Nuclear Tests Banned: US, UK, USSR Sign Test Ban Treaty

Radioactive fallout from nuclear tests was showing up in children's milk, and three superpowers decided they had finally gone far enough. On August 5, 1963, the United States, the Soviet Union, and the United Kingdom signed the Partial Nuclear Test Ban Treaty in Moscow, prohibiting nuclear weapons tests in the atmosphere, in outer space, and underwater. Underground testing remained permitted, a compromise that made the agreement possible but limited its scope. The path to the treaty had been agonizing. Negotiations had dragged on since 1955, stalling repeatedly over verification. The Soviets refused to allow on-site inspections on their territory, which the Americans insisted were necessary to distinguish underground nuclear tests from earthquakes. Meanwhile, testing accelerated. The Soviet Union detonated a 50-megaton hydrogen bomb, the largest explosion in human history, in October 1961. Atmospheric testing by all three powers was depositing strontium-90 into the global food chain, a health risk that turned public opinion sharply against continued testing. President Kennedy made the treaty a personal crusade. His commencement address at American University in June 1963, where he urged Americans to reexamine their attitudes toward the Soviet Union and the Cold War, is considered one of the finest speeches of his presidency and helped create the political space for negotiations. When Premier Khrushchev signaled willingness to accept a partial ban excluding underground tests, talks moved remarkably quickly. The negotiations in Moscow took just ten days. The Senate ratified the treaty 80-19, with opposition coming mainly from military hawks who feared it would constrain American nuclear development. More than 100 nations eventually signed. The treaty did not end the nuclear arms race, as both superpowers continued underground testing for decades, but it eliminated the most visible and health-damaging form of nuclear testing and established the principle that nuclear weapons could be subject to international agreement. Kennedy considered it his greatest accomplishment. He was assassinated three months later.