Adolf Hitler was known for telling his subordinates what he wanted to be done and letting them to figure out how to do it (and sometimes even the specifics of what was to be done) by themselves. He seldom (if ever) cared about how it was done – only that it was done.
Although Aktion T4 was formally managed by Reich Chancellery (a government entity) the man put by Hitler in charge of all administrative issue was Reichsleiter (national NSDAP leader) Philipp Bouhler.
Party machine usually worked far more efficiently than a government one (the SS was even more efficient); therefore, it is no surprise that Bouhler gave the Gauleiters (regional party leaders) the authority over the euthanasia process in the corresponding regions/provinces.
Which in some cases led to horrifying (and far more devastating than it might seem at the first glance) results. As it would happen with the Holocaust two years later, the first mass murders of individuals with seemingly incurable mental illnesses and/or physical disabilities or deformities happened on German-occupied territories, not in Germany. And the victims were non-Germans (in this case, Poles).
It happened during so-called Operation Tannenberg which killed about 20,000 “undesirable” Poles (i.e. potential members of the Resistance) – political and social activists, intellectuals, scholars, clergy, actors, former officers of Polish Armed Forces, etc.
It is not clear whether the idea of murdering individuals with disabilities in Poland came from above (from Himmler or Heydrich) or was the initiative of Einsatzgruppen commanders (I strongly suspect the former).
In the end, it did not matter – what mattered that all psychiatric hospitals and mental asylums of the Wartheland (administrative subdivision formed from parts of Polish territory annexed in 1939 during World War II) were emptied.
Emptied brutally and murderously – SS men of Einsatzkommando 16, Selbstschutz (paramilitary units comprised of Polish residents of German blood) and Einsatzkommando-Einmann entered the hospitals, rounded up all patients and unceremoniously shot them right then and there.
Apparently some Gauleiters had the same inclination as their Führer – to choose the most radical solution to the problem at hand (in this case, the problem of mentally and/or physically handicapped).
Hence it is no surprise that the idea of simply shooting adult mental patients soon spread from occupied Poland to adjoining areas of Germany. Another contributing factor to the “final solution” of the abovementioned problem was that these were exactly the areas where Germans wounded in the Polish campaign were expected to be accommodated. Which created not insignificant a demand for hospital space.
So the Gauleiter of Pomerania, Franz Schwede-Coburg (who later no less actively deported the Jews to death camps), sent 1,400 patients from five Pomeranian mental hospitals to several locations in occupied Poland, where they were shot or murdered in gas vans. Most likely, the deportation was carried out by the regional units of the Allgemeine SS.
The Gauleiter of East Prussia, Erich Koch (subsequently Reichskommissar of Ukraine – immensely brutal even by Nazi standards), had 1,600 patients sent in the same general direction and to the same fate.
All in all, more than 8,000 Germans with mental and/or physical disabilities and/or deformities were killed in this initial wave of killings carried out on the orders of local officials (ultimately, of course, these orders came from above one way or the other).
The idea of sending thousands of “undesirable” individuals to the areas in German-occupied territories – and thus “out of sight” of the general public and possible protesters – was a major stepping stone to the “final solution of the Jewish question” – and another “layer of snow” for the “Holocaust avalanche”.
In exactly the same way, the SS will send tens and hundreds of thousands of Jews from Germany, Austria, Bohemia and Moravia, France, Low countries, Hungary, etc. to Einsatzgruppen firing squads in Latvia, Lithuania, Belarus, Ukraine, Russia and to the death camps of Poland.
Not all Gauleiters were so radical – or passionate about exterminating the mentally and/or physically handicapped. Some chose to let the government officials do this job in their own way. Which was (not surprisingly) similar to the process used in euthanizing children.
All hospitals, nursing homes, old-age homes and sanatoria supplied to the Aktion T4 administrators (they were required to do so by their superiors) names of all patients who had been institutionalized for five years or more, who had been committed as “criminally insane”, who were of “non-Aryan race” (i.e. Jewish) or who had been diagnosed with any on a list of conditions provided by their superiors.
As with child inmates, adults (actually, their report cards – no examinations in person were conducted and no medical histories were studied) were assessed by a panel of medical experts, working at the Aktion T4 offices in Berlin.
As sometimes the experts had to deal with hundreds of reports at a time, their examination of the reports was cursory (to put it mildly). On each report they marked a “+” (death), a “-“ (life), or occasionally a “?”. The latter meant that they were unable to decide whether the individual in question should be euthanized or not.
Three “death” verdicts condemned the person and as with reviews of children, the evaluation process became less rigorous, the range of conditions considered “unsustainable” grew broader and zealous Nazis further down the chain of command increasingly made decisions on their own initiative.
Which predictably increased the percentage of patients condemned to death – and thus a total number of individuals to be killed. As from the very beginning the number of adults exceeded the number of children by at least an order of magnitude, Aktion T4 executioners needed to use some other method than lethal injection (which was also emotionally hard on doctors and nurses to the point of being almost unbearable).
As I have already mentioned, secrecy was not a serious concern for T4 planners. Unlike the logistics that was overwhelmingly driven by the needs of the war effort. Consequently, it was decided to establish killing centers (miniature death camps) not in occupied Poland, but in Greater Germany.
Ultimately, six euthanasia centers were set up – Brandenburg an der Havel (in the state/province of Brandenburg), Grafeneck Castle in Baden-Württemberg, Schloss Hartheim near Linz in Austria, Sonnenstein in Saxony, Bernburg in Saxony-Anhalt and Hadamar in Hesse.
The same facilities were later used to kill mentally sick prisoners transferred from concentration camps in Germany, Austria and occupied parts of Poland under the auspices of Aktion 14f13.
The murder tool was (predictably) the gas chamber camouflaged as a shower room (the same disguise will be later used in the Holocaust death camps in Treblinka, Sobibor, Belzec, Auschwitz, Chelmno and Majdanek). Only euthanasia centers used pure carbon monoxide (stored in steel cylinders) as a killing agent.
The prison doctor operated a manometer valve to allow carbon monoxide to enter the gas chamber. The steel cylinders themselves were supplied by Mannesmann, the filling (i.e. carbon monoxide gas) was made by IG Farben in Ludwigshafen (BASF). Bodies were burned in the center’s crematorium (the same process will be subsequently used in Auschwitz).