This is covered by the first episode of the World at War. <a href="https://www.youtube.com/watch?v=0b4g4ZZNC1E" rel="nofollow">https://www.youtube.com/watch?v=0b4g4ZZNC1E</a>
Robert Paxton's five stages of fascism, a classic read: <a href="http://pryan2.kingsfaculty.ca/pryan/assets/File/Paxton's%205-Stages%20of%20Fascism.pdf" rel="nofollow">http://pryan2.kingsfaculty.ca/pryan/assets/File/Paxton's%205...</a>
Recommended: Ian Kershaw's books on Hitler.<p><a href="https://www.amazon.com/Hitler-Ian-Kershaw-ebook/dp/B00BJIMCA8/" rel="nofollow">https://www.amazon.com/Hitler-Ian-Kershaw-ebook/dp/B00BJIMCA...</a>
I recommend "The Ominous Parallels" [1] for a detailed examination of the philosophical and historical causes of Nazi Germany, and how these causes have echoes resonating in the US today.<p>[1] <a href="https://www.amazon.com/Ominous-Parallels-End-Freedom-America/dp/081282850X" rel="nofollow">https://www.amazon.com/Ominous-Parallels-End-Freedom-America...</a><p>(the now-flagged book review was <a href="https://www.nytimes.com/2018/06/14/books/review/benjamin-carter-hett-death-of-democracy.html" rel="nofollow">https://www.nytimes.com/2018/06/14/books/review/benjamin-car...</a>)