Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission (fission or atomic bomb) or a combination of fission and nuclear fusion reactions (thermonuclear weapon), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter. Nuclear weapons have had yields between 10 tons (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). Yields in the low kilotons can devastate cities. A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatons of TNT (5.0 PJ). Apart from the blast, effects of nuclear weapons include extreme heat and ionizing radiation, firestorms, radioactive nuclear fallout, an electromagnetic pulse, and a radar blackout. The first nuclear weapons were developed by the United States in collaboration with the United Kingdom and Canada during World War II in the Manhattan Project. Production requires a large scientific and industrial complex, primarily for the production of fissile material, either from nuclear reactors with reprocessing plants or from uranium enrichment facilities. Nuclear weapons have been used twice in war, in the 1945 atomic bombings of Hiroshima and Nagasaki that killed between 150,000 and 246,000 people. Nuclear deterrence, including mutually assured destruction, aims to prevent nuclear warfare via the threat of unacceptable damage and the danger of escalation to nuclear holocaust. A nuclear arms race for weapons and their delivery systems was a defining component of the Cold War. Strategic nuclear weapons are targeted against civilian, industrial, and military infrastructure, while tactical nuclear weapons are intended for battlefield use. Strategic weapons led to the development of dedicated intercontinental ballistic missiles, submarine-launched ballistic missile, and nuclear strategic bombers, collectively known as the nuclear triad. Tactical weapons options have included shorter-range ground-, air-, and sea-launched missiles, nuclear artillery, atomic demolition munitions, nuclear torpedoes, and nuclear depth charges, but they have become less salient since the end of the Cold War. As of 2025, there are nine countries on the list of states with nuclear weapons, and six more agree to nuclear sharing. Nuclear weapons are weapons of mass destruction, and their control is a focus of international security through measures to prevent nuclear proliferation, arms control, or nuclear disarmament. The total from all stockpiles peaked at over 64,000 weapons in 1986, and is around 9,600 today. Key international agreements and organizations include the Treaty on the Non-Proliferation of Nuclear Weapons, the Comprehensive Nuclear-Test-Ban Treaty and Comprehensive Nuclear-Test-Ban Treaty Organization, the International Atomic Energy Agency, the Treaty on the Prohibition of Nuclear Weapons, and nuclear-weapon-free zones.

Tables

· Testing and deployment

Fission

Country

Fission