Aktion T4 (German, ) was an involuntary euthanasia program which targeted people with disabilities and the mentally ill in Nazi Germany. The terms "T4" or "Aktion T4" were first used in post-war trials against doctors who had been involved in the killings.

The name T4 is an abbreviation of  4, a street address of the Chancellery department set up in early 1940, in the Berlin borough of Tiergarten, which recruited and paid personnel associated with Aktion T4. Certain German physicians were authorised to select patients "deemed incurably sick, after most critical medical examination" and then administer to them a "mercy death" (). In October 1939, Adolf Hitler signed a "euthanasia note", backdated to 1 September 1939, which authorised his physician Karl Brandt and Reichsleiter Philipp Bouhler to begin the killing.

Although the T4 programme officially ended in August 1941, killings took place from September 1939 until the end of World War II in Europe in 1945. Between 275,000 and 300,000 people were killed in psychiatric hospitals in Germany, Austria, occupied Poland, the Protectorate of Bohemia and Moravia (now the Czech Republic), and the Soviet Union. The number of victims was originally recorded as 70,273 but this number has been increased by the discovery of victims listed in the archives of the former East Germany. About half of those killed were taken from church-run asylums. In June 1940, and Fritz von Bodelschwingh, who served as directors of sanatoriums, protested against the killings, being members of the Lutheran Confessing Church.

The Holy See announced on 2 December 1940 that the policy was contrary to divine law and that "the direct killing of an innocent person because of mental or physical defects is not allowed". Bishop Theophil Wurm of the Lutheran Confessing Church "wrote an open letter denouncing the policy." Beginning in the summer of 1941, protests were led in Germany by the Roman Catholic bishop of Münster, Clemens von Galen, whose intervention led to "the strongest, most explicit and most widespread protest movement against any Nazi policy since the beginning of the Third Reich", according to Richard J. Evans.

Several reasons have been suggested for the killings, including eugenics, racial hygiene, and saving money. Physicians in German and Austrian asylums continued many of the practices of until the defeat of Germany in 1945, in spite of its official cessation in August 1941. The informal continuation of the policy led to 93,521 "beds emptied" by the end of 1941. Technology developed under , particularly the use of lethal gas on large numbers of people, was taken over by the medical division of the Reich Interior Ministry, along with the personnel of , who participated in the mass murder of Jewish people under Operation Reinhard. The number of people killed was about 200,000 in Germany and Austria, with about 100,000 victims in other European countries. Following the war, a number of the perpetrators were tried and convicted for murder and crimes against humanity.

Background At the beginning of the twentieth century, the sterilisation of people carrying what were considered to be hereditary defects and in some cases those exhibiting what was thought to be hereditary "antisocial" behaviour, was a respectable field of medicine. Canada, Denmark, Switzerland and the United States had passed laws enabling coerced sterilisation. Studies conducted in the 1920s ranked Germany as a country that was unusually reluctant to introduce sterilisation legislation.

The policy and research agenda of racial hygiene and eugenics were promoted by Emil Kraepelin. The eugenic sterilisation of persons diagnosed with (and viewed as predisposed to) schizophrenia was advocated by Eugen Bleuler, who presumed racial deterioration because of "mental and physical cripples" in his Textbook of Psychiatry,

The German eugenics movement had an extreme wing even before the Nazis came to power. As early as 1920, Alfred Hoche and Karl Binding advocated killing people whose lives were "unworthy of life" (). Darwinism was interpreted by them as justification of the demand for "beneficial" genes and eradication of the "harmful" ones. Summarising their views, Robert Lifton wries, "The argument went that the best young men died in war, causing a loss to the of the best genes. The genes of those who did not fight (the worst genes) then proliferated freely, accelerating biological and cultural degeneration". In his book Mein Kampf (1924), Hitler wrote that one day racial hygiene "will appear as a deed greater than the most victorious wars of our present bourgeois era". The advocacy of eugenics in Germany gained ground after 1930, when the Depression was used to excuse cuts in funding to state mental hospitals, creating squalor and overcrowding.

Many German eugenicists were nationalists and antisemites, who embraced the Nazi regime with enthusiasm. Many were appointed to positions in the Health Ministry and German research institutes. Their ideas were gradually adopted by the majority of the German medical profession, from which Jewish and communist doctors were soon purged. In the 1930s, the Nazi Party had carried out a campaign of propaganda in favour of euthanasia. The National Socialist Racial and Political Office (NSRPA) produced leaflets, posters and short films to be shown in cinemas, pointing out to Germans the cost of maintaining asylums for the incurably ill and insane. These films included The Inheritance (, 1935), Victims of the Past (, 1937), which was given a major première in Berlin and was shown in all German cinemas, and I Accuse (, 1941) which was based on a novel by Hellmuth Unger, a consultant for "child euthanasia".

In July 1933, the "Law for the Prevention of Hereditarily Diseased Offspring" prescribed compulsory sterilisation for people with conditions thought to be hereditary, such as schizophrenia, epilepsy, Huntington's chorea and "imbecility". Sterilisation was also legalised for chronic alcoholism and other forms of social deviance. The law was administered by the Interior Ministry under Wilhelm Frick through special Hereditary Health Courts (), which examined the inmates of nursing homes, asylums, prisons, aged-care homes and special schools, to select those to be sterilised. It is estimated that 360,000 people were sterilised under this law between 1933 and 1939.

Within the Nazi administration, the idea of including in the programme people with physical disabilities had to be expressed carefully, because the Reich Minister of Propaganda, Joseph Goebbels, had a deformed right leg. After 1937, the acute shortage of labour in Germany arising from rearmament, meant that anyone capable of work was deemed to be "useful", exempted from the law and the rate of sterilisation declined.

Implementation

Karl Brandt, Hitler's doctor, and Hans Lammers, the head of the Reich Chancellery, testified after the war that Hitler had told them as early as 1933—when the sterilisation law was passed—that he favoured the killing of the incurably ill but recognised that public opinion would not accept this. In 1935, however, Hitler told the Leader of Reich Doctors, Gerhard Wagner, that euthanasia would be easier to deal with during wartime and he intended "in the event of a war radically to solve the problem of the mental asylums."

Wagner informed the heads of a number of relevant medical institutions of Hitler's intentions and several responded enthusiastically. Hermann Pfannmuller, director of the Eglfing-Haar mental hospital near Munich, had already been conducting tours of his institution since 1933 to show the SS and other visitors those patients who he considered to be unworthy of life.

The first centralised Nazi euthanasia programme involved infants. In 1939 Hitler instructed Brandt to evaluate a petition sent by two parents for the "mercy killing" of their infant son, Gerhard Kretschmar who was blind and had physical and developmental disabilities. Following Brandt's investigation, the child was killed in July 1939. Hitler instructed Brandt to proceed in the same manner in all similar cases.

Brandt and the head of the Chancellery of the Führer, Philipp Bouhler, subsequently founded the Reich Committee for the Scientific Registering of Hereditary and Congenital Illnesses as a front organisation for the child euthanasia programme. On 18 August the committee issued an order to relevant health authorities requiring them to register infants up to the age of three with specified disabilities and medical conditions. The first child killed in special children's wards under the centralised programme was in summer 1940, although officials in some institutions had already begun killing children. By the end of the war more than 5,000 children had been killed.

In the summer of 1939, Hitler called a conference with Leonardo Conti, Reich Health Leader and State Secretary for Health in the Interior Ministry, and Hans Lammers, Chief of the Reich Chancellery, where he gave verbal authorisation for adult involuntary euthanasia. In October Hitler signed an unofficial decree (backdated to 1 September) authorising Brandt and Bouhler to set up a programme for the "mercy killing" of incurable adult patients. Brandt and Bouhler established a number of front organisations, including the Reich Cooperative for State Hospitals and Nursing Homes (Reichsarbeitsgemeinschaft Heil- und Pflegeanstalten), to maintain its secrecy. The programme later became known as Operation T4, after the address of its headquarters at 4 Tiergarten Straße in Berlin.

Killing of children

Brandt and Bouhler assigned the management of the child euthanasia programme to Chancellery official Viktor Brack and his subordinates such as Hans Hefelmann and Richard von Hegener.

From August 1939 the Interior Ministry registered children with disabilities, requiring doctors and midwives to report all cases of newborns with severe disabilities; the 'guardian' consent element soon disappeared. Those to be killed were identified as "all children under three years of age in whom any of the following 'serious hereditary diseases' were 'suspected': idiocy and Down syndrome (especially when associated with blindness and deafness); microcephaly; hydrocephaly; malformations of all kinds, especially of limbs, head, and spinal column; and paralysis, including spastic conditions".

The reports were assessed by a panel of medical experts, of whom three were required to give their approval before a child could be transferred to a "special children's ward" for extermination. The first of these wards was established in the summer of 1940. Eventually 30 were established in various hospitals throughout the Reich.

The Ministry used deceit when dealing with parents or guardians, particularly in Catholic areas, where parents were generally uncooperative. Parents were told that their children were being sent to "Special Sections", where they would receive improved treatment. The children sent to these centres were kept for "assessment" for a few weeks and then killed by injection of toxic chemicals, typically phenol; their deaths were recorded as "pneumonia". Autopsies were usually performed and brain samples were taken to be used for "medical research". Post mortem examinations apparently helped to ease the consciences of many of those involved, giving them the feeling that there was a genuine medical purpose to the killings.

When the Second World War began in September 1939, less rigorous standards of assessment and a quicker approval process were adopted. Older children and adolescents were included and the conditions covered came to include