German U-Boat Crews, 1914-45 by Gordon Williamson
U-boat crews were an elite part of the German Navy, fighting the elements as well as enemy destroyers. In both World Wars they strangled the vital transatlantic supply line that fed the war effort. But there were always too few U-boats and too many destroyers, and life expectancy in the submarine fleet was short as they fought an uneven contest in the icy seas of the North Atlantic.