Yes, the historical Captain von Trapp was a fascist. He was a vocal supporter of the Austrofascist under both Engelbert Dollfuß and his successor Kurt Schuschnigg.

Austria's first republic – meaning democratic Austria between the foundation of the republic in 1918 and its end in 1934 – was ideologically incredibly divided with a lot of support for socialism in the industrial proletariat and the urban population of Vienna and the ultra-catholic christian-social movement with a good smattering of völkisch and Nazi-eswque deutschnational movements.

To illustrate this, it is best to refer to the July Revolt of 1927, also known as the Justic Palace Fire. Both the major parties in Austria had armed wings throughout the 1920s as a result of the armed conflicts after the foundation of the Republic in 1918/19. On January 30, 1927 several men of the Frontkämpfervereinigung Deutsch-Österreichs, which was the deutschnational armed wing (Adolf Eichmann was a member for example) shot from a restaurant at the social democratic Republikanischer Schutzbund who was engaged in a demostration. They killed an 40-year-old WWI veteran and an eight year old child. When the perpetrators were tried the same year, the justices decided that they acted in self-defense (wrongly). This lead to such an outrage that members of the Republikanischer Schutzbund set fire to the justice palace where the verdict was handed down and street fighting broke out in Vienna.

It was in this kind of ideologically charged atmosphere that in 1933 oppositon to a certain piece of legislation lead to the three parliamaentary presidents resigning in turn. Bieng leaderless for a short period, the Austrofascist under Dollfuß used the situation to enact a coup and prevent parliament from meeting again and taking over power.

Dollfuß almost immediately instituted a policy of persecuting Social Democrats as their main political enemies. Austrofascism as a movement was inspired by Italian Fascism and the catholic social teachings and aimed at the establishment of a corporative state, seeking to solve the class conflict not by the abolition of private property of the means of production but rather by a corporative solution where essentially everyone would know their places and organized in chambers (a la commerce chamber) and thus be forced to solve the class conflicts arising between workers and the bourgeoise. This made allusions to a "third way" between capitalist liberal democracy and socialism but in teallity was heeavily inspired and very close to actial fascism. And while the Austrofascists were Austrian nationalists to a degree that they opposed a unifaicaiton of Germany and Austria under the conditions of Nazism, their main enemey were the other enemies of Nazism, Social Democrats.

Their programm of persecution escalated very quickly. Heimwehr – the armed wing of the Austroafascist and where von Trapp was a member – together with police began a campaing of arrest that escalated very quickly in early Austroafascist rule in 1934. Resistance among Social Democrats spread, whcih ultimately resulted in an armed stand-off between Heimwehr ans Austrian Army on one-side and Republikanischer Shcutzbund on the other. In this situation, the Dollfuß decided to use artillery to shell Viennese apartment blocks where Social Democrats had barricaded themselves despite the fact that women and children were still within these blocks. Over a hundred people were killed and several hundreds were wounded. It was de facto a civil war.

Because of their opposition to the unification of Germany and Austria under the contions of Nazism – German supremacy, the dissulotion of Austrian authorities and self-government –, it was the Nazis who tried to initiate a coup against the former coupists of the Austrofascists. It was in this situaiton that Dollfuß was killed by a Nazi. And this is how the campaign of persecution against the Nazis started in Austria. So, this in effect lead to a situation where the Austrofascists persecuted both Nazis and the enemies of Nazis, Social Democrats. And the also the reason why later the Nazi regime persecuted Austrofascists and put them in concentration camps together with the social democrats who had spent the early 30s in Austrofascists concetration camps.

It is also important to highlight here that Austrofascists were also not opposed to Anti-semitism. They introduced measures very similar to anti-Jewish measures in Nazi Germany in the early 30s. So their idoelogical opposition did not extend to this point as well as to many other points. The main Axis of conflict between them and the Nazis revolved around Austria as an independant nation resp. the role of Austria in a unification with Germany. Loyality to them and the Vaterländische Front was not a unifying factor of anti-Nazism in Austria since they imprisoned the other opponents of Nazism.

As a last point: While they talked about a potential return to the Monarchy, they never went for it. The Habsburgs were around and very eager to take over but it never came to it since their model was more Italian Fascism than the genuine political Legitism of the Austrian political scene.

The summary hee is that the historical von Trapp was a supporter of a murderous fascist regime that shelled women and children with artillery who held dangerous and anti-democratic political beliefs that by twist of fate were opposed to Nazism yet still fascists. His lionization in American popular culture is entirely based upon the twisted narrative he created for himself and in reality, the man was politically highly dubious.

Thank you for your answer /u/commiespaceinvader.

I know you have answered a lot of follow-up questions, but if I may offer one: how possible was a Habsburg restoration during this time?

I know Otto von Habsburg was willing to return to take over the government. I read that he opposed Nazism and the Anschluss. Was there some public interest in this?