About 52,000 prisoners were estimated to be held there during its time of operation. The prisoners were mainly from the resistance movements in German-occupied territories. It was a labor camp, a transit camp and, as the war went on, a place of execution. Some died from the exertions of their labor and malnutrition. There were an estimated 22,000 deaths at the camp, including its network of subcamps. Many prisoners were moved to other camps; in particular, in 1944 the former head of Auschwitz concentration camp was brought in to evacuate the prisoners of Natzweiler-Struthof to Dachau as the Allied Armies neared. Only a small staff of Nazi SS personnel remained until the camp was liberated by the French First Army under the command of the U.S. Sixth Army Group on 23 November 1944.