Japanese midget subs which attacked Pearl Harbor OTD 1941 are generally underrated
I think that it is a symptom of the way that they were portrayed by US forces at the time. Partly propoganda (understandable, not judging) and partly because the US Navy doctrine didn't appreciate or particularly understand the potential of midget submarines. Also because later Japanese midget submarines were suicide craft and those are the ones history remembers more(?).
The popular account of Pearl Harbor records that the attack started at 0748hrs local time on 7th December 1941 when hundreds of Imperial Japanese Navy (IJN) aircraft appeared over the anchorage and started their attacks. This simplistic version of events suffices for school textbooks and Hollywood movies but the military engagements actually started nearly five hours earlier at 0357hrs. And these first encounters were not against aircraft, but a midget submarine.
The japanese Ko-Hypteki two-man sub was technologically advanced and incredibly fast and long ranged for an all-electric boat even today. And it could be launched from a submerged host submarine which was also a first in Special Forces history and is something which few current dry subs can do (even the latest S351 DCS being bought by US Navy (/USSOCOM) cannot.
Japan's weakness was that the crews made these attacks one way missions and there wasn't enough of a trained pipeline of crew to keep up the momentum.
Counter-views welcome. My article on Ko-Hyoteki ift.tt/2BR3GvZ