Is a Nuclear-Armed Japan Inconceivable?


Would it be better for the United States if Japan had nuclear weapons? That is what Republican presidential candidate Donald Trump suggested, contrary to nearly seventy years of U.S foreign policy, that a nuclear Japan would be preferable. In an interview with The  New York Times, he stated, “you have, probably, North Korea has them…And, would I rather have North Korea have them with Japan sitting there having them also? You may very well be better off if that’s the case.” This week, in an interview with CBS News, Trump stated, when asked if he had reversed his position on Japanese defense, “maybe they will, maybe they won’t.”

Is Trump right? Is a nuclear Japan feasible or even desirable?

In Japan, the reply has been a firm no. In response to Trump’s comments, Foreign Minister Fumio Kishida stated, “it is impossible that Japan will arm itself with nuclear weapons.” In unpacking this statement, we are provided with half of the answer to these questions. As the only country that has had nuclear weapons used against it, Japan has generally foregone overt militarization and has focused on providing national security, overseas peace-keeping operations, and disaster relief. In my recent discussions with Japanese officials, military officers, and civilians it is clear that Japan, unlike some of its counterparts in East Asia, view the acquisition of nuclear weapons extremely unfavorably. This was highlighted during President Obama’s recent visit to Hiroshima where Japanese Prime Minister Shinzo Abe stated, “this tragedy must not be allowed to occur again. We are determined to realize a world free of nuclear weapons.”

The distaste for having their own nuclear deterrent coupled with being in a dangerous neighborhood has required that Japan turn to other countries, like the United States, for security.   It is here, in the U.S.-Japanese alliance, “the cornerstone of Japan’s diplomacy”, according to Shinzo Abe, that we find the rest of the explanation.

For the past 70 years, since the introduction of nuclear weapons, it is the policy of the United States to counter proliferation and curb the expansion of the nuclear club. The United States has been very successful in providing hefty incentives to states that stop their exploration or pursuit of nuclear weapons. One of these inducements, an extended nuclear deterrent, obliges the United States to provide defense and security to allies in the event of an attack or conflict. Rather than disregarding domestic public opinion and risking punishment in the international community, Japan can rely on America’s nuclear arsenal.

This is how the United States has been able to use its protection to constrain risky behavior among its allies. Research in political science would suggest that these types of alliances may entrap and force the United States to get involved when allies take unnecessary risks to get their way. Neil Narang and I show in a recent working paper, however, that nuclear umbrellas can positively shape ally behavior. We find that protected allies, like Japan, are not any more likely to engage in risky business and instead use the alliance to reap political and economic gains.

This is not to say that Japan has no bargaining power of its own. Japan maintains one of the highest latent nuclear capacities in the world. Experts argue that if Japan were to desire nuclear weapons its “break out” time would be short. But it’s this capability that provides Japan with leverage. In a new working paper, Gene GerzhoyRachel Whitlark, and I find that this capability doesn’t necessarily embolden countries. Instead, they use it, short of opting to get nuclear weapons, to settle disputes, gain concessions, and side-step external aggression.

These factors, coupled with Japan’s own distaste for nuclear weapons, suggest that despite Donald Trump’s perspective and potential policy, if elected to the presidency, a nuclear-armed Japan is virtually unthinkable and highly undesirable.

Scholarship also importantly suggests that nuclear allies present dramatically different risks for the United States and the world than do non-nuclear allies. The United States often extends security to allies in dangerous neighborhoods in the hope that this protection can curb conflict, reduce tension, and mitigate the need for an ally to develop their own nuclear weapons. No doubt regional nuclear proliferation would significantly change this calculus. More nuclear allies could mean more chances for escalatory conflict, arms-racing among adversaries, and nuclear accidents that pose significant and unnecessary risks to U.S national and international security.

Given these concerns and the ever-growing threats to international stability and security that the United States and other countries face every day, it is imperative that the next U.S. president and her/his foreign policy remain focused on stopping the spread of nuclear weapons as it has successfully done (notwithstanding a few notable exceptions) for the past 70 years.


Rupal N. Mehta is an Assistant Professor in the Department of Political Science at the University of Nebraska-Lincoln (



Image: White House