The Arditi del Popolo was an Italian militant anti-fascist group founded at the end of June 1921 to resist the rise of Benito Mussolini's National Fascist Party and the violence of the Blackshirts paramilitaries. It grouped revolutionary trade-unionists, socialists, communists, anarchists, republicans, as well as some former military officers, and was co-founded by Mingrino, Argo Secondari, Gino Lucetti – who tried to assassinate Mussolini on 11 September 1926 – the deputy Guido Picelli and others. The Arditi del Popolo were an offshoot of the Arditi elite troops, who had previously occupied Fiume in 1919 behind the poet Gabriele d'Annunzio, who proclaimed the Italian Regency of Carnaro. Those who split to form the Arditi del Popolo were close to the anarchist Argo Secondari and were supported by Mario Carli. The formazioni di difesa proletaria later merged with them. The Arditi gathered approximately 20,000 members in summer 1921.
Composed of socialists, anarchists and communists, the Arditi del Popolo were not supported by leftist parties. The Arditi were criticized by the socialist newspaper Avanti! on July 7, 1921, following a demonstration in Rome the previous day. On July 10, 1921, Lenin wrote in the Pravda an article praising the Arditi and criticizing the Bordigan tendency of the PCd'I which opposed militant anti-fascism. On August 3, 1921, the PSI signed a " pacification pact" with Mussolini and his Fasces of Combat on 3 August 1921, while the General Confederation of Labour and the PSI refused to officially recognize the anti-fascist militia. Furthermore, the PCd'I ordered its members to quit the organization because of the presence of non-communists in its ranks. The PCd'I organized by themselves some militant groups, but their actions were relatively minor and the party kept a non-violent, legalist strategy. The Bordigan tendency was opposed by the Marxist philosopherAntonio Gramsci, and many communist activists, who supported the Arditi. In October 1921, the Comintern criticized the "sectarian policy" of the PCd'I, who threatened those of its members who supported the Arditi with disciplinary measures. However, after the alignment of Gramsci and of L'Ordine Nuovo to the PCd'I's direction, the anarchist Umanità Nova newspaper remained the sole mouthpiece of the workers' movement which supported the Arditi del Popolo.
One of the Arditi's most important successes was in Parma in August 1922, when 350 arditi, directed by the World War I veterans Antonio Cieri and Guido Picelli, successfully defended the city against a 20,000-man fascist offensive headed by Roberto Farinacci, who would join the Grand Council of Fascism in 1935, and Italo Balbo, one of the four main planners of the March on Rome. The Arditi benefitted from massive popular support in this task. But with the complicity of state security forces, the fascists assassinated and detained most of the leaders of the anti-fascist movement, which was completely dismantled by 1924.
