The Republic of Korea (ROK) and Japan are the two most important US allies in Asia. The Defense Department has dubbed the US-ROK alliance the “linchpin of peace and prosperity” and the US-Japan alliance the “cornerstone of peace and security.”

But the alliance system can only realize its full potential — and confront major regional and global challenges — if the third side of the strategic triangle, Japan-ROK relations, functions well. Strained relations and wavering US commitment to the region, however, threaten to weaken the US-led alliance architecture in Asia.