Partial Nuclear Test Ban Treaty

• 1. Introduction

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  On the 5th of August 1963, three governments gathered in Moscow to sign a document that had taken nearly two decades of argument, scientific dispute, and near-catastrophe to produce. The Partial Nuclear Test Ban Treaty forbade nuclear weapons tests everywhere except underground. It came with no enforcement mechanism for violations, no halt to the arms race it was meant to slow, and no membership from France or China, two countries that would keep detonating weapons in the atmosphere for years after. And yet the treaty marked a turning point. Since 1980, every declared nuclear-weapons state has confined its tests to underground facilities, and the concentration of radioactive particles in the atmosphere fell substantially in the years following the treaty's entry into force on the 10th of October 1963.

  How did a document so limited come to exist at all? The answers run through a Japanese fishing crew caught in radioactive ash, a Soviet bomb fifty times more powerful than anything that had come before, a scientific community divided against itself, and two leaders shaken by how close the world had come to annihilation over Cuba.

• 2. Fallout and Public Fear

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  On the 1st of March 1954, the United States detonated a thermonuclear device at Bikini Atoll during Operation Castle. The Castle Bravo test was expected to yield a certain magnitude of explosive force. It produced 15 megatons of TNT, more than double what had been predicted. Radioactive particles spread over more than 11,000 square kilometers, reaching inhabited atolls including Rongelap and Utirik. Japanese fishermen aboard a vessel called the Lucky Dragon were showered with what witnesses described as ashes of death.

  In the same year, a Soviet test sent radioactive contamination drifting over Japan. The double blow fixed public attention on the consequences of above-ground detonations in a way that official reassurances could not easily undo. By 1957, support for a test ban among the American public had climbed from roughly 20 percent in 1954 to 63 percent.

  The strontium-90 problem drove much of that shift. Scientists and citizens organized the Baby Tooth Survey, a campaign that used what its organizers described as modern media advocacy techniques to translate the data into terms ordinary people could understand. Their findings confirmed that strontium-90 was accumulating in the bones of young children at measurable levels. Lewis Strauss, the Atomic Energy Commission chairman, and Edward Teller, widely known as the father of the hydrogen bomb, argued that fallout at the dose levels experienced in the US was relatively harmless. Their reassurances increasingly failed to persuade.

  Nobel Peace Prize laureate Albert Schweitzer organized antinuclear protests endorsed by Pope Pius XII. The chemist and Nobel laureate Linus Pauling gathered an anti-test petition signed by more than 9,000 scientists across 43 countries, including the elderly and infirm Albert Einstein. The AEC would eventually concede that even low levels of radiation were harmful, a significant reversal.

• 3. The Science of Detection

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  Before any treaty could be written, a fundamental technical problem had to be solved: how do you know when someone has detonated a nuclear weapon underground? On the 19th of September 1957, the US conducted its first contained underground test at the Nevada Test Site, codenamed Rainier. The Rainier shot immediately complicated the push for a comprehensive ban, because underground detonations could not be distinguished from earthquakes with the instruments then available.

  In the summer of 1958, the nuclear powers convened what became known as the Conference of Experts in Geneva. The US delegation was led by James Fisk, a vice president at Bell Telephone Laboratories. The British sent William Penney, who had led their delegation to the Manhattan Project. The Soviets were represented by Evgenii Fedorov. Four techniques were examined: measurement of acoustic waves, seismic signals, radio waves, and inspection of radioactive debris.

  By the end of August 1958, the experts had devised a control program called the Geneva System, involving 160-170 land-based monitoring posts, 10 sea-based monitors, and occasional aircraft flights over land following any suspicious event. The conference declared in a communiqué dated the 21st of August 1958 that the scheme could detect 90 percent of underground detonations accurate to 5 kilotons, and atmospheric tests with a minimum yield of 1 kiloton.

  The optimism did not survive contact with later data. Results from the Hardtack underground tests of 1958 persuaded US scientists, including Hans Bethe, who personally supported a ban, that the Geneva System was too optimistic. Where the conference had believed the system could detect underground tests down to 5 kilotons, the revised US estimate placed the lower threshold at 20 kilotons. For reference, the bomb dropped on Hiroshima had an official yield of 13 kilotons. Work by researchers at the Livermore National Laboratory and the RAND Corporation, commissioned by Teller, found that a technique called decoupling could artificially dampen the seismic signal of a 300-kiloton detonation to appear as a 1-kiloton event. These findings were confirmed even by scientists who favored a ban.

• 4. Khrushchev's Calculation

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  Nikita Khrushchev's political situation in the late 1950s was more precarious than it appeared from the outside. In the summer of 1957, the Anti-Party Group, composed of former Stalin allies Lazar Kaganovich, Georgy Malenkov, and Vyacheslav Molotov, attempted to replace him as General Secretary with Nikolai Bulganin. The attempt was defeated in June. By October 1957, Khrushchev had forced out defense minister Georgy Zhukov, described at the time as the nation's most powerful military man. On the 27th of March 1958, he compelled Bulganin to resign and took the premiership himself.

  From that position of consolidated but still fragile authority, Khrushchev approached test-ban negotiations as an opportunity to present the Soviet Union, in his own framing, as both powerful and responsible. He had declared at the 20th Communist Party Congress in 1956 that nuclear war should no longer be seen as fatalistically inevitable. He was personally troubled by the weapons and would later recount his belief that they could never actually be used.

  At the same time, Khrushchev was expanding the Soviet nuclear arsenal and in early 1960 announced the demobilization of 1.2 million troops, shifting resources toward nuclear capabilities. On the 31st of October 1961, the Soviet Union detonated the Tsar Bomba over the island of Novaya Zemlya, a 50-megaton device that remains the most powerful human-made explosion in history. A report by a group of American scientists led by Hans Bethe concluded that Soviet laboratories had likely been operating at full capacity throughout the testing moratorium, anticipating its end.

  The asymmetry in underground test experience shaped Khrushchev's eventual acceptance of a partial ban. By 1962, the US had conducted 89 underground tests. The Soviet Union had conducted two. Soviet weapons designers argued that a ban on atmospheric tests would therefore favor the American side, since underground testing required different, more expensive infrastructure that the US had already developed.

• 5. Kennedy's Dilemma

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  John F. Kennedy entered the presidency in January 1961 committed to a comprehensive test ban, which he saw as the central tool for slowing what he called the Nth-country problem: the cascade of nations that would acquire nuclear weapons once one or two additional states crossed the threshold. While still a candidate, Kennedy had named France, China, and Sweden as potential entrants into the nuclear club, arguing that each new state crossing the line weakened the security of both the US and the Soviet Union.

  The internal politics of his own government made progress difficult. The Joint Chiefs of Staff, the Atomic Energy Commission, and the Department of Defense pushed for continued testing. Teller continued to argue in early 1962 that nuclear fallout presented no serious health concern and that testing was essential for advancing second-strike capability. Then-Secretary of Defense Robert McNamara privately acknowledged that resumed atmospheric tests were not really necessary, but he was an outlier in the defense establishment.

  Kennedy himself, according to the record, hated the idea of reopening the race. Hubert Humphrey described the moratorium as a ray of hope to millions of worried people and warned that its termination might turn the political tides in the world in behalf of the Soviets. John Kenneth Galbraith, then the ambassador to India, told Kennedy in June 1961 that resumed testing would cause the gravest difficulties in Asia, Africa, and elsewhere. Adlai Stevenson, then the UN ambassador, also opposed the resumption.

  Kennedy ultimately sided with William Foster, head of the Arms Control and Disarmament Agency, who argued that failing to respond to the Soviet test series risked allowing Moscow to run a second series that could produce a significant strategic advantage. On the 2nd of March 1962, Kennedy announced that atmospheric testing would resume by the end of April unless Moscow accepted the Anglo-American proposal. The moratorium was lifted on the 25th of April 1962.

• 6. The American University Speech

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  By the spring of 1963, the path to a comprehensive ban had closed. The gap between the US and Soviet positions on on-site inspections could not be bridged: the US and UK proposed 20 inspections per year; Khrushchev offered three, and eventually withdrew even that offer in April 1963. A resolution backed by 34 US Senators, led by Humphrey and Thomas J. Dodd, called on Kennedy to pursue a partial ban instead, with national monitoring and no on-site inspections.

  On the 10th of June 1963, Kennedy delivered his commencement address at American University in Washington, dedicating the speech to what he called the most important topic on earth: world peace. He appealed to Americans to abandon what he described as a distorted and desperate view of the other side and to pursue a more practical, more attainable peace based on concrete actions and effective agreements. He announced a unilateral halt to US atmospheric testing and an agreement with Khrushchev and Macmillan to resume comprehensive test-ban negotiations in Moscow.

  Khrushchev later called it the greatest speech by any American President since Roosevelt. The domestic reception was more mixed. Republican Senator Barry Goldwater labeled it a dreadful mistake. Everett Dirksen, the leader of Senate Republicans, called it another case of concession, and he and Charles Halleck warned that the renewed negotiations might end in virtual surrender.

  Kennedy's choice of chief negotiator signaled how seriously he took the Moscow talks. W. Averell Harriman, a former ambassador to the Soviet Union with a well-established personal standing in Moscow, was selected for the role. The Soviet delegation was led by Foreign Minister Andrei Gromyko. Britain sent Quintin Hogg, though Kennedy's advisor Arthur Schlesinger privately assessed that Hogg was ill-prepared on the technicalities and consumed by a desire to get a treaty at almost any cost.

• 7. After Moscow

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  Norman Cousins, the editor of a major US periodical and an antinuclear activist, had spent months in 1962 and 1963 carrying messages between Kennedy and Khrushchev in an unofficial capacity. His shuttle diplomacy was aided by Pope John XXIII, who served as an intermediary and remained, in Cousins' account, at the center of negotiations. In a letter to Kennedy dated the 30th of October 1962, written in the immediate aftermath of the Cuban Missile Crisis, Khrushchev had proposed a non-aggression treaty between NATO and the Warsaw Pact, a complete halt to nuclear testing, and the total elimination of nuclear weapons. Kennedy's formal response was cautious, but through Cousins he communicated that he felt constrained by hardliners within his own national security apparatus.

  The Cuban Missile Crisis had changed the political conditions in ways that made a partial agreement possible where a comprehensive one had failed. Khrushchev later recounted that he saw test-ban negotiations after Cuba as the prime venue for easing tensions. Soviet nuclear scientists, including Andrei Sakharov, Yulii Khariton, and Igor Kurchatov, had argued that atmospheric testing carried severe consequences for human health, and their arguments contributed to Khrushchev's willingness to accept a partial ban.

  The treaty that emerged banned all test detonations except those conducted underground. France and China, neither a signatory, continued atmospheric testing until 1974 and 1980 respectively. Two signatories, Israel and South Africa, may have violated the treaty in what became known as the 1979 Vela incident. Since 1980, all declared nuclear-weapons states have tested only underground, and no non-underground test has been confirmed since that year. Sakharov, who had been part of the Tsar Bomba design team in 1961 and had estimated in 1958 that a single one-megaton clean bomb would cause 6,600 deaths over 8,000 years, would go on to become one of the most prominent voices in the Soviet antinuclear movement.