Surcouf and the cruiser-submarine contradiction

Surcouf's twin 8-inch guns promised efficient attacks on merchant ships, with shells occupying less space and weight than torpedoes. Using the guns required the submarine to surface, while torpedoes could be fired from the concealment in which an ambush submarine was safest. The large guns were intended to destroy targets quickly from beyond the reach of their likely armament. The submarine hull nevertheless provided an unstable gun platform, making accurate heavy-gun fire difficult. Two guns also fell short of the roughly three needed for effective salvo ranging in this period. The design could operate its weapons, but doing so compromised the concealment that justified building a submarine.