If you’re going up against the mob, you’d better have a gang. The New York Police Department put one together back in 1904. New immigrants, and new kinds of crime, were flooding the city and the old Irish cops on the beat didn’t understand either. It was time to launch a special force. They called it “The Italian Squad.”

Paul Moses’ latest book pays homage to these officers in “The Italian Squad: The True Story of the Immigrant Cops Who Fought the Rise of the Mafia.” It’s also a story of ethnic stereotypes, immigration battles, and police brutality. It began one sweltering turn-of-the-century summer, as the city faced a shocking wave of violence.