Though offering a greatly extended range, the IXC/40 was slower to dive and easier to spot on sonar—life-or-death factors for its crew. (Illustrations by Ian Palmer, from New Vanguard #55 Kriegsmarine U-boats 1939-45, by Gordon Williamson, © Osprey Publishing, Ltd.)

Illustrations by Ian Palmer, from New Vanguard #55 Kriegsmarine U-boats 1939-45, by Gordon Williamson, © Osprey Publishing, Ltd.