Staggering losses in the Battle of the Atlantic during 1942 led many U.S. Navy officials to believe that Germany’s Kriegsmarine was receiving assistance from Axis sympathizers on the U.S. East Coast and had spies in New York City. To counter this threat, the Office of Naval Intelligence’s (ONI’s) District Intelligence Office (DIO) in the Third Naval District sought assistance from an unlikely ally to help secure the waterfront: the Mob.By using informants from organized crime families, which in this time period were referred to simply as “the underworld,” the DIO was able to secure the waterfront and the coastline around...