This is a book I'd very much like to read. Does it have your endorsement?

I don't much like the other response on this thread so far. Going back to 1348 is not very useful or informative. "Skipping ahead 500 years" sort of defeats the purpose of explaining an historical continuity. Plenty of nations had antisemitism. In the 1880's or 1890's, the Czar's Russia was a far worse place to be a Jew than Germany; many Eastern Jews made their way as refugees to the Reich at that time.

It is also a mistake to go back too far in history to find the continuity. Actually, the 30 year period r/thisisredrocks says should not be examined are in fact exactly the years we should be looking at. Make it 50-60 years and we're close to a good answer. Though it will never be possible to understand this issue fully. [Edit, I may have somewhat exaggerated r/thisisredrocks' position.]

I had played with multiple answers to your question, but I am going to stick to one, noting - noting well - that this is not a complete picture of events.

The Nazis were more successful than you might even think possible in isolating the activities of mass murder; there was no need to brutalize or brainwash the mass of Germans.

In fact, most Germans would not have wanted to murder Jews, or even Poles, though perhaps there was something approaching a "silent majority," if you will, of folk who feared the Jews and thought they should be taken down a notch. But World War One had created a whole generation of brutalized men, quasi-criminals who craved a life of violence, and organized themselves into "Freikorp" militias after 1918. (I wrote a bit about these groups last week) These were the men responsible for the assassinations of Foreign Minister Rathenau and Matthias Erzberger early in the 20's; in terms of the demographic and psychological profiles of these militia, it is essentially true to say that their heirs were the SA and SS. These were clubs of dispossessed and angry men who believed in the efficacy of violence in creating a new German world. These were the sorts of men the Nazis recruited to carry out their genocidal, brutal vision in the east. It was not necessary to condition the masses of Germans - a small subset of the most fanatic were preconditioned. Meanwhile, the camps were all located in occupied territories, and the mass graves were dug on Soviet territory. The average German might catch a rumor of these crimes and would have every psychological reason to write them off as literally outlandish rumors, and the average German soldier could be convinced that partisans and political criminals were being dealt with violently, yes, but nothing more. It was easy to cast Jews or Poles as partisans and political enemies. Didn't these groups have every reason to be angry at Germans, after all? It was always a plausible explanation that Jews, Poles and others represented a real internal security risk, not just a racial dilemma in the abstract. Add to all that the fact that from 1914 to 1939, German political life had been becoming increasingly brutal and violent and, perhaps, if the average German could convince themself that there was only limited violence happening, perhaps that would even have seemed normal, especially under the conditions of war.

You'll never reach the horizon of trying to find "the ultimate sources" of German violence, but a genealogical sketch might look like this: With the unification of Germany, nationalist racism, antisemitism and hatred of Poles (the largest minority in the empire) became ways of asserting a German identity separate from the quasi-democratic state despised by so many intellectuals and conservatives. Kaiser Wilhelm II nurtured a culture of jingoism and militarism in the run up to World War II, and the high staff, especially under Hindenburg and Ludendorff, pursued a brutal policy of occupation, population transfers, and endless war, even when it should have been clear that Germany did not stand a chance of imposing a Carthaginian peace on the West. Promised the moon, asked to make every sacrifice, a whole generation of German men could not come to believe that their struggle had resulted in an un-German democracy. In their mind they never stopped fighting, and they poisoned the next generation, latching onto the racial ideas that had moved German radical-conservatives for two generations already, but carrying them out with unforeseen and unprecedented brutality.

There's a sketch. Much more can be said. But, in my opinion, going back much further than the reign of Kaiser Wilhelm II will not produce much good history.

You’re not alone in your struggle to comprehend the sheer hatred which was leveled against Nazism’s enemies during World War Two. Harold Porter was a young American soldier assigned to assist the prisoners of Dachau soon after their liberation, and his first letter home to his parents warned that he knew they would “hesitate to believe me no matter how objective and factual I try to be.” Sometimes he even felt himself “trying to deny what I am looking at with my own eyes,” knowing nonetheless that what he had “seen in the past few days will affect my personality for the rest of my life.”^1 The official report of the United States Army, on what they had found at Dachau and what they knew of its history, echoed his sentiment. Its author wrote that “there are no words in English which can adequately describe the Konzentrations-Lager at Dacahu. In spite of the fact that one had known of its existence for years, had even spoken to people who had spent some time there, the first impression comes as a complete, a stunning shock. One had always had – in the back of one’s mind – the reservation ‘But surely it is impossible for human beings to do this to other people.’”^2 The question which confronted people then, as it confronts us now, is how was it that a people with a history and culture not unlike our own could have fallen so far astray as to have aided or at least acquiesced to such boundless cruelty?

One possible answer is that which your question seems to nod towards; the idea that the German people were not like ourselves. This construction supposes that there was something ingrained within their culture which not only allowed, but in fact precipitated the social and political isolation of Jews and others, such that genocide was made possible. In Hitler’s Willing Executioners, Daniel Goldhagen argues that the perpetrators of the Holocaust were animated by “a particular type of antisemitism that led them to conclude that Jews ought to die.”^3 To his mind, Germany was surfeit with a brand of hatred which “more or less governed the ideational life of civil society,”^4 and he traces its origin as far back as the 1840s, when he attributes “those holding essentialist notions about Jews” as having first begun “to adopt the vocabulary and the conceptual foundation of ‘race.’”^5 Consequently, his argument places responsibility for the Holocaust upon the shoulders of willing Germans who had born an ancestral and visceral hatred for Jews onto the killing fields of Belarus and Poland. Should all that be true, the legitimization of violence against Jews and other victims of the Holocaust demands very little explanation, since it could be considered as organic to Germans.

But, while it’s evident that anti-Semitism played a foundational role in Nazi ideology and their subsequent actions against Jewish populations, it is nevertheless insufficient as a complete explanation for the participation of Germans in genocide. As Christopher Browning rightly points out, if “German anti-Semitism” was “the sole and sufficient motivation of the Holocaust killers,”^6 and if such indefatigable anti-Semitism had existed before and quite apart from institutional efforts by the Nazi’s to promote and enforce it, then it’s implausible that it could suddenly have disappeared in 1945 or remained suppressed into the modern day. Despite the fact that both Goldhagen and Browning based their research in the same juridical records relating to Reserve Police Battalion 101, they reached very different conclusions about the personal character and motives of its members.

Contrary to the idea that these German genocidaires were committed Nazis or anti-Semites who were but chaffing for the opportunity to kill, Christopher Browning argues that they were in fact those who “were least likely to be considered apt material out of which to mold future mass killers.”^7 As a matter of recruitment, the men who were employed at the point of action, where rhetoric met reality in actual killing, were not selected by any sort of “careful choosing of personnel particularly suited for mass murder.”^8 Reserve Police Battalion 101 was allocated the task of murdering Jews because “it was the only kind of unit available for such behind-the-lines duties” and not because “it was composed of men specially selected or deemed particularly suited”^9 for it. Rather than these men possessing some basically different characteristic, Browning presents a picture of men who were not, besides the fact that they killed, notably distinct or identifiably different from society as a whole. His is a conclusion which is echoed by Abram De Swaan, who argues that while the “habitus” of the society in which genocidaires lived undoubtedly affected their decisions, and influenced the range of things which they could conceive as possible, the “broad and strong consensus” which “prevails in the social sciences about which personality traits distinguish genocidal perpetrators from other human beings” is that there are none.^10

It was this suspicion which prompted the now infamous post-war social experiments at Yale and Stanford. In an effort to examine what circumstances might impel an individual to obey a seemingly impossible order, a series of investigations were designed to test the limits of obedience to authority, the most famous of which were Stanley Milgram’s experiments at Yale and the Stanford Prison Experiment conducted by Phillip Zimbardo. The first involved subjects administering electric shocks to presumed compatriots (who were actually actors) according to their opposite’s performance at memory tasks. The second placed subjects in variable role-playing positions, as either guard or prisoner, in order to investigate how people respond to and exert authority. The prison experiment was called off after abusive behavior among the subjects escalated to the point that some experimenters worried that it would “go too far.”^11 Against the general expectation of the times, it transpired that most participants in these experiments were willing to obey, even when obedience caused apparent harm. In words which eerily echoed Jean-Paul Sartre’s warning that “anybody, at any time, may equally find himself victim or executioner,”^12 Phillip Zimbardo concluded that “any deed that any human has ever committed, however horrible, is possible for any of us – under the right or wrong situational circumstances.”^13 Their shared conclusion was grim, namely that massive violence need not require particular legitimization beyond the thin veneer of authoritative sanction.

This guy, Jordan Peterson, clinical psychologist and professor at the Univ. of Toronto, has a lecture on this very subject in his Personality and Its Transformations course. Here is the 2015 version. He has actually conducted his own experiments on figuring out the connections between orderliness, conscientiousness, and disgust, and well, he talks about these things at length, and in relation to the Nazis, and then into the Gulags too. I linked this particular video, but there is one for 2014 and one for 2016. You should peruse them as you see fit. His other lectures are equally as dope. You can check out the lecture titles to get an idea of what he'll talk about, or you can start at the beginning and work your way through them. Obviously, for a complete understanding of the material, it would be best to start at the beginning and work your way up but each video can stand alone on its own with ease. I enjoy these lectures immensely, and you might also; hopefully. I don't know if I'm breaking any r/askhistorians rules but I hope this helps nonetheless.