The Japanese ship Montevideo Maru wasn’t marked as carrying POWs, and on July 1, 1942, a U.S. submarine fired four torpedoes, sinking the vessel in less than 10 minutes.The Japanese ship Montevideo Maru wasn’t marked as carrying POWs, and on July 1, 1942, a U.S. submarine fired four torpedoes, sinking the vessel in less than 10 minutes.