Could pacifist Japan ever arm itself with nuclear weapons?
Ellen Thomas
Could pacifist Japan ever arm itself with nuclear weapons?
The nation's 'three nos' are under strain amid concern over U.S. security commitments
https://www.japantimes.co.jp/commentary/2025/09/23/japan/can-japan-arm-itself-with-nuclear-weapons/
Is there any scenario where pacifist Japan could decide to arm itself with nuclear weapons?
The answer to the above question would have been “never” for most Japanese over the past 80 years. Being the only country to have experienced a nuclear attack, Japan strongly resists the very topic.
Pacifists will argue that nuclear weapons are forbidden under the 1947 Constitution, although there is no such prohibition in the supreme law of the nation. Since 1957, the Japanese government has consistently stated that Article 9 does not technically prohibit Japan from acquiring or developing nuclear weapons solely for its “self-defense.”
Prime Minister Eisaku Sato stated in 1967 that Japan’s official policy on nuclear weapons has been the “three nos” — no to possessing, no to producing and no to permitting the introduction of nuclear weapons into Japanese territory.
In 1968, Sato expanded the policy by promoting nuclear energy for peaceful purposes, global nuclear disarmament, reliance on the U.S. nuclear deterrent for protection against nuclear attack and the three nos. With the Vietnam War underway and other regional tensions, these principles kept the “nuclear option” open should Japan’s existence be threatened.
Since then, the nuclear debate waxed and waned with the rise of the North Korean threat since the 1990s and into the 2000s, but the nuclear option silently remained a last resort.
Legal impediments to Japan developing a nuclear deterrence are twofold: its membership in the nuclear Non-Proliferation Treaty and Japan’s own Atomic Energy Basic Law, which, since 1955, restricts the nation’s use of nuclear energy to “peaceful purposes” and bans research and development for weapons production.
Japan entered into a series of bilateral nuclear cooperation treaties with the U.S., France, the U.K., Canada and Australia, under which it receives a supply of natural and enriched uranium, as well as nuclear energy technology, for “peaceful purposes.”
On the other hand, there are no material or technical obstacles to Japan producing a nuclear weapon on its own. As of last December, the country currently 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. after they reprocessed spent fuel from Japan’s nuclear power plants for future use in mixed-oxide power plants.
The nation has the technical capability to enrich this to weapons-grade material in short order. Once enriched, the plutonium held in Japan alone would be enough to build 1,000 bombs.
Likewise, Japan has advanced machining and manufacturing capabilities, including miniaturization, enabling it to produce weapon components and a range of potential delivery systems such as intermediate-range missiles, ships, submarines and aircraft.
It has always been a question of having the will to act and the belief that the U.S. nuclear deterrence commitment to Japan was beyond question.
But the strategic environment in East Asia has grown ever more tense. While China continues to threaten Taiwan with military invasion, it has doubled its nuclear weapons to an estimated 600 and deployed a triad of land, air and submarine systems. It is believed China will field over 1,000 state-of-the-art nuclear weapons by 2030.
North Korea continually expands its nuclear arsenal currently estimated at 50, with enough material on hand to assemble up to 90. It has successfully demonstrated intercontinental ballistic missiles and is working to deploy a nuclear ballistic-missile submarine.
Russia repeatedly issues threats of nuclear attack against Ukraine and any country that aids in its defense, demonstrating the power of nuclear blackmail. Russia now openly supports the nuclear and missile programs of North Korea.
While whispers grow louder, Japan avoids the hard decisions on the strength of the U.S. nuclear deterrence commitment. The hope was that Japan could keep punting until it faced existential threats and the U.S. commitment was no longer credible.
And indeed, two recent developments call that commitment into question.
First, in imposing new tariffs and demanding $550 billion in new investments in America over the next 40 months, U.S. President Donald Trump ripped up a legally binding bilateral trade agreement that he personally negotiated with his “great friend” and former Prime Minister Shinzo Abe. If Trump will not respect an agreement that he made with Abe, will he respect one that has remained unamended for the most part since 1960?
Second, according to Politico, American defense planners have presented to the U.S. secretary of defense a draft National Defense Strategy that would shift its focus from China to the homeland. That would be a significant departure from previous administrations. The U.S. will now prioritize the defense of North and South America and explicitly deprioritize both Russia and, shockingly, China, which was named the U.S.’s biggest threat in Trump’s first term.
Pointing to the ongoing dispatch of U.S. naval vessels and aircraft to Venezuela, much commentary speculates that Trump could be preparing to accept Russian hegemony in Eastern Europe and Central Asia and to bump China down as a secondary priority to homeland security.
The pending Trump defense strategy closely aligns with what senior officials have been stating since they took office. It signals that Washington may be ready to gradually disengage from the Indo-Pacific, which converts the U.S. nuclear deterrent commitment to Japan into one that is conditional or “transactional” in nature. That exposes Japan to nuclear blackmail at the very least.
Sato’s conditions for the three nos are unraveling. The NPT regime has failed to prevent proliferation. Nuclear disarmament had Ukraine as its big victory, but has now become a case study for what not to do. And, the U.S. “nuclear umbrella” is leaky.
All of those dictate that it is time for tough discussions about how Japan should secure its own independent deterrence. There can be no higher priority for Japan’s leadership than that.
