In October 1941, work began on Auschwitz II, or Birkenau, located outside the nearby village of Brzezinka. There the SS later developed a huge concentration camp and extermination complex that included some 300 prison barracks; four large so-called Badeanstalten (German: “bathhouses”), in which prisoners were gassed to death; Leichenkeller (“corpse cellars”), in which their bodies were stored; and Einäscherungsöfen (“cremating ovens”). Another camp (Buna-Monowitz), near the village of Dwory, later called Auschwitz III, became in May 1942 a slave-labour camp supplying workers for the nearby chemical and synthetic-rubber works of IG Farben. In addition, Auschwitz became the nexus of a complex of 45 smaller subcamps in the region, most of which housed slave labourers. During most of the period from 1940 to 1945, the commandant of the central Auschwitz camps was SS-Hauptsturmführer (Capt.) and ultimately SS-Obersturmbannführer (Lieut. Col.) Rudolf Franz Hoess (Höss).

However, this regulation was soon waived and there is ample evidence that full Nazi Party members served in the Wehrmacht in particular after the outbreak of World War II. The Wehrmacht Reserves also saw a high number of senior Nazis enlisting, with Reinhard Heydrich and Fritz Todt joining the Luftwaffe, as well as Karl Hanke who served in the army.
After the failure of the Beer Hall Putsch in 1923, and his subsequent trial and imprisonment, Hitler decided that the way for the Nazi Party to achieve power was not through insurrection, but through legal and quasi-legal means. This did not sit well with the brown-shirted stormtroopers of the SA, especially those in Berlin, who chafed under the restrictions that Hitler placed on them, and their subordination to the party. This resulted in the Stennes Revolt of 1930-31, after which Hitler made himself the Supreme Commander of the SA, and brought Ernst Röhm back to be their Chief of Staff and keep them in line. The quashing of the SA's revolutionary fervor convinced many businessmen and military leaders that the Nazis had put aside their insurrectionist past, and that Hitler could be a reliable partner [279][280]
Following the camp's liberation, the Soviet government issued a statement, on 8 May 1945, that four million people had been killed on the site, a figure based on the capacity of the crematoria and later regarded as too high.[185] Höss told prosecutors at Nuremberg that at least 2,500,000 people had been murdered in Auschwitz by gassing and burning, and that another 500,000 had died of starvation and disease.[186] He testified that the figure of over two million had come from Eichmann.[187][d] In his memoirs, written in custody, he wrote that he regarded this figure as "far too high. Even Auschwitz had limits to its destructive possibilities."[189] Raul Hilberg's 1961 work, The Destruction of the European Jews, estimated that up to 1,000,000 Jews had died in Auschwitz.[190]
To complete this mission, Hitler ordered the construction of death camps. Unlike concentration camps, which had existed in Germany since 1933 and were detention centers for Jews, political prisoners and other perceived enemies of the Nazi state, death camps existed for the sole purpose of killing Jews and other “undesirables,” in what became known as the Holocaust.
On 15 September 1935, the Reichstag passed the Nuremberg Laws, prohibiting marriages between Jews and people of Germanic extraction, extramarital relations between Jews and Germans, and the employment of German women under the age of 45 as domestic servants in Jewish households.[12] The Reich Citizenship Law defined as citizens those of "German or kindred blood". Thus Jews and other minorities were stripped of their citizenship.[13] By the start of World War II in 1939, around 250,000 of Germany's 437,000 Jews had emigrated to the United States, Palestine, the United Kingdom, and other countries.[14][15]
As a result of the Holocaust, the term "concentration camp" carries many of the connotations of "extermination camp" and is sometimes used synonymously. Because of these ominous connotations, the term "concentration camp", originally itself a euphemism, has been replaced by newer terms such as internment camp, resettlement camp, detention facility, etc., regardless of the actual circumstances of the camp, which can vary a great deal.