So, this is part two. My focus in this article will only be on Germany itself. This article will briefly detail the history of the Nazi Party, it's roots and what it did in power.
In narrowing this to Germany, one needs to look at the various nationalist movements that sprang up in 19th century Germany. I go back to the gymnast movements that sprang up in Prussia after the defeat of Napoleon. Led by Friedrich Ludwig Jahn, this group espoused a unified Germany. They also advocated for a healthy, active lifestyle and many of Jahn's followers participated in the failed 1848 Revolution. Jahn himself wanted to create a constitutional monarchy. A darker aspect was Jahn's antisemitism and his intolerant attitudes towards Poles and priests (he also disliked the French but this was understandable) and he even participated in a book burning. His ideas influenced Richard Wagner and by extension, Hitler.
This was the start of the Pan-Germanic movement. The Brothers Grimm, Wagner, Jahn and others supported Pan-Germanism or the idea of uniting all Germanic people under one flag. Originally this was under Austria but after the reunification of Germany in 1871 it shifted to the north. The sources I read think that Hitler became exposed to these ideas while in Vienna, along with the antisemitic attitudes these groups espoused (though it seems that Hitler was hardly a hardcore antisemite while in Vienna. He did business with Jews and seemed quite friendly with a few). These Pan-Germanic movements were antisemitic and highly nationalistic but mostly fringe parties. Their interests aligned with the growth of antisemitic parties in Germany before World War I. They also remained on the fringe with some of their ideas incorporated into conservative parties.
The loss of the war sent shockwaves through German society and the terms later imposed via the Versailles Treaty poisoned the very beginnings of the Weimar Republic. Far-right groups sprang up to contest the Republic from the very beginning. One of these groups was called The German Worker's Party (In German Deutsche Arbeiterpartei or DAP). Founded by Anton Drexler in 1919, it espoused nationalism but keyed towards workers. It was both anti-Marxist but also anti-Capitalist. It was antisemitic in outlook. The DAP wanted to break Bavaria away from Germany and form a union with Austria. This is the party that Adolf Hitler joined in 1919.
I will not go into Hitler's biography. To say that Adolf Hitler is one of the most studied figures in history is an understatement. He is certainly a fascinating figure but I feel this would be a tangent to this article. Suffice to say that the end of the war shattered his world, just like it did for millions of Germans. He remained in the army after the war ended because there was nothing in his life that would encourage him to leave. He became an intelligence agent with his targets the various political parties that sprang up after the war. The army was particularly concerned with political parties on the left after the various Communist uprisings that threatened the Weimar Republic. Hitler's task was to identify which groups were a threat while simultaneously trying to influence workers away from Communism. Hitler attended a DAP meeting in September of 1919. While there Hitler argued with a professor who argued for Bavarian separation from Germany. Drexler became impressed by hearing Hitler speak and encouraged him to join. Hitler joined after receiving permission to do so from his commanding officer. He quickly became a prominent member due to his beliefs and his skills as an orator. In order to become more attractive to a wider section of the population the party changed its name to the Nationalist Socialist Workers Party on February 24th, 1920 (in German, Nationalsozialistische Deutsche Arbeiterpartei or NSDAP). Hitler eventually supplanted Drexler and became the sole leader in July of 1921.
The NSDAP remained very much a fringe party and the butt of jokes after the failed Beer Hall Putsch in 1923. The membership remained small and likely would have remained so if not for the Great Depression in 1929. By the Summer of 1933 the NSDAP became the largest party in Germany though this support started to same somewhat that Fall. Conservatives in Germany helped Hitler become Chancellor in January of 1934.
I realize I blew through whole chunks of history but I didn't want to get bogged down in it. For those who want more details I can provide them in comments.
So, what was National Socialism? The party set forth a 25-point program that explained what it believed in:
Much is made about its very socialist tone but the reality is that economics frankly bored Hitler. Hitler even clarified that the NSDAP respected private property:
"Since the NSDAP stands on the platform of private ownership it happens that the passage" gratuitous expropriation concerns only the creation of legal opportunities to expropriate if necessary, land which has been illegally acquired or is not administered from the view-point of the national welfare. This is directed primarily against the Jewish land-speculation companies. "
Unlike Communists the state was not the primary employer, the primary employer remained private companies. The state channeled resources to massive rearmament but private companies remained in charge of production research and development. The NSDAP did channel money to public works in order to stimulate employment but those were planned for by previous administrations. Hitler simply implemented them.
At its heart the NSDAP was expansionist and antisemitic. Hitler wanted to unite Germans under Germany but also wanted to expand to give Germans more living space and access to resources like food and metals. Hitler wanted this expansion to occur on European soil, he didn't want colonial empires like the British and French. Hitler believed this expansion made most sense in the USSR because in his mind the Jews were responsible for the Communists taking control of the USSR. He believed that this represented both an opportunity and a threat, an opportunity because Jews could only cause chaos making the USSR an easy target, a threat that this chaos would spill into Europe and help the Communists take over in Europe.
The goals of the NSDAP started with overturning the Versailles Treaty, then uniting Germans under a greater Germany and finally expanding into Eastern Europe. In Hitler's mind this left no room for Socialists, Communists or Jews. Hitler showed some flexibility in working with Slavic nations as long as he remained the dominant partner but in instances where Slavs defied him like Poland or Czechoslovakia the Germans sought to dominate and then replace. Hitler generally kept other Fascist movements like the Arrow Cross in Hungary at arms length, preferring to operate with similar right-wing governments like his own.
National Socialism was the most successful of the various right-wing Fascist movements that sprang up in Europe during the early to middle part of the 20th century. It's hard to say how it would have evolved, Hitler's ambitions clashed with other powers that led to war and his downfall.