Does Japan Have Nuclear Weapons?

, China project manager and senior analyst | May 1, 2020, 11:31 am EST
Bookmark and Share

This post is a part of a series on Reversing a Dangerous Course

Japan does not have its own nuclear weapons. The Japanese government considered developing them in the past, but decided this would make Japan less secure. Japanese opinion polls consistently express strong public opposition to nuclear weapons. So do their elected representatives.

There is, however, a small group of non-elected Japanese bureaucrats with close ties to the U.S. defense establishment who insist U.S. nuclear weapons should be “the core of Japan’s security arrangements.” Wonks refer to this supposed core as “extended nuclear deterrence.” Journalists and politicians, especially in Japan, call it a “nuclear umbrella.”

Target Practice

The first time Japanese officials were allowed to see how this umbrella works was in 1957 during a military exercise. A large fleet of Soviet bombers were supposed to attack U.S. military bases in Japan. U.S. forces simulated launching nuclear weapons into the skies over Japan to wipe them out.

The Japanese officials invited to this exercise must have been horrified. They sent a letter to the U.S. Joint Chiefs of Staff asking, “Would the free world sacrifice one of its own countries by means of unrestricted nuclear warfare in order to gain ultimate victory?” The chiefs replied, “The atomic weapons which would be used against enemy forces would be selectively employed to assure minimum damage to the country and its population.”

The Buildup

The Japanese government successfully resisted U.S. efforts to deploy nuclear weapons on U.S. military bases in Japan. But a secret codicil of the 1960 security treaty allowed U.S. nuclear-armed naval vessels and aircraft to transit Japan.

When the treaty was signed the United States controlled of the island of Okinawa, which it captured during World War II. Not long after the 1957 exercise the United States began a nuclear buildup on Okinawa that peaked around 1,200 weapons in 1967.

A 1968 non-public Japanese government study concluded the costs of Japan developing its own nuclear weapons were high and the security benefits negligible. Shortly afterward, Japan joined the Nuclear Non-Proliferation Treaty (NPT) as a non-nuclear weapon state.

Non-Nuclear Principles

One year later Japanese public opposition to U.S. control of Okinawa, and to the presence of U.S. military bases in Japan, forced the United States to give it back. Because the 1960 security treaty forbid the deployment of U.S nuclear weapons in Japan, the nuclear weapons in Okinawa were removed before the island was returned in 1972.

Prime Minister Eisaku Sato, who negotiated the Okinawa agreement, was awarded the Nobel Peace Prize for leading Japan into the NPT. He told the Nobel committee he established “three non nuclear principles” that were reaffirmed by Japan’s national legislature. The principles state Japan will not manufacture, possess or bring nuclear weapons into Japan.

The three principles do not have the force of law. But Japanese officials–even those who secretly ignore them–repeatedly express fealty whenever questioned. The secret codicil that allows U.S. nuclear-armed ships and planes to transit Japan violates the third principle, which is probably why Japanese officials denied its existence until an opposition government officially exposed it in 2010.

Prospects for the Future

The Japan Defense Agency conducted a second non-public study on whether Japan should develop its own nuclear weapons before agreeing to a permanent extension of the NPT in 1995. The study concluded that even in a worse-case scenario where both the U.S.–Japan alliance and the NPT collapsed, it was still “not favorable for Japan to take the nuclear option.”

This suggests Japan is highly unlikely to develop its own nuclear weapons in the future.

Still, that small group of Japanese bureaucrats with close ties to the U.S. defense establishment continues to work hard to maintain the role of U.S. nuclear weapons in Japanese security policy.  They opposed President George H.W. Bush’s 1991 decision to unilaterally remove all U.S. nuclear weapons from Asia. They told the U.S. Congress they support preparations to redeploy U.S. nuclear weapons in Okinawa. And they applauded the Trump administration’s decision to bring U.S. nuclear weapons back into Asia.

These Japanese officials only speak in private and take exceptional measures to keep their comments secret. That’s probably due to concerns about Japanese public opinion. A 2015 NHK poll showed that only 10.3 percent of respondents felt the nuclear umbrella was necessary, down from 20.8 percent in 2010.

This tiny but powerful minority is also preventing the Japanese government from signing the Treaty on the Prohibition of Nuclear Weapons (TPNW). Japanese supporters of the treaty, led by the survivors of Hiroshima and Nagasaki, are pressing the Japanese government to sign.

You can help by supporting their appeal.

Header image: Chairman of the Joint Chiefs of Staff/flickr. (DoD photo by Navy Petty Officer 2nd Class Dominique A. Pineiro

Posted in: Japan, Nuclear Weapons Tags:

Support from UCS members make work like this possible. Will you join us? Help UCS advance independent science for a healthy environment and a safer world.

Show Comments


Comment Policy

UCS welcomes comments that foster civil conversation and debate. To help maintain a healthy, respectful discussion, please focus comments on the issues, topics, and facts at hand, and refrain from personal attacks. Posts that are commercial, self-promotional, obscene, rude, or disruptive will be removed.

Please note that comments are open for two weeks following each blog post. UCS respects your privacy and will not display, lend, or sell your email address for any reason.