The process of closing the Nazi concentration camps during World War II started in 1944 and continued through January of 1945. The process of closing these concentration camps took several weeks to carry out.
Nazi Germany utilized 20,000 concentration and work camps between 1933 and 1945, primarily used to imprison the Jewish populations of areas under German control. In a few of the concentration camps, Nazi physicians conducted medical experiments on people imprisoned in the camp that often led to the death of the patients. The deaths of the Jewish population in a concentration camp was often carried out by using a gas chamber.