A long-range raider with six or more forward torpedo tubes

A more workable cruiser-submarine concept would make long-range commerce raiding its purpose and torpedoes its main weapon. Torpedoes still had problems as the Second World War began, but continuing development made a larger torpedo load worth considering. The suggested boat would fire six or more torpedoes forward and carry two to three reloads per tube. The reloads would require a large, heavy submarine, whose endurance could make it useful in the Pacific or Indian Ocean. An Indian Ocean cruise from Alexandria illustrates the distances envisaged. A large gun would still demand seakeeping and target visibility that the submarine could not supply at a safe fighting distance. To use it effectively, the submarine would risk entering decisive escort range, or a battleship's secondary-armament range if it attacked a battle line.