Submarines played a major role in the war at sea in the years 1939-45, and this major reference book describes all the classes of vessel that were deployed by the eighteen combatant nations during those years. They were responsible for the sinking of 33 million tons of merchant shipping, with the German and U.S. navies achieving the greatest advantage with this devastating strategic weapon. This new edition of a classic work has been completely redesigned and overhauled to make the most of the author's superb collection of photographs and will appeal to a wide new audience for whom this important work has been unavailable for many years.