When the Navy learns that Japanese freighters are hugging the coast of Japan in order to evade US submarines, the Trigger is sent to the area to lay mines to force Japanese shipping out into deeper waters. USS Trigger (SS-237) a Gato-class submarine. From 3 Dec 1942 to 22 Jan 1943, the submarine conducted a combined minelaying and offensive patrol, in waters surrounding Japan. On 20 December, she began planting a minefield off Inubo Saki, Honshu. Trigger planted the northern half of the field and was working on the southern part when a cargo ship passed her, heading into the newly-laid mines. Five minutes later, a violent explosion rocked the captain of the Trigger gets to see the freighter while an escort circled her. The submarine later heard another explosion from the direction of the minefield and, when she surfaced the next day, found the field was covered by smoke.