On May 1, 1947, in Portella della Ginestra, a town in the province of Palermo, Labour Day turned tragic. Thousands of farmers, families, and left-wing activists had gathered to celebrate May Day and, above all, the recent electoral success of the People's Bloc, the united list of Communists and Socialists, in the Sicilian regional elections of April 20. It was a moment filled with hope, with agrarian reforms, the end of large estates, and greater rights on the horizon. Farmers occupied uncultivated land in the Sicilian countryside and demanded the implementation of the Gullo Decree, which temporarily authorised the assignment of uncultivated and underused land. This alarmed landowners, the Mafia, and conservative sectors.

Suddenly, machine-gun fire erupted from the surrounding hills for several minutes, and panic ensued. Fire struck the defenceless crowd, killing 11 people, including women and children, and injuring dozens. The actual perpetrators were the bandit Salvatore Giuliano, who claimed responsibility for the attack as an act against the communists, but doubts and suspicions immediately arose regarding the instigators and cover-ups. The massacre was not an isolated incident of banditry, but the climate was already charged with political and social tension: peasant struggles were challenging the power of large landowners, while the advance of the left was frightening large sectors of the state and the elite. It thus became a violent signal to halt change.

The trials never fully revealed who ordered the massacre. Giuliano died in a firefight in 1950, and his lieutenant, Gaspare Pisciotta, was later poisoned in prison after making accusations. Much of the truth was lost with them, leaving enduring questions. The Portella della Ginestra massacre marked the beginning of political violence shaping Italy's destiny, and is seen by some as the start of the country's tumultuous "strategy of tension."