The A7M question leads into the danger of judging Japanese weapons by stereotype. Japanese planners had explored submarine-borne aircraft since about 1922 and accumulated roughly two decades of experience operating seaplanes from submarines. The I-400's aircraft spaces were heavily sealed and compartmented, so the concept was not an improvised novelty even if its strategic use remained questionable. Allied observers were more willing to believe German performance claims than comparable Japanese and Italian claims. Institutional learning and intelligence bias matter here as much as the submarine itself.
Notable Point · 37:49-40:46
I-400 grew from two decades of submarine-aircraft experience
The I-400 was the mature end of a Japanese submarine-aircraft line dating to the early 1920s, and Allied dismissiveness risked obscuring that accumulated experience.