Alfred Ploetz founded the German Society of Racial Hygiene in 1905. However, a eugenic social agenda only gathered support after the humiliating loss of WWI, when Germans felt beset by adversaries both outside and inside their borders.
In 1927, the Rockefeller Foundation provided funds to construct the Kaiser Wilhelm Institute for Anthropology, Human Heredity, and Eugenics in Berlin, which came under the directorship of the appropriately named Eugen Fischer. Adolf Hitler read Fischer's textbook Principles of Human Heredity and Race Hygiene while in prison at Landsberg and used eugenical notions to support the ideal of a pure "Aryan" society in his manifesto, Mein Kampf (My Struggle).
When Hitler came to power in 1933, he charged the medical profession with the task of implementing a national program in race hygiene. The first key element was the enactment, in 1934, of a law permitting involuntary sterilization of feebleminded, mentally ill, epileptics, and alcoholics. ERO Superintendent Harry Laughlin's model sterilization law was closely modeled, and his contributions to race hygiene were recognized with an honorary degree from the University of Heidelberg. The "marriage laws" of 1935 prohibited unions between "Aryans" and Jews, as well the eugenically unfit.
By the outbreak of WWII, in 1939, an estimated 400,000 people had been sterilized. However, in 1940 the need for hospital beds for wounded soldiers prompted a "final solution" for "lives not worth living." Psychiatrists and medical doctors identified more than 70,000 mental patients who were poisoned with carbon monoxide in extermination centers at psychiatric hospitals.
After gassing of mental patients ceased in 1941, medical and other personnel with euthanasia experience were reassigned to concentration camps in Poland, where hydrogen cyanide gas was used to kill Jews, gypsies, Slavs, and Social Democrats.