 Complete the following phrase:  The death squad units of the Einsatzgruppen were formed under the direction of Heydrich and operated by the SS before and during World War II. In September 1939, they operated in territories occupied by the German armed forces following the invasion of Poland. Men for the units were drawn from the SS, the SD, and the police. Originally part of the SiPo, in late September 1939 the operational control of the Einsatzgruppen was taken over by the RSHA. When the killing units were re-formed prior to the 