Japan’s reported proposal to merge the Korean Peninsula, East China Sea and South China Sea into a single operational theater with the U.S. military, combined with the Pentagon’s quiet upgrade of U.S. Forces Japan (USFJ) into a joint warfighting command, risks locking South Korea out of the region’s emerging security architecture at a moment when Seoul is politically unprepared to respond.

With former President Yoon Suk-yeol removed from office and Acting President Han Duck-soo serving in a limited caretaker capacity ahead of the June 3 snap election, key decisions shaping the future of South Korea’s defense posture are being made elsewhere.