Partial Test Ban Treaty (1963): Ending Atmospheric Nuclear Tests

The Partial Nuclear Test Ban Treaty, also called the Limited Test Ban Treaty, was signed in Moscow on 5 August 1963 by the United States, the United Kingdom and the Soviet Union. It banned nuclear weapon tests in the atmosphere, in outer space and underwater, while still allowing tests underground. Agreed less than a year after the Cuban Missile Crisis, it was the first major arms control agreement of the nuclear age and sharply reduced the radioactive fallout spreading around the planet.

Background: fallout and public alarm

From 1945 to the early 1960s the nuclear powers carried out hundreds of tests, many of them in the open air. Hydrogen bombs released radioactive material high into the atmosphere, from where it spread worldwide. The American Castle Bravo test of 1954 contaminated Marshall Islanders and the crew of a Japanese fishing boat, the Lucky Dragon No. 5, causing international outrage.

In the same year India’s prime minister, Jawaharlal Nehru, called for a halt to nuclear testing. Scientists warned that radioactive isotopes such as strontium-90 were entering the food chain. In St Louis, a survey of children’s milk teeth begun in 1958 found that strontium-90 levels had risen sharply in children born after atmospheric testing began. Campaigns such as the British Campaign for Nuclear Disarmament, founded in 1958, and the American group Women Strike for Peace, active from 1961, kept the issue in the public eye.

Negotiations and the moratorium

Formal talks between the United States, Britain and the Soviet Union began in Geneva in 1958, and the three powers observed an informal moratorium on testing from late 1958. The main obstacle was verification. Underground tests were hard to distinguish from earthquakes, and the West insisted on on-site inspections, which the Soviet Union regarded as a cover for espionage. A conference of scientific experts from East and West, meeting in Geneva in the summer of 1958, had concluded that a worldwide network of control posts could detect most tests, but the two sides disagreed about how many posts and inspections were really needed.

The moratorium collapsed in 1961. The Soviet Union resumed testing in September, including the record-breaking Tsar Bomba on 30 October, and the United States resumed testing soon after. In 1962 both powers conducted large test series in the atmosphere. On 9 July 1962 the American Starfish Prime test exploded a warhead about 400 kilometres above the Pacific. It created an artificial radiation belt that damaged several satellites and disrupted electrical systems in Hawaii, highlighting the dangers of nuclear explosions in space.

The breakthrough of 1963

The Cuban Missile Crisis of October 1962 convinced both Kennedy and Khrushchev of the need to reduce tensions. Talks on a comprehensive ban stalled over the number of annual on-site inspections: the Soviet Union offered two or three, while the United States sought more.

On 10 June 1963 Kennedy gave a commencement address at American University in Washington, later known as the “Strategy of Peace” speech. He called for a reassessment of the Cold War and announced that high-level talks would soon begin in Moscow. Khrushchev responded favourably and proposed a limited ban that did not require inspections. British Prime Minister Harold Macmillan, who had long pressed both superpowers to reach agreement, strongly supported the initiative. During the talks Khrushchev also proposed a non-aggression pact between NATO and the Warsaw Pact, but the Western powers declined to link this to the test ban, and the negotiators focused on the narrower agreement.

Negotiations opened in Moscow on 15 July 1963. The US delegation was led by W. Averell Harriman and the British by Lord Hailsham, while Soviet Foreign Minister Andrei Gromyko represented the Soviet side. The text was initialled on 25 July after only ten days of talks. The next evening Kennedy presented the agreement to the American people in a televised address. Quoting a Chinese proverb, he said that “a journey of a thousand miles must begin with a single step”, and urged the country to take that step.

Terms of the treaty

The treaty is short. Its main provisions are:

• Each party undertakes not to carry out any nuclear weapon test explosion, or any other nuclear explosion, in the atmosphere, in outer space or underwater, including territorial waters and the high seas.
• Underground explosions are banned only if they cause radioactive debris to spread outside the territory of the state conducting the explosion.
• The treaty has unlimited duration, but a party may withdraw with three months’ notice if extraordinary events have jeopardised its supreme interests.
• The treaty was open to all states.

Signature and ratification

The treaty was signed in Moscow on 5 August 1963 by US Secretary of State Dean Rusk, Soviet Foreign Minister Andrei Gromyko and British Foreign Secretary Lord Home, in the presence of Khrushchev and UN Secretary-General U Thant. It was opened for signature by other states on 8 August, and more than 100 countries signed within a few months.

In the United States, ratification required a two-thirds vote in the Senate. After hearings in which some military leaders and scientists such as Edward Teller expressed doubts, the Senate approved the treaty on 24 September 1963 by 80 votes to 19. Kennedy signed the instrument of ratification on 7 October, and the treaty entered into force on 10 October 1963.

Consequences

The treaty brought a dramatic fall in atmospheric testing by the three original parties, and levels of radioactive fallout in the environment declined over the following years. The amount of radioactive carbon-14 in the atmosphere, which had nearly doubled because of testing, peaked in the mid-1960s and then began a long decline. Scientists now use this “bomb pulse” to date tissues and other materials formed during those years. It also helped establish a pattern of superpower cooperation on arms control.

Its limits were clear. Testing moved underground, and the United States and Soviet Union carried out more tests in the years after 1963 than before. France and China refused to sign; France tested in the atmosphere until 1974 and China until 1980. The treaty did not slow the growth of nuclear arsenals.

Legacy

The Partial Test Ban Treaty was the first in a series of agreements, including the Outer Space Treaty of 1967 and the Nuclear Non-Proliferation Treaty of 1968. Later steps included the Threshold Test Ban Treaty of 1974, which limited the size of underground tests. The Comprehensive Nuclear-Test-Ban Treaty, banning all nuclear explosions, was opened for signature in 1996 but has not entered into force because several key states have not ratified it.

Timeline

• 1954, 1 March: The Castle Bravo test spreads fallout across the Pacific.
• 1958, 31 October: Test ban talks open in Geneva amid an informal testing moratorium.
• 1961, 1 September: The Soviet Union resumes nuclear testing.
• 1962, October: The Cuban Missile Crisis brings the superpowers to the brink of war.
• 1963, 10 June: Kennedy delivers his American University “Strategy of Peace” speech.
• 1963, 15 July: Negotiations open in Moscow.
• 1963, 5 August: Rusk, Gromyko and Home sign the treaty in Moscow.
• 1963, 24 September: The US Senate approves the treaty by 80 votes to 19.
• 1963, 10 October: The treaty enters into force.

Why it matters

The Partial Test Ban Treaty was the first concrete step in controlling nuclear weapons after the near-catastrophe of 1962. Although it did not stop the arms race, it ended most atmospheric testing by the major powers, protected public health from fallout and showed that the Cold War rivals could reach binding agreements.