The time-and-range problem begins when a large submarine surfaces, clears its guns for action, and approaches a convoy or armed merchant ship. Surcouf needed roughly three minutes and thirty-five seconds to prepare after surfacing, while its practical fire-control range was far shorter than the nominal reach of its 8-inch guns. A closing destroyer could enter effective range before the submarine was ready, and even an armed freighter could return fire during the approach. Any shell damage to the pressure hull might prevent submergence, giving the cruiser submarine an even more dangerous glass jaw than a surface raider. Gun ammunition looked cheaper and more compact than torpedoes, yet the operating concept exposed the submarine's greatest vulnerability precisely when it needed to fight.
Chapter · 28:08-43:03
Surcouf and the cruiser-submarine glass jaw
Surcouf's 8-inch guns promised economical commerce raiding, but slow action preparation, limited fire control, weak protection, and closing escorts made the concept dangerously fragile.