Japan's strategic depth lies at sea

Two Hyugas and two Izumos gave Japan four helicopter-destroyer hulls, enough to keep one at sea and another available while the rest trained or maintained. Carrier-based air defence places heavier demands on that small force because Japan has little strategic depth on land. Its depth lies in surrounding seas, where protected sea lines of communication provide routes for resupply and manoeuvre rather than merely marking territory. Japan may eventually order another pair of aviation ships, even though no direct successor was then listed. LHD projects had been under discussion since 2014, and one plausible option is a ship between the Canberra and America classes that could combine F-35B operations with well-deck amphibious capacity. More flight decks and well decks would let Japan place a defended task group in one of its disputed maritime zones, turning hull availability into practical deterrence and crisis-management capacity.