Weiss had previously been the Commandant of the Neuengamme concentration camp from 1940 to 1942. From September 1942 until the end of October 1943, Weiss was the Commandant of Dachau. During his time as the Commandant of Dachau, some of the worst atrocities had occurred, including the building of the gas chamber and the medical experiments conducted for the German air force. In spite of this, several former prisoners testified in his defense when he was put on trial at Dachau in the first American Military Tribunal in November 1945.
Killing on a mass scale using gas chambers or gas vans was the main difference between the extermination and concentration camps. From the end of 1941, the Germans built six extermination camps in occupied Poland: Auschwitz II-Birkenau, Majdanek, Chełmno, and the three Operation Reinhard camps at Belzec, Sobibor, and Treblinka II. Maly Trostenets, a concentration camp in the Reichskommissariat Ostland, became a killing centre in 1942. Gerlach writes that over three million Jews were murdered in 1942, the year that "marked the peak" of the mass murder of Jews. At least 1.4 million of these were in the General Government area of Poland.
After 1942, the economic functions of the camps, previously secondary to their penal and terror functions, came to the fore. Forced labor of camp prisoners became commonplace. The guards became much more brutal, and the death rate increased as the guards not only beat and starved prisoners, but killed them more frequently. Vernichtung durch Arbeit ("extermination through labor") was a policy—camp inmates would literally be worked to death, or to physical exhaustion, at which point they would be gassed or shot. The Germans estimated the average prisoner's lifespan in a concentration camp at three months, due to lack of food and clothing, constant epidemics, and frequent punishments for the most minor transgressions. The shifts were long and often involved exposure to dangerous materials.
Adolf Hitler became chancellor of Germany on January 30, 1933, and in March of that year the first Nazi concentration camp opened in the town of Dachau, just outside Munich, a major city in southern Germany. The camp initially housed political prisoners, and its first group of detainees consisted primarily of socialists and communists. Hilmar Wäckerle (1899-1941), an official in the “Schutzstaffel” (a Nazi paramilitary organization commonly known as the SS), served as the first commandant of Dachau.
The workers who constructed the original buildings were housed in camps near Fallingbostel and Bergen, the latter being the so-called Bergen-Belsen Army Construction Camp. Once the military complex was completed in 1938/39, the workers' camp fell into disuse. However, after the German invasion of Poland in September 1939, the Wehrmacht began using the huts as a prisoner of war (POW) camp.