 At the camps of Operation Reinhard, including Bełżec, Sobibór, and Treblinka, trainloads of prisoners were destined for immediate death in gas chambers designed exclusively for that purpose.The mass killing facilities were developed at about the same time inside the Auschwitz II-Birkenau subcamp of a forced labour complex, and at the Majdanek concentration camp.In most other camps prisoners were selected for slave labor first; they were kept alive on starvation rations and made available to work as required.