Japan's non-nuclear weapons policy

Developmental history

Following World War II, the atomic bombings, at Hiroshima and Nagasaki and the deconstruction of their imperial military, Japan came under the US "nuclear umbrella" on the condition that they would not produce nuclear weapons. The requirement was imposed by the United States that Japan might develop nuclear weapons, as the technology to develop a nuclear device became known around the world. This was formalized in the Security Treaty Between the United States and Japan, a corollary to the Treaty of Peace with Japan, which authorized the U.S. to deploy military forces in Japan in order "to contribute to the maintenance of the international peace and security in the Far East and to the security of Japan against armed attack from without". The treaty was first invoked in 1953 when, following a series of Japanese airspace violations by Soviet MiG-15s, the Japanese Foreign Ministry requested U.S. intervention.

Early public opposition

In the years after the occupation, with the atomic bombings of Hiroshima and Nagasaki still fresh in the Japanese consciousness, public sentiment was strongly against the use, and even presence on Japanese soil, of nuclear weapons. This sentiment was evidenced by the widely reported accidental irradiation of the Daigo Fukuryu Maru from a U.S. hydrogen bomb test in 1954. News of the incident aroused public fears over radiation and outcry against atomic and nuclear weapons testing.

On 28 July 1955, the U.S. announced its intention to equip military bases in Japan with Honest Johns, conventional missiles which could also be fitted with atomic warheads. The Eisenhower Administration and Hatoyama Cabinet had been arranging for the deployment since March, but the announcement sparked outrage in the Diet and public protest. Okazaki and Hatoyama were forced to make assurances to the Diet that the missiles would not be equipped with nuclear warheads on Japanese territory, and that the United States would have to consult with the entire government before introducing nuclear weapons into Japan.

The language of the Atomic Energy Basic Law, adopted in December 1955, reflects the public sentiment, restricting "the research, development and utilization of atomic energy" to "peaceful purposes". Nuclear power is used in Japan.

In 1957, Prime Minister Nobusuke Kishi stated his opinion that nuclear weapons were not technically prohibited by Article 9 of the Peace Constitution, though for reasons of humanity and in accordance with popular sentiment national policy should prohibit both their use and introduction. (Even this interpretation of the Constitution, however, drew criticism.) Prime Minister Ikeda Hayato reaffirmed the policy in 1962.

Japanese religious leaders were strongly opposed to nuclear weapons— Josei Toda, second President of the Soka Gakkai, issued a declaration, on 8 September 1957, for the complete abolition of nuclear weapons.

Satō's "Four Pillars" Policy

Liberal Democratic Party (LDP) President Eisaku Satō was elected Prime Minister in December 1964 (only a month after China revealed its nuclear weapons capability with a test explosion). Although privately supportive of Japanese nuclearization, circumstances led Prime Minister Satō to first articulate the now-standard Three Non-Nuclear Principles, and he is remembered for his contributions to non-proliferation. Most significantly, he was determined to reacquire the island of Okinawa from U.S. occupation. Frustrated by strong public sentiment against the U.S. nuclear presence there, Satō struck a deal with the Johnson Administration, exchanging control of Okinawa for Japan's entry into the Nuclear Non-Proliferation Treaty (NPT).

To ease public misgivings about his administration's nuclear ambitions, Satō introduced the Three Non-Nuclear Principles to the Diet in 1967. Retroactively, to lessen the principles' restriction on Japanese military defense options, in 1968 Satō broadened the principles into the "Four Pillars Nuclear Policy" of (1) promoting the use of nuclear power for peaceful purposes, (2) global nuclear disarmament, (3) reliance on the U.S. nuclear deterrent for protection from nuclear attack, and (4) the Three Principles. In particular, the fourth pillar called for adherence to the principles "under the circumstances where Japan's national security is guaranteed by the other three policies", implying that a change of circumstances might allow Japan to develop a nuclear program. Amid anxiety over U.S. involvement in the Vietnam War, aggression between North and South Korea, and tense Cross-Strait relations, this stipulation served to reassure the Diet that the nuclear option would still be considered if any of the conflicts escalated to threaten Japanese national security.

This policy of nuclear abstention was justified internally by the 1968/1970 Report, the product of a secret study commissioned by the Satō Government (leaked to the public in 1994). The document was a comprehensive cost-benefit analysis of the nuclear option from technical, economic, political, and international perspectives. Ultimately favoring non-nuclearization, the document concluded that the U.S. nuclear deterrent sufficed to deter outside aggression. It also stressed both Japan's extreme vulnerability to nuclear attack (high population density) and the likelihood of international isolation in the wake of a nuclear weapons program. Though Satō thought little of the principles and was pliant in his enforcement of the principle of nonintroduction, in view of popular opinion and the embracing of the policy by the rival Social Democratic Party, he and the LDP also remained vocally supportive.

In 1970, as desired by the U.S. but after much hesitation and with some key stipulations, Japan signed the NPT; and in 1972, relieved of U.S. nuclear weapons, Okinawa reverted to Japanese rule. The Diet passed a resolution formally adopting the principles in 1971, though they were not made law. Eisaku Satō was presented with the Nobel Peace Prize in 1974, in large part for his work toward Japan's entry into the NPT. In his Nobel Lecture (on the seventh anniversary of his original statement to the Diet), Satō reiterated and discussed the Three Non-Nuclear Principles and expressed hope and confidence that future governments would adopt them as well.