Will America's Asian Allies Go Nuclear?

How to keep South Korea and Japan's atomic ambitions in check

In Northeast Asia, where national security still overwhelmingly dominates the perspectives and behavior of states, nuclear proliferation, both vertical and horizontal, is gaining stronger momentum. China’s recent but substantial investment in modernizing its nuclear arsenal and improving its reprocessing capacity is alarming its neighbors, as well as the United States. The nuclear pursuits of North Korea and, in particular, the acceleration of nuclear and missile tests seem to be spiraling, whereas diplomatic efforts to stop Pyongyang's nuclear path have been futile to date. In addition to its fourth nuclear test in January 2016, a series of missile and rocket tests and the recent firing of a submarine-launched ballistic missile (SLBM), Pyongyang is reportedly preparing another nuclear weapons test in the coming months.

However, China and North Korea are not the only countries in Northeast Asia that are a cause for concern to the international community. Two close U.S. allies with advanced nuclear technology, South Korea and Japan, are also considered potential nuclear powers that might be able to develop a nuclear arsenal within a relatively short time frame, should they decide to do so. Growing concerns about nuclear proliferation in the region have cast doubts about whether these U.S. allies will continuously stay out of the military nuclear race. If South Korean and Japanese leaders came to be placed under more serious internal or external pressure due to growing military tensions, they might be tempted to pursue less restrained policy decisions about nuclear armament.

Under the current circumstances, it is widely assumed the two countries have no incentive to develop their own nuclear weapons as they are protected by U.S. extended nuclear deterrence. North Korea’s nuclear tests, though, have not only threatened them, but also changed geopolitical calculations about nuclear weapons in the region. Located at a distance that North Korea’s short- or medium-range missiles can reach, South Korea and Japan are directly threatened by Pyongyang's military provocations, whereas the mainland United States cannot be targeted with North Korea’s current intercontinental ballistic missile technology. In the near future, U.S. allies might become more suspicious about the United States’ commitment to its allies as the dynamic of alliance politics is changing. For instance, the increasing possibility that Donald Trump, asserting that U.S. allies should take more responsibility for their defense and even develop their own nuclear weapons, may become the Republican presidential candidate, is troubling for these countries. The Japanese government promptly reacted to Trump’s statement saying that “[i]t is impossible that Japan will arm itself with nuclear weapons,” which was an unusual response to a foreign-policy pledge made by a prospective presidential candidate overseas.

Some policy experts argue that South Korea and Japan would not attempt to join the nuclear club regardless of their level of nuclear capability. The decision to go nuclear would certainly bring a major risk of political and economic isolation. Moreover, as previous U.S. administrations have done, Washington would not simply let them develop their own nuclear weapons. Currently, there is no reason to believe that the United States would risk losing its influence in the region and stand by growing military tension and domino effects caused by nuclear newcomers. Needless to say, South Korea and Japan, both state parties to the Nuclear Nonproliferation Treaty (NPT), would not want to join North Korea as the only country having ever withdrawn from the treaty which they have been upholding for almost half a century. Finally, Japan’s own experience with atomic bombs in the Second World War is another aspect to be considered; antinuclear sentiments are deeply rooted in the identity of many Japanese, and the Japanese government might not willingly abandon its position as the only “victim” of a nuclear attack by pursuing nuclear armament.