Hitler tends to get all the press with loads of movies, books, papers, and such discussing his rise to power and the conversion of Germany from the Weimar Republic. So much so that I realize I have nothing more than a few dry facts from Wikipedia to outline his renunciation of Socialism and rise of power.
What were the conditions in Italy that led to such a such popularity of Fascism?
Prelude
Italy did not come out of the First World War in good shape. Between 1919 and 1920 frustrated (and unemployed) demobilized soldiers aligned themselves alternatively with militant communist groups or militant fascist groups, both of which were bent on shaking up the social order. The socialist-dominated governing coalitions (headed by Nitti between 1919-1920 and Giolitti between 1920-1921) proved unable to deal with the economic and social crisis, and by the end of 1920 army regiments in Central Italy were in open revolt. Communist paramilitary activity was so widespread the years 1919 and 1920 in Italy are called the "Red Biennium."
The Election of 1921
The Italian Elections of 1921 resulted in a three-way tie, with the Socialists winning 24% of the vote, the Catholics (Partito Popolare Italiano, PPI) winning little over 20%, and the fascist dominated "Blocco Nazionale" coalition getting a little less than 20% of the vote.
Socialist leader Ivanoe Bonomi was able to round up a coalition of moderates thanks in part to the expulsion of communist sympathizers from the Socialist Party immediately prior to the election. However, the inherent incompatibility of the Socialist agenda with that of the Catholics (whose voted were necessary to keep the government afloat) as well as Bonomi's tolerance of fascist paramilitary activity against the communists (unpopular within his own party, but arguably necessary to avoid a revolution^1 ) meant that this government would lose a vote of confidence in February 1922.
The liberal Luigi Facta was then prodded to the head of the ruling coalition by the King. However, the Liberals were minority members in the coalition and the larger Socialist-Catholic deadlock was still unresolved while the country continued to spiral into chaos. Facta's cabinet reshuffle on August 1st 1922 did little to improve the situation.
King Victor Emanuel
The day after Facta's cabinet reshuffle fascist party leadership ordered their paramilitaries (the famous "Blaskshirts") to occupy the city of Ancona as a sort of experiment to see just how dependent the government had become on the paramilitaries to maintain order.
The government didn't react. In fact, it couldn't: army regiments in Ancona had been the first to revolt back in 1920, and Italian authorities were fearful that the army, who saw the fascist paramilitaries as allies in the struggle against communist revolts, would defect to the fascist leader Mussolini if they were mobilized against him.
The fascist show of force in Ancona is not only significant because it marks the first attacks on the government (and not their usual targets, the communists) but because it went so smoothly the Fascist leadership began planning larger shows of force from then on as extension of parliamentary debate "By Other Means."
Four days before the decisive march on Rome, the Blackshirts marched on Naples, occupying the city without government opposition. The government came to the panicked realization that a large-scale confrontation between the government and the fascist militias would be inevitable.^2
On October 27th 1922, in cities with large fascist majorities Blackshirt militias occupied major public buildings, while thirty thousand fascist demonstrators boarded trains to Rome (Mussolini stayed behind in Milan, lest something go wrong). The heads of Italian security forces met with the King and prime minister late that evening. The King inquired if the army was inclined to defend Rome, and General Diaz answered, "The army will certainly do its duty, but it better not be put to the test."^3 The hypothesis of declaring a state of emergency was briefly floated, but the consensus seems to have been that most army units deployed would simply defect to Mussolini.
The following morning, Facta and his ministers tried to prod Victor Emmanuel into declaring a state of emergency, but the King replied to Facta, "The only thing that can follow a state of emergency is civil war. Now, one of us must be sacrificed." It would seem that the king was done with putting together haphazard coalitions to keep extremists out of power, and Facta resigned that evening.^4 The next day, the fascists were camped outside the city, effectively encircling it. It would seem that if the fascists were not given the government, they would seize it.
The March on Rome
On October 29th a series of telegrams were exchanged between the King in Rome and Mussolini in Milan, culminating in an invitation extended to the Fascist leader to meet the King. On the evening of October 30th, Mussolini arrived in Rome, and met with the King for over an hour. Once an accord was reached in order to form a governing coalition, Mussolini gave word to his supporters to enter the city. Only one column encountered resistance from left-wing militants, but otherwise the city was occupied without difficulty. On October 31st, Mussolini's supporters paraded before the king in their iconic black shirts.
Here we can open a whole discussion as to what Victor Emanuel's motivations were, especially because accounts differ with regards to what precisely was said. Victor Emanuel seems to have been doubtful of the army's loyalty, especially because there was whispering of a secret pact to usurp the throne brokered by Mussolini and the King's cousin the Duke of Aosta, for whom the King harbored a near-pathological jealousy, exacerbated by Duke of Aosta's status as a hero of the first world war. The King had always favored tacit support of the fascist militias against the communists, and it would seem that he didn't see any alternatives once the fascists proved to be (according to him) impossible to stop.
The Mussolini Cabinet
The first cabinet was composed of, in addition to Benito Mussolini as Prime Minister, three fascists, two Catholics, two social democrats, two liberals (from two different parliamentary factions), one nonfascist nationalist, the chiefs of staff of the Army and Navy, and an independent.
On November 16, Mussolini presented his cabinet to the chambers of parliament, and obtained a vote of confidence (306 in favor, 116 against, and 7 abstained). In January 1923, he institutionalized his Blackshirt militias as the "National Security Militia," significantly facilitating the implementation of policy.
Fascist Repression
The following election in April 1924, the fascists obtained 60% of the seats in parliament, and constituted a government without resorting to a coalition. However, the results were contested as fraudulent; as the Blaskshirts had presided over many polling stations, plus a new electoral law passed in November of the previous year was contrived to give a large bonus to whomever won a plurality. Especially harsh criticism came from the leader of the Socialist Party Giacomo Matteotti, who not only contested the legitimacy of the elections before parliament (Matteotti would later be found murdered on June 10th, 1924).
The following election in 1929 the ballots listed only fascist candidates and the voting options were "Yes" and "No." (in theory, if "No" won a second election would be held with pre-approved lists of candidates from other parties). "Yes" gained 98% of votes. The next elections were held with the same system in 1935, and 99% of citizens voted "Yes." These two times, there was no opposition to contest the results, however the consensus is that they were fraudulent.
Sources:
Le origini della guerra civile: L’Italia dalla guerra al Fascismo Fabio Fabbri, (UTET) Turin, 2009.
As for English Sources I'm not sure how how outdated you consider Italy from liberalism to fascism, 1870-1925 by Christopher Seton-Watson, but I'd assume it gives a good overview (my textbooks cite it as an english source).
I'm very sorry I don't know of anything newer in English, I'm not active in academia and believe it or not this sub is my primary source of updates on english-language scholarship. The main problem when discussing post-unification Italian history (and why I avoid it) is that interpretations are still very politicized to this day, and good source material is hard to come by.
Footnotes:
It is unclear how much of this policy was requested by King Victor Emanuel. Certainly, the King was fearful of ending up like the Tzars of Russia at the hands of the communists and was also fearful of using the army, possibly suspecting that the armed forces wanted to depose him in favor of his more popular cousin, the Duke of Aosta.
There even was an attempt to organize a counter-march of moderates, but moderate people unfortunately don't tend to form armed militias.
Translation: LOL no.
King Victor Emmanuel seemed to have come to believe he could use the Fascist's militia to stop both the communists and the army from deposing him. Perhaps he hoped to keep Mussolini in check by parliamentary means. The scheme obviously didn't go as planned.