Mixed Message: Japan’s Conflicted Stance on Nuclear Disarmament

In August 1945, in the closing days of World War II, the United States detonated two atomic bombs over the cities of Hiroshima and Nagasaki. America is thus far the only country to make use of nuclear weapons in wartime, and Japan remains the sole victim of such an attack.

That was almost 80 years ago. In the intervening decades, Japan and the United States have forged a strong alliance, which “remains the cornerstone of peace, security and prosperity in the Indo-Pacific and beyond,” according to the joint statement issued by Prime Minister Ishiba Shigeru and President Donald Trump this past February. Moreover, integral to that relationship (according to the same statement) is America’s ongoing “commitment to the defense of Japan, using its full range of capabilities, including nuclear capabilities.”

Herein lies Japan’s nuclear dilemma.

Under the Nuclear Umbrella

In 1967, the Japanese government announced a policy of not possessing, producing, or permitting the introduction of nuclear weapons. The government has continued to profess these “three nonnuclear principles,” which enjoy the support of the great majority of Japanese voters. Yet the Japan-US alliance places Japan under the protection of America’s extended nuclear deterrence, or “nuclear umbrella.” In other words, the bilateral security relationship is at heart a nuclear alliance. Reconciling these two realities is a delicate balancing act.

Epitomizing the dilemma is Japan’s stance vis-a-vis the Treaty on the Prohibition of Nuclear Weapons (TPNW), which calls for a blanket ban on the development, testing, possession, use, and threat of use of nuclear arms. The TPNW, which came into effect in 2021, traces its origin in part to the horrors of Hiroshima and Nagasaki, as suggested in the preamble’s reference to the “unacceptable suffering of and harm caused to the victims of the use of nuclear weapons (hibakusha).” Yet the Japanese government, while hailing the TPNW as “an important treaty that could be regarded as a final passage to a world without nuclear weapons,” has declined to become a signatory on the grounds that, without the participation of any of the nuclear-weapon states, it offers no practical path to denuclearization.

The third meeting of the parties to the TPNW opened on March 3 this year at UN Headquarters in New York. Although the meeting is open to observers as well as signatories, Japan declined to attend. That decision drew intense criticism from a number of civil society groups in Japan, including Nihon Hidankyō (Japan Confederation of A- and H-Bomb Sufferers Organizations), winner of the 2024 Nobel Peace Prize. Nihon Hidankyō Co-chair Tanaka Terumi called Japan’s failure to put in an appearance not merely regrettable but “pathetic.”

The Japanese government has made it clear that it regards the Treaty on the Nonproliferation of Nuclear Weapons (NPT)—not the TPNW—as the foundation for international efforts toward nuclear disarmament and nonproliferation. But why decline even to attend the TPNW meeting as an observer?

At a press conference on February 18, Minister for Foreign Affairs Iwaya Takeshi addressed the question. He pointed out that the nonproliferation movement is being undermined by growing divisions between the designated nuclear-weapon states, which stand by the concept of deterrence, and those nonnuclear states that reject deterrence and call for a total ban. He claimed that Japan, as the sole victim of a nuclear attack, had a great influence on nonproliferation efforts and argued that any indication of support for the TPNW could make it harder for Japan to gain widespread support for its efforts to bring the two sides together under the NPT. To many, this explanation seemed to overstate Japan’s clout.

Surely the main factor behind the government’s decision was the other reason Iwaya cited during his press conference. As the foreign minister succinctly put it, “extended nuclear deterrence is indispensable to the protection of the lives and property of the Japanese people and to this country’s independence and peace,” and the TPNW is “incompatible with extended nuclear deterrence.” By attending the TPNW meeting, even as an observer, the government would “send the wrong message regarding Japan’s policy on nuclear deterrence and thereby risk compromising its own peace and security.”

In a word, extended deterrence is impossible under the TPNW, which bans not only the use of nuclear weapons but also the threat of their use and any support for countries in violation of those prohibitions. As a beneficiary of America’s nuclear umbrella, Japan is in no position to tell the United States that it must never, under any circumstances, make use of nuclear weapons.

Binding and Nonbinding Norms

The fact that nuclear weapons have not been used against any population or locale since the 1945 bombings of Hiroshima and Nagasaki has led to broad agreement among scholars that there is a strong normative aversion to the use of nuclear weapons (although experts disagree as to whether that aversion is strong enough to be considered a taboo).

In Japan, the norm of nonuse is particularly strong and widespread. It finds expression in the oft-heard slogan No More Hiroshimas and in the inscription on the Cenotaph for the Atomic Bomb Victims in Hiroshima Peace Memorial Park: “Let all the souls here rest in peace; For we shall not repeat the evil.” In keeping with this norm, the Japanese government does not openly condone the use of nuclear weapons. But that is merely an example of superficial conformance with identity-defining customs, a “constitutive effect” of norms.

Norms can also have a more binding “regulative effect,” constraining behavior through the threat or implication of penalties against violators. The Japanese government, however, has always stopped short of conferring any explicit regulative effect on the norm of nonuse of nuclear weapons. For example, in regard to the nuclear disarmament resolutions that come before the UN General Assembly each year, Japan has refused to vote for any that prohibited the use of nuclear weapons, with the sole exception of the first such declaration, adopted in 1961. My own research has concluded that pressure from Washington lay behind Japan’s change in posture.

The TPNW seeks to impose strong regulative norms in the form of an international law that bans the use of nuclear weapons and nuclear testing and, further, prohibits the stationing of other countries’ nuclear weapons systems or other forms of support. Since 1962, at the height of the Cold War, the Japanese government has distanced itself from such efforts, and its decision to skip the March meeting of the parties is consistent with that stance. Underlying the policy is the presence of the United States, which Tokyo cannot afford to ignore.

A Non-Issue in Washington?

But would Washington actually have objected to Japan’s attendance as an observer at a meeting of the parties to the TPNW? Having traveled to the United States to observe the March meeting (which had not yet begun as of this writing), I stopped in Washington DC, where I had the opportunity to discuss these matters with former government officials and experts in the field of disarmament and nonproliferation. All were of the opinion that no one in Washington cared about the meeting one way or the other.

Of course, the experts and officials with whom I met were all people in the disarmament field. They could not be expected to speak for President Donald Trump, who proudly flaunts his America First disdain for international norms. Indeed, given Trump’s tendency to view policy through the prism of personal animus and zero-sum deal making, it may have been prudent of the Japanese government to deny him an opportunity to complain of Japan’s ingratitude toward the United States.

In truth, however, attendance or non-attendance at such conferences is the least of Tokyo’s problems right now. A more serious question is whether Japan can even depend on the US nuclear umbrella with Trump as president. Another is what Japan can really do as the only country to suffer a nuclear attack to prevent nuclear war in the future.

There are no simple answers to these questions. But until Japan starts grappling with them seriously, its call for “a world without nuclear weapons” will have no more weight than an advertising slogan.

(Originally published in Japanese on March 5, 2025. Banner photo: Nihon Hidankyō’s Hamasumi Jirō speaks at the third Meeting of States Parties to the Treaty on the Treaty on the Prohibition of Nuclear Weapons in New York on March 3, 2025. © Kyōdō.)