[3][4] As a lawyer he successfully defended the party newspaper La Voce Repubblicana against a defamation lawsuit, after an article had accused high-ranking Fascist Italo Balbo of having ordered the assassination of anti-fascist priest Giovanni Minzoni.

While in Switzerland he maintained contacts with the Giustizia e libertà group and offered logistical support to various anti-fascists, including Sandro Pertini, to whom he procured a counterfeit passport, and Giovanni Bassanesi and Gioacchino Dolci, who flew over Milan in July 1930 to throw propaganda leaflets.

Pacciardi's original intent was to organize a non-political volunteer group at direct disposal of the Popular Front government, on the model of the Garibaldi Legion which had helped France in the early phases of World War I.

Through the good offices of other exiled anti-fascists like Socialist Pietro Nenni and Communist Luigi Longo he received a hearing from Francisco Largo Caballero in early September 1936, but the Spanish Prime Minister wasn't interested in the proposal and only changed his mind when the Comintern decided to establish the more sizeable and better-funded International Brigades.

In May 1937, when the "Garibaldi" was asked to suppress anarchist and POUM fighters in Barcelona as part of internal purges of the Republican camp, Pacciardi instructed acting commander Carlo Penchienati to refuse.

Finally, at the urging of Penchienati and Nenni, Pacciardi accepted the post of vice divisional commander for the duration of the next offensive, as a gesture to improve the unity and morale of the brigade.

[5] Sources more sympathetic to the Communist point of view have also blamed his departure on his adherence to traditional models of military leadership, like the separation between officers' and troops' quarters, as well as the leave request, which has been interpreted as unviable in the context of the war effort or even as an outright proposal to dissolve the brigade rather than accept a reduction of personal authority.

Forced to flee by the German invasion of France, he and his wife finally reached New York aboard the liner Serpa Pinto on 26 December 1941, after traveling through Algiers, Casablanca and Mexico with false documents.

In the United States Pacciardi supported the unsuccessful efforts of the Italian-American Mazzini Society, of which he had been a member since its founding in 1939, to organize volunteer groups to take part in World War II on the Allied side.

Despite his growing dislike of Communism, during this time Pacciardi pursued a line of cooperation and unity between all anti-fascist forces, which was a cause of friction with the rest of the Society and ultimately prompted him to resign his membership.

He supported Giovanni Conti's hardline opposition to any form of cooperation with the Italian monarchy, which put Republicans at odds with the other anti-fascist parties, who were organized in the National Liberation Committee and held ministries in the royal government.

With the end of the Italian monarchy the Republican Party entered a coalition government for the first time, with Cipriano Facchinetti serving as Minister of War in the De Gasperi II Cabinet.

[13] By December 1947, however, Pacciardi changed his position due to a growing perception of the Soviet threat, and became deputy Prime Minister along with Liberal Luigi Einaudi and Social Democrat Giuseppe Saragat.

[16] In 1963, when Christian Democratic leader Aldo Moro set up a cabinet that included PSI ministers for the first time in sixteen years, Pacciardi voted against it in dissent with his own party and was expelled from PRI.

[19] Violante claimed that the plan would have seen Pacciardi lead an emergency program which would have dissolved Parliament, established a single legal trade union, abolished parliamentary immunity, banned left- and far-right parties and set up concentration camps and special tribunals for high-profile politicians.

In its promoters' view, while PCI and the neo-fascist Italian Social Movement would have been outlawed, the government would have been overall respectful of civil liberties and only held power for a limited time, something that has been questioned by commentators like political philosopher Norberto Bobbio, who had exchanged numerous letters with Sogno in previous years.

[23] Conservative journalist Indro Montanelli dismissed the accusations as libelous, spread by the left against a political opponent,[24] and supporters have suggested that the actions of the former PRI leader were always meant to be within the framework of the Italian Constitution.