Assessing Northeast Asia Nuclear Domino: Japanese Responses
Past Events

Assessing Northeast Asia Nuclear Domino: Japanese Responses

International Joint Seminar

“Assessing Northeast Asia’s Nuclear Domino: The North Korean Nuclear Threat and Japanese Responses”

July 2, 2021, 18:30-20:45 (Webinar)

Co-hosted by Asia Pacific Leadership Network for Nuclear Non-Proliferation and Disarmament (APLN), Sejong Institute, and Pugwash Japan.

In cooperation with International Peace Research Institute, Meiji Gakuin University (PRIME)Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA)



There is a concern that the nuclear threats from the DPRK may trigger a “nuclear domino” in the Northeast Asia region.

This workshop is the second one of three series of workshops planned and focused on Japanese Responses. The first one was held in Seoul in May focusing on South Korean’s responses, with the third to be held in Seoul in November. Experts from civil society and Parliamentarians alike from both South Korea and Japan were invited to speak at the events.

Opening Remarks

Prof. Seigo Hirowatari (President, Pugwash Japan) and Prof. Chung-in Moon (Chairman, Sejong Institute) made opening remarks on behalf of the hosting organizations. Prof. Hirowatari pointed out that how the US new Administration and South Korea would respond to the increasing nuclear threats from DPRK, with the US putting more emphasis in dealing with China, as the key issue to be discussed here. It is especially, as  Hirowatari noted, important to note that the Japanese government justifying and legitimizing the increase in defense expenditure and even altering Constitution Article 9 using the threats from DPRK and China as the reasons. He emphasized the importance of developing a deeper understanding of nuclear threats here and now, as well as pointing out the importance of an intellectual exchange between the ROK and Japan even as the relationship between the two countries is said to be worsening.

Prof. Moon outlined the project, saying it was originally planned for the year previous, but was postponed due to the COVID-19 pandemic. He expressed his appreciation for the generous support from Open Society Foundations which made it possible to have three series of workshops this year. He hoped that the third workshop, planned to be held in Seoul, could be held not on-line, but face-to-face. He then summarized the current situation on DPRK nuclear issues, pointing out that we cannot see any prospect for moving to the solution. The relationship between North and South Korea has scarcely improved, notes Prof. Moon. Because of the tense situation, some conservative groups in Seoul have now begun to claim that South Korea should also develop nuclear weapons of their own. Moon suspected that a similar argument could transpire in Japan, and said that the purpose of this workshop was to get possible suggestions in order to prevent such a ‘Nuclear Domino.’

Moderator: Prof. Keiko Nakamura (RECNA) First Session: Paper Presentations

There are three paper presentations in the first session.

The first paper, entitled “Japanese responses to nuclear threats in Northeast Asia: Possible Nuclear Option for Japan?”, was presented by Prof. Tatsujiro Suzuki (RECNA) and Prof. Takao Takahara (PRIME). Takahara confirmed that there are significant constraints against Japan going nuclear, despite the fact that it has long since been a source of international concern.

Of immediate relevance is the strong aversion against nuclear weapons that is deeply rooted amongst the majority of the population, stemming from the historical experience of Hiroshima/Nagasaki and the Bikini Atoll incident, and is currently expressed in the unfaltering public support of the Treaty on the Prohibition of Nuclear Weapons (TPNW). No Japanese politician can ignore this. Secondly, there are significant international legal constraints, most notably the Nuclear Non-Proliferation Treaty (NPT). In addition, bilateral nuclear cooperation agreements on the peaceful use of nuclear energy prohibit any diversion of civilian nuclear materials/facilities for military purposes. Thirdly, there are domestic legal constraints, such as the Atomic Energy Basic Act which stipulates that Japanese nuclear activities shall be limited to peaceful purposes. Moreover, for the last half a century, Japan has upheld the “Three Non-nuclear Principles” as a national policy, if not a legally binding norm. Fourthly, the current US commitment to provide “extended nuclear deterrence” (i.e. a “nuclear umbrella”) to Japan continues to be the major constraint over Japan’s nuclear options, as has been intended since the mid-1960’s. Finally, Prof. Takahara referred to the general understanding that the Peace Clause of the Japanese Constitution (Article 9) prohibits Japan from having nuclear weapons as they are inhumane and offensive. This interpretation has provided a base for Japan’s non-nuclear culture, whilst pro-nuclear politicians assert that the Constitution leaves space for “purely defensive” nuclear weapons.

Meanwhile, Prof. Suzuki drew attention to how, after the DPRK’s missile test in the late ‘90s, the “taboo” of discussing “nuclear options” in Japan has waned. He classified pro-nuclear option arguments into three groups; 1) Fully independent nuclear option, 2) Partial nuclear option (not posessing one’s own nuclear weapon, but relaxing the three non-nuclear principles to allow the introduction of nuclear weapons on native soil or to allow a “nuclear sharing” scheme with the US), and 3) Latent nuclear option (maintaining the technological and economic capabilities to manufacture a nuclear weapon). In addition, Suzuki cited four factors which might encourage such pro-nuclear arguments; 1) Increasing nuclear and military threats from neighboring countries, 2) the (in)credibility of the US nuclear umbrella, 3) Nationalism (Gaullism) or Ambition for Great Power, and 4) Technological hedging. Adding on to those four existing and past factors, he suggested three more risk factors for the future; 1) Generational change and lack of education, 2) a Unified Korea armed with nuclear weapons, and 3) the collapse of the global non-proliferation regime. Lastly, he pointed out the importance of meeting in events such as these in order to exchange frank views between experts from academia and civil society.

The second paper, entitled “How to avoid nuclear cascade in East Asia”, was presented by Prof. Nobumasa Akiyama (Hitotsubashi University). He first concluded that Japan is unlikely to go nuclear but noted that if such a decision is made, it will not be by security experts, but by politicians with an “irrational or unreasonable” cause. He then explained the complex geopolitical situations, especially the “nuclear intensity” in East Asia, examing how the nuclear weapons of Russia/US/China and the DPRK are concentrated in the region. He laid particular emphasis to how the US-China military expansion (not only nuclear, but also conventional weapons) are posing serious security threats to Japan. Prof. Akiyama then explained that Japan is trying to respond to those increasing threats by strengthening a US-Japan alliance. He noted due to differing interests and the lack of common recognition concerning the DPRK’s nuclear and missile programs that there has not been a consensus among the countries in the region. He again noted that when responding to the threats coming from the DPRK, any nuclear option has not been considered by Japan as a reasonable choice.

In order to prevent a “nuclear cascade” in the region, he compared two alternatives: 1) the Northeast Asia Nuclear Weapon Free Zone (NEA-NWFZ) and 2) Strengthening extended nuclear deterrence and its credibility forthwith. For NEA-NWFZ, he raised the issue “credibility” of “negative security assurance” (NSA) given by nuclear weapon countries like China. So long as there exists distrust between China and the US, China will not join the NWFZ unless US military bases are removed from Japan (which, in turn, pose a threat to China). But the US is unlikely to accept such a condition. Prof. Akiyama also noted that the denuclearization of the DPRK would be a pre-condition to establishing the NWFZ, but the prospects for doing so seem poor. Thus, Prof. Akiyama concluded that establishing the NWFZ would not solve existing issues. He also gave critical views on the Japanese government’s current plan to strengthen the US-Japan security alliance and conventional military forces available, such as missile defense. However, Prof. Akiyama observed that, from the mid-to-long-term point of view, such military options would be inadequate and, unless the security environment were to be improved, a military expansion race is unavoidable. Finally, Prof. Akiyama recommended that we need to establish an “arms control/disarmament” scheme in the region. In order to overcome the “differences” between China and the US on arms control, Prof. Akiyama emphasized the need for confidence-building measures—in particular, engaging the appointment of “appropriate” persons who are directly associated with nuclear deterrence.

Third paper, entitled “Young Generations in Japan and Nuclear Weapons/Atomic Bombings”, was presented by Prof. Hideko Shibasaki (Nagaoka University of Technology). First, she emphasized the importance of education on social responsibility of scientists for students who would become future scientists/engineers, giving the names and works done by famous Japanese physicists such as Hideki Yukawa and Shinichiro Tomonaga.

Afterwards, she presented her opinion/knowledge survey among Japanese science/technology major students, comparing the responses with foreign students in Japan and students from the US. The results were striking. For the question of “Was dropping the atomic bombs over Hiroshima and Nagasaki the right decision?”, the percentage of Japanese students saying “Yes” was 39%, compared to 21% by American and other foreign students. As to the question of “Are nuclear weapons necessary?”, again, the percentage of Japanese students responding “Yes” was 30% higher than 17% (US students) and 25% (foreign students). For the prospect of “abolition of nuclear weapons”, Japanese students were most pessimistic (19% saying “it’s possible”) compared to 66% (US) and 39% (foreign students). Finally, concerning nuclear deterrance, Japanese students gave the most positive answer (57% responded with “It is effective”) compared to 41% (US) and 48% (foreign students). With regard to existing knowledge on nuclear weapons and previous experience on them (e.g., visting a bomb museum or listening to a hibakusha’s testimony), Japanese students gave the lowest scores. Given those polling results, Prof. Shibasaki pointed out the importance of education youth on nuclear bombs as well as on World War II, which should provide students with views from the aggressors, not just victims of the War. Lastly, she emphasized the importance of peace education, including the famous Russell-Einstein Manifesto, for students who aspire to be scientists or engineers.

Second Session: Panel Discussion

In the Second Session, four Japanese panelists, one each from the United States and ROK, made brief comments, followed by a Q&A session.

The first to speak was Prof. Peter Hayes (Nautilus Institute). He chiefly made comments concerning  Prof. Akiyama’s paper. He first agreed with Prof. Akiyama’s point that the geopolitical security situation in Northeast Asia is very complex, but noted that Prof. Akiyama emphasized threats from US-Russia nuclear weapons rather than those from the DPRK. Prof. Hayes interpreted that threats from DPRK are not the largest risk in the region. Furthermore, regarding Prof. Akiyama’s comments on a Nuclear Weapon Free Zone in Northeast Asia, Prof. Hayes pointed out that the DPRK would not provide Negative Security Assurance (NSA) against South Korea and Japan, but rather it should commit itself to eliminate nuclear weapons within a certain time frame with legally binding verification scheme. The DPRK (and the ROK), Prof. Hayes noted, would get NSA from the US, as well as China and Russia. This would provide additional assurance to the DPRK/ROK/Japan than the current NFU commitment by China or the assurance provided by the “nuclear umbrella.” Prof. Hayes likewise pointed out that there is no reason for the US to leave their military bases from the ROK nor Japan, believing that China will not push that far. As an ending note, Prof. Hayes pointed out that the Northeast Asia Nuclear Weapon Free Zone (NEA-NWFZ) is the only practical multilateral, legally binding arrangement which could provide NSA against non-nuclear weapon states in the region, and that nuclear deterrence would remain effective against nuclear weapon states even under the NWFZ, as is the case for Australia.

The second to speak was Masakatsu Ota (Kyodo News). He examined the history and current status of the US-Japan security alliance. First, Prof. Ota explained the history of how Japan made the “extended nuclear deterrence” provided by the US one of the main pillars of its security policy. This policy originates from the Korean War in the 1950s, with the target of extended nuclear deterrence changing as time goes by. It turned from China (‘60s), to the former Soviet Union (70~80s), then the DPRK (90~2000s), and now the DPRK and China (2010~2020) — especially China. Prof. Ota further noted that the additional purpose of extended nuclear deterrence was that of “non-proliferation”. If the credibility of extended nuclear deterrence deteriorates, it would accordingly increase the risk of proliferation in Japan and the ROK, according to a former senior government official. Prof. Ota observed that the current trend of shifting the emphasis on Chinese threats could have grave implications for policy debates on Japan’s security issues. He suggested that the fundamental problem in Northeast Asia is the lack of an appropriate framework for “arms control and disarmament” between China and the US, as well as among other related countries in the region. He concluded that it is very unlikely for Japan to go nuclear. But, if the US were to introduce a new policy which would “reduce the role of nuclear weapons drastically”, some politicians and security experts may express their unwillingness to accept such a policy and may begin to emphasize the need of enhancing extended nuclear deterrence and strengthening conventional deterrence capabilities. Prof. Ota raised questions about such a trend and argued that the Japanese government and its political leaders must fulfill an important role in establishing a new security, disarmament, and arms control framework, in order to reduce overall dependence on nuclear weapons.

Up next was Dr. Hiromichi Umebayashi (Peace Depot). First, he made a comment on Prof. Akiyama’s views on the NEA-NWFZ. He responded to Prof. Akiyama’s comment (i.e., that there seems to be little merit for the DPRK), quoting the English translation of the Panmunjom Declaration of “Denuclearization of Korean Peninsula” by DPRK, which was the “Nuclear Weapon Free Zone of Korean Peninsula”. Dr. Umebayashi suggested that this translation could imply that the DPRK may eventually be willing to accept the concept of the NWFZ. Going further, he added that past statements by the DPRK statements consistently claimed that “the DPRK will give up nuclear weapon if certain conditions are met”. So, the key question is, what are these conditions? Dr. Umebayashi then introduced a proposal made by a former senior US government official, Dr. Morton Halperin, which was “a comprehensive approach for security in Northeast Asia,” including the NWFZ. He explained that Dr. Halperin’s proposal has great utility as it addresses the need for the establishment of regional security regimes, not just the NWFZ, including the ending of the Korean War, a permanent peace regime in the Korean Peninsula, etc. These are the conditions which the DPRK is asking for. In this regard, Dr. Umebayashi said, the issues Prof. Akiyama raised have been addressed by the proposal.

Subsequently, Dr. Umebayashi made a comment on Suzuki and Takahara’s papers. He noted there are several local governments who declare themselves a “nuclear-free city/town,” reflecting a strong anti-nuclear public opinion. ‘Mayors for Peace’ is a good example of such a network. According to Dr. Umebayashi,  99.6% of Japanese 1,741 local municipalities, i.e. 1,734 mayors, currently participate in the Mayors for Peace movement, making for 92% of Japan’s local governments declaring themselves as “nuclear-free.” If the Japanese government wants to develop nuclear weapons, they would have to overcome the immense anti-nuclear sentiment of public opinion. He believed that the anti-nuclear consciousness of such local governments and especially among the younger generations needs to be revitalized in order to greatly promote anti-nuclear policy, in particular the promotion of the NWFZ.

Next to speak was Dr. Wookshik-Cheon (Korea Peace Network). He addressed the key fundamental questions on the DPRK to be discussed. They are; Why does the DRPK want to keep nuclear weapons? If the US, ROK and Japan were to maintain or strengthen their military power against DPRK, what would happen? As for the first question, Dr. Cheon stressed that we should provide such conditions that the DPRK would no longer need nuclear weapons. For the second question, he said that the DPRK has no choice but to increase their nuclear and missile capabilities, i.e. noting that this is a classic “security dilemma.” Next, Dr. Cheon posed another fundamental problem, in so far that there is deep mistrust and fear against China. He was particularly concerned about the issue of Taiwan, as a small military conflict there may lead to a larger military conflict in the region. Dr. Cheon emphasized the need to establish a new framework within which to address those issues. As a specific proposal, he recommended to establish Korean Peninsula Nuclear Weapon Free Zone which could later be expanded to include Japan. He also suggested such NWFZ will not allow possession of uranium enrichment and reprocessing facilities. Finally, he emphasized the importance of historical education. In the ROK, he said, it is part of student education that the dropping of the nuclear bomb ended the Japanese occupation, but that it did not include the consequences of the bombs. Dr. Cheon proposed that the ROK and Japan cooperate together towards the common goal of peace and stability in the region.

The fifth speaker was Dr. Akira Kawasaki (Peace Boat, ICAN). He made a comment on the Treaty on Prohibition of Nuclear Weapons (TPNW) and on the risk of nuclear deterrence. He noted that the TPNW is strongly supported by the Japanese public, but that it is not as popular among politicians and the government. According to the “Parliamentarian Watch” project, only 28% supported the TPNW, 42% by prefectural governors and 33% by local municipal parliaments. Then, Dr. Kawasaki noted that the dependence on nuclear deterrence means that Japan would be likely to support or request the US’s decision to use or threaten to use nuclear weapons. Therefore, Dr. Kawasaki claimed, the key question should not whether Japan will go nuclear, but rather whether Japan continues to depend on nuclear deterrence or not, as nuclear deterrence encourages or supports the use of nuclear weapons. Dr. Cheon recommended that countries in the region collaborate on studying the real humanitarian impacts of nuclear weapon use in Northeast Asia.

The final speaker was Ms. Yumi Kanazaki (Chugoku Shimbun). She first introduced the current status of peace-related activities in Hiroshima. The number of visitors to the Hiroshima Peace Memorial Museum significantly increased to 175 million people in 2019, thanks to the visit by the former US President Obama in 2016. However, Ms. Kanazaki was shocked to see the polling results of Japanese students conducted by Prof. Shibasaki. She then understood from the paper by Suzuki and Takahara that, so long as extended nuclear deterrence is credible, Japan is unlikely to go nuclear. Ms. Kanazaki claimed that such an assumption is based on the idea that nuclear deterrence is both effective and necessary. If that is true, she said, then Japan has only two options; going nuclear, or continuing to depend on the ‘nuclear umbrella.’ This is exactly why the TPNW prohibits nuclear deterrence (i.e. threatening to use nuclear weapons). Thus, depending on nuclear deterrence means that Japan will eventually accept the use of nuclear weapons. She emphasized that we all should recognize such a linkage. Ms. Kanazaki pointed out that in order to prevent the “nuclear domino”, we need “a domino of public opinion against nuclear weapons.” She was concerned that the general public’s anti-nuclear views may be weakened unless we continue to educate the masses on peace.

Finally, Ms. Kanazaki introduced the existence of Korean hibakusha who were brought to Japan during the War and now preside in Korea. There are about 2,000 such Korean hibakusha who received an “atomic bomb victim certificate” by the Japanese government. According to the polling of those Korean hibakusha, while the notion that atomic bombs ended the Occupation era has not changed, 74% of those think that “nuclear bombs should have never been used for whatever reasons”. The polls also revealed their opinions that nuclear weapons ought never be used against any country, or that the Korean government, working with the Japanese government, should continue educating on the humanitarian consequences of the use of nuclear weapons.

The number of hibakusha is declining every year. Ms. Kanazaki quoted the words by Ms. Beatrice Fihn, Executive Director of ICAN, citing that “the real expert of nuclear weapons are the hibakusha.” She concluded that the ROK and Japan should work together to document and recount the experiences of hibakusha. Such cooperation and diplomacy by civil society can stop the nuclear domino, she concluded.

Q&A session

Q: For the NEA-NWFZ, how about establishing a Korean Peninsula NWFZ first, and then expanding the zone to envelop other countries in the region, including Japan?

A: Yes, that is a very practical idea. Yet, if the NWFZ were to be limited only to the Korean Peninsula, that may not be enough to establish peace and security in the region. A ‘Korean Peninsula-only’ NWFZ would still require the participation of Russia and China, and Japan would be the only country not participating in this scenario. So, it would necessarily be an unstable treaty. Adding onto this, historically, US bases in S. Korea and Japan are operated and managed under a single authority in order to maintain extended nuclear deterrence. So, regional stability can be best achieved if Japan participate in the NWFZ from the get-go.

Q: If the US decided to introduce nuclear weapons into Japan, will Japan be able to say “NO”?

A: Legally speaking, Japan can reject such a decision from the American side, but politically it would be impossible. If the US were to introduce nuclear weapons into Japan, the risk of nuclear war would be greater, along with the possibility of Japan becoming a target of nuclear attack. The US could still make such a decision privately if it wished. It is not possible to verify whether the US plans to introduce nuclear weapons to Japan or not. Most likely, the US believes that it is more reasonable to deploy conventional missiles or enhance existing missile defense capabilities.

Closing Remarks: Prof. Tomohiro Inagaki (Hiroshima University, Chair of Pugwash Japan) ended the webinar, expressing his appreciation towards the sponsoring organizations, interpreters, secretariat, and all speakers, as well as panelists. Lastly, he warmly thanked the audience for joining and posing questions.