I am sure there are more qualified contributors to discuss National Socialism; for the purpose of comparison I'll cover that part as well – referring for the most part to I. Kershaw's Hitler and R. Evans' The coming of the Third Reich. If you have follow up questions on the specifics of the National Socialist Regime I may not be able to answer all of them exhaustively.

 

Italian Fascism and German National Socialism came to power in a similar fashion. They both took their first steps as one of the many radical movements that developed on the ground of the anti-establishment right; drawing inspirations from nationalist themes and attempting to develop a social platform alternative to that of the Socialists. While some notable differences exist on the nature of the two processes (considering that the NSDAP took far longer to became a viable political option), both the movements enjoyed their first boost of popularity in the war veterans area of the public opinion (which does not mean necessarily among the veterans proper but rather among that portion of the public opinion that read the war experience as the affirmation of a new aristocracy of combatants) but came to be a relevant political force only through their influence on the land workers (which happened relatively soon for Italian Fascism, i.e. before the actual foundation of the National Fascist Party; but only years after the failed putsch in the case of National Socialism).

At these point (which would be around 1921-22 for Italy and 1932-33 for Germany) both political forces found themselves uplifted to power by the (more or less – a significant portion of the Italian moderates, liberals and Catholics both, were supportive of Mussolini's first government experience) conservative establishment, that was looking for a mass force that could solidify the Government in opposition to the Socialist threat (as far as the German situation goes, there is some legitimate doubt that a genuine belief motivated such choice; and that therefore the conservative government group was more concerned with self preservation).

The fact that Mussolini's rise to power – or rather his party's rise to power – was comparatively much faster can in part be explained with the fact that, by 1919, Mussolini was already an established political personality: a former Socialist leader, later voice of the interventionist movement, war veteran, chief and founder of a well read and overall respectable paper; Mussolini had held baptism for a few political organizations of the veteran area among which that of the Combatants' Fasci, which will lead to the institution of the PNF in 1921. By that time Fascism was a minority (around 7%) parliamentary force but its influence in the nation was enhanced by its violent overcharge, mostly deployed against the Socialists. And while the violence gave rise to doubts among various observers, Mussolini seemed to rise above it and his skillful tactical choices leading to October 1922 made him a palatable choice for the position of Prime Minister even in the eyes of those moderates who were concerned with the fascist violence.

On the other hand, little doubt exist that Hitler's first political steps were more clumsy – to the point where his entire political survival was due to favorable circumstances – and he appears to have been chosen more as an animal that could be domesticated by the establishment, than as a leader for the nation in his own right.

Once gained power though, National Socialism soon covered any lost ground and moved rapidly (and abruptly) towards a more complete radicalization – furthering in a way the development of a competing structure over the previously existing state's functions, while Fascism moved far more slowly, retaining a large portion of the state apparatus.

This difference was due to both ideological and structural features of the two Regimes in their environments.

The National Socialist "ideology" for what we can legitimately put together was born out of a broad class of theories – beginning in the late 19th Century – that described history in term of a biological struggle between "entities", an evolutive process where some entities were more advanced, stronger, harbingers of progress, empowered with a right to rule or displace others. There are tie-ins here with more old school new world racism, but the biological-scientific tone is a feature of 19th Century.

The definition of this entities was what differentiated this various movements. For some it was a cultural definition, identity of language, common tradition, heritage; for other it was racial identity. In a sense for the National Socialist it was both: the entity was the German volk, the community of the people, which was at the same time a cultural and racial unity – which is why National Socialism made very little difference between what was culturally outside of the volk and racially outside of the volk. In this sense the purpose of National Socialism was to create a "State" that was more than a mere structure over the people, but a summation in itself of the identity of the volk; which is a more complex and, if you will dramatic, concept than a mere statement of racial superiority.

For Italian Fascism this entity was more loosely defined: it was the cultural and ethical heritage of the Italian people, coming all the way from Rome. A history that included the idea of a hierarchy of people federated together – which is why the racial issue was much less relevant in Fascism and essentially reduced itself to and establishment of a 19th Century colonialist mentality that viewed the Italians as leaders of the "Mediterranean peoples", with the Africans at the lowest rank.

With this in mind, if both movements framed history as a process of struggle towards self affirmation – a view that both leaders, to different extent, shared – for the National Socialist this fight was an absolute necessity, immediate, that required mobilizing the entire nation - volk - forces towards a titanic effort, that could not take any form that was not eventually that of war. In the context of Italian Fascism this was much more of a general tendency, that would ultimately bring some “nations/peoples/cultures” to fade into obscurity and others to gain or “regain” their place under the sun. That Mussolini believed (at least since the 1930s) that a war was coming, does not mean that he saw that eventual conflict as a culminating moment of Italian history, or even of his own personal trajectory. And while the Fascist did very little to prepare for a large scale conflict – that they had no hopes of winning by themselves anyway – the National Socialists soon oriented their internal policies towards an imminent war; with those policies subordinated to war needs already in time of peace and the solution to economical and social issues to be found in the final victory.

Another ideological difference was that of racism; which is not to say that Italian Fascism did not have its racist features but these were – for the most part, as I mentioned earlier – a rehash of the “colonial” racism that had been adopted during the first expansion attempts in Africa and existed as one of the many shades of the Italian social culture but was neither a core of the Fascist beliefs nor of the Fascist policies (a fact that will begin to change by the mid 1930s with the Ethiopian war but would never reach the extreme significance that race would have in the definition of the National Socialist Regime).

Race, in the meaning of a biological, social, cultural and even political identifier was a core element of National Socialism. Those elements extraneous to the German volk had to be removed if there was to be hope of achieving that final victory – therefore the Regime had to be ruthless. A point that becomes even more striking when you focus on the most infamous form this belief took in the National Socialist Regime: that of the persecution of the Jews – which was for the National Socialist ideology a necessary step in the process of self affirmation of the German people.

This necessity was completely absent in the case of Italian Fascism and when persecution measures were eventually introduced, they were so for entirely instrumental purposes and not as a goal in themselves. I actually have written a bit about the subject recently in this post.