Above all, the appointment of Hitler as Chancellor of Germany on January 30, 1933 which paved the way for him to implement the perverse ideology he had documented in his book ‘Mein Kampf’ about 10 years earlier. It’s the major event. Ervin Staub, a professor of psychology at the University of Massachusetts, is famous for his works on the psychology of mass violence and genocide and he wrote a book called “The Roots of Evil: The Origins of Genocide and Other Group Violence”, see
http://www.amazon.com/Roots-Evil-Origins-Genocide-Violence/dp/0521422140/
Staub studied many conflicts and wars including WWII, Vietnam and more recently the genocide in Rwanda. I quote:
“The groundwork gets laid during severe social upheavals, like economic crises and political chaos, in places that have a history of divisions between a dominant group and a less powerful one. The turmoil causes members of a majority group to find appealing the ideologies that scapegoat a weaker group, blaming them for the problem and envisioning a better future that ‘they’ are preventing. The hatred spreads all the more readily when the majority group has itself been victimized in the past and still feels wounded or wronged.”
Hitler’s NSDAP (Nazi party) got 43.9% on March 5, 1933, the last election in Germany before WWII which also means that the majority voted for other parties. Apart from open antisemitism the Nazi party portrayed the German population as victims of the Treaty of Versailles signed in 1919.
What Hitler really had in mind including all the brutality that would follow had been documented in his book ‘Mein Kampf’, however few people had really read it. It took quite some time before ‘Mein Kampf’ became a bestseller. Simply counting the numbers of printed copies can also be misleading. From 1936 on every married couple received a free copy at the civil registry office. Not many of them actually read anything, let alone the whole thing.
In his book ‘The Second World War’ Winston Churchill felt that after Hitler’s ascension to power no other book deserved more intensive scrutiny than ‘Mein Kampf’, and called the book the new Koran of faith and war: turgid, verbose, shapeless, but pregnant with its message.
Over time more and more people realized that Hitler meant every word he wrote, but this took time. Even many Jews didn’t realize at first that the ghettos were just created to become a giant waiting rooms for the trains to the extermination camps. The true dimensions of Hitler’s plan took quite a while for people to realize. I haven’t read ‘Mein Kampf’ and I won’t. It’s too disgusting and it’s promoting one of the most perverse ideologies ever invented. There are summaries available on the web. It tells us about Nazi brutality. Understanding what happened in the regular army is a different matter. Most of this brutality and sometimes war crimes is about unleashing the beast hidden inside human beings. Wars, especially longer ones change people fundamentally. This horrible phenomenon isn’t restricted to WWII.