were killed.[291] Another mass shooting early in 1942 claimed the lives of over 10,000 Jews in Kharkov.[292]