The world is watching Japan's reaction to North Korea's nuclear test for signs that it may go nuclear itself. Japan, already a virtual nuclear superpower, could build an arsenal ranked only behind the U.S. and Russia. It possesses plenty of fissile material, and its space program's advanced rockets could easily be converted to carry nuclear payloads. The nation also clearly has the financial capacity to join the nuclear club. Finally, Japan's pacifist Constitution could be interpreted to tolerate the possession of nuclear weapons for purely defensive objectives, or for deterrence by retaliation.
Yet, many obstacles stand in the way. First, testing would pose a problem because of the lack of an appropriate explosion site on the heavily populated archipelago, as well as the more remote Pacific islands. It is ironic that the World War II-era Japanese Empire is said to have located its rudimentary nuclear weapons development facilities in what is now North Korea.
Second, a nuclear Japan would most likely accelerate a regional nuclear arms race which could destabilize the status quo in which Japan prospers. A domino effect would spark arms races between China and India and between India and Pakistan.
Third, Japan's prestige as a champion of nuclear disarmament would be irreversibly tarnished. Encouraged by the U.S. in 1993, then Japanese Prime Minister Morihiro Hosokawa declared that he favored an indefinite extension of the Non-Proliferation Treaty (NPT). A nuclear Japan might accelerate the disintegration of the NPT regime, which serves Japan's long-term enlightened interests as a major trading nation that is dependent on global security and stability.
Finally, Japan's nuclearization may jeopardize the U.S.-Japan alliance, should the U.S. regard the move as a challenge to U.S. superiority or a manifestation of Japanese mistrust in the U.S nuclear umbrella. The alliance is key to Tokyo's security strategy, and without it, Japanese security would be threatened and defense outlays would skyrocket.
Accordingly, Prime Minister Shinzo Abe's avowal, "Japan shall not go nuclear," is well taken as adhering to Japan's established non-nuclear policy. This policy reflects not merely the trauma of Hiroshima and Nagasaki, but also a cold calculation of the country's geo-strategic, diplomatic, and economic interests.
True, North Korea's escalating brinksmanship poses a snowballing threat to Japan, but that threat is not yet imminent or existential. North Korea needs several years more, if not a decade, to build effective nuclear warheads and install them on ballistic missiles. Thus, Japan does not need to respond out of panic and can take time to consider its options.
Reasonably enough, Japanese political leaders are accelerating their examination of military policy options against North Korea, and exploring whether the overly pacifist legal arrangements that straitjacket Japan's security policy can be rectified. The Abe administration is considering swift acquisition and deployment of a theater missile defense (TMD) system, and some leaders of the ruling Liberal Democratic Party are actively discussing whether to obtain surgical strike capabilities, from which Japan has abstained.
Regrettably the TMD shield is at best porous, due to technological imperfection. Surgical strike capabilities also may not satisfy in the event of conflict, as Japan's intelligence organs would be unable to locate many of North Korea's underground nuclear facilities and mobile missile launchers. Thus, Japan's next-generation passive and active defense capabilities are only marginally effective.
Public opinion is dynamic, and it is difficult to predict Japan's ultimate decision on nuclear weapons. However, the threat from North Korea is likely to worsen, and the Japanese government and public may begin to favor a domestic nuclear capability. The U.S. is well advised to recognize this possibility, and to look beyond the simple dichotomy of endorsing or attempting to forbid a Japanese nuclear program. There is a third way for Japan to deal with the North Korean threat, if it becomes imminent and existential.
In exchange for a vow from Tokyo to not develop an indigenous nuclear weapon, the U.S. should agree to lease 100 or 200 tactical nuclear warheads to Japan. Japan can afford the economic burden, it possesses the military sophistication to maintain-and if necessary to launch-nuclear warheads, and it has proven over 60 years that it is a responsible and mature democracy. Potential risks are also manageable: the U.S. would retain control of the electronic maps (TERCOM) loaded into the cruise missiles on which the warheads are installed, and the missiles could be launched only with U.S. consent. Furthermore, the leasing agreement would contain a sunset clause, mandating that Japan return the warheads to American control when the rising threat from North Korea wanes.
Such a solution is not without precedent, as the U.S. and Canada attempted a similar program to counter the Soviet threat in the1960s. More importantly, this arrangement would avoid upsetting the global security order, as a demonstrated Japanese nuclear capability could, and would satisfy a likely Japanese need for a greater sense of protection from North Korea.