The sea had become a mass grave by 1941 as Hitler's four capital warships--Scharnhorst, Gneisenau, Tirpitz, and Bismarck, the largest warship on the ocean--roamed the wind-swept waves, threatening the Allied war effort and sending thousands of men to the icy depths of the North Atlantic. Bristling with guns and steeled in heavy armor, these reapers of the sea could outrun and outgun any battleship in the Allied arsenal. The deadly menace kept Winston...