The men aboard USS Jack (SS-259) knew the sea was watching. The South China Sea, under a blanket of storm clouds and shrouded moonlight, offered the perfect cover for a night attack—and the perfect trap if they were spotted.

In was the early hours of June 30, 1944, the boat had been tracking a large enemy convoy spotted on the previous day. Radar and periscope observations had revealed three groups of ships steaming eastward, each guarded by alert Japanese escorts. The crew had worked out the speed and bearing. Now it was time to strike.