Every Sunday, he recited his catechism before the countess and if he did well, he received a silver coin, which he recalled as "generous but humiliating".

The socialist paper in the town was edited at the time by Benito Mussolini, later the Fascist dictator of Italy.

Nenni was arrested in 1911 for his participation in a socialist protest against Italy's imperialistic war in Libya alongside Mussolini and was imprisoned for seven months.

[4] When the war was over, Nenni founded, together with some disillusioned revolutionary ex-servicemen, a group called "Fascio", which was soon dissolved and replaced by a real Fascist body.

In 1923, after the Fascist March on Rome, Nenni became the editor of PSI's official organ, Avanti!, and engaged in antifascist activism.

Nenni had worked in Paris as a correspondent of the Avanti in 1921 and had become acquainted with Léon Blum, Marcel Cachin, Romain Rolland and Georges Sorel.

In the early 1960s, Nenni facilitated an "opening to the centre-left" enabling coalition governments between the PSI and the Christian Democrats and leading the socialists back into office for the first time since 1947.

[7] He formed a centre-left coalition with Saragat, Aldo Moro and Ugo La Malfa, and favored a reunion with the PSDI.

[citation needed] Although the reunification attempts between the socialists and Giuseppe Saragat's breakaway Social Democrats resulted in the formation of a joint list Unified PSI–PSDI, both parties fared poorly in the 1968 Italian general election.

[8] He resigned as head of the PSI and was made a senator for life in 1970 and in 1971 he ran unsuccessfully for President of Italy.