 After the Anschluss, the Austrian SS was folded into SS-Oberabschnitt Donau. The third regiment of the SS-Verfügungstruppe (Der Führer) and the fourth Totenkopf regiment (Ostmark) were recruited in Austria shortly thereafter. On Heydrich's orders, mass arrests of potential enemies of the Reich began immediately after the Anschluss. Mauthausen was the first concentration camp opened in Austria following the Anschluss. Before the invasion of the Soviet Union, Mauthausen was the harshest of the camps in the Greater German Reich.
