Aktion T4 in the context of "Karl Brandt"

Nazi Germany used six extermination camps (German: Vernichtungslager), also called death camps (Todeslager), or killing centers (Tötungszentren), in Central Europe, primarily in German-occupied Poland, during World War II to systematically murder over 2.7 million people—mainly Jews—in the Holocaust. The victims of death camps were primarily murdered by gassing, either in permanent installations constructed for this specific purpose, or by means of gas vans. The six extermination camps were Chełmno, Bełżec, Sobibor, Treblinka, Majdanek and Auschwitz-Birkenau. Extermination through labour was also used at the Auschwitz and Majdanek death camps. Millions were also murdered in concentration camps, in the Aktion T4, or directly on site. Additionally, camps operated by Nazi allies have also been described as extermination or death camps, most notably the Jasenovac concentration camp in the Independent State of Croatia.

The National Socialists made no secret of the existence of concentration camps as early as 1933, as they served as a deterrent to resistance. The extermination camps, on the other hand, were kept strictly secret. To disguise the mass murder, even in internal correspondence, they only referred to it as "special treatment," "cleansing," "resettlement," or "evacuation." The SS referred to the extermination camps as concentration camps. Their internal organizational structures were also largely identical. The term "extermination camp" was only used later in historical scholarship and in court cases and serves to further categorize the camps.

United States of America v. Karl Brandt, et al., commonly known as the Doctors' Trial, was the first of the twelve "Subsequent Nuremberg trials" for war crimes and crimes against humanity after the end of World War II between 1946 and 1947. The accused were 20 physicians and 3 SS officials charged for their involvement in the Aktion T4 programme and Nazi human experimentation.

The Doctors' Trial was held by United States authorities at the Palace of Justice in Nuremberg in the American occupation zone before US military courts, not before the International Military Tribunal. Seven of the accused were sentenced to death by hanging, five were sentenced to life imprisonment, four were given prison sentences from 10 to 20 years, and seven were acquitted.

Operation Tannenberg (German: Unternehmen Tannenberg, Polish: Operacja Tannenberg) was one of the first anti-Polish extermination actions by Nazi Germany in German-occupied Poland from September 1939 to January 1940. The operation was conducted with the use of the Sonderfahndungsbuch Polen, a proscription list of more than 61,000 members of the Second Polish Republic's elite were to be arrested then interned or shot.

Around 20,000 Poles were arrested and killed by the Einsatzgruppen in a number of mass killings during Operation Tannenberg, which was followed by the shooting and gassing of hospital patients and disabled adults as part of the wider Aktion T4 programme.

The Volkskörper, literally translated as either "national body" or "body national", was the "ethnic body politic" in German population science beginning in the second half of the 19th century. It was increasingly defined in terms of racial biology and was incorporated into Nazi racial theories. After 1945 the term was largely used synonymously with population in anthropology and geography (similarly to ethnicity or nation-state). In political parlance, however, the Volkskörper served as a metaphor for an organic and biological understanding of the unity between the Volk and the Volksgemeinschaft, its broader society. In German politics during the 19th and 20th centuries, it was used especially in anti-Semitic and racial hygiene texts to semantically differentiate the Volk, conceived as a biological and racial unit, from so-called "parasites", "pests" and "diseases". In this naturalistic sense "excretion" was construed in such a way as to define elements of the population as disease-causing and therefore needing to be expelled. The metaphor of the body national was therefore closely related to the Nazi regime's racial system and justified the enactment of policies like Aktion T4.