In 1939, Hitler decided to invade Poland. Heydrich decided the "Einsatzgruppen" would follow the regular German Army. Their job would be to kill the most important people in Polish society, like clergy, teachers, and members of the academia. They would also kill anyone who refused to agree with Nazi ideas or rules. Adolf Hitler said: "...there must be no Polish leaders; where Polish leaders exist they must be killed[.]" The Einzatsgruppen followed this plan by killing about 65,000 civilians by the end of 1939. These people included Polish leaders, Jews, prostitutes, Roma people, and people with mental illnesses.