Majdanek concentration camp in the context of "Warsaw Ghetto Uprising"

Nazi Germany used six extermination camps (German: Vernichtungslager), also called death camps (Todeslager), or killing centers (Tötungszentren), in Central Europe, primarily in German-occupied Poland, during World War II to systematically murder over 2.7 million people—mainly Jews—in the Holocaust. The victims of death camps were primarily murdered by gassing, either in permanent installations constructed for this specific purpose, or by means of gas vans. The six extermination camps were Chełmno, Bełżec, Sobibor, Treblinka, Majdanek and Auschwitz-Birkenau. Extermination through labour was also used at the Auschwitz and Majdanek death camps. Millions were also murdered in concentration camps, in the Aktion T4, or directly on site. Additionally, camps operated by Nazi allies have also been described as extermination or death camps, most notably the Jasenovac concentration camp in the Independent State of Croatia.

The National Socialists made no secret of the existence of concentration camps as early as 1933, as they served as a deterrent to resistance. The extermination camps, on the other hand, were kept strictly secret. To disguise the mass murder, even in internal correspondence, they only referred to it as "special treatment," "cleansing," "resettlement," or "evacuation." The SS referred to the extermination camps as concentration camps. Their internal organizational structures were also largely identical. The term "extermination camp" was only used later in historical scholarship and in court cases and serves to further categorize the camps.

A gas chamber is an apparatus for killing humans or animals with gas, consisting of a sealed chamber into which a poisonous or asphyxiant gas is introduced. Poisonous agents used include hydrogen cyanide and carbon monoxide. High concentration carbon dioxide is typically used in gas chambers for animals.

Operation Reinhard or Operation Reinhardt (German: Aktion Reinhard or Aktion Reinhardt; also Einsatz Reinhard or Einsatz Reinhardt) was the codename of the secret German plan in World War II to exterminate Polish Jews in the General Government district of German-occupied Poland. This deadliest phase of the Holocaust was marked by the introduction of extermination camps. The operation proceeded from March 1942 to November 1943; about 1.47 million or more Jews were murdered in just 100 days from late July to early November 1942, a rate which is approximately 83% higher than the commonly suggested figure for the kill rate in the Rwandan genocide. In the time frame of July to October 1942, the overall death toll, including all killings of Jews and not just Operation Reinhard, amounted to two million killed in those four months alone. It was the single fastest rate of genocidal killing in history.

During the operation, as many as two million Jews were sent to Bełżec, Sobibór, and Treblinka to be murdered in purpose-built gas chambers. In addition, facilities for mass-murder using Zyklon B were developed at about the same time at the Majdanek concentration camp and at Auschwitz II-Birkenau, near the earlier-established Auschwitz I camp.