Himmler recorded in his diary that the men of the SS Einsatzgruppen assigned to mass murder were "finished for the rest of their lives... either neurotics or brutes". What do we know about the actual psychology of rank-and-file SS after the war?

Part 1

Before getting to the question, which has only a very brief answer, some context on the Himmler quote is necessary.

Himmler didn't maintain a diary as such, meaning a book/notebook where he recorded his private thoughts. What he maintained is a so-called "duty diary" (Dienstkalender), meaning a notebook where he wrote down all dates, meetings, appointments, and activities related to his work as Reichsführer SS plus sometimes a quick note what happened when and where. This is what the duty diary looks like. You can see here his appointments for 18.9.1943 which include entries like "SS Obergruppenführer Berger [Head of the SS Main Office Gottlob Berger] and Stabschef Möckel [Chief of Staff of the Hitler Youth Helmut Möckel]"; "Situation report with Führer"; and "Lunch with Führer". The duty diaries for 1941/42 were discovered in the Special Archive in Moscow in the mid-1990s and published by Peter Witte and Michael Wildt in 1999 and recently the duty diaries for 1943–1945 and 1937–1938 have also been found and are currently being prepared for publication by the German Historical Institute in Moscow.

The mentioned quote does not come from the duty diaries but has been reported long already in 1945 since it was relayed by Erich von dem Bach-Zelewski, Higher SS and Police Leader in Minsk and plenipotentiary for anti-Partisan warfare in the occupied Soviet Union about a visit of Himmler's to Minsk and a mass execution undertaken there by Einsatzgruppe B under the leadership of Arthur Nebe on August 15, 1941. Bach-Zelewski in his capacity very much responsible for the murder of thousands had an interesting post-war career, so to speak. Arrested by US authorities in August 1945, he was one of the few high-ranking Nazis who declared that he would appear as a voluntary witness for the prosecution at the International Military Tribunal's trial of the main war criminals in Nuremberg. He willingly and extensively testified against Himmler and others at Nuremberg and spoke openly and candidly about the Holocaust and the mass murder in the Soviet Union. Some historians assume that because of this, he never faced a trial for war crimes and was never extradited to either Poland or the Soviet Union. Rather, the West Germans sentenced him twice for the murder of political opponents in the 1930s but he only served 15 years of prison until his death in 1973. While he spoke openly in Nuremberg, he later gave evidence for Eichmann's defense when the latter was tried in Jerusalem and wrote several texts in which he later contradicted his own testimony in Nuremberg. Jan Kreutz of Hamburg University has a study of von dem Bach forthcoming that seems rather interesting as it explores his biography in a new and exciting way but I digress.

Anyways, the cited quote was relayed by Bach-Zelewski in his testimony about Himmler's visit to Minsk in 1941. It's part of a 60-page handwritten testimony by Bach that can be viewed translated and machine typed in the Yad Vahsem Archives today (YVA, O.18/90) and that can also be read here. It was printed in the August 23, 1946 edition of the New York newspaper Aufbau, which you can read (in German) here. It is this account by Bach-Zelwski that has contributed to the notoriety of this particular visit of Himmler to Minsk, which consisted of a report about the mass murder in the Pripjet area on August 14, the mass execution and visit to a POW camp on August 15, and subsequently a tour of the Ghetto and a mental asylum. Himmler would also later in October visit Mogilew to see a mass execution and in February 1943 visit the Sobibor camp to see the mass-gassings there.

We know for certain that Himmler was there. The mass execution is noted in duty diary and there even exists film footage of his visit. Some historians however, such as Christian Gerlach, Volker Ries, and Jochen Lang, doubt the exact content of Bach's description, including the "savages" quote and in the larger context call into the question his narrative that because Himmler witnesses mass-shootings, he ordered a more "humane" method for the executioners to be found. Himmler noted in his duty diary that he gave a speech to the men of Einsatzgruppe B while in Minsk about the necessity of their task and would later return to the topic in his Posen Speech in October 1943 when he said:

Most of you here know what it means when 100 corpses lie next to each other, when there are 500 or when there are 1,000. To have endured this and at the same time to have remained a decent person — with exceptions due to human weaknesses — has made us tough, and is a glorious chapter that has not and will not be spoken of. Because we know how difficult it would be for us if we still had Jews as secret saboteurs, agitators and rabble-rousers in every city, what with the bombings, with the burden and with the hardships of the war.

While this is consistent with the above, Bach-Zelewski's narrative that because Himmler was so repulsed by the mass shootings that he ordered new methods to be found has been called into somewhat into question by Gerlach et.al., not just because nothing of the like is reported about his visits to Mogilew and Sobibor but also because gassing as a means of mass murder had already been mentioned before by this point. The first experiments with gassing had already taken place in October 1939 in the Posen concentration camp under the auspices of Albert Widmann, chemist and member of the Criminal Technical Institute (KTI), Department V D 2 (Chemistry and Biology). Widmann would then work on developing stationary gas chambers to be used in the T4 Action to murder mentally and physically handicapped inmates of institutions in both Germany and Poland and would go on to develop the first gas van used by the Sonderkommando of Hermann Lange to murder Polish inmates of mental asylums throughout 1940. It was Lange with whom Bach-Zelewski and Arthur Nebe got in touch with shortly after the Himmler visit in Minsk and inquired about seeing the gas van in action.

However, Gerlach points out that already on August 8, 1941 a Wehrmacht officer reported about his visit to Liepaja in Latvia that rumors were abound that the Germans were planning to murder Jews with gas and – more importantly – that on July 28, 1941 Viktor Brack, one of the main perpetrators of the T4 action, had visited the Wehrmacht's General Quarter Master, General Thomas, to inquire about receiving material support for their special mission from the Führer. Since the T4 program had not planned any sort of expansion for the summer of 1941, it stands to reason that what they wanted was material support for their development of the second generation of gas vans, which subsequently saw action with the Einsatzgruppen in October 1941.

In light of this, Gerlach et. al. have rejected the idea that Himmler ordered new methods of mass killing to be developed for the Einsatzgruppe because of his concerns for the mental well-being of his men. Rather, it seems that he informed Bach-Zelewski and Nebe while in Minsk that in order to provide a faster method of killing, gas vans were in development and that they should get in touch with Lange and the KTI about these new methods, which both of them dutifully did.

In short, the veracity of Bach-Zelewski's narrative about the development of new killing methods because of Himmler's concern has been called into question somewhat. While Himmler at several times referred to the genocide as a "difficult/hard but necessary duty" and something to be "endured" [durchgehalten], the development of new methods of gassing as way to support the killing operations precedes his visit to Minsk and there is a lack of similar stories about Himmler's later visits to either mass killings or concentration camps.