The killing of the severely disabled child later identified as Gerhard Kretschmar (the “Knauer child” case) became a key catalyst for the regime’s move from coerced sterilization toward systematic murder of disabled people, after Hitler authorized Karl Brandt to handle similar cases.
The regime established the Reich Committee for the Scientific Registration of Serious Hereditary and Congenital Illnesses to register children deemed “unfit,” enabling organized selections and the expansion of child killings in clinics and institutions.
Adolf Hitler signed a secret authorization (backdated to 1939-09-01) empowering Philipp Bouhler and Karl Brandt to begin killing patients deemed “incurably sick,” providing the political cover for the centralized adult “euthanasia” program later known as Aktion T4.
The administrative office coordinating the planned patient killings initially operated from Columbus House (Potsdamer Platz, Berlin) beginning in autumn 1939, before moving to Tiergartenstraße 4 the following year.
At Brandenburg an der Havel, a trial killing using gas was carried out in January 1940, helping standardize carbon-monoxide gassing that became central to the T4 killing process.
Mass murder under the centralized “euthanasia” program began at Grafeneck, where gassing operations started (widely cited as among the first operational T4 killing sites) and thousands of psychiatric patients were killed in 1940.
The Brandenburg T4 killing facility murdered patients primarily via carbon-monoxide gas between February and October 1940, with victims transported under deception and records falsified to conceal the killings.
From April 1940, the program’s central office operated from a villa at Tiergartenstraße 4, Berlin, organizing transports, staffing, finances, and the medical “expert” selection system that decided who would be killed.
At Hartheim Castle (near Linz, Austria), murders using carbon monoxide in a gas chamber began in May 1940, making Hartheim a major T4 killing center and later a site used in subsequent killing operations.
The Pirna-Sonnenstein facility began killing operations at the end of June 1940, becoming one of the six principal T4 gassing centers and later a conduit of personnel and techniques into wider Nazi mass-murder programs.
At Bernburg, systematic gassing of disabled patients began on 1940-11-21 after the site was converted as a replacement for Brandenburg, reflecting the program’s continued institutional expansion and operational refinement.
The Hadamar killing center began gassing operations in mid-January 1941 (documented as 1941-01-13 at the Hadamar memorial), becoming the sixth and last of the main T4 killing sites established for the centralized phase.
Bishop Clemens August Graf von Galen publicly condemned the killings in his third major sermon on 1941-08-03, a highly influential protest that was widely circulated and contributed to increased public scrutiny of the program.
On 1941-08-24, Hitler ordered the official suspension of the centralized gassing program, responding to rising public awareness and protest; despite this “pause,” killings continued later through decentralized methods and related actions.
Euthanasia and Aktion T4 (1939–1941)
