Withdrawing the US commitment
to Japan’s defense could change Japan’s strategic calculus
—
and profoundly alter the security dynamics of
the entire region
The prospect of an American president who would withdraw the longstanding US commitment to Japan’s defenses, urging Tokyo to go it alone, challenges every aspect of Japan’s strategic
calculus. For those in Japan who have chafed against dependency on the United States, Trump’s blithe statement that Japan would ultimately end up a nuclear power anyway seems to validate their argument that the United States
would betray Japan in the end. The debate in Japan would not necessarily lead to the decision to acquire nuclear weapons; it is equally possible that the US retreat from its commitment to Japan would open up a debate over a
variety of choices, including an alliance with another nation in Asia, a neutral or unaligned state, or a reorganization of Japan’s military for autonomous defense. Popular opinion would not naturally shift to support for the nuclear
option. Whatever choices are debated within Japan, other nations in Asia would be highly sensitive to a Japan untethered from the United States. A kaleidoscopic series of changes in attitudes in Seoul, Beijing, and Tokyo would
result. It is too difficult to consider all possibilities, but South Koreans would be particularly anxious about Tokyo’s choices. Should the US simultaneously end its longstanding alliances with both Japan and South Korea, as Trump has
suggested, Northeast Asia would be transformed. Popular sentiments in both Japan and South Korea have become very sensitive to each other, and a potent cycle of reactive nationalism could result. Seoul’s choices would feed into
the Japanese debate. Seoul might see acquiring nuclear weapons as its only path forward for coping with a nuclear North Korea. Or it could seek greater accommodation with Beijing. A South Korea under the protection of China
would strengthen Japanese calls for an autonomous military capability, including discussion of a nuclear option if Tokyo planners felt the Seoul-Beijing links were antagonistic to Japan. Greater strategic cooperation between Beijing
and Tokyo could also result, with a condominium of China, South Korea, and Japan emerging to challenge US interests in the Pacific. Whether nuclear proliferation would result, or whether America’s non-nuclear allies would seek
nuclear protection elsewhere, Asia’s geostrategic balance would undergo tremendous change. The Japanese people may not change their opinion on nuclear weapons, and their leaders may resist the impulse to acquire them. But
Japan’s neighbors will likely hedge on the possibility that Japan will return to its status as a fully autonomous military power.
