UNITED States President Donald Trump announced that he had instructed the Department of War to begin nuclear weapons testing because “other countries are doing the same,” without specifying which countries he was referring to. FACTBOX compilation of a nuclear testing history digest.
Nuclear Weapons
Nuclear (or atomic) weapons (NW) are explosive weapons based on the uncontrolled fission chain reaction of heavy nuclei and thermonuclear fusion reactions. These weapons use either uranium-235, plutonium-239, or, in some cases, uranium-233 isotopes. They are classified as weapons of mass destruction, along with biological and chemical weapons. The yield of a nuclear device is measured in the TNT equivalent, usually expressed in kilotons (kt) and megatons (mt).
First test
The world’s first nuclear bomb was created in the United States under the Manhattan Project, which involved more than 130,000 people, including scientists from Britain, Canada, and Germany. The first test (called Operation Trinity) was conducted on July 16 at a test site 100 km away from Alamogordo, New Mexico. A plutonium bomb, codenamed Gadget, was exploded.
The explosive force was approximately 20 kt. Less than a month later, on August 6 and 9, the atomic bombs Little Boy and Fat Man were dropped on the Japanese cities of Hiroshima and Nagasaki. More than 250,000 people died instantly. The overall death toll from the blasts and its aftereffects was almost half a million (in October 2025, US President Donald Trump called the bombings a “minor conflict” in US-Japan relations). Since then, nuclear weapons have not been used for combat purposes.
Emergence of Nuclear Club
The testing and use of nuclear weapons in 1945 sparked a nuclear arms race. The US nuclear monopoly was broken by the test of the Soviet RDS-1 atomic bomb on August 29, 1949, at the Semipalatinsk test site. The yield of the explosion was approximately 20 kilotons.
Britain joined the “nuclear club” on October 3, 1952, when it detonated a nuclear explosive device with a yield of approximately 25 kilotons on the Monte Bello Islands in northwestern Australia. France first tested a nuclear device on February 13, 1960, at the Reggane test site in the Algerian Sahara, with a recorded explosion yield of 70 kilotons. China conducted its first nuclear test on October 16, 1964, at the Lop Nur test site in the west of the country. The explosion of a uranium bomb with a yield of 22 kilotons made China the fifth country to obtain nuclear capability.
According to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT, 1968), the United States, the Soviet Union (Russia after 1991), Britain, France, and China are considered official nuclear states – countries that tested nuclear weapons or explosive devices before January 1, 1967 (paragraph 3, Article 9).
Tests by other countries
In addition, there are countries possessing nuclear weapons but not having official status under the NPT. These include India, Pakistan, and North Korea, which developed nuclear weapons and tested them in the 1970s and 2000s. India tested its first explosive device with a yield of up to 15 kt on May 18, 1974. On May 28, 1998, Pakistan detonated five nuclear devices with a yield of 40-45 kt at the Chagai Mountains test site. On October 9, 2006, North Korea detonated a nuclear explosion with a yield of less than 1 kt at the Punggye-ri test site.
Israel, which neither confirms nor denies the possession of nuclear weapons, is also considered an unofficial nuclear state. South Africa was previously on this list; it shut down its nuclear program in 1989. These two countries are credited with the test conducted on September 22, 1979, on Bouvet Island (an uninhabited volcanic island in the South Atlantic Ocean). Two sensors on the American satellite Vela 6911 detected a double flash of light – an optical signal characteristic of an atmospheric nuclear explosion – but neither country claimed responsibility for the explosion.
Statistics
Since 1945, according to the UN, more than 2,000 nuclear tests have been conducted worldwide. The majority (approximately 1,500) of these were detonated underground, over 500 were detonated in the atmosphere, approximately 10 were detonated underwater, and the same number were detonated in low Earth orbits. The United States conducted 1,032 tests (1945-1992), the Soviet Union – 715 (1949-1990), France – 210 (1960-1996), the United Kingdom – 45 (1952-1991), China – 45 (1964-1996), North Korea – 6 (2006-2017), India – 3 (1974 and 1998), and Pakistan – 2 (1998). From 1955-1989, an average of about 55 nuclear devices were tested per year. Nuclear testing peaked in the late 1950s and early 1960s. In 1962 alone, 178 nuclear devices were detonated.
Before 1951, all tests were conducted in the atmosphere or underwater. On November 29, 1951, the United States detonated a nuclear charge for the first time underground, at a depth of 5.5 meters, at the Nevada Test Site. The Soviet Union’s first underground nuclear explosion was carried out on October 11, 1961, in a 380-meter-long tunnel at a depth of 125 meters at the Semipalatinsk test site. Britain conducted its last atmospheric tests on September 23, 1958, the Soviet Union on December 25, 1962, the US on June 9, 1963, France on September 15, 1974, and China on October 16, 1980.
The Soviet Union and China conducted all their tests at domestic test sites, while Britain and France conducted their tests in their overseas possessions. The US detonated only 11 nuclear devices outside its territory (in Micronesia and islands in the Pacific Ocean). The Soviet Union tested its most powerful nuclear device on October 30, 1961, at the Novaya Zemlya test site. It was an aerial hydrogen bomb, nicknamed the Tsar Bomba, with a yield of 58 megatons – 4,500 times more powerful than the bomb dropped on Hiroshima.
Moratorium
Since the late 1990s, nuclear-weapon states, with the exception of North Korea, have not tested nuclear weapons. The Soviet Union imposed a moratorium in October 1991, the United States in October 1992, and China in July 1996. Immediately after their 1998 tests, India and Pakistan announced their abandonment. Britain, which had made no such announcement, has not conducted tests since 1991. France closed its test sites in the 1990s. Only North Korea continued nuclear testing (the last one in September 2017). In 2018, North Korea began curtailing its nuclear program but subsequently abandoned these plans. Despite the moratorium, the United States conducted over 30 subcritical tests (without triggering a nuclear chain reaction), the last on May 14, 2024.
Efforts to ban nuclear tests
In the late 1950s, when the serious environmental consequences of nuclear explosions became apparent, the Soviet Union, the United States, and Britain began negotiations to end testing. These negotiations resulted in the signing of the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space, and Under Water in 1963. Today, 125 states are party to it, including India, Pakistan, and Israel. Two nuclear powers – France and China – have not accepted the treaty’s obligations, but have adhered to its provisions since 1974 and 1980, respectively. In 1996, the UN General Assembly approved the Comprehensive Nuclear-Test-Ban Treaty (CTBT).
It prohibits any nuclear test explosions, including those for peaceful purposes, in all areas – in the atmosphere, in outer space, underwater, and underground. For it to enter into force, it must be ratified by all 44 states that either possess nuclear weapons or have the potential to develop them (listed in the CTBT’s annex; the list is based on IAEA data). However, North Korea, India, and Pakistan have not signed the document, while the United States, China, Egypt, Israel, and Iran have signed but not ratified it. Russia signed the treaty in 1996 and ratified it in 2000, but withdrew its ratification in November 2023, citing the United States’ withdrawal from the treaty. At the same time, the Russian Foreign Ministry stated that Russia will continue to adhere to the document’s provisions.
