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