When Germany invaded Poland in September 1939, triggering World War II, Adolf Hitler ordered that the Polish leadership and intelligentsia be destroyed. Approximately 65,000 civilians, viewed as inferior to the Aryan master race, had been killed by the end of 1939. In addition to leaders of Polish society, the Nazis killed Jews, prostitutes, the Roma, and the mentally ill. SS-Obergruppenführer Reinhard Heydrich, then head of the Gestapo, ordered on 21 September 1939 that Polish Jews be rounded up and concentrated into cities with good rail links. Initially the intention was to deport them to points further east, or possibly to Madagascar. Two years later, in June 1941, in an attempt to obtain new territory, Hitler invaded the Soviet Union.
Repeat selections took place several times during the day in roll calls. Inmates who had become weak or ill were separated from the ranks and sent to the gas chambers. A brutal regimen based on a set of punishments and torture was invoked in the camp. Few managed to survive. In Auschwitz-Birkenau, more than 1,100,000 Jews, 70,000 Poles, 25,000 Sinti and Roma (Gypsies) and some 15,000 prisoners of war from the USSR and other countries were murdered.
The 1930 elections changed the German political landscape by weakening the traditional nationalist parties, the DNVP and the DVP, leaving the Nazis as the chief alternative to the discredited Social Democrats and the Zentrum, whose leader, Heinrich Brüning, headed a weak minority government. The inability of the democratic parties to form a united front, the self-imposed isolation of the Communists and the continued decline of the economy, all played into Hitler's hands. He now came to be seen as de facto leader of the opposition and donations poured into the Nazi Party's coffers. Some major business figures, such as Fritz Thyssen, were Nazi supporters and gave generously and some Wall Street figures were allegedly involved, but many other businessmen were suspicious of the extreme nationalist tendencies of the Nazis and preferred to support the traditional conservative parties instead.
Nazi Germany maintained concentration camps (German: Konzentrationslager, KZ or KL) throughout the territories it controlled before and during the Second World War. The first Nazi camps were erected in Germany in March 1933 immediately after Hitler became Chancellor and his Nazi Party was given control of the police by Reich Interior Minister Wilhelm Frick and Prussian Acting Interior Minister Hermann Göring. Used to hold and torture political opponents and union organizers, the camps initially held around 45,000 prisoners. In 1933–1939, before the onset of war, most prisoners consisted of German Communists, Socialists, Social Democrats, Roma, Jehovah's Witnesses, homosexuals, and persons accused of 'asocial' or socially 'deviant' behavior by the Germans.