There is very little doubt that the fascist squads played a decisive role in Mussolini's ascension to Prime Ministry in 1922. They were not - as the official narrative of the "Fascist Revolution" would maintain - an irresistible force of revolutionary youth sweeping away the remnants of the liberal State in their glorious March on Rome. But they were decisive nonetheless.

That Mussolini's rise to power was the result of a political maneuver - rather than a coup - and, thus, to a degree at least, organic to traditional forms of political negotiation was manifest already to contemporaries (and, indeed, many contemporaries didn't regard Mussolini's "takeover" as a marked discontinuity from the post unitary tradition of alternance between "liberal" and "authoritarian" governments - see for instance Salvemini, De Gasperi, Einaudi, Albertini, among many others). It could hardly be otherwise, given how many of those contemporaries (Orlando, Salandra, Giolitti abd a score of political and administration figures) had been directly involved in "negotiating" Mussolini's appointment. The decisive function of the squads should not be looked for in the supposed "takeover" of October 1922; but rather in the previous months when those groups - haphazard and inconsistent in comparison to the regular army - had proven quite effective in pursuing a different design.

Mussolini had been - to steal a fortunate analogy from Repaci's quite dated La Marcia su Roma - playing on two tables: the "institutional" one, where he had been working to establish his "government" profile at least since the formation of the National Fascist Party in 1921; the "movement" one, where the fascist squads ended up serving multiple converging functions (or, at least, Mussolini was able to drive impulse from those, at times incoherent, directions) necessary for the establishment of Mussolini's political profile and for determining the circumstances which brought him to power.

First; as an instrument of agrarian reaction, the squads were able to collect funds, men and local support (which Mussolini had proved largely unable to do by his own means in 1919). Originally structured as instruments of pressure against the socialist land workers organizations, they rapidly evolved (in the zones of more marked social conflict) into mass organizations incorporating both laborers and the local middle classes, able to represent both a political challenge (through their non indifferent numbers) and a direct violent threat for the socialist (and, in the end, even liberal) administrations. Furthermore, even if they did at times struggle to retain those relations after the original causes of conflict had subsized, their very presence served as a renewed source of tension preventing normalization.

Second; through their para-military organization and thanks to the more or less open solidarity of the public force (and often, of the State's administration), they were able to substantially undermine the cohesion and strength of the socialist organizations, and, with that, the political weight of the Socialist Party, de facto erasing the negotiation power of the "left" liberal groups and of the socialist reformers, and conversely strengthening the position of those "national" groups which sought a "popular" alternative on the right.

Third; the ambiguous collocation of fascist violence - as a "reaction violence", a defense of the institutions against the "Bolshevik tide" (an interpretation common to large portions of the liberal world as well) - left room for a characterization of the squads as operating a form of (at times overzealous but ultimately benign) "legalitarian violence" (or, to cite from Gentile, of "ethical violence"). That is, violence which aspired at restoring the authority of the State rather than undermining it (as the Corriere della Sera suggested already in the Spring of 1922, the action of the fascist squads would not, eventually, restore the authority of the old liberal State, but rather promote something a tad different: the "fascist authority of the State")

Fourth; this specific collocation proved extremely effective at undermining the already declining authority of the liberal State. The State had proven unable to suppress the socialist violence, to protect and sustain the prestige and dignity of the military, police forces and of the administration of the State (all elements manifest in the last labored attempts to regain full and effective control made by Giolitti during his final service as prime minister). The fascists had sought to that themselves. Or, taking a less sympathetic point of view, the State was proving unable to restrain or to quell the fascist violence, leaving the room open to any sort of unruly movement of masses: either Bolshevik degeneration or capitalistic reaction. The socialists themselves, subject to fascist violence and ofttimes left without recourse with the public authorities, had no particular commitment to the liberal State which they identified (not without reason) with traditional forms of bourgeois oppression. Whatever the source and value ascribed to the authority of the State, the fascist squads had managed to supplant it by either taking charge of it, or by usurping it, or by structurally representing it.

Fifth; while locally defined - each led by one or few notable figures - all squads more or less recognized the national leadership of Mussolini, or at least his role of "political reference" for the movement. There was, therefore, no better candidate than Mussolini himself in order to attempt the "normalization", or "institutionalization" of fascism. Mussolini was careful enough to avoid the pitfall of a proposed designation as Minister of Interior in a government led by Salandra or Giolitti (which would have put him in the untenable position of being in charge of public order, without being able to provide full satisfaction to the "movement") and to push for the Prime Ministry. This was granted to him on October 28^th 1922 and confirmed by a large parliamentary majority a few days later.

I tried to be concise (I had to) in addressing the impact of the fascist squads and their role in Mussolini's designation. If there are unclear points, feel free to ask for further clarification. A much more detailed examination can be found in Vivarelli's Storia delle origini del fascismo (especially vol. 2-3).