A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion reactions, producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter.
The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is an international treaty whose objective is to prevent the spread of nuclear weapons and weapons technology, to promote cooperation in the peaceful uses of nuclear energy, and to further the goal of achieving nuclear disarmament and general and complete disarmament. Between 1965 and 1968, the treaty was negotiated by the Eighteen Nation Committee on Disarmament, a United Nations-sponsored organization based in Geneva, Switzerland.
Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as "Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT. Proliferation has been opposed by many nations with and without nuclear weapons, as governments fear that more countries with nuclear weapons will increase the possibility of nuclear warfare, de-stabilize international or regional relations, or infringe upon the national sovereignty of nation states.
Nuclear warfare, also known as atomic warfare, is a military conflict or prepared political strategy that deploys nuclear weaponry. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear warfare can produce destruction in a much shorter time and can have a long-lasting radiological result. A major nuclear exchange would likely have long-term effects, primarily from the fallout released, and could also lead to secondary effects, such as "nuclear winter", nuclear famine, and societal collapse. A global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to various scenarios including the extinction of the human species.
North Korea has a military nuclear weapons program and, as of June 2023, is estimated to have an arsenal of approximately 30 nuclear weapons and sufficient production of fissile material for six to seven nuclear weapons per year. North Korea has also stockpiled a significant quantity of chemical and biological weapons. In 2003, North Korea withdrew from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). Since 2006, the country has conducted six nuclear tests at increasing levels of expertise, prompting the imposition of sanctions.
The Russian Federation is known to possess or have possessed three types of weapons of mass destruction: nuclear weapons, biological weapons, and chemical weapons. It is one of the five nuclear-weapon states recognized under the Treaty on the Non-Proliferation of Nuclear Weapons.
The United States is known to have possessed three types of weapons of mass destruction: nuclear, chemical, and biological weapons. The U.S. is the only country to have used nuclear weapons on another country, when it detonated two atomic bombs over two Japanese cities of Hiroshima and Nagasaki during World War II. It had secretly developed the earliest form of the atomic weapon during the 1940s under the title "Manhattan Project". The United States pioneered the development of both the nuclear fission and hydrogen bombs. It was the world's first and only nuclear power for four years, from 1945 until 1949, when the Soviet Union produced its own nuclear weapon. The United States has the second-largest number of nuclear weapons in the world, after the Russian Federation.
The United Kingdom possesses, or has possessed, a variety of weapons of mass destruction, including nuclear, biological, and chemical weapons. The United Kingdom is one of the five official nuclear weapon states under the Treaty on the Non-Proliferation of Nuclear Weapons. The UK renounced the use of chemical and biological weapons in 1956 and subsequently destroyed its general stocks.
The People's Republic of China has developed and possesses weapons of mass destruction, including chemical and nuclear weapons. The first of China's nuclear weapons tests took place in 1964, and its first hydrogen bomb test occurred in 1966 at Lop Nur. Tests continued until 1996, when the country signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT), but did not ratify it. China acceded to the Biological Weapons Convention (BWC) in 1984 and ratified the Chemical Weapons Convention (CWC) in 1997.
India possesses nuclear weapons and previously developed chemical weapons. Although India has not released any official statements about the size of its nuclear arsenal, recent estimates suggest that India has 164 nuclear weapons and has produced enough weapons-grade plutonium for up to 200 nuclear weapons. In 1999, India was estimated to have 800 kilograms (1,800 lb) of separated reactor-grade plutonium, with a total amount of 8,300 kilograms (18,300 lb) of civilian plutonium, enough for approximately 1,000 nuclear weapons. India has conducted nuclear weapons tests in a pair of series namely Pokhran I and Pokhran II.
Pakistan is one of nine states that possess nuclear weapons. Pakistan began developing nuclear weapons in January 1972 under Prime Minister Zulfikar Ali Bhutto, who delegated the program to the Chairman of the Pakistan Atomic Energy Commission (PAEC) Munir Ahmad Khan with a commitment to having the device ready by the end of 1976. Since PAEC, which consisted of over twenty laboratories and projects under reactor physicist Munir Ahmad Khan, was falling behind schedule and having considerable difficulty producing fissile material, Abdul Qadeer Khan, a metallurgist working on centrifuge enrichment for Urenco, joined the program at the behest of the Bhutto administration by the end of 1974. Producing fissile material was pivotal to the Kahuta Project's success and thus to Pakistan obtaining the capability to detonate a nuclear weapon by the end of 1984.
Many nations continue to research and/or stockpile chemical weapon agents despite numerous efforts to reduce or eliminate them. Most states have joined the Chemical Weapons Convention (CWC), which required the destruction of all chemical weapons by 2012. Twelve nations have declared chemical weapons production facilities and six nations have declared stockpiles of chemical weapons. All of the declared production facilities have been destroyed or converted for civilian use after the treaty went into force.
Nuclear sharing is a concept in NATO's policy of nuclear deterrence, which allows member countries without nuclear weapons of their own to participate in the planning for the use of nuclear weapons by NATO. In particular, it provides for involvement of the armed forces of those countries in delivering nuclear weapons in the event of their use.
The United States was the first country to manufacture nuclear weapons and is the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II. Before and during the Cold War, it conducted 1,054 nuclear tests, and tested many long-range nuclear weapons delivery systems.
A tactical nuclear weapon (TNW) or non-strategic nuclear weapon (NSNW) is a nuclear weapon that is designed to be used on a battlefield in military situations, mostly with friendly forces in proximity and perhaps even on contested friendly territory. Generally smaller in explosive power, they are defined in contrast to strategic nuclear weapons, which are designed mostly to be targeted at the enemy interior far away from the war front against military bases, cities, towns, arms industries, and other hardened or larger-area targets to damage the enemy's ability to wage war. As of 2024, tactical nuclear weapons have never been used.
A nuclear triad is a three-pronged military force structure of land-based intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and strategic bombers with nuclear bombs and missiles. Countries build nuclear triads to eliminate an enemy's ability to destroy a nation's nuclear forces in a first-strike attack, which preserves their own ability to launch a second strike and therefore increases their nuclear deterrence.
This timeline of nuclear weapons development is a chronological catalog of the evolution of nuclear weapons rooting from the development of the science surrounding nuclear fission and nuclear fusion. In addition to the scientific advancements, this timeline also includes several political events relating to the development of nuclear weapons. The availability of intelligence on recent advancements in nuclear weapons of several major countries is limited because of the classification of technical knowledge of nuclear weapons development.
United States 
Soviet Union 
Russia 
China 
France 
United Kingdom 
India 
Pakistan 
Israel 
North Korea 
South Africa 
Kazakhstan 
Ukraine 
Belarus 
Lithuania 
