The Utility of Nuclear and Conventional Forces in the Second Nuclear Age: A Japanese Military Perspective

In the recent debate on Japan’s security policy, the proliferation of WMD and their delivery means, such as missiles, has been one of the central issues. This issue is particularly critical to Japan, given North Korea’s acceleration of its nuclear weapons program alongside its long-range missile project. Japan’s new National Security Strategy (NSS) and National Defense Program Guidelines (NDPG) focus on both nuclear proliferation and the emerging nuclear threat posed by North Korea. At the same time, tension between Japan and China in the East China Sea has been increasing, while tensions between China and countries in the South China Sea have similarly been on the rise.

This essay will present a Japanese perspective on the nuclear dimension of regional security by, first, explaining Japan’s nuclear-related policies; second, discussing the roles of nuclear forces in Japan’s security policy; and, third, exploring Japan’s security strategy for managing a possible stability-instability paradox in the region, with particular emphasis on the East China Sea.

Japan’s Non-Nuclear Policy and Nuclear Forces

One of the most important aspects of Japan’s security policy since World War II is its non-nuclear policy based on the “three non-nuclear principles,” referring to the principles of not possessing nuclear weapons, not producing them, and not permitting their entry into Japan.¹ Not only does Japan adhere to these three principles as fundamental elements of its national policy, but Japan’s Atomic Energy Basic Law also prohibits the country from manufacturing or possessing nuclear weapons. Furthermore, Japan ratified the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in June 1976 and put itself under strict obligation not to produce or acquire nuclear weapons as a non-nuclear weapons state.

Japan’s possession of nuclear weapons, however, is not necessarily restrained by its constitution. While designed to make the nation as peaceful as possible, the constitution does not exclude outright Japan’s pursuit of nuclear options. The government’s basic interpretation is that Article 9.2 of the constitution does not prohibit the possession of force that is within the minimum range necessary for self-defense.² Therefore, if the weapon in question, whether conventional or nuclear, is within these bounds, it is not constitutionally banned. If thus confined to the minimum necessary level for self-defense, the possession of nuclear weapons is considered constitutional for Japan. Here it should be noted that the minimum necessary level applies to the limit of individual self-defense and does not include collective self-defense in the government’s interpretation of the constitution.

The Role of Nuclear Forces in Japan’s Security Strategy

Japan has continuously relied on the United States to deter nuclear threats against itself and has maintained that “the extended deterrence of the United States with nuclear deterrence at its core is indispensable.”³ At the same time, conventional elements of deterrence have become more important in recent years with dramatic improvements in technologies such as ballistic missile defense and precision-guided weapons. U.S. reliance on conventional elements of deterrence has increased alongside the reduction in the size of the U.S. nuclear arsenal. Furthermore, as Japan improves its ballistic missile defense and other capabilities for deterrence by denial, it no longer needs to depend solely on nuclear forces to maintain credible nuclear deterrence. Although Japan currently has no intention of acquiring nuclear weapons, it is worth exploring why Japan would not be better off possessing its own nuclear option. This section of the essay aims to clarify the utility of nuclear weapons for Japan from a military point of view based on Robert Art’s analysis of the different roles of force: deterrent, defensive, compellent, and swaggering use.

Deterrent use of nuclear weapons

According to Art, the deterrent use of force is “the deployment of military power so as to be able to prevent an adversary from doing something that one does not want him to do and that he might otherwise be tempted to do by threatening him with unacceptable [End Page...