Racists are people who believe that innate, inherited characteristics biologically determine human behavior. The doctrine of racism asserts that blood is the marker of national-ethnic identity. Racism, including racial antisemitism (prejudice against or hatred of Jews based on false biological theories), was always an integral part of German National Socialism (Nazism). The Nazis perceived all of human history as the history of a biologically determined struggle among people of different races. After the Nazis came to power, they passed the Nuremberg Laws in 1935, which codified a supposedly biological definition of Jewishness. According to Nazi theories of race, Germans and other northern Europeans were "Aryans," a superior race. During World War II, Nazi physicians conducted bogus medical experiments seeking to identify physical evidence of Aryan superiority and non-Aryan inferiority. Despite killing countless non-Aryan prisoners in the course of these experiments, the Nazis could not find any evidence for their theories of biological racial differences among human beings.
Nazi racism produced murder on an unprecedented scale. During World War II, the Nazi leadership set about what they referred to as an "ethnic housecleaning" in the occupied Eastern territories of Poland and the Soviet Union. This policy included the murder and annihilation of so-called enemy "races," including the genocide of European Jews and the destruction of the leadership of the Slavic peoples. Nazi racists viewed the mentally and physically ill as a biological danger to the purity of the Aryan race. After careful planning, German physicians began to murder disabled residents of institutions throughout Germany in an operation that they euphemistically called "euthanasia."