Japan’s nuclear debate, long treated as a political taboo, is resurfacing. Last week, Japan’s former defense minister, Nakatani Gen, made the most explicit public statement to date on the need for Japan to introduce nuclear-powered submarines (SSNs). Prime Minister Sanae Takaichi earlier last month also hinted at a possible revision of the third principle of the country’s longstanding non-nuclear policies that prohibits the introduction of nuclear weapons into Japan’s territory.
Japan’s recent stir over nuclear weapons is unlikely to be realized in the near future, given its pacifist policy. The country adheres to a set of laws and protocols that prohibit it from pursuing nuclear development. The Chief Cabinet Secretary, Minoru Kihara, has reaffirmed that the non-nuclear principles will remain in place while the national security documents are revised. However, Japan should reconsider introducing nuclear weapons to Japanese soil, given the deteriorating security environment in the region.
With Russia repeatedly issuing nuclear attack threats against Ukraine, North Korea continually expanding its nuclear arsenal, China doubling its nuclear weapons, and South Korea’s recent deal with the US over nuclear-powered submarines, Japan remains the only major power without them. In such a state, while Japan, adhering to the Non-Proliferation Treaty (NPT), will not possess or produce nuclear weapons, it should at least allow US nuclear weapons on its soil to exercise extended deterrence.
Earlier this month, Takaichi told the Japanese parliament that a hypothetical Chinese attack on Taiwan could provoke a military response from Tokyo and would be regarded as a threat to Japan. A conflict in the region escalating into war would likely render Japan vulnerable to a Chinese attack, considering Japan’s Yonaguni Island is just about 110 km from Taiwan. Japan and the US have only four bases within range of the Senkaku Islands—a disputed territory claimed by China, Japan, and Taiwan—whereas China possesses approximately two dozen military bases within reach.
Furthermore, the argument that Japan having nukes on its soil will raise alarm in East Asia is flawed. China, Russia, and North Korea already have nuclear weapons. China is steadily increasing its fleet of SSNs. South Korea and North Korea are both expected to acquire nuclear submarines in the near future. Seoul will be latent to produce nuclear weapons in a time of crisis. Taiwan, despite a real threat from China, has not gone nuclear yet. Unless Beijing uses an overt nuclear threat against Taipei, it is unlikely that the latter will consider possessing nukes. Furthermore, Japan is already a latent nuclear power, often referred to as having a ‘bomb in the basement.’ As of 2024, it owns 45.5 tons of separated plutonium, with approximately 9 tons in Japan and the remaining 36.5 tons “temporarily” stored by France and the U.K. It has the technical capability to enrich them to weapons-grade material in short order.
Pacifists are the ones most concerned about nuclear weapons, given that Japan is the only country to have suffered atomic bombing. However, they need to understand that the government is considering allowing nuclear weapons on Japanese soil “in the event of a crisis,” as hinted by the government’s top spokesman. Japan is already under the US extended deterrence. In times of crisis, the US may need to use Japanese territory for nuclear weapons. As far as SSNs are concerned, Japan’s defense activity today is no longer confined to its national borders. It has shifted towards a more regional-focused defense posture. Over the years, there has been a growing political and public willingness in Japan to loosen the non-nuclear principle. In a 2020 poll, while around 75% of the Japanese public supported a global ban on nuclear weapons, recent polls have shown that they recognize the necessity of nuclear weapons for deterrence. A poll conducted in Hiroshima in August 2025 found that 53% of respondents believe that “the U.S. nuclear umbrella is necessary for now.”
The Japanese government itself regards the US nuclear weapons to be an inevitable part of its security policy. Article 9 of Japan’s constitution renounces “the threat or use of force as a means of settling international disputes.” However, the government, since 1957, has consistently stated that this article does not technically prohibit Japan from acquiring or developing nuclear weapons solely for its “self-defense.” The 2013 and 2018 National Defence Program Guidelines state that “In dealing with the threat of nuclear weapons, US extended deterrence, with nuclear deterrence at its core, is essential. Japan will closely cooperate with the United States to maintain and enhance its credibility.” Japanese officials have often emphasized their opposition to a potential US no-first-use policy and their insistence on nuclear capabilities.
Furthermore, in October 2016, Japan voted against the United Nations General Assembly’s initiative to launch negotiations on a nuclear weapons ban. Last month, Defense Minister Shinjiro Koizumi stated that examining the feasibility of building a nuclear-powered submarine should be considered, given Japan’s deteriorating security environment. Japan has also declined to sign or ratify the Treaty on the Prohibition of Nuclear Weapons (TPNW). While Foreign Minister Takeshi Iwaya stated that the reason was that the treaty did not involve all the nuclear-armed states, actually, signing would mean that Japan would have to forgo the US’s extended nuclear deterrence.
Deterrence and disarmament are equally indispensable for Japan. Given that Japan is surrounded by nuclear powers, nuclear disarmament is far from reality, and the nuclear threat will continue to exist in the coming years. Therefore, at minimum, the best option for Japan is to revise its third principle of allowing US nuclear weapons on its soil, at least in times of crisis. While maintaining a long-term vision for disarmament, it is more practical for Japan to maintain a short-term vision prioritizing deterrence.