History: Summary

Five decades of struggle to end nuclear testing

Jawaharlal Nehru

The struggle to end nuclear testing is six decades old. Back in 1954, nine years after the "Trinity" test - the word’s first nuclear explosion, conducted in Alamogordo, New Mexico, United States, on 16 July 1945 - the Prime Minister of India, Jawaharlal Nehru, advocated a “standstill agreement” on nuclear testing.

1963: Partial Test Ban Treaty (PTBT)

President Kennedy ratifies the PTBT, 7 October 1963.

By the mid-1950s, the United States and the Soviet Union started conducting high-yield thermonuclear weapon testing in the atmosphere. The radioactive fallout from these tests gave rise to increasing international criticism, leading to the first victory for test-ban advocates: the Partial Nuclear Test-Ban Treaty (PTBT) signed in 1963 banned nuclear testing in outer space, the atmosphere and under water, but not underground. While the PTBT reduced radioactive fallout, nuclear weapons testing not only continued - albeit underground - but also increased greatly in numbers (see graph).

1968: The Nuclear Non-Proliferation Treaty

Negotiating the NPT.

Another important milestone was reached in 1968 with the adoption of the Nuclear Non-Proliferation Treaty (NPT), which laid the foundation of the nuclear non-proliferation and disarmament regime. A comprehensive ban on nuclear testing was discussed, but not agreed upon. However, it features in the NPT’s preamble and was promised by the nuclear weapon States during the 1995 and 2000 NPT Review Conferences.

Scientific experts and representatives participating in the Fifth Session of the Ad Hoc Group of Scientific Experts, held in Geneva, February-March 1978.

The Group of Scientific Experts (GSE)

Scientists from different countries have conducted joint research into monitoring technologies and data analysis methods for the verification of a comprehensive test ban since 1976 in the so-called Group of Scientific Experts (GSE). Only three decades later, however, the political climate was ripe: In 1994, the United Nations’ disarmament body, the Conference on Disarmament (CD) in Geneva, began formal negotiations on the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which lasted until 1996.

The CTBT was negotiated in the Conference on Disarmament in Geneva 1994-1996.

Onerous Negotiations at the CD

Thanks to the GSE’s scientific groundwork, the CD was able to reach consensus on the verification regime relatively quickly. Other negotiations proved rather more protracted, including those on:

  • Reaching a common definition of a nuclear test (any nuclear test explosion, as well as “peaceful nuclear explosions” but not so-called subcritical tests).
  • Whether to include a binding time plan for nuclear disarmament.

While the first two issues were finally resolved, the CD, which operates by consensus, could not reach a decision on the last one. The Treaty was therefore introduced directly to the U.N. General Assembly, where it was adopted on 10 September 1996.

The core provisions of the CTBT (see summary / full text as PDF) are:

  • Prohibition of all nuclear explosions anywhere, by anyone.
  • Entry into force: the CTBT will enter into force after it has been signed and ratified by the 44 States listed in Annex 2 to the Treaty, i.e. the States that had nuclear power or research reactors at the time.

A norm against nuclear testing

With the CTBT’s opening for signature on 24 September 1996, a de-facto international norm on nuclear testing was established. While all States Signatories to the CTBT have observed it, only three non-signatories have not: the nuclear tests by India and Pakistan in 1998 as well as those of the Democratic People’s Republic of Korea (DPRK) in 2006, 2009 and 2013 have all provoked universal condemnation including unanimously adopted sanctions by the U.N. Security Council.

To date, most of the world’s countries (see Treaty status map) have signed and ratified the CTBT, including the three nuclear weapon States France, United Kingdom and Russia.

The Creation of the CTBTO

Click image for fullscreen interactive map on the current status of the IMS build-up.

In parallel to the opening of the Treaty for signature, the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) was created, whose mandate is the establishment of the CTBT’s verification regime and the promotion of signatures and ratifications of the Treaty so that it can enter into force.

When complete, the IMS will consist of 337 monitoring facilities. It will be complemented by an intrusive on-site inspection regime applicable once the Treaty has entered into force. Already today, the CTBTO’s experts are confident that their system can detect and identify any militarily relevant nuclear test anywhere on the planet.


First chapter:
1945-54: Early efforts to restrain nuclear testing