The interwar treaty settlement gave the British, American, and Japanese navies equal aggregate submarine tonnage, an unusual parity within a system that limited other categories differently. One proposed explanation is that Britain and the United States recognized how submarines suited Japan's defensive requirements. Another is that confidence in ASDIC and American anti-submarine capabilities encouraged an underestimate of the threat. Some people in the 1930s already believed submarines had been mastered. Submarines continued to evolve, as did aircraft carriers, cruisers, and destroyers.
Notable Point · 46:23-48:36
Treaty submarine parity and confidence in ASDIC
Equal treaty submarine tonnage for Britain, the United States, and Japan raises two possible explanations: Japanese defensive needs and overconfidence in anti-submarine technology.