Nazism developed several hypotheses concerning race. The Nazis claimed to scientifically measure a strict hierarchy of human race; the 'master race' was said to be the most pure stock of the Aryan race; which was narrowly defined by the Nazis as being identical with the Nordic race; followed by other sub-races of the Aryan race.

At the bottom of this hierarchy were 'parasitic races' (of 'non-Aryan' origin) or 'Untermenschen' ('sub-humans'); which were perceived to be dangerous to society. In Nazi literature; the term 'Untermensch' was applied to the Slavs; including Russians; Serbs; and ethnic Poles.