カステランマレーゼ戦争
Through his Mafia boss allies Magaddino and Gaspar Milazzo, Aiello arranged a meeting with Joe Masseria, the capo di tutti capi based in New York City, seeking support in Aiello's efforts against Capone. During the meeting Masseria offered to support Aiello in exchange for control of the east side of Chicago, which would allow Aiello to keep the city's west side. The offer infuriated Aiello, who threatened Masseria and ordered him to leave the city. In turn, Masseria spread false rumors that Aiello attempted to kill Masseria, giving him a pretext to support Capone in retaliation. Mafioso Joseph Bonanno later described as a key incident in starting the Castellammarese War in New York City. Masseria openly supported Capone, requiring a strong alliance with him following the death of Masseria ally Giuseppe Morello. He also offered territory to Milazzo if he betrayed Aiello, an offer Milazzo rebuffed and considered insulting. As a result, Aiello backed Salvatore Maranzano in the Castellammarese War, providing the Maranzano forces with $5,000 a week for their war chest.