From 1941/42 onwards, the SS transferred ever greater numbers of concentration camp prisoners to work as forced labourers in subcamps located across Austria. At first the prisoners were mainly used in construction work building transport routes, power stations and factories. In the second half of the war they were increasingly forced to work in the arms industries. Starting at the end of 1943, thousands of inmates were deployed in the construction of underground production sites that would be protected from air raids.
Over 40 subcamps had been set up by the liberation of the Mauthausen/Gusen concentration camp. At the beginning of March 1945, around 64,000 out of a total 83,000 concentration camp prisoners were being held in one of the subcamps.
- = Mauthausen
- = Mauthausen subcamps
- = Castle Hartheim