Announced in 1967, the Three Non-Nuclear Principles forbid the possession, production, and introduction of nuclear weapons and became a cornerstone of Japan’s security policy. Prime Minister Satō simultaneously negotiated the reversion of Okinawa and pressed the United States to remove nuclear arms stationed there. He also signed the 1968 Nuclear Non-Proliferation Treaty, formally committing Japan to the global disarmament framework. These moves helped ease tensions in East Asia and provided a model for non-nuclear national policy.

During the Cold War, East Asia faced instability from China’s nuclear tests and the Vietnam War. The Satō administration introduced the Three Non-Nuclear Principles to reconcile domestic anti-nuclear sentiment with reliance on the U.S. nuclear umbrella, creating a policy framework that balanced deterrence and disarmament ideals. This unique model of “non-nuclear defense under extended deterrence” later informed proposals for nuclear-weapon-free zones in the Asia-Pacific. Although secret agreements on nuclear transit during Okinawa reversion revealed contradictions, Satō’s success in officially removing U.S. nuclear weapons from Okinawa was internationally acclaimed.

From the 1965 U.S.–Japan summit onward, Satō pursued a dual-layered strategy: maintaining a tacit nuclear transit understanding while projecting a public anti-nuclear stance. In February 1967 he declared the Three Non-Nuclear Principles in the Diet, signed the NPT in March 1968, and secured Diet ratification in 1973. The 1971 Okinawa Reversion Agreement achieved “reversion on a par with the mainland” without nuclear arms, using the NSC “prior consultation” clause to constrain future deployment. Satō’s policy operated as a confidence-building measure and remains a canonical case in comparative studies of institutionalizing non-nuclear identity.