Nuclear Testing 1945 - today

The beginning of the nuclear era

The United States launched the Nuclear Age in the pre-dawn hours of 16 July 1945 when it detonated a 20-kiloton atomic bomb code-named ”Trinity“ at Alamogordo, New Mexico.

The United States launched the Nuclear Age in July 1945 when it detonated a 20-kiloton atomic bomb code-named ”Trinity“ at its test site in Alamogordo, New Mexico.

Under the umbrella of the “Manhattan Project”, the test’s original purpose had been to confirm that an implosion-type nuclear weapon design was feasible. It also gave United States’ scientists and the military an idea of what the actual size and effects of such nuclear explosions would be before using them in combat.

While the Alamogordo test demonstrated many of the explosion's effects, it failed to provide a meaningful comprehension of radioactive nuclear fallout, which was not well understood by project scientists until years later.

The United States dropped two atomic bombs on Japan towards the end of World War II: one an untested gun-type fission bomb called “Little Boy” on Hiroshima on 6 August 1945; another implosion-type bomb tested at Alamogordo for the first time a month earlier and called “Fat Man” on Nagasaki on 9 August. Together these two bombs killed some 200,000 Japanese citizens by the end of 1945, with additional deaths subsequently from cancer and other diseases attributable to radiation exposure.

From “hot war” to Cold War

The first USSR nuclear test "Joe 1" at Semipalatinsk, Kazakhstan, 29 August 1949.

No sooner was World War II brought to a close in August 1945 than an all-out technical-industrial nuclear weapons race ensued between the two newly emerging superpowers, the United States and the Soviet Union. Between 1946 and 1949, the United States conducted an additional six tests. Then on 29 August 1949, the Soviet Union tested its first atomic bomb, “RDS-1”. This test marked the beginning of the “Cold War” nuclear arms race between the two superpowers.

With the Soviet Union’s first atomic bomb test on 29 August 1949, the “Cold War” nuclear arms race between the the USSR and the United States was on.
The Castle Bravo test created the worst radiological disaster in the United States' testing history. Bikini Atoll, Marshall Islands, 1 March 1954.

At the outset, neither the United States nor the Soviet Union had many nuclear weapons to spare so their nuclear testing was relatively limited. However, by the 1950s the United States had established a dedicated test site (on 27 January 1951, the first of over 900 nuclear tests was conducted at the Nevada Test Site) and was also using a site in the Marshall Islands (Pacific Proving Grounds) for extensive nuclear testing. The Soviet Union also began testing on a limited scale, primarily in Semipalatinsk in the Soviet Republic of Kazakhstan. Early tests were used primarily to ascertain the military effects of nuclear weapons and to test new weapon designs.

Exacerbated tensions and an atmosphere of pervasive fear and suspicion catalyzed competition to build more powerful and sophisticated bombs. During the 1950s new hydrogen bomb designs were tested in the Pacific, as were new and improved fission weapon designs.

In 1954 India’s Prime Minister Jawaharlal Nehru became the first stateman to call for a “stand still” agreement on nuclear testing.

The United Kingdom became the third country to test nuclear weapons on 3 October 1952 with "Hurricane" test conducted at the Montebello Islands in Western Australia. Initially, the United Kingdom tested in Australia and later at Christmas Island in the Pacific Ocean. From 1958 onwards its programme was closely coordinated with that of the United States through the UK-US Mutual Defense Agreement and the UK tests were conducted jointly with the United States at the Nevada Test Site.

The first hydrogen bomb

On 1 November 1952 the United States became the first country to test a hydrogen bomb. The Castle Bravo test on 1 March 1954 yielded 15 megatons and was the largest nuclear weapon ever detonated by the United States. By accident, the inhabited atolls of Rongelap, Rongerik and Utirik were contaminated with radioactive fallout, as was the Japanese fishing trawler Lucky Dragon. The controversy over radioactive fallout from testing activities caused great international concern.

Jawaharlal Nehru, India’s Prime Minister was the first statesman to call for a standstill agreement on nuclear testing in 1954.

India’s Prime Minister Jawaharlal Nehru was the first statesman to call for a “stand still” agreement on nuclear testing on 2 April, 1954. However, this did little to stop the extensive nuclear testing that characterized the following 35 years, not subsiding until the end of the Cold War in the late 1980s.

From 1955 to 1989, the average number of nuclear tests conducted every year was 55. Nuclear testing peaked in the late 1950s and early 1960s. The year 1962 alone saw as many as 178 tests: 96 conducted by the United States and 79 by the Soviet Union. This was the year of the Cuban Missile Crisis when the Cold War threatened to become a nuclear war. The preceding year had seen the testing of the largest nuclear weapon ever exploded, the Soviet Union’s “Tsar Bomba” with an estimated yield of 50 megatons. It was tested at the Novaya Zemlya test site near the Arctic Circle.

France and China became nuclear weapon States in 1960 ("Gerboise Bleue") and 1964 ("Operation 596") respectively, with both nuclear programmes intended to provide credible nuclear deterrents. France initially tested in Algeria, and later on in the South Pacific. China conducted all its nuclear tests at Lop Nur in Xinjiang Province.


The 1963 Partial Test Ban Treaty banned nuclear testing, including testing for peaceful purposes, in the atmosphere, underwater and in space … but not underground.

The early 1960s also saw the introduction of the only testing limitation effort that had concrete effects on how testing was conducted during the Cold War. The 1963 Partial Test Ban Treaty banned nuclear testing for military and for peaceful purposes, in the atmosphere, underwater and in space. The Treaty was important from an environmental point of view, curbing the radioactive fallout closely associated with atmospheric tests, but did little to prevent overall nuclear testing, which largely moved underground.

Burgeoning nuclear arsenals

The world’s nuclear arsenals ballooned throughout the Cold War, from slightly more than 3,000 weapons in 1955 to over 37,000 weapons by 1965 (United States 31,000 and the Soviet Union 6,000), to 47,000 by 1975 (United States 27,000 and Soviet Union 20,000), and over 60,000 in the late 1980s (United States 23,000 and the Soviet Union 39,000).

According to the Nuclear Threat Initiative, Israel initiated a nuclear programme in the 1950s, and had completed the R&D phase of its nuclear weapon programme in 1966, although it has not, to public knowledge, tested such a weapon. Israel has adopted a so-called “nuclear ambiguity policy”, neither confirming nor denying its nuclear status. It is not a party to the 1968 Non-Proliferation Treaty, and it has signed but not ratified the CTBT. For more information about Israel and the CTBT, click here.

Officially, India became the sixth nation to develop nuclear weapons, conducting the "Smiling Buddah" nuclear test on 18 May 1974, declared as a "peaceful" nuclear explosion.

In 1982, one additional nation, South Africa, acquired nuclear weapons, according to the Monterey Institute’s Center on Non-Proliferation Studies. To public knowledge, South Africa did not conduct any nuclear tests (see also the Vela incident). Less than ten years later, with the anticipated transition to a majority-elected government, South Africa dismantled all of its nuclear weapons, the only nation to date that voluntarily relinquished the nuclear arms under its complete control. The dismantling was completed in 1991. The same year, South Africa acceded to the 1968 Non-Proliferation Treaty as a non-nuclear weapon State. It voted overwhelmingly to end apartheid on 18 March 1992.

Underground nuclear testing was banned by the 1996 Comprehensive Nuclear-Test-Ban Treaty, which bans all nuclear explosions on Earth.

The world did not witness any significant decrease in nuclear testing activities and nuclear weapons acquisition among the nuclear weapon States until the early 1990s. The total number of  nuclear tests in the second half of the 1980s amounted to as many as 174.

But warmer relations between the Soviet Union and the United States from the mid-1980s prepared the way, as did the fall of the Berlin Wall in 1989 and the 1991 dissolution of the Soviet Union, which was superseded by the Russian Federation. Belarus, Kazakhstan and Ukraine who, together with Russia, had hosted the Soviet nuclear arsenal, became non-nuclear weapon States under the Non-proliferation Treaty. The USSR's main test site, Semipalatinsk in Kazakhstan, was closed in 1991.

Moratoria on nuclear testing

In 1990, the Soviet Union proposed a moratorium on nuclear testing that was agreed to by the United Kingdom and the United States. This created an opportunity to move ahead for those advocates who, for decades, had promoted a comprehensive ban on all nuclear testing.

Some six nuclear tests were conducted between 1998 and 2009: two by India and two by Pakistan in 1998, one by the Democratic People’s Republic of Korea in 2006 and another one by the DPRK in 2009.

The Soviet Union’s last nuclear test took place on 24 October 1990; the United Kingdom’s on 26 November 1991 and the United States’ ("Divider") on 23 September 1992. France and China conducted their last tests in January and July 1996 respectively, before signing the Comprehensive Nuclear-Test-Ban Treaty on the day it opened for signature, 24 September 1996, together with the other three nuclear weapon States and 66 other countries. France closed and dismantled all its nuclear test sites in the 1990s – the only nuclear weapon State to date that has done so.

Breaking the de facto moratorium

About seven nuclear tests were conducted between 1998 and 2013: two by India and two by Pakistan in 1998 and one by the Democratic People’s Republic of Korea (DPRK) in each 2006, 2009 and 2013, thus breaking the de facto moratorium that the CTBT had established.

India conducted two underground nuclear tests, code-named “Shakti (Power) ‘98”, on 11 and 13 May 1998 at its Pokhran underground testing site. In contrast to India’s initial nuclear test in 1974, this time there were no claims that these were “peaceful tests”. On the contrary, government officials were quick to emphasize the military nature of the explosions.

A scant two weeks later, Pakistan reacted, conducting two underground nuclear tests at its Ras Koh range.

Both India and Pakistan immediately moved to announce unilateral moratoriums on nuclear testing and have conducted no nuclear tests since 1998.

The announced nuclear test by the DPRK on 9 October 2006 broke the eight-year-long de facto moratorium and was against the letter and spirit of the Comprehensive Nuclear- Test-Ban Treaty.

The DPRK is the only country to have conducted nuclear tests in this century - on 9 October 2006, 25 May 2009, 12 February 2013 and 6 January 2016. All four events were quickly, reliably and precisely detected by the verification regime. After each of the tests, the UN Security Council unanimously adopted sanction resolutions. The DPRK's actions were met with near-universal expressions of concern, including for violations of the letter and spirit of the CTBT.

To read more about the  efforts and treaties curbing and banning nuclear testing, see The Treaty: History