Ice, that passage in the novel is based loosely on the real-life Castellemmarese War of 1930-31--but Puzo changed roles and names in some places, and made errors.

Capone played a minor role in the real-life war, which was between Guiseppe Masseria and Salvatore Maranzano for the title of Capo di Tutti Capi. Masseria intended to wipe out the leadership of all the Mafia factions in the US that were led by men from the Sicilian town of Castellemmare del Golfo. Capone was not a Mafioso, nor was his "Outfit" a Mafia family. But since he was the wealthiest and most powerful gangster in Chicago, Masseria tried to enlist his support. Capone sent him some money and paid lip service to his cause. But he did not--repeat, not-- send him any shooters. A good thing, too, since Masseria was killed. Capone's lukewarm support of Masseria left him on good terms with Maranzano and, after Maranzano was assassinated, with Maranzano's successors. In fact, Charlie Luciano, who formed the Commission after arranging for Maranzano's death, appointed Capone as the Commission's first chairman, even though Capone wasn't Sicilian.