Supporters wait for President Trump outside the Kasumigaseki Country Club in Kawagoe, north of Tokyo, on Nov. 5, 2017. (Issei Kato/Reuters)

President Trump is visiting Tokyo on Monday at a time of renewed national security debates within Japan. North Korea’s recent missile launches and nuclear tests have again prompted discussion in Tokyo on Japan’s policy against becoming a nuclear state.

Although Japan has long had the technical ability to develop nuclear weapons — its “nuclear hedge” — it has refrained from doing so. Japan instead remains firmly committed to its 1967 Three Non-Nuclear Principles of not developing, not possessing and not introducing nuclear weapons.

This is not the first time that Japan has reexamined those principles. Similar debates transpired after China’s hydrogen bomb test in 1967, the Soviet Union’s deployment of medium-range nuclear missiles in Siberia during the 1980s and North Korea’s first nuclear test in 2006.

Is this time different? Reacting to North Korea’s threatening behavior, former Japanese defense minister Shigeru Ishiba stated in September that Japan should at least debate the decision not to permit the introduction of nuclear weapons on Japanese territory. Ishiba implied that Tokyo should consider asking Washington to deploy tactical nuclear weapons in Japan.

President Trump spoke to the press after arriving in Japan and meeting with Prime Minister Shinzo Abe on Nov. 5. (The Washington Post)

This latest debate is likely to end in the same way as previous debates, however. Japan will continue to adhere to its Three Non-Nuclear Principles and forswear nuclear weapons. Here are three reasons for that:

1) Staying non-nuclear is part of Japan’s national identity

The Three Non-Nuclear Principles are a clear part of Japan’s national identity, not simply a policy preference. Repeated polls indicate overwhelming popular support for the three principles in Japan. A 2014 Asahi newspaper poll revealed that support for the principles had risen to 82 percent, compared with 78 percent in a 1988 poll. Despite growing concerns about North Korea’s nuclear program and China’s military power during this period, Japanese support for remaining non-nuclear actually increased.

Even after the provocative North Korean missile launches over Japan in August and September, a Fuji News Network poll showed that nearly 80 percent of the Japanese population remained opposed to Japan becoming a nuclear weapons state. And nearly 69 percent opposed having the United States bring nuclear weapons into Japan.

The legacy of the Hiroshima and Nagasaki atomic bombings leave many Japanese convinced that their country has a moral responsibility to promote global nuclear disarmament — as well as to forgo nuclear weapons of its own. The 2011 Fukushima nuclear plant disaster has reinforced this view.

In fact, increasing numbers of Japanese believe that the U.S. “nuclear umbrella” is unnecessary for Japanese security. A June 2010 NHK survey revealed that 20.8 percent felt that U.S. nuclear deterrence is necessary for Japan’s security in both the present and future, while 34.8 percent believed it unnecessary. The June 2015 NHK poll showed that only 10.3 percent thought the U.S. nuclear umbrella is necessary for both the present and the future — 48.9 percent responded that it is unnecessary now and later.

2) Powerful players in Japanese politics can block nuclear acquisition

In addition to public opposition to nuclear weapons, Japan has significant “veto players” — crucial political or economic actors that are likely to block efforts to develop nuclear weapons.

Japan has a robust nuclear energy industry. But public acceptance of nuclear energy in the 1950s resulted from a fundamental political bargain: nuclear energy, but no nuclear weapons.

As security scholar Jacques Hymans argues, the development of nuclear energy in Japan boosted the number of Japanese government agencies and private-sector actors that are committed to the peaceful use of nuclear power — and can serve as a formidable opposition to any political move toward acquiring nuclear weapons. These veto players include powerful economic ministries, regulatory commissions, industrial groups and prefectural governments.

The international nonproliferation regime and public opposition to nuclear weapons give these veto players leverage in Japan’s policy process. The International Atomic Energy Agency has closely monitored Japan’s reprocessing programs, for instance. Japan’s nuclear energy program is also tied to bilateral agreements and multilateral bodies such as the Nuclear Suppliers Group that embody nonproliferation principles.

 3) Japan has good national security reasons to stay non-nuclear

There’s also a realist security calculation to consider. North Korean nuclearization is alarming, but it does not pose such an acute danger that Japanese leaders will be motivated to pay the high political costs necessary to weaken, much less revoke, the Three Non-Nuclear Principles.

North Korea acquiring the ability to deliver a nuclear weapon against the United States may weaken the protective U.S. nuclear umbrella somewhat, but U.S. nuclear and conventional military capabilities should be adequate to deter a North Korean nuclear attack on Japan.


North Korean test missiles flew over northern Japan in September, prompting Japanese government alerts telling citizens to seek shelter underground or in a building. (Courtesy of Kate Whitcomb)

During the 2016 presidential campaign, Donald Trump criticized several U.S. alliances and mused that it might be desirable for Japan to develop nuclear weapons. But after assuming office, President Trump and his foreign policy team have repeatedly confirmed the U.S. defense commitment to Japan. The continuing presence of U.S. military forces in Japan, South Korea and the Western Pacific makes this commitment credible to deter potential aggressors and to reassure Japan.

Given the powerful U.S. nuclear arsenal, including ballistic missiles deployed on nuclear submarines, any U.S. tactical nuclear weapons in Japan itself would constitute a marginal increase in deterrence. But the political cost of rescinding the third non-nuclear principle would be high.

Japanese defense policymakers are more likely to focus on other ways to respond to the North Korea threat, such as acquiring the Aegis Ashore missile defense system and perhaps a conventional strike capability.

A realistic review of Japanese security requirements is likely to conclude that the best way to counter the North Korea threat is to promote defense cooperation with the United States, invest in conventional defense capabilities and increase pressure on North Korea — while looking for an opportunity for constructive negotiations with Pyongyang.

And there’s a final consideration: A Japanese bomb would probably destabilize the country’s relations with China and South Korea. At a time when North Korea is making the international politics of the region complicated, Japan is likely to stay its non-nuclear course rather than make a disruptive nuclear move of its own.

Mike Mochizuki holds the Japan-U.S. Relations Chair in Memory of Gaston Sigur at the Elliott School of International Affairs at George Washington University. He is co-editor of “Nuclear Debates in Asia: The Role of Geopolitics and Domestic Processes.”