This week, Pope Francis made a historic visit to Hiroshima and Nagasaki. On Sunday, the pontiff was clear in his call for global nuclear disarmament, stating, “The use of atomic energy for purposes of war is immoral. … As is the possession of atomic weapons.”

This message resonated with the large segment of the Japanese public who vehemently opposes nuclear weapons and prompted a question to Chief Cabinet Secretary Yoshihide Suga about Japan’s own reliance on the U.S. nuclear umbrella. Suga responded that the long-standing policy is “realistic and appropriate.”

Suga’s response may have been concise and resolute, but we are likely to see a revisiting of the nuclear weapons debate in Japan. The region has witnessed North Korea’s development of increasingly devastating nuclear technology and more sophisticated delivery vehicles. Fears of U.S. abandonment will lead many to question whether Japan may indeed pursue its own nuclear arsenal — which is technically feasible given the country’s technology and availability of nuclear material.

Amid these discussions, it is necessary to have the right context for understanding the discourse, including Japan’s positions toward nuclear weapons, as well as the strategic and political costs of pursuing a domestic nuclear arsenal. Given that background, one finds that the most likely outcome is the status quo, no matter how passionate the debate.

On the surface, Japan’s position toward nuclear weapons is clear. On Dec. 11,1967, Prime Minister Eisaku Sato (Prime Minister Shinzo Abe’s great-uncle) announced Japan’s “Three Non-Nuclear Principles” to the Diet, noting that it was his responsibility “to achieve and maintain safety in Japan under the Three Non-Nuclear Principles of not possessing, not producing and not permitting the introduction of nuclear weapons, in line with Japan’s Peace Constitution.” The Diet later codified part of the principles in law, meaning that renewed legislative action is a prerequisite to any formal pursuit  of a domestic nuclear arsenal.

While domestically that policy is black and white, Japan’s foreign policy takes a different approach. The government has consistently recognized the need for nuclear deterrence, achieving this by relying on the U.S. nuclear umbrella. The allies periodically renew this deterrence commitment in senior-level joint statements and offered an explicit reference to it in the 2015 Guidelines for U.S.-Japan Defense Cooperation. Those defense guidelines reassured that “the United States will continue to extend deterrence to Japan through the full range of capabilities, including U.S. nuclear forces.”

The allies also routinely conduct an “Extended Deterrence Dialogue” between senior U.S. and Japanese foreign policy and defense officials, the activities and discussions of which are anchored in the issue of nuclear deterrence.

Japan has also taken a measured approach to the international community’s activities toward nuclear disarmament. Where Japan can call for disarmament without impact to its nuclear umbrella, it does. In 1970, Japan signed the Nuclear Non-Proliferation Treaty and ratified it in 1976. The 2020 Review Conference for that treaty is upcoming, and Japan will take the opportunity to renew its commitment to the provisions of the treaty. Also, for the past 26 years, Japan has co-sponsored an annual United Nations General Assembly resolution calling for the total elimination of nuclear arms.

However, neither of those activities have binding impacts on existing nuclear deterrent capabilities. That is why Japan’s approach to the recent 2017 Treaty on the Prohibition of Nuclear Weapons differed: With this treaty, signatories accept a prohibition from developing, testing, producing, stockpiling, transferring and using or threatening the use of nuclear weapons, as well as assisting other countries to engage in prohibited activities or seeking assistance from anyone engaged in actions that violate the treaty. In other words, signing onto the treaty would mean Japan would have to change its position toward the U.S. nuclear umbrella, which is a bridge too far despite its own domestic principles.

Policies are not permanent though, and the nuclear weapons debate in Japan re-emerges every so often. It is especially salient now as North Korea has successfully tested nuclear weapons and demonstrated an effective delivery vehicle through its medium- and long-range ballistic missile testing. Compounding the debate are concerns related to U.S. foreign policy, especially alliance commitments. The doubt that exists within Japanese political, bureaucratic and academic circles may generate impetus to revisit the serious issue of nuclear proliferation as it has done in the past.

Several leading politicians, including former Liberal Democratic Party Secretary-General and prime minister-hopeful Shigeru Ishiba have already commented that Japan should have the freedom to build nuclear weapons if it wishes to do so. He is not alone in this position, but advocates of nuclear weapons face strong opposition both from the public and from within their respective political parties.

It should be clear that a firm commitment to develop a domestic nuclear arsenal is a “third rail” issue. Official government policy has always centered on the three non-nuclear principles, and bureaucrats involved in foreign policy and defense understand the sensitivities of the topic with regional partners and adversaries.

Even formally debating the idea among government officials would have ripple effects in the strategic environment, with China, South Korea and North Korea the most likely to issue strong rebuke. Actually pursuing a domestic nuclear arsenal would escalate responses exponentially.

Besides this practical strategic impact, the political costs are too great for politicians to weather. The Japanese public is traditionally wary of offensive military capabilities as it is, and the historical, cultural and social constructs since 1945 reinforce the country’s “nuclear allergy.” Formally raising the issue of producing nuclear weapons would throw the political landscape into disarray, and decisively pursuing development would be the move that breaks up the ruling coalition and fuels the opposition parties to topple the LDP.

To put this into context: We are currently seeing the Abe administration being targeted in the Diet and the media for how he selected guests to attend a cherry-blossom viewing party — imagine what would happen if Abe announced his intent to produce nuclear weapons. The reaction would be, well, atomic.

Because of this, no party has wished to tie its identity to this issue, and none will. Even within the LDP, nuclear weapons present an issue that is far different from other controversial security agenda items. Constitutional amendment, the other “third rail” policy objective, is written into the LDP charter while the non-nuclear principles have been the law of the land since 1967. As such, there are LDP heavyweights who strongly oppose even broaching the idea of an independent nuclear arsenal, let alone putting it to the Diet for discussion for changing the non-nuclear principles. For those that may be on the fence, when presented with the option of retaining control of the government or producing nuclear weapons, it is safe to assume that those lawmakers would prefer to keep their jobs, no matter what their individual beliefs may be.

Is there a threshold where Japan eschews political costs and pursues nuclear technology? In all things politics, it is foolish to answer “never” to anything, but the threshold here is extremely high. In short, there would have to be a complete abandonment by the U.S. as an ally. Many observers will argue that uncertainty about the U.S. position toward North Korea or the debates over cost-sharing may be enough for Japan to consider it, but that is not the case. As long as the U.S. nuclear umbrella exists, the Japanese government will not have the political impetus to change its course.

So if it is an untenable policy position, why the political rhetoric? Of course, there are always the true believers who want a nuclear-armed Japan. However, politicians are politicians, and some know that they can capture the attention of domestic and foreign audiences with talk of nuclear armament. That attention and the leverage that comes from fear of Japanese nuclear proliferation presents opportunities for Japanese political leaders to shape current and near-term policy discourse, both foreign and domestic. Even in those cases, however, it is a political tactic with little actionable weight behind it.

In sum, the shifting strategic paradigm in Northeast Asia will likely renew the nuclear debate in Japan, but that does not mean we should expect any substantive change to Japanese policy. To put it clearly, the impetus for Japan to pursue a domestic nuclear arsenal would have to outweigh two major costs: one, upsetting the regional strategic paradigm; and two, inviting domestic political criticism that would likely generate a massive loss of Diet seats and bring about a change in government. While there may be a recognition among Japanese political leaders that possession of nuclear weapons is “immoral,” as far as Japan’s defense policy is concerned, the devil it knows is better than the devil it doesn’t.

Michael MacArthur Bosack is the special adviser for government relations at the Yokosuka Council on Asia-Pacific Studies. He previously served in the Japanese government as a Mansfield fellow and is a former officer in the U.S. Air Force.

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