On a crisp May morning in 1939, the crew of the USS Squalus set out from Portsmouth, New Hampshire, unaware that they were about to write one of the most remarkable chapters in submarine history. The Squalus was new. She was sleek, modern, and powerful. A Sargo-class submarine, she had been launched only the previous September, and commissioned into service just two months before. Her commander, Lieutenant Oliver Naquin, a Naval Academy graduate and seasoned submariner, had a reputation for discipline, attention to detail, and the quiet confidence needed to lead a crew through the perilous underworld of undersea warfare.