Japan began a naval war without its support system

Asked for counterintuitive Pacific War facts, the answer stresses that Japan initiated a major naval war before building the training, escort, and replacement systems its strategy required.

Question

What are the most counterintuitive facts about the Pacific War for a newcomer?

Short answer

Japan launched an aggressive naval war before fully preparing carrier and pilot replacement, convoy escorts, or the logistics needed to sustain its decisive-battle strategy.

Notes

Japan entered the war in December 1941 but did not bring its rapid carrier and pilot expansion to full momentum until 1943. It also had not created the yards, escort fleet, or convoy organization needed to protect merchant shipping, despite treaty freedom to build small sloops. The navy sought a decisive campaign while postponing the institutional preparation that might have sustained it. Its planners assumed superior Japanese ships and crews could offset lower numbers, leaving too little margin in destroyers, escorts, and logistics.