Killing centers were established by the Nazis. These killing centers were simply just "death factories." Almost 2,700,000 Jews were murdered in these centers, either by asphyxiation with posionous gas, or by shooting. The first of these camps was Chelmno. Not only Jews, but some Gypsies, were also gassed here in mobile gas vans. Belzec, Dobibor and Treblinka were all opened in 1942 in Generalgouvenement (territory in the interior of occupied Poland.) These camps were refered to as the "Operation Reinhard camps." In these camps the German SS (major paramilitary organization under Adolf Hitler and the Nazi Party) killed exactly 1,526,500 Jews between March of 1942 and November of 1943. All of the people that arrived at these camps were sent to the death in the gas chambers as soon as they arrived (excluding a small amount that were chosen for a special work team called the Sonderkommandos.)The largest of these centers was Auschwitz-Birkenau. By spring of 1943 this camp had four operating gas chambers, in which they murdered up to 6,000 Jewes a day.
Though many believe that Majdanek was the sixth killing center, more recent research has shed more light. Majedanek was primarily to concentrate the Jews that the Nazis were sparing temporaily for froced labor. It also occasionally was a killing site for the victims that couldn't be killed at Operation Reinhard centers. Majdanek also consisted of a stroage place for the property taken for the Jewish victims at the killing centers. The SS believed their centers to be top secret. To obliterate all the traces of gas, prisoner work untis (the Sonderkommandos, mentioned earlier) were forced to remove the corpses and cremate them.
"Killing Centers: An Overview." United States Holocaust Memorial Council. 10 June 2013. Web. 8 February 2014.
"Shoes and clothing of prisoners found at Auschwitz-Bikenau." Scrapbookpages. n.d. Web. 8 February 2014.