The institution unique to the Holocaust was the extermination camp: It had not existed before and has never been re-created. Approximately half of the Jewish victims of the Nazis died in extermination camps, and the camps, especially Auschwitz, have come to define the Holocaust in the public mind. It was the mechanization and industrialization of killing that characterized this genocide, and these features received their fullest expression in the camps, where the Germans demonstrated most completely their organizational skills and their thoroughness. The extermination camps were unquestionably a product of modernity – the killing not only was done by modern methods using scientific advances, but even more importantly it relied on the bureaucratic method of organization that had not been possible before the twentieth century.

As Raul Hilberg argued more than fifty years ago, the two components of mass killing – concentration camps and the use of gas for extermination – had already existed: The Nazi innovation was to bring these elements together. Understanding that mass killing could only occur in wartime, the Nazis began using carbon monoxide gas in its euthanasia program soon after World War II began. Using the euphemism of euthanasia, the Nazis killed approximately 70,000 mentally or physically handicapped German children and adults. In the next stage the euthanasia program was taken to Poland to kill handicapped Poles and Jews.