Concentration camps were different from death camps. Some of the more infamous concentration camps were Buchenwald, Bergen-Belsen, Dachau, and Ravensbrück. These were prison camps which the Nazis set up before World War II started. The Nazis sent people who they did not want in their society to these concentration camps. The Nazis forced millions of people to do forced labor in the concentration camps. Prisoners in concentration camps made up about 25% of the workers in Nazi Germany. Even though the concentration camps were not designed for mass murder, over 75% of the people sent to these camps died because of starvation, illness, exhaustion, executions, and physical abuse.