British estimates were broadly right about the limits imposed by Japanese industry but wrong about the composition of the fleet being built. Analysts missed Yamato's true displacement and 18.1-inch armament while giving too much weight to reports of conventional battlecruisers. The more damaging blind spots concerned the Type 93 Long Lance and the Imperial Japanese Navy's emphasis on long-range torpedo attack by surface ships and aircraft. Secrecy mattered, but expectations about commerce raiding and foreign shipbuilding also shaped what intelligence officers found plausible. Royal Navy submarines demonstrated that close reconnaissance inside Japanese waters could produce valuable photographs and observations. The passage distinguishes a tolerable error in overall fleet balance from failures to recognize capabilities that would directly shape combat.
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British intelligence misses Yamato and the Long Lance
Andrew Boyd's study contrasts mistaken estimates of Japanese capital ships with more damaging failures to understand torpedoes and aerial attack doctrine.