Fascism is the original Red-Brown Alliance

 Neither popular answer to the question of why “Socialism” is in the name of “National Socialism” is entirely correct.  They were not indistinguishable from other Socialists on everything but the Nationalism v Internationalism question.  But neither can a claim it was all a lie to trick the working class with no sincerity behind it hold up to scrutiny.

The term “Red-Brown Alliance” is one of many used for the concept of the Far Left and Far Right being sometimes allied in mutual disdain for some aspect of the current Status Quo.  The reason the color Brown is referenced in that term is because in the post WW2 era Fascism is the Far Right.   But in the 19th Century the Far Right was regular old fashioned Royalism, in France it was being a Bourbon-Legitimist.  While the Far Left included both Internationalists and Nationalists, both Socialists and Jacobins while The Center was Burkean Conservatism and Constitutional Monarchy.

The Philosophical groundwork for trying to be both a Monarchist and Revolutionary at once was laid by Thomas Carlyle who romanticized Medieval Europe and French Revolutionaries at the same time.  His works were popular in the Antebellum South and in Germany.  In The South it helped the Proto-Confederates from a justifying ideology that married Robert Filmer Paternalism with Jeffersonianism.

However the aftermath of the Franco-Prussian War is where Proto-Fascism begins to take shape on the ground.  

In France it resulted in Revanchism and the creation of the Ligue des Patriotes in 1882 by Paul Déroulède.  In 1883 the last heir to Charles X died and so the Legitimists were split between those who now supported the Orleans line and the Carlists, this opened the door for a fusion of Ultra Royalism with the Bourgeois Nationalism of the Oleanists.  But importantly this was contemporary with the rise of Revanchism, that was the pan ideological phenomena.  Revanchism helped spawn a new mode of Antisemitism in France as France’s Ashkenazi Population became included in French Germanophobia.  In 1886 Édouard Drumont published La France juive (Jewish France).  

In Germany meanwhile their Victory in the Franco-Prussian War emboldened the Volkisch Movement allowing Pan-Germanism to become no longer just a liberal but also an Imperialist goal as well as appealing to Social Reactionaries.  All while Modern Antisemitism got its start there.

1888 and early 1889 saw the rise and fall of Georges Ernest Boulanger whose ideologically vague movement was founded on three Principles, Revanchism, Revision of the Constitution and Restoration of The Monarchy.  One influential student of that movement was Maurice Barres. 

Later 1889 also saw the formation of the Second International where Nationalists were formally disowned from the Socialist movement.

From 1984 the Dreyfus Affair became a new animating that untied Socialists and Royalists. Maurice Barres wrote La Cocarde (The Cockade) to defend his ideas, attempting to bridge the gap between the far-left and the far-right and went on to become a leader of the before mentioned Ligue des Patriotes.

At this time Action Française was founded by Maurice Pujo, Henri Vaugeois, Jacques Bainville and Léon de Montesquiou, and then was later lead by Charles Maurras.  Charles Maurras created the ideology of Integral Nationalism combining Olreanist Royalism with the Mutualist Anarchism of Proudhon.  A student of his was Georges Valois. And he would also influence Jean Denis and the Rexist Party in Belgium.

Hubert Lagardelle and Gustave Hervé were other Anti-Reformist French Socialist who became radicalized by Nationalism during the WWI era, Mussolini himself cited Lagardelle as an origin point for Fascism. Herve founded in 1919 the Parti socialiste national (PSN) which was openly Class Collaborationist, and he openly vocally supported Mussolini.

Most of the key founders of Italian Fascism were formers Leftists of some kind, not just Mussolini himself.  The common denominated was not which ideological subgenre they came from, they included form Marxists and Leninists and Syncalists and Futurists and Anarchists of both Collectivist and Individualist varieties.  The common denominator was they were all people who supporting Italy entering WWI because of their Nationalism.