Birkenau was the largest camp in the Auschwitz complex. It became primarily a centre for the mass murder of Jews brought there for extermination, and of Roma and Sinti prisoners during its final period. Sick prisoners and those selected for death from the whole Auschwitz complex – and, to a smaller extent, from other camps – were also gathered and systematically killed here. It ultimately became a place for the concentration of prisoners before they were transferred inside the Third Reich to work for German industry. Most of the victims of the Auschwitz complex, probably about 90%, were killed in the Birkenau camp.
The crematoria consisted of a dressing room, gas chamber, and furnace room. In crematoria II and III, the dressing room and gas chamber were underground; in IV and V, they were on the ground floor. The dressing room had numbered hooks on the wall to hang clothes. In crematorium II, there was also a dissection room (Sezierraum). SS officers told the victims they were to take a shower and undergo delousing. The victims undressed in the dressing room and walked into the gas chamber, which was disguised as a shower facility; signs in German said "To the baths" and "To disinfection". Some inmates were even given soap and a towel.
When the Nazis came to power in Germany, they quickly moved to suppress all real and potential opposition. The general public was intimidated by the arbitrary psychological terror that was used by the special courts (Sondergerichte). Especially during the first years of their existence when these courts "had a strong deterrent effect" against any form of political protest.