Japan's neglected need for convoy escorts

Did Japan have an effective answer to the American submarine campaign?

No; it lacked sufficient escorts and should have used treaty opportunities to build many more sloops before the war.

Japanese merchant losses exposed an institutional failure to invest in numerous modest escorts before the war. American submarines imposed enormous damage on a maritime economy that depended on moving resources across long sea lanes. Article 8 offered room for the slower, well-armed sloops needed to protect those routes without consuming limited treaty tonnage. The Imperial Japanese Navy prioritized other combat capabilities and entered the war without enough escort hulls. Once losses accelerated, an effective convoy system could not be improvised quickly enough from the available force.