Not quite. Max Allan Collins was partially inspired by the Baby Cart Assassin film/manga series (a.k.a. Lone Wolf and Cub), but he based his story more-or-less directly on real events involving Irish gangster John Looney, federal lawman Eliot Ness and Chicago mobsters Al Capone and Frank Nitti. There was a real-life lieutenant of Looney who was betrayed by his superior.
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