Several navies were drawn to cruiser submarines by the apparent economy of carrying shells instead of large numbers of torpedoes. Once testing exposed the concept's operational weakness, unusually large boats such as Britain's X1 and France's Surcouf also became national prestige statements. The Japanese I-400 class pursued a different and more promising set of ideas with aircraft instead of repeating the gun-raider formula. Even that alternative required assembling, launching, and recovering seaplanes while the submarine remained exposed on the surface. Technical appeal and prestige could keep such concepts alive after their combat assumptions began to fail.
Notable Point · 40:50-43:03
Prestige kept cruiser submarines attractive after testing
Large gun submarines survived as national prestige projects even though testing exposed their fragility, while Japan's I-400 class pursued a different but still awkward aviation concept.