Nazi race and biological ideology
The völkisch state must see to it that only the healthy beget children .... Here the state must act as the guardian of a millennial future .... It must put the most modern medical means in the service of this knowledge. It must declare unfit for propagation all who are in any way visibly sick or who have inherited a disease and can therefore pass it on.
Both academic and popular racial ideology and arguments for eugenics were active before the Nazis took power.
Ernst Rudin, for example, was a German psychiatrist and eugenicist who advocated, with Alfred Hioche and Karl Bindong, of the idea that doctors should destroy "life devoid of value." He was among the architects of the July 1933 Law for the Protection of Hereditary Health, which established the Nazi criteria for mandatory sterilization. Rudin was one of Josef Mengele's university teachers. In 1935, he was chairman of the German Association of Neurologists and Psychiatrists. 
The Nazi notion of race was based on actual history, but heavily distorted to justify their views. Indo-European peoples did expand widely, probably out of the Caucasus, about 2000 BCE, most modern languages of Europe, Iran and North India are in the Indo-European language family, the Teutonic languages — German, Scandinavian, Dutch and English — are one branch of that family, and "Aryan" is one term for Indo-European. In the Nazi view, however, "Aryans" were superior to other races and the Teutonic branch the "purest" and most developed Aryans. The Nazis even considered the Slavs and Gypsies, both Indo-European groups, inferior, but the great focus of their persecutions was on the "sub-human" non-Indo-European Jews.
The Nazi symbol, the swastika, has a long history dating all the way back to the neolithic era. It has been a Hindu and Buddhist religious symbol for several millennia. The Nazis considered it an Aryan symbol because of the association with the Vedic peoples, Sanskrit-speaking Indo-European invaders of North India.
Detailed policy development
- Main Staff Office of the Reichscommissioner for the Strengthening of Germanism, Reichskommissar fuer die Festigung des Deutschen Volkstums, commonly known as “ RKFDV ”, which reported directly to Heinrich Himmler, head of the SS
- RuSHA, the Main Race and Settlement Office (Rasse-und Siedlungshauptamt), part of the RSHA of the SS
- VOMI, the Repatriation Office for Ethnic Germans (Volksdeutsche Mittelstelle)
- Lebensborn, the Well of Life Society
Doctrine from these staff offices guided the extrajudicial detention and genocide of Jews and other groups that violated Nazi racial concepts, as well as deportation and slave labor. These were conducted by other organizations.
- Robert Jay Lifton (1986), The Nazi Doctors: medical killing and the psychology of genocide, Basic Books, p. 21
- Adolf Hitler, Mein Kampf, quoted by Lifton, p. 21
- Gerald Posner and John Ware (1986), Mengele: the Complete Story, McGraw-Hill, ISBN 0070505985, pp. 9-10
- Henry Friedlander (1997), The Origins of Nazi Genocide: From Euthanasia to the Final Solution, University of North Carolina Press
- "Trial of Ulrich Greifelt and Others, United States Military Tribunal, Nuremberg, 10th October 1947-10th March 1948", Law Reports of the Trials of War Criminals. United Nations War Crimes Commission. Vol. XIII., 1949, p. 1