On the afternoon of February 9, 1942, smoke billowed over Manhattan’s west side as a fire consumed SS Normandie, a huge French luxury liner being converted into an American World War II troop transport. Although witnesses reported sparks from a worker’s acetylene torch started the blaze, many feared Nazi saboteurs were to blame, particularly in light of the arrest of 33 German agents in the Duquesne Spy Ring only months earlier. In the inferno’s wake, the U.S. Office of Naval Intelligence became so concerned about enemy spies operating along New York’s waterfront that it enlisted a most unlikely partner in the war effort—the Mafia.

In March 1942, with the recruitment of Fulton Fish Market kingpin Joseph “Socks” Lanza, Naval Intelligence officers launched the top-secret “Operation Underworld.” Lanza agreed to furnish union cards to agents operating undercover in the market and aboard coastal fishing fleets. Authorities were particularly concerned that pro-fascist sympathizers of Germany’s top ally, Italian dictator Benito Mussolini, lurked among the Italian immigrants who worked as longshoremen in New York.

However, Lanza explained that their cooperation could be secured by the imprisoned mobster Charles “Lucky” Luciano, who still wielded absolute power on the docks even after six years behind bars. With his top aide Meyer Lansky acting as an intermediary, Luciano agreed to assist the government and ordered his capos to act as lookouts and report any suspicious activity. Luciano’s contacts even assisted in the Allies’ 1943 amphibious invasion of Sicily by providing maps of the island’s harbors, photographs of its coastline and names of trusted contacts inside the Sicilian Mafia, who also wished to see Mussolini toppled.

Still, with between 20 and 40 years left on his sentence, Luciano filed a petition for executive clemency on May 8, 1945—the same day World War II ended in Europe. Ironically, the man who had prosecuted the mobster a decade earlier, New York Governor Thomas E. Dewey, pardoned Luciano in January 1946 due to his assistance in the war effort and ordered him deported to his native Italy.

The ultimate effectiveness of “Operation Underworld” has been questioned, but no other ships suffered the same fate as Normandie for the duration of World War II.