Squadrismo (IPA: [skwaˈdrizmo]) consisted of Italian fascist squads, mostly from rural areas, who were led by the ras from 1918–1924. As a movement, it grew from the inspiration many squadristi leaders found in Benito Mussolini, but was not directly controlled by Mussolini, and each squad tended to follow their own local leader. The squadrismo has been described as a “very undisciplined set of local bosses” where Mussolini attempted to assert some type of leadership control, although he had “not appointed” them nor had he usually met them. According to historian Stanley G. Payne, the "new mass Fascism had not been created by Mussolini," but the squadrismo had sprung up around him in rural areas, first starting in northern Italy.
Attempting to imitate Lenin’s October revolution in Italy, socialist and communist elements engaging in strikes, the occupation of factories and stores, seizures of farms, incitement of riots, bombings, and killings. In 1919, several hundred death occurred from political turmoil, mostly resulting from the “activities by Socialists or the army or police. ” Many farmworker strikes attempted to “coerce smallholders as well as laborers into Socialist unions.” Across much of Italy “trains and barracks, banks and public buildings were attacked by mobs,” while many structures were draped in red banners as revolutionaries declared that Italy had “passed wholly into the hands of the Communists.” After a bombing took place, the Socialist deputy Cagnoni praised the bombers for planting the explosives that killed 20 patrons in a crowded Milan theater. The political disorder provoked a violent backlash from the business community, farmers and landowners, who organized a slew of “diverse middle-class defense leagues.” 
Since Giovanni Giolitti, Prime Minister of Italy, had refused to “interfere with either party”, squadristi leaders organized punitive and vigilante “reprisals” under the opinion that they had “to replace an absent or a timid public authority,” but went far beyond the normal type of official action taken to legally discipline criminal acts. The mostly autonomous rural paramilitary squads took the position that “violence could only be met by greater violence,” which lead to violent incidents that began to resemble a civil war.
The first militant group to counteract the violence of revolutionary socialists was the Italian Nationalist Association (ANI), who “organized the first significant nationalist militia” under the blue-shirted Sempre Pronti (Always Ready) banner, leading a planned assault on the Bologna Camera del Lavoro as early as July 15, 1919. They had developed competing squadristi paramilitary units across Italy, and were seen as rivals to Mussolini until 1923. When Mussolini announced his March on Rome in October 1922, the Italian Nationalist Association opposed the march, assuring King Emmanuel III that “their own Sempre Pronti militia was ready to fight the Blackshirts” if they entered Rome. During its early years, the ANI had taken on some of the sheen of revolutionary syndicalism to promote a proletarian nationalism. Its most popular spokesman was Enrico Corradini, who linked leftism with nationalism by asserting that Italy was a "proletarian nation" that had been exploited by international capitalism.
To combat the revolutionary socialists, Fascist squads participated in strikebreaking, organizing tax strikes in socialist controlled towns and intimidating voters at election time. In other incidents, they would humiliate their victims by compelling them to drink large quantities of castor oil, binding their naked bodies to trees, or making them “swallow live toads.” Some targeted socialists were killed, others were “threatened with being clubbed or having their shops set fire” if they failed to stop selling their socialist newspapers. By 1922, prominent ras leaders such as Dino Grandi and Italo Balbo had taken control of many towns in the Po Valley such as Ferrara and Bologna. The squadrismo led a campaign of terror in 1920 and 1921 in northern Italy in which several thousand people were killed, tens of thousands were injured, and tens of thousands were forced to leave.
In an effort to end the escalating violence between the socialist and Squadistsi militias, Mussolini signed an interim Pact of Pacification on Aug. 2 or 3, 1921 with the Italian Socialist Party (PSI) and General Confederation of Labor (CGL), causing most ras in the Northern provinces of Italy to denounce the peace pact. Mussolini had planned to assimilate the mostly self-organizing Squadrismo into his movement, but the violence against socialists was compromising his strategy of not wanting to “lose his position on the left” that included the establishment of a “Fascist Labor Party” or “National Labor Party. 
A number of squadristi leaders voiced opposition to Mussolini’s leadership and plastered posters in the city of Bologna, denouncing “Mussolini as a traitor to Fascism,” Some squadristi paramilitary units completely abandoned Mussolini’s Fascist Revolutionary Party (PFR) and his fasci movement. There were secret anti-Mussolini meetings that fixated on “Mussolini’s lingering leftist loyalties,” which included his leadership of the Italian Socialist Party (1912–1914) and his admiration for Vladimir Lenin. According to historian Richard Pipes, during this turbulent times of infighting, “Mussolini would have been glad as late as 1920–21 to take under his wing the Italian Communists, for which he had great affinities.”
Many prominent ras pushed for new leadership, lending their support to Gabriele D’Annunzio to “replace Mussolini.” Grandi and Balbo sought an audience with radical nationalist D’Annunzio in August 1921, and offered him a position to lead the squadristi in an “insurrectionary march on Rome.” D’Annunzio was vague about in his reply. In September 1919 D’Annunzio and his force of 2,000 armed followers consisting primarily of ex-soldiers marched into Fiume and occupied it for fifteen months.
Mussolini went on the offensive and disparaged the squadrismo, declaring that provincial Fascism was “no longer liberation, but tyranny; no longer protector of the nation, but defense of private interests and of the dullest, deafest, most miserable caste that exists in Italy.” In another terse response, Mussolini warned: “I shall defend this pact with all my strength, and if Fascism does not follow me in collaboration with the Socialists, at least no one can force me to follow Fascism.”
Mussolini was unable to gain significant control over the squadrismo in order to preserve his old alliance of national syndicalists, revolutionaries and Futurists. At the Third Fascist Congress in Rome on Nov. 7–10, 1921, Mussolini was pressured to concede to the majority delegation of squadristi leaders and members, abandoning his plans for a “Fascist Labor Party” and forced to accept the party as an “association of the fasci and their storm squads.” In return for his concessions, Mussolini was recognized as the undisputed leader of the newly renamed National Fascist Party.
The action squads were to become identified by their black shirts, a motif which ultimately coined the name Blackshirts and became the inspiration for Adolf Hitler’s S.A. in the Third Reich. Mussolini and his followers selected the iconic black shirts of the laborers in the Italian cities of Romagna and Emilia, who had originally “adopted their uniforms from the anarchists.”