Sometimes the groups of "Sonderkommandos" were very big. As the Nazis killed more and more people in the concentration camps, they wanted more "Sonderkommandos". By 1943, at Birkenau concentration camp (also called "Auschwitz II"), the groups of "Sonderkommando" included 400 prisoners. But when many more Jews from Hungary were sent to the camp in 1944, the Nazis added 500 more "Sonderkommando".