“For half a century, ACA has been providing the world … with advocacy, analysis, and awareness on some of the most critical topics of international peace and security, including on how to achieve our common, shared goal of a world free of nuclear weapons.”

– Izumi Nakamitsu
UN High Representative for Disarmament Affairs
June 2, 2022
Not Going Nuclear: Japan’s Response to North Korea’s Nuclear Test
Share this

Hajime Izumi and Katsuhisa Furukawa

Since North Korea’s nuclear test on October 9, 2006, there has been considerable foreign speculation that the explosion might prompt Japan to develop its own nuclear weapons arsenal. These views do not reflect the relatively restrained reaction in Japan itself. Although the test helped break a public taboo on discussing the possibility of a Japanese nuclear capability, there is little serious desire to replace the U.S. nuclear umbrella with a homegrown nuclear option.

Indeed, the discussions themselves may have been aimed in part at shoring up the credibility of U.S. extended deterrence. Rather than relying on nuclear weapons, Japan’s security policy seems more geared toward strengthening cooperation with the United States while shoring up global nonproliferation efforts.

North Korea’s nuclear test certainly shocked the Japanese public. Just after the test, an Asahi Shimbun poll found that 82 percent of the respondents were “concerned.” Some 44 percent of those polled felt a “strong threat” from North Korea, and 38 percent felt “some level of threat.” It seems, however, that such concerns were neither deep nor sustained. The Japanese public in general did not demonstrate active interest in taking any specific measures, such as establishing underground shelters. Rather the Japanese media focused primarily on the radioactive contamination risks the test might pose to Japan. Having recognized that such risk was almost nonexistent, the public interest on this issue faded away promptly.

After November 2006, the Japanese media’s coverage of North Korea focused more on Pyongyang’s decades-old abduction of Japanese citizens than concern over North Korea’s current nuclear weapon programs. There is a view among some experts that the Japanese public’s “sense of loathing” toward the Kim Jong Il regime may have overridden its perception of the threat emanating from North Korea’s missiles and nuclear-weapon programs.

The Japanese government also has been restrained in several regards in its response to the tests. First, although it imposed sanctions on North Korea, Tokyo appears to place a higher priority on the abductions matter. Following his 2006 inauguration, Japanese Prime Minister Shinzo Abe quickly established within his cabinet an office to manage the abductions issue. Abe did not create an equivalent office to address Pyongyang’s nuclear or missile programs, despite his repeated statements that North Korea’s nuclear weapons presented the gravest threat to Japan, nor was any voice raised among the Japanese media in support of establishing such an office.

Second, Tokyo remains reluctant to negotiate with North Korea on ballistic missile development and deployment, although Japan is the country that should be most concerned about Pyongyang’s medium-range ballistic missile programs.

Third, despite North Korea’s nuclear testing and missile firings, Japan has not seriously discussed or received strong domestic pressure to increase the defense budget. The reduction of the government’s accumulated deficit, almost 150 percent of Japan’s gross domestic product (GDP), still remains one of Tokyo’s top priorities, and the defense budget remains at less than 1 percent of GDP. Each military service branch of the Japanese Self-Defense Forces, for instance, has been forced to cut back on personnel and procurement.

Fourth, soon after North Korea’s nuclear test, Japanese officials discussed the need to enact new legislation to enable interdiction and inspection of North Korean ships with suspected weapons of mass destruction (WMD)-related cargoes on the high seas, but such discussion has faded. Similarly, Japanese officials also weighed procuring and deploying an offensive weapon system to take out North Korea’s missile launching sites. This discussion has faded as well.

To be sure, Tokyo has speeded up deployment of proposed anti-missile systems, and a limited number of politicians and experts have argued in favor of Japan pursuing a nuclear option. It is difficult, however, to find convincing evidence that the Japanese public feels so gravely threatened by North Korea’s nuclear program that they want to take concrete action as a response. Most Japanese regard foreign countries’ concerns about Japan’s nuclear future as exaggerated. In fact, the Japanese media rarely conducts any extensive or serious discussion about Japan’s nuclear weapons capability or what might constitute Tokyo’s nuclear doctrine if it were to pursue such an option.

Changing Regional Security Environment

Speculation that Japan might pursue nuclear weapons surfaced first in the aftermath of China’s initial nuclear tests in the 1960s and then during the North Korean nuclear crisis in 1993-1994, as well as at the time of the international negotiations over the nuclear Nonproliferation Treaty (NPT) both in the 1970s and in 1994-1995. With the 2006 North Korean test, those concerns have been renewed, especially in the United States and a few Asian countries. Some countries fear North Korea’s possession of nuclear weapons might lead to a potential tsunami of nuclear proliferation in Asia that would engulf Japan and force it to shift its position on nuclear armament.

This overstates the influence of North Korea on the thinking of Japanese defense authorities. Although North Korea’s WMD programs certainly represent one of the gravest threats to Japan’s national security, the North Korean challenge is not necessarily regarded as the sole determinant factor shaping Japan’s national security strategy.

 Other problems Tokyo is concerned about include:

• The increasing capabilities of China’s People’s Liberation Army (PLA), particularly its ballistic missiles capabilities that can strike targets in Japan;

• The activities of the PLA Navy (PLAN) that have been conducted in a manner inconsistent with the Law of the Sea treaty, occasionally even violating this pact;

• The uncertain future of a reviving Russia;

• Ongoing territorial disputes with China, Russia, South Korea, and Taiwan;

• Nontraditional security threats, including natural disasters, infectious diseases, man-made accidents, and terrorism; and

• Japan’s perceived vulnerability to an energy supply cutoff because it depends heavily on oil from the Middle East.

Indeed, there is even a widespread view among Japanese security experts that North Korea’s provocations provide Japan with legitimate cover to advance its defense posture and capability in order to meet these threats and uncertainties, especially those related to China.

As it weighs the North Korea threat, Japan also has to place equal if not greater value on strengthening its bilateral alliance with the United States. Perhaps even more importantly, Tokyo today aspires to enhance its diplomatic standing in the world in order to balance against China’s rising political influence. To do so, Japan is seeking a permanent seat on the UN Security Council and trying to foster regional integration and institutionalization in Asia, with the aim of shaping rather than reacting to the global and regional security environment.

The changing geopolitical landscape in Asia is prompting Japan to resort to a new diplomatic principle of “value-oriented diplomacy,” emphasizing the adoption of universal values and disciplines as major diplomatic instruments, such as democracy, freedom, the rule of law, and the market economy.

Japan is currently embarking on a new major diplomatic initiative to build an “arc of freedom and prosperity” around the outer rim of the Eurasian continent through diplomacy that emphasizes values.[1] Tokyo decision-makers regard Japan’s international reputation as an asset the country has nurtured since the end of World War II. They regard it as too valuable to throw away simply for the sake of establishing its own nuclear deterrent against North Korea’s nuclear weapons programs.

Debating Japan’s Nuclear Option

To be sure, since North Korea expelled International Atomic Energy Agency inspectors in December 2002, there has been some open debate in Japan about whether to acquire nuclear weapons. This discussion has been fairly marginal, however, and included several consistent characteristics.

First, a limited number of conservative politicians have for decades argued for a vision of Japan with an independent military capability.

Second, it still remains very difficult and controversial for many Japanese politicians to advocate nuclear weapons. Careless comments by Cabinet members on this matter can trigger a huge controversy. For example, Shoichi Nakagawa, chairman of the Policy Research Council of the ruling Liberal Democratic Party (LDP), made public remarks on Japan’s nuclear option repeatedly after North Korea’s nuclear test, which made world headlines. He continued to repeat this remark despite strong pressures from the other LDP leaders to retract his comments. Even he, however, did not go beyond saying that Japan needed open discussions on its nuclear option.

Third, as noted, a majority of the Japanese public does not yet seem to perceive neighboring countries’ nuclear weapons as an issue of the highest priority. In fact, the presence of nuclear weapons on the neighboring continent is nothing new to Japan. Since the 1960s, Japan has learned to “peacefully” co-exist with Chinese nuclear weapons. (In a sense, this may be a reflection of the public’s tacit confidence in the credibility of U.S. extended deterrence.)

Fourth, it is no longer taboo to discuss nuclear strategy and the hypothetical possibility that Japan could require such weapons. Although a nuclear option is still unacceptable to the general public, there is recognition that such an option should be discussed openly. Within the national security community, experts are raising voices to call for pragmatic debate on Japan’s nuclear option, but no one dares to take the lead in such a discussion because the issue is still relatively sensitive. Leading this kind of discussion could negatively affect the government’s funding of an individual researcher’s work.

Overall, a majority of the Japanese public does not support the possession of nuclear weapons, at least so far, and there is only limited support for even examining whether Japan’s nuclear weapons would contribute to strengthening deterrence against any adversary and whether Japan would actually be able to develop nuclear weapons if it should decide to do so.

The Utility of Japan’s Nuclear Armament

Technically, experts have long contended that Japan possesses the basic capabilities to produce crude nuclear weapons. Indeed, Japanese Foreign Minister Taro Aso said last fall that “Japan is capable of producing nuclear weapons.” But he added, “We are not saying we have plans to possess nuclear weapons.”

Japan has nuclear fuel-cycle programs that produce reactor-grade plutonium, although in the form of mixed-oxide fuel, for civilian purposes. Japan also has the M-V and H2-A rockets, which have potential intercontinental capabilities.

Japan has not yet established the warhead control technology necessary for operational missiles. In addition, Japan does not have the basic infrastructure that would be essential for nuclear weaponry, including a nuclear doctrine, a stringent legal framework to protect classified information, a unified command and control system, or a unified intelligence system.

Moreover, Japan’s use of any nuclear material has been strictly regulated by bilateral and international treaties. It is illegal for Japan to use its plutonium for weapons purposes without the consent of its treaty counterparts, unless Japan dare follow the brinksmanship strategy of North Korea. Even the proponents of Japan’s nuclear armament acknowledge that Japan would not be able to develop nuclear weapons without the approval and cooperation from other countries, most importantly the United States, because of Japan’s obligations under bilateral treaties to use imported nuclear materials, equipment, facilities, and technologies for peaceful purposes.

Furthermore, Japan’s scientific and academic communities still remain within the pacifist tradition despite the general trend toward Japan becoming a more “normal country.” It would take enormous effort to establish a working relationship between these communities and the national security community. This would invariably make it difficult to mobilize resources essential for the construction of any sophisticated nuclear weapon.

Additionally, under Japan’s democratic government, selecting the location of nuclear weapons facilities could prove a painstaking process. Over the past decades, for instance, the selection of a location for a radioactive-waste storage site has faced strong opposition from local communities nationwide.

The Japanese government has quietly re-examined its nuclear option several times, most poignantly in the 1960s when China conducted its first nuclear test. All such examinations have reached the same conclusion: Japan’s possession of its own nuclear arsenal had little strategic merit. These studies have determined that a nuclear Japan could motivate a number of other countries to pursue nuclear development, and Japan could not secure a location to store nuclear weapons safely given its geographic limitations. Even the option to base nuclear weapons on submarines could not be completed before a decade and would require an enormous amount of investment, a challenge given Japan’s current budget deficit.

Furthermore, Japan believes that the credibility of the international nonproliferation regimes is still intact. These regimes are certainly imperfect, but Japan believes they have established legitimacy in the international community. As a result, Japan has intensified its efforts to strengthen these regimes by complementing them with various national, bilateral, and multilateral measures. Japan assesses that the relative costs associated with noncompliance with the treaties outweigh and should continue to outweigh the relative costs associated with observing the regimes.

Lastly, most of the pragmatic thinkers who support examining, though not necessarily pursuing, Japan’s nuclear option favor a strong Japanese-U.S. alliance. For example, former Japanese ambassador to Thailand, Hisahiko Okazaki, one of Japan’s most prominent strategic thinkers, argues that Japan’s nuclear armament should proceed in tandem with the strengthened bilateral alliance with the United States, while recognizing that the potential utility of Japan’s own nuclear weapons could be fairly marginal. In his view, the real utility of Japan’s discussion of a nuclear option may lie in its utility to indirectly press the United States to continue its nuclear commitment to protect Japan.[2]

Indeed, this also has been the line of thinking among some of Japan’s key strategic thinkers over the past decades. In the 1970s, Takuya Kubo, then bureau director of defense policy of Japan’s Defense Agency, wrote an article articulating Japan’s defense posture: “[I]f Japan prepares latent nuclear capability by which it would enable Japan to develop significant nuclear armament at anytime…the United States would hope to sustain [the] Japan-U.S. security system by providing [a] nuclear guarantee to Japan, because otherwise, the U.S. would be afraid of a rapid deterioration of the stability in…international relations triggered by nuclear proliferation.” [3] Even today, the authors have met several journalists and officials who have also expressed similar views, although privately.

Japan’s Deterrence Posture

Given those relative merits and demerits, Tokyo’s decision-makers have been pursuing another option as a response to North Korea’s nuclear testing, in contrast to the political rhetoric surrounding the nuclear option. These policymakers are determined to continue efforts to strengthen deterrence on multiple fronts by further institutionalizing the bilateral alliance with the United States and by developing a comprehensive national security posture. In fact, over the past years, Japan has been developing a comprehensive national security strategy to cover and integrate a wide range of areas, including assurance, dissuasion, deterrence, denial, defense, and damage confinement as well as crisis management, in order to keep up with the changing security environment.

The strongest indirect supporter of these efforts has been North Korean leader Kim Jong Il. Since the 1990s, Japan’s national security policy and the Japanese-U.S. alliance have consistently evolved every time when there was a crisis on the Korean Peninsula.

After the North Korean crisis in 1993-1994, Japan decided to redefine its roles and missions within the alliance, announced a Japan-U.S. Joint Declaration on Security in 1996, and created the new Japanese-U.S. defense guidelines in 1998. When North Korea launched the Taepo Dong missile over Japan that same year, Japan decided to embark on joint research into missile defenses with the United States. After the September 11, 2001, terrorist attacks and the new North Korean crisis since 2002, Japan has strengthened its alliance with the United States by demonstrating its support for U.S. military operations in Afghanistan and for the reconstruction of postwar Iraq. In addition, in the aftermath of the October 2006 North Korean nuclear test, Japan has launched a new initiative to cooperate with NATO and other U.S. allies and friendly countries to tackle issues of global security jointly so that Japan will be regarded as a responsible global stakeholder.

Japan has also been steadily strengthening its deterrence capability, as defined by its “National Defence Program Guidelines (NDPG) for FY 2005 and After.” In contrast to the previous NDPG, which defined Japan’s national security almost solely in terms of Japan’s homeland defense, it has clearly introduced protecting the international security environment as an essential component that defines Japan’s national security. This document offers three approaches to achieve Japan’s national security: Japan’s own defense efforts, Japan’s cooperation with the United States, and Japan’s cooperation with the international community. The last element provides the basic rationale for Japan Self-Defense Forces actively to participate in operations abroad in coordination with the United States and the United Nations.

Traditionally, the Japanese-U.S. alliance has focused primarily on bilateral cooperation at a strategic level, that is, Japan’s reliance on the U.S. nuclear umbrella, without any specific definition of the two militaries’ roles and missions and without any concrete joint military planning. The alliance was not really structured to deal effectively with security problems at tactical or theater levels. As Sugio Takahashi, senior fellow of the Japan National Institute of Defense Studies, argues, the current process of strengthening the bilateral alliance would enhance the credibility of deterrence by filling in the “blank spot” in the escalation ladder from the tactical and theater levels to the strategic level.

The strengthening of the Japanese-U.S. alliance has been implemented in tandem with a U.S. effort to forge an alliance network in the Asia-Pacific region consisting of multiple bilateral alliance systems. For example, U.S. allies and friendly countries have conducted regular multilateral joint exercises. The strengthened Japanese-U.S. alliance, supplemented by multilateral security dialogues, is expected to constitute an indispensable basis for constructing this dense alliance network in the Asia-Pacific region. It also is expected to serve as an essential confidence-building tool among Asian-Pacific nations to enhance the credibility of deterrence and even to enable adoption of coercive measures against hostile countries or WMD proliferators when inevitable. In addition, Japan has been striving to initiate cooperation with NATO with the intention of attaching a global horizon to its bilateral alliance with the United States.

Japan also is accelerating deployment of a two-tiered integrated missile defense system that consists of sea-based systems to be deployed on Aegis destroyers and a land-based Patriot system. After North Korea’s July 2006 missile launches and its October 2006 nuclear weapons test, the Japanese government has decided to shorten the system’s deployment schedule. The entire architecture of the missile defense system is scheduled to be completed by the end of fiscal year 2011. The Japanese government decided in early 2006 that the missile defense interceptor (the SM-3 missile) was already deployable because it had demonstrated a reasonable record of interceptions. The SM-3 missiles are scheduled to be introduced on Japan’s Aegis destroyers in this fiscal year. The infrastructure on the Aegis destroyers also has been improved in order to perform the missile defense mission.

The primary immediate objective of the anti-missile system is to defeat incoming medium-range ballistic missiles, particularly North Korea’s Nodong missiles. Japanese defense officials have demonstrated increasing confidence in the system’s ability to intercept medium-range ballistic missiles, a capability that is improving steadily. There is an emerging view among Japanese defense officials that as Japan increases the number of deployed interceptors in the coming years, the system could be expected theoretically to negate an adversary’s missiles, such as North Korea’s Nodong missiles, by outpacing their speed of deployment. Whether this will occur depends on the resources available for Japan’s anti-missile system versus that of its adversary.

Simultaneously, the missile defense system is expected to complicate an adversary’s strategic calculation about the probability of a successful attack on Japanese targets, thereby creating uncertainty regarding the relative merits of launching such a missile toward Japan. This would further strengthen deterrence.

The current plan is to have Japan’s system operate autonomously, independent from the U.S. system against longer-range missiles. As such, it remains unclear to what extent the Japanese government’s and the U.S. government’s command and control systems will be integrated when these systems are deployed or what level of interoperability can be achieved between the two militaries. Additionally, it is unclear whether Japan can legally intercept any long-range ballistic missiles heading toward the United States because doing so could violate the Japanese government’s interpretation of its constitution, which prohibits itself from engagement in the act of collective self-defense. Abe has launched a commission to examine these issues.

Japan’s Strategic Push

In addition to the above efforts, Japanese officials would like more detailed discussions with their U.S. counterparts on U.S. nuclear doctrine and strategy, including its operational details, as an additional measure to sustain the credibility of U.S. extended deterrence. There have been few bilateral discussions on such matters so far. Although Japan must establish stringent mechanisms for information protection before discussing such sensitive matters with the United States, once it does so, the Japanese government may want to have a regularized bilateral mechanism to discuss the strategic details, somewhat similar to the institutional framework of the Nuclear Planning Group of NATO.

In fact, Japanese government officials and experts have recently been discussing the possibility of establishing a Japan-U.S. Nuclear Planning Group. As Michael Green, former senior director for Asian affairs on the National Security Council in the Bush administration, has said, Tokyo may want to have “some control of the U.S. nuclear umbrella.”

Certainly, Japanese security experts and officials have expressed frustration over the ambiguous nature of U.S. declaratory policy about its nuclear umbrella. There is an emerging view in Japan that it should ask for a more explicit statement of policy from the U.S. government, for example, by revising the bilateral defense guidelines to state that the United States would retaliate with nuclear weapons if Japan were to be attacked by an adversary’s nuclear weapon. Indeed, as they manage the alliance, U.S. policymakers would be well advised to consider how to manage Japan’s increasing aspiration to be consulted in the formation of the U.S. nuclear posture and to participate in the operation of U.S. extended deterrence. This should capture more attention than worries that Japan will pursue a nuclear weapons option.


As noted, Japan’s domestic reaction to North Korea’s nuclear test has been much more restrained than predicted by some foreign experts, particularly in the United States. Similar predictions followed China’s nuclear tests in the 1960s and the North Korea nuclear crisis of 1992-1994. Then, as now, these predictions have proven ill founded.

It is difficult to find in Japan any major public leader who strongly advocates Japan’s pursuit of its own nuclear option or who questions the credibility of U.S. nuclear deterrence. Shifts in Japan’s regional security environment and strategic culture from pacifism to realism in recent years have ended the taboo on discussing publicly the hypothetical possibility that Japan might pursue a nuclear option. After North Korea’s October 2006 nuclear test, Japanese media highlighted remarks by a limited number of Japanese politicians, including Cabinet members, who argued in favor of a public discussion about Japan’s nuclear option. Others countered that such a discussion could invoke regional concerns about Japan’s nuclear intentions. Tokyo’s decision-makers are concerned that such a discussion might undermine the trust it has fostered with its neighbors since the end of World War II. These political leaders deem retaining this trust to be of greater value to Japan than developing a nuclear deterrent against North Korea.

Thus, the consensus in Japan today favors continued reliance on the Japanese-U.S. alliance, the U.S. nuclear umbrella, and missile defense to negate North Korea’s nuclear capability. Of course, the credibility of U.S. extended deterrence is key here. Certainly, Japanese political leaders and strategic planners aspire to secure the credibility of U.S. extended deterrence. In the minds of Japanese political leaders and strategic planners, the answer to this challenge is not whether to pursue Japan’s nuclear option, but rather how to secure some control or participation in the process of shaping and sustaining U.S. extended deterrence. The focus is to examine what type of bilateral mechanism may be appropriate to conduct regularized dialogue with the United States on nuclear strategy issues, whether in official or unofficial channels, and what agenda Japan may want to discuss as well as what type of information the United States may want to share with Japan under what conditions. In a way, Japan and the United States now have a unique opportunity to shape each other’s priorities in the realm of nuclear strategic affairs.

Hajime Izumi is a professor at the University of Shizuoka in Shizuoka, Japan. Katsuhisa Furukawa is a research fellow at the Research Institute of Science and Technology for Society at the Japan Science and Technology Agency in Tokyo.


1. Taro Aso, “Arc of Freedom and Prosperity: Japan’s Expanding Diplomatic Horizons,” Speech at the Japan Institute of International Affairs Seminar, November 30, 2006, Tokyo.

2. Hisahiko Okazaki, “Time to Consider a Nuclear Strategy for Japan,” Daily Yomiuri, April 8, 2007.

3. Takuya Kubo, “Boueiryoku Seibi no Kangaekata [A framework to consider the arrangement of Japan’s defense capabilities],” February 20, 1971, found at http://www.ioc.u-tokyo.ac.jp/~worldjpn/documents/texts/JPSC/19710220.O1J.html (in Japanese).