With the acrobatic and unconventional interactions between U.S. President Donald Trump and North Korean leader Kim Jong Un, the world’s attention is now fixed on the prospect of North Korea’s nuclear disarmament.

The success or failure of the coming negotiation process remains to be seen, particularly given the two top leaders’ seemingly unpredictable egos. Yet, whichever way it ends, the postwar international order of the Asia-Pacific region will eventually collapse or disintegrate into a chain of ensuing strategic interactions across the region. Most likely this will be manifested as the “Japan question” due to the country’s role as a linchpin within the regionwide U.S. hub-and-spokes system of bilateral alliances. Why is that?

A successful outcome to the negotiations means the North’s nuclear disarmament in exchange for U.S. assurance of the Kim regime’s survival. This involves the replacement of the 1953 Korean Armistice Agreement with a peace treaty, depriving the U.S. military presence in South Korea of its raison d’etre. The change will naturally lead to a withdrawal of U.S. forces and an eventual termination of the existing U.S.-South Korea alliance.

The Japan-U.S. alliance is inseparably linked to the U.S.-South Korea alliance. Major U.S. military bases in Japan are designated to serve as U.N. bases in the event the United States serves as the lead nation of U.N. forces in Korea with wartime operational control. At the time of a North Korea contingency, therefore, the U.S. will use these bases for forward deployment, power projection and logistic support, while the U.S. forces in South Korea will function as a trip wire.

This structure evolved during the process that took place from Japan’s defeat in 1945 to the U.S.-led Occupation and Japan’s new independence in 1952, which was made possible by the concurrent conclusions of the San Francisco Peace Treaty and the Japan-U.S. Mutual Security Treaty. The process overlapped significantly with the Korean War (1950-1953), Japan’s remilitarization in 1952 and the conclusion of the Japan-U.N. Status of Forces Agreement of 1954. These pieces constitute an integral whole. Therefore, when one of them is pulled out the structure doesn’t hold.

More concretely, a withdrawal of U.S. forces from South Korea will likely lead to a significant reduction of U.S. forces in Japan and, possibly, a total withdrawal while retaining their access to those bases in the event of a Japan contingency. Such a trend is already seen in the U.S. Marine Corp.’s significantly hollowed-out presence in Okinawa, which has resulted from rotational deployment.

Obviously, with huge cumulative debts that are still growing fast, the U.S. is becoming less fiscally able and politically willing to continue its defense commitment to its allies. President Barack Obama stated that “America is not the world’s policeman.” Trump’s “America First” is merely an outright expression of this systemic constraint. When the decline is more serious, therefore, the U.S. will possibly withdraw its defense commitment to Japan. Then the country will need its own nuclear deterrent against major nuclear powers, especially China.

Alternatively, a failure of the negotiations will mean the North’s completion of nuclear ballistic missiles in the near future that can reach the continental U.S. It is unlikely that the U.S. would launch a pre-emptive strike against these missiles, because it involves the high risk of a North Korean retaliation, and Japan’s megalopolises and U.S. bases might suffer nuclear attacks. Once these missiles are completed, the U.S. extended nuclear deterrence will become far less credible, driving Japan to possess a minimum deterrence to patch the porous U.S. nuclear umbrella.

In either way, Japan will be pressed to be more self-reliant in the best-case scenario and strategically independent in the worst, which would necessitate that it go nuclear. This course of action seems plausible, although the speed and magnitude of Japan’s nuclearization will depend on the state of America’s relative decline.

To avoid such a course, Japan would most likely seek recourse in a multilateral security treaty system that could replace the existing Japan-U.S. alliance. Such an option is reminiscent of the post-World War I Washington Treaty System (1921-1936), which was designed in vain to underpin the Asia-Pacific security order. The system consisted of the Nine-Power Treaty for China issues and the Four-Power Treaty for Pacific issues.

Yet, the system existed only on paper and did not function well in spite of Japan’s reliance on it because the other parties merely passed the buck to one another without shouldering any significant security burden.

Behind the course of events was the Anglo-U.S. competition between a hegemonic power experiencing acute relative decline and a rising challenger power. To avoid a war, the two had to replace the Anglo-Japan alliance with the Washington Treaty System, even though the alliance had long served as the backbone of Japan’s security and the regional status quo.

The past Anglo-U.S. rivalry shares significant parallels with the present U.S.-China competition, which not only puts Japan in a strategic predicament but also jeopardizes the regional security order. Japan and the world should prepare for a grave structural crisis.

Masahiro Matsumura is a professor of international politics and national security at St. Andrew’s University (Momoyama Gakuin Daigaku) in Osaka.

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