Initially numbering 2,700 men (and ultimately 4,250 in Poland), the "Einsatzgruppen"s mission was to kill members of the Polish leadership most clearly identified with Polish national identity: the intelligentsia, members of the clergy, teachers, and members of the nobility. As stated by Hitler: "... there must be no Polish leaders; where Polish leaders exist they must be killed, however harsh that sounds". SS-"Brigadeführer" Lothar Beutel, commander of "Einsatzgruppe" IV, later testified that Heydrich gave the order for these killings at a series of meetings in mid-August. The "Sonderfahndungsbuch Polen" — lists of people to be killed — had been drawn up by the SS as early as May 1939, using dossiers collected by the SD from 1936 forward. The "Einsatzgruppen" performed these murders with the support of the "Volksdeutscher Selbstschutz", a paramilitary group consisting of ethnic Germans living in Poland. Members of the SS, the Wehrmacht, and the "Ordnungspolizei" also shot civilians during the Polish campaign. Approximately 65,000 civilians were killed by the end of 1939. In addition to leaders of Polish society, they killed Jews, prostitutes, Romani people, and the mentally ill. Psychiatric patients in Poland were initially killed by shooting, but by spring 1941 gas vans were widely used.