This procurement counterfactual concerns a design Japan did not select. The I-400 aircraft-carrying concept was an expensive way to deliver a small air strike. Redirecting those resources toward conventional long-range submarines with many torpedoes and a practical four-inch deck gun could have created a more persistent threat. Such boats might have remained off the American coast instead of depending on one elaborate aircraft mission. The comparison weighs operational persistence and weapon volume against technological novelty.
Notable Point · 2:04:25-2:05:14
A long-range submarine alternative to the I-400 class
The resources devoted to aircraft-carrying I-400 submarines could have produced more useful long-range attack boats for operations off the United States.