The superman, his German title is ubermensch, but I prefer to fall him, "the overman" since the former tends to conjure up a comic book and film character. Nietzsche would have had forty fits had he known, perhaps he is turning in his grave.
Like most of the ideas in Nietzsche's writings people tend to make of him what they will and not necessarily what Nietzsche intended. The problem is compounded by the difficulty in reading him and the fact that he does develop his ideas without necessarily correcting what went before. To do him justice he does try to do this in
Ecce Homo, though that was written three months before his final breakdown, and he tends to go on a bit about those he does not like, including Richard Wagner who had once been a friend and father figure to him.
There are folk who are avidly pro-Nietzsche and those who are equally rabidly against him. Many of the pro-Nietzsche faction deny he ever had any connection with the dictator but I do not think this can be substantiated. That some people considered Hitler to be the overman may well be true, not because he was but since among admirers of Hitler, and to judge by Dr. Goebbels' propaganda, there were many of these, a lot thought so.
That opinions such as this when Nietsche actually deplored the Bismarckian state in which he lived are clearly contradictory of what Nietzsche actually taught is inevitable. People have the remarkable gift of taking what they want from a well-known philosopher's teachings, and rejecting what does not suit them. The Bible is a case in point with rival Christian sects stressing their own particular doctrines regardless of whether the Bible, in its entirety, actually supports them or not.
Another idea, the will to power, was picked up on by Nazi Supporters. It is interesting that Leni Riefenstahl's technically and artistically superb film of the 1934 Nuremberg party rally is entitled The Triumph of the Will. The Nietzschean connection is clear. That Nietzsche intended it to be used in this way is far from the truth. The mass of the German populace who had never read any of Nietzsche were not to know this, it was a fine title, and what more can a brilliant young film maker want?
Intriguingly enough Hitler sent, by the hand of Field Marshall Kesselring, a copy of the collected works of Nietzsche to his friend Mussolini. Whether this stiffened the Italian resistance to the advance of the allied forces is questionable. Indeed it is questionable whether Mussolini ever bothered to read it, he had far more serious things on his mind at the time. However it is indicative that Hitler knew of Nietzsche and approved of and valued his works. That being so he must have known something of the teaching of the philosopher. (Kershaw, p597, Vol.II, Nemesis.)
In his early days in Vienna Hitler's friend Kubizek, whom Ian Kershaw describes as, “naïve and impressionable,” said that Hitler was never without books, that they, “were his world”. Kubizek also said that his friend arrived in Vienna, “with four cases, mainly of books”. Much later he claimed that Hitler had read a lot of the German and other classics, Goethe, Schiller, Dante, Herder, Ibsen, Schopenhauer and Nietzsche. This Kershaw says, “has to be taken with a large pinch of salt.” He does not however enlarge on this and explain the reasons for his skepticism. (Kershw, Vol.I, Hubris.p41.)
It was in the Landsberg prison, after the abortive Munich putsch that Hitler claimed to have read widely. He told Hans Franck that he had read Houston Stewart Chamberlain, Ranke, Treitschke, Marx, Bismarck and various war memoirs. Nietzsche is not mentioned. (Kershaw, vol.I p.244.) John Toland, an American biographer and prize winning author, takes a less skeptical view and says that Hitler, in Landsberg, really did read Nietzsche. (John Tolund, Adolf Hitler, p187.)
Mein Kampf, Hitler's biography and political testament, is not helpful since he gives very few quotations. Either he was too concerned to put his ideas into print or he liked to express ideas as his own. He would not be the first to read other people's thoughts and then claim they were the product of his own brain. We all probably do this more often that we can admit since an idea, once lodged in our memory, does in fact become our own regardless of its origins. Of course one ought to mention one's sources but Hitler was a practicing exponent of political ideas and not really an originator. His Nazi party owed more to the mass of ideas current in pre-1914 German youth and military movements than to a coherent philosophy of Hitler's making.