Asia Defense | Security | East Asia

Takaichi, the Three Non-Nuclear Principles, and a Strained US Nuclear Umbrella

For Japan, the most immediate question is not whether to pursue nuclear weapons itself, but whether to allow its ally’s nuclear-capable assets on Japanese soil.

Eighty-one years after the atomic bombings of Hiroshima on August 6, 1945, and Nagasaki on August 9, Japan is confronting an increasingly difficult contradiction: how to uphold its identity as the only country to have suffered atomic attack in wartime while strengthening deterrence against an increasingly formidable group of nuclear-armed neighbors.

The dilemma came into sharper focus during this year’s Hiroshima and Nagasaki commemorations. Prime Minister Takaichi Sanae stated that Japan “maintains” its Three Non-Nuclear Principles and reaffirmed Tokyo’s commitment to pursuing a world free of nuclear weapons. Yet when asked whether the principles would continue to be explicitly affirmed in the three strategic documents her government plans to revise by the end of the year, Takaichi declined to prejudge the wording.

That ambiguity matters. Japan’s Three Non-Nuclear Principles – not possessing, not producing, and not permitting the introduction of nuclear weapons into Japanese territory – trace back to former Prime Minister Sato Eisaku’s 1967 declaration and have long stood as a symbol of Japan’s postwar identity.

The tension was particularly visible in Nagasaki on August 9. Mayor Suzuki Shiro described nuclear weapons as an “absolute evil,” warned of the dangers of relying on nuclear deterrence, and urged the government to uphold the Three Non-Nuclear Principles. Takaichi, by contrast, reiterated Japan’s current adherence to the principles while emphasizing a “realistic and practical” approach toward achieving a world without nuclear weapons.

The strategic backdrop underpinning the Three Non-Nuclear Principles has shifted considerably. China is rapidly expanding and modernizing its nuclear forces, North Korea continues to develop nuclear weapons and increasingly sophisticated missiles, and Russia remains one of the world’s two largest nuclear powers while deepening military cooperation with both Beijing and Pyongyang.

At the same time, doubts about the credibility of U.S. extended nuclear deterrence have grown harder to dismiss. Jennifer Lind and Daryl G. Press argued in Foreign Affairs this summer that the traditional U.S. nuclear umbrella is coming under increasing strain as adversaries acquire more credible means of striking the U.S. homeland. Their argument revives a long-standing concern about “decoupling”: whether Washington would risk devastating retaliation against the United States in order to defend an ally such as Japan or South Korea.

Put more starkly, the question is this: Would an American president risk Los Angeles to defend Tokyo or Seoul?

Under an “America First” posture in Washington, that question carries added political weight. The credibility of extended deterrence ultimately depends on whether an adversary believes Washington would accept the risk of nuclear retaliation to defend an ally.

Inside Japan, meanwhile, the reluctance to discuss nuclear deterrence openly is gradually eroding. Defense Minister Koizumi Shinjiro has argued that nuclear issues can no longer simply be avoided in policy discussions. Former Joint Staff Chief Kawano Katsutoshi has similarly questioned whether Japan can indefinitely assume that the American nuclear umbrella will hold, calling for a broader national debate.

Takaichi herself raised the underlying issue well before becoming prime minister. In a 2024 book, she revealed that, as a Cabinet........

© The Diplomat