Auschwitz was a group of concentration camps run by Nazi Germany during World War II. There were three large camps at Auschwitz, and 3 smaller ones. Auschwitz I was the main camp, which held prisoners from 1940-1945. Auschwitz II (Birkenau) was the largest extermination camp (death camp) run by Nazi Germany during The Holocaust. Auschwitz III (Monowitz) and the subcamps were forced labor camps where prisoners worked as slaves. These camps were established because there were too many Polish prisoners and not enough room in "local" prisons to hold them in.