The German submarines that sank over 8,000 merchant vessels and nearly brought victory to Germany get their first due in a 30-year chronicle, based on eyewitness accounts, interviews with U-boat aces, and research in just-released German naval documents. Over 100 photos, charts, and diagrams show the strategic and tactical evolution of U-boat offensives in both WWI and WWII, with records of losses on both sides, along with technical advances and methods used for defending against them.