Action T4

Action T4 (German: Aktion T4) was the mass murder via involuntary euthanasia, from July 1939 to August 1941, of those deemed "defective" by the Nazi Party, overseen by Philipp Bouhler and Karl Brandt. It is unknown how many were killed during Action T4, but it is known to be over 70, 273. Several reasons have been suggested, chiefly eugenics and racial hygiene.

Implementation
At the time of the Nazi Party's election, eugenics and the prevention of those considered defective from reproducing was a large talking point due to the actions of those such as Harry Laughlin. In 1933, Nazi Minister of the Interior Wilhelm Frick passed the Law for the Prevention of Hereditarily Diseased Offspring, a law prescribing the involuntary sterilisation of those with conditions such as Huntingdon's Disease and schizophrenia that were believed to be hereditary, thus paving the way for Nazi eugenics. It is estimated that 360, 000 were sterilised under the law. Around the time that the law was passed, Nazi Party leader Adolf Hitler began to consider the killing of those who were mentally ill or disabled, as testified by Brandt, Hans Lammers and Gerhard Wagner. He also informed Lammers and Leonardo Conti that he wanted the mentally ill exterminated during a 1939 conference.

Action T4 began in July 1939, when Gerhard Kretschmar, a boy with severe developmental disabilities, was euthanised on Brandt's orders at the behest of Hitler. Soon after, Hitler signed the "euthanasia order", authorising Bouhler and Brandt to begin the killing of those deemed "defective".

Extermination
Following the euthanasia order, Hitler established the Reich Committee for the Scientific Registering of Serious Hereditary and Congenital Illnesses, an office for registering disabled and mentally ill children as "defective", with Brandt, Ernst-Robert Grawitz and Viktor Brack at the helm. As a result of the euthanasia order, all children three or under who were suspected of suffering from Down syndrome, intellectual disability, blindness, deafness, microcephaly, hydrocephaly or what was referred to as "spastic conditions" were killed at extermination centres through injections of phenol, with their deaths generally written off as pneumonia. The program was also used to target Jewish children, who were generally approved as eligible for euthanasia without any review as part of The Holocaust.

During the course of Action T4, Bouhler, Brandt, Conti and Werner Heyde began plans to extend the killings to adults. Soon after the commencement of Action T4, the Nazi invasion of Poland occurred, and Reinhard Heydrich, the man in charge of the invasion, collaborated with Action T4, ordering German Einsatzkommando units to murder disabled adult Poles, along with other untermenchsen they found. Mentally and physically disabled Polish adults were captured and taken to fake clinics, where they were either shot or killed in improvised Gas Chambers. Several gas chamber killings were witnessed by Heinrich Himmler, providing the inspiration for their later use in the Holocaust. The killings later spread to other Nazi-occupied countries under the direction of men such as Erich Koch, Grawitz, Brack and August Becker.

Suspension
On 24th August 1941, Hitler officially suspended Action T4, following widespread public outrage at the killings and the transfer of many key personnel to the Eastern Front in order to fight against Joseph Stalin. However, the killing of disabled adults and children continued, albeit less systematically, whenever Bouhler and Brandt could get away with it, with many being taken and euthanised after air raids to cover up their killings. By the time the Nazis were defeated, around 100, 000 had been killed as part of Action T4. After the Nazi defeat, Bouhler and others committed suicide, and many other perpetrators were convicted after the war, including Brandt and Brack.