TheInfoList

A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive force from
nuclear reaction In nuclear physics Nuclear physics is the field of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and t ...
s, either
fission Fission, a splitting of something into two or more parts, may refer to: Biology * Fission (biology), division of a single entity into two or more parts and the regeneration of those parts into separate entities resembling the original * Mitochondri ...

(fission bomb) or a combination of fission and reactions (
thermonuclear bomb lenses2) Uranium-238 Uranium-238 (238U or U-238) is the most common isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the ...
). Both bomb types release large quantities of energy from relatively small amounts of matter. The
first test ''First Test'', is a fantasy novel by Tamora Pierce, the first book in the series ''Protector of the Small''. It details the first year of Keladry of Mindelan's training as a page of Tortall. Plot introduction ''Protector of the Small'' is set i ...
of a fission ("atomic") bomb released an amount of energy approximately equal to . The first thermonuclear ("hydrogen") bomb
test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * Test (2013 film), ''Test'' (2013 film), an American film * Test ( ...
released energy approximately equal to . Nuclear bombs have had
yield Yield may refer to: Measures of output/function Computer science * Yield (multithreading) is an action that occurs in a computer program during multithreading * See generator (computer programming) Physics/chemistry * Yield (chemistry), the amou ...
s between 10 tons TNT (the
W54 The W54 (also known as the Mark 54 or B54) was a tactical nuclear warhead A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that de ...
) and 50 megatons for the
Tsar Bomba The Tsar Bomba (), (code name A code name, call sign or cryptonym is a code word or name used, sometimes clandestinely, to refer to another name, word, project, or person. Code names are often used for military A military, also known ...
(see
TNT equivalent TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy As energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ ...
). A thermonuclear weapon weighing little more than can release energy equal to more than . A nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and
radiation upThe international symbol for types and levels of ionizing radiation (radioactivity) that are unsafe for unshielded humans. Radiation, in general, exists throughout nature, such as in light and sound. In physics Physics (from grc ...

. Since they are
weapons of mass destruction A weapon of mass destruction (WMD) is a nuclear weapon, nuclear, Radiological weapon, radiological, chemical weapon, chemical, biological agent, biological, or any other weapon that can kill and bring significant harm to numerous humans or cause ...
, the
proliferation of nuclear weapons 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 Weapo ...

is a focus of
international relations International relations (IR), international affairs (IA) or international studies (IS) is the scientific study of interactions between sovereign states. In a broader sense, it concerns all activities between states—such as war, diplomacy ...
policy. Nuclear weapons have been deployed twice in war, by the United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to 1945. It involved —including all of the great powers—forming two opposing s: the and the . In a total war directly involving m ...
.

# Testing and deployment

Nuclear weapons have only twice been used in
war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (news ...
, both times by the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in . It consists of 50 , a , five major , 326 , and some . At , it is the world's . The United States shares significan ...

against
Japan Japan ( ja, 日本, or , and formally ) is an in . It is situated in the northwest , and is bordered on the west by the , while extending from the in the north toward the and in the south. Japan is a part of the , and spans of coveri ...

near the end of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to 1945. It involved —including all of the great powers—forming two opposing s: the and the . In a total war directly involving m ...
. On August 6, 1945, the U.S. Army Air Forces detonated a
uranium Uranium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

gun-type
fission bomb A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission, fission (fission bomb) or from a ...
nicknamed "
Little Boy "Little Boy" was the codename for the type of atomic bomb A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructiv ...

" over the Japanese city of
Hiroshima is the capital of Hiroshima Prefecture is a prefecture of Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , image_coat = Imperia ...
; three days later, on August 9, the U.S. Army Air Forces detonated a
plutonium Plutonium is a radioactive decay, radioactive chemical element with the Symbol (chemistry), symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating plutoni ...

implosion-type fission bomb nicknamed "
Fat Man "Fat Man" (also known as Mark III) is the codename for the type of nuclear bomb A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destructive f ...

" over the Japanese city of
Nagasaki is the capital and the largest city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. ...

. These bombings caused injuries that resulted in the deaths of approximately 200,000
civilians Civilians under international humanitarian law are "persons who are not members of the armed forces A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typica ...
and
military personnel Military personnel are members of the state's armed forces A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovere ...
. The ethics of these bombings and their role in Japan's surrender are subjects of
debate Debate is a process that involves formal discussion on a particular topic. In a debate, opposing arguments are put forward to argue for opposing viewpoints. Debate occurs in public meetings, academic institutions, and legislative assemblies. It ...
. Since the
atomic bombings of Hiroshima and Nagasaki The United States detonated two nuclear weapons A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destructive force from nuclear reactions, e ...
, nuclear weapons have been detonated over 2,000 times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
, the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a that spanned during its existence from 1922 to 1991. It was nominally a of multiple national ; in practice and were highly until its final years. The ...
(succeeded as a nuclear power by
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...
), the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for the United Kingdom. Some prefer to use Britain as shorth ...
,
France France (), officially the French Republic (french: link=no, République française), is a List of transcontinental countries, transcontinental country spanning Western Europe and Overseas France, overseas regions and territories in the Ame ...
,
China China (), officially the People's Republic of China (PRC; ), is a country in . It is the world's , with a of more than 1.4 billion. China spans five geographical and 14 different countries, the in the world after . Covering an area of ap ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
,
Pakistan Pakistan, . Pronounced variably in English as , , , and . officially the Islamic Republic of Pakistan, is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a popul ...
, and
North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia, constituting the northern part of the Korean Peninsula. It borders China and Russia to the north, at the Yalu River, Yalu (Amnok) and Tu ...
.
Israel Israel (; he, יִשְׂרָאֵל, translit=Yīsrāʾēl; ar, إِسْرَائِيل, translit=ʾIsrāʾīl), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a ...
is believed to possess nuclear weapons, though, in a
policy of deliberate ambiguity A policy of deliberate ambiguity (also known as a policy of strategic ambiguity, ''strategic uncertainty'') is the practice by a government A government is the system or group of people governing an organized community, generally a State ...
, it does not acknowledge having them.
Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin Berlin (; ) is the and by both area and population. Its 3,769,495 inhabitants, as of 31 December 2019 makes it the , according to population within city l ...

,
Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of Italian Peninsula, a peninsula delimited by the Alps and List of islands of Italy, several islands surrounding it, whose ...

,
Turkey Turkey ( tr, Türkiye ), officially the Republic of Turkey, is a country located mainly on Anatolia Anatolia,, tr, Anadolu Yarımadası), and the Anatolian plateau. also known as Asia Minor, is a large peninsula in Western Asia and ...

,
Belgium Belgium ( nl, België ; french: Belgique ; german: Belgien ), officially the Kingdom of Belgium, is a country in Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on cont ...

and the
Netherlands ) , national_anthem = ( en, "William of Nassau") , image_map = EU-Netherlands.svg , map_caption = , image_map2 = BES islands location map.svg , map_caption2 = , image_map3 ...

are
nuclear weapons sharing Nuclear sharing is a concept in NATO's policy of nuclear deterrence, which involves member countries without nuclear weapons of their own in the planning for the use of nuclear weapons by NATO. In particular, it provides for the armed forces ...
states.
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. With over Demographics of South Africa, 60 million people, it is the world's List of countries by population, 23rd-most ...

is the only country to have independently developed and then its nuclear weapons. The
Treaty on the Non-Proliferation of Nuclear Weapons The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is an international treaty A treaty is a formal, legally binding written agreement between actors in international law Inte ...
aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned. Modernisation of weapons continues to this day.

# Types

There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, and those that use fission reactions to begin
nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products ...

reactions that produce a large amount of the total energy output.

## Fission weapons

All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs). This has long been noted as something of a
misnomer A misnomer is a name that is incorrectly or unsuitably applied. Misnomers often arise because something was named long before its correct nature was known, or because an earlier form of something has been replaced by a later form to which the nam ...
, as their energy comes from the
nucleus ''Nucleus'' (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA ...
of the atom, just as it does with fusion weapons. In fission weapons, a mass of
fissile material In nuclear engineering Nuclear engineering is the branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, veh ...
(
enriched uranium Enriched uranium is a type of uranium Uranium is a chemical element with the Symbol (chemistry), symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 9 ...
or
plutonium Plutonium is a radioactive decay, radioactive chemical element with the Symbol (chemistry), symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating plutoni ...

) is forced into
supercriticality A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its atomic nucleus, nuclear properties (specifically, its nuclear fission nuclear c ...

—allowing an
exponential growth Exponential growth is a process that increases quantity over time. It occurs when the instantaneous Rate (mathematics)#Of change, rate of change (that is, the derivative) of a quantity with respect to time is proportionality (mathematics), proport ...

of
nuclear chain reaction 300px, A possible nuclear fission chain reaction: 1) A uranium-235 atom absorbs a neutron">uranium-235.html" ;"title="nuclear fission chain reaction: 1) A uranium-235">nuclear fission chain reaction: 1) A uranium-235 atom absorbs a neutron, ...
s—either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically-fueled
explosive lens An explosive lens—as used, for example, in nuclear weapons—is a highly specialized shaped charge. In general, it is a device composed of several explosive charges. These charges are arranged and formed with the intent to control the shape o ...
es. The latter approach, the "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500
kiloton TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy As energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ ...
s) of
TNT Trinitrotoluene (; TNT), or more specifically 2,4,6-trinitrotoluene, is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more ...

().Hansen, Chuck. ''U.S. Nuclear Weapons: The Secret History.'' San Antonio, TX: Aerofax, 1988; and the more-updated Hansen, Chuck,
Swords of Armageddon: U.S. Nuclear Weapons Development since 1945
" (CD-ROM & download available). PDF. 2,600 pages, Sunnyvale, California, Chuklea Publications, 1995, 2007. (2nd Ed.)
All fission reactions generate
fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Oth ...
, the remains of the split atomic nuclei. Many fission products are either highly
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small, dense region consisting of s and s ...

(but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of
radioactive contamination represents two-thirds of the United States' high-level radioactive waste by volume. Nuclear reactors line the riverbank at the Hanford Site along the Columbia River in January 1960. Radioactive contamination, also called radiological contaminatio ...
. Fission products are the principal radioactive component of
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast Nuclear Blast is an independent record label and mail order record distributor with subsidiaries in Germany, the United Sta ...
. Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in the surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most commonly used fissile materials for nuclear weapons applications have been
uranium-235 Uranium-235 (235U) is an Isotopes of uranium, isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope th ...

and
plutonium-239 Plutonium-239 (239Pu, Pu-239) is an isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but differe ...

. Less commonly used has been
uranium-233 Uranium-233 (233U) is a fissile Isotopes of uranium, isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons and as a Nuclear fuel, reactor fuel. It has been use ...

.
Neptunium-237 Neptunium (93Np) is usually considered an artificial element, although trace quantities are found in nature, so a standard atomic weight The standard atomic weight (''A''r, standard(E)) of a chemical element Image:Simple Periodic Table Cha ...

and some isotopes of
americium Americium is a synthetic radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the ...

may be usable for nuclear explosives as well, but it is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute.

## Fusion weapons

The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs), as they rely on fusion reactions between isotopes of
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

(
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific elemen ...

and
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucl ...

). All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions. Only six countries—
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in . It consists of 50 , a , five major , 326 , and some . At , it is the world's . The United States shares significan ...

,
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

, United Kingdom, China, France, and
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

—have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged
thermonuclear weapon A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation . Its greater sophistication affords it vastly greater destructive power than first-generation s, a more compact size, a lower mass, or a combination of these ...
is controversial.
North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia, constituting the northern part of the Korean Peninsula. It borders China and Russia to the north, at the Yalu River, Yalu (Amnok) and Tu ...

claims to have tested a fusion weapon , though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it is more efficient. Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. In the
Teller-Ulam design A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon ...

, which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel (
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucl ...

,
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific elemen ...

, or
lithium deuteride Lithium hydride is an inorganic compound with the formula Lithium, LiHydride, H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and i ...
) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated,
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, it ...
s and
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency ...

s emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

s, which can then induce fission in materials not normally prone to it, such as
depleted uranium Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy or D-38) is uranium Uranium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is ...
. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of the yield comes from the final fissioning of depleted uranium. Virtually all thermonuclear weapons deployed today use the "two-stage" design described above, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to criticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated, the
Tsar Bomba The Tsar Bomba (), (code name A code name, call sign or cryptonym is a code word or name used, sometimes clandestinely, to refer to another name, word, project, or person. Code names are often used for military A military, also known ...
of the USSR, which released an energy equivalent of over , was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements. Fusion reactions do not create fission products, and thus contribute far less to the creation of
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast Nuclear Blast is an independent record label and mail order record distributor with subsidiaries in Germany, the United Sta ...
than fission reactions, but because all
thermonuclear weapon A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation . Its greater sophistication affords it vastly greater destructive power than first-generation s, a more compact size, a lower mass, or a combination of these ...
s contain at least one
fission Fission, a splitting of something into two or more parts, may refer to: Biology * Fission (biology), division of a single entity into two or more parts and the regeneration of those parts into separate entities resembling the original * Mitochondri ...
stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past the
tropopause The tropopause is the atmospheric boundary that demarcates the troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of w ...
into the
stratosphere File:Stratosphere Temperature Trend.jpg, This image shows the temperature trend in the lower stratosphere as measured by a series of satellite-based instruments between January 1979 and December 2005. The lower stratosphere is centered around 18 k ...

, where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion.

## Other types

There are other types of nuclear weapons as well. For example, a
boosted fission weapon Boost or boosting may refer to: Science, technology and mathematics * Boost (automotive engineering) A turbocharger, colloquially known as a turbo, is a turbine-driven, forced induction device that increases an internal combustion engine's p ...
is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of the fission bomb core. The external method of boosting enabled the
USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a socialist state that spanned Eurasia during its existence from 1922 to 1991. It was nominally a Federation, federal union of multiple national Republics of ...

to field the first partially-thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles. The detonation of any nuclear weapon is accompanied by a blast of
neutron radiation Neutron radiation is a form of ionizing radiation Ionizing radiation (ionising radiation) consists of subatomic particles or electromagnetic waves that have sufficient energy to ionization, ionize atoms or molecules by detaching electrons from the ...
. Surrounding a nuclear weapon with suitable materials (such as
cobalt Cobalt is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical element ...

or
gold Gold is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numb ...

) creates a weapon known as a
salted bomb A salted bomb is a nuclear weapon A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive force from nuclear reac ...
. This device can produce exceptionally large quantities of long-lived
radioactive contamination represents two-thirds of the United States' high-level radioactive waste by volume. Nuclear reactors line the riverbank at the Hanford Site along the Columbia River in January 1960. Radioactive contamination, also called radiological contaminatio ...
. It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct. In connection with the
Strategic Defense Initiative The Strategic Defense Initiative (SDI), derisively nicknamed the "''Star Wars'' program", was a proposed missile defense Phased Array Ballistic Missile Early Warning System at RAF Fylingdales">Ballistic_Missile_Early_Warning_System.html" ; ...
, research into the
nuclear pumped laser A nuclear pumped laser is a laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplificat ...
was conducted under the DOD program
Project Excalibur Project Excalibur was a Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory (LLNL) is a federal research facility in Livermore, California, United States The United States of America (USA), commonly known as ...
but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target. During the
Starfish Prime Starfish Prime was a high-altitude nuclear test conducted by the United States, a joint effort of the United States Atomic Energy Commission, Atomic Energy Commission (AEC) and the Defense Threat Reduction Agency#History, Defense Atomic Support ...
high-altitude nuclear test in 1962, an unexpected effect was produced which is called a
nuclear electromagnetic pulse A nuclear electromagnetic pulse (commonly abbreviated as nuclear EMP, or NEMP) is a burst of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, it ...
. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling a nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area. Research has been done into the possibility of pure fusion bombs: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the
United States Department of Energy The United States Department of Energy (DOE) is a cabinet Cabinet or The Cabinet may refer to: Furniture * Cabinetry, a box-shaped piece of furniture with doors and/or drawers * Display cabinet, a piece of furniture with one or more transp ...
divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment". Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurring
isotopes Isotopes are two or more types of atoms that have the same atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of ...
(178m2Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in the hafnium controversy) have been proposed as possible triggers for conventional thermonuclear reactions.
Antimatter In modern physics Modern physics is a branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and ...

, which consists of
particles In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or chemical , chemical properties ...

resembling ordinary
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic particl ...
particles in most of their properties but having opposite
electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respectively). Like c ...
, has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it is feasible beyond the military domain. However, the U.S. Air Force funded studies of the physics of antimatter in the
Cold War The Cold War was a period of tension between the and the and their respective allies, the and the , which began following . Historians do not fully agree on its starting and ending points, but the period is generally considered to span ...
, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion. Most variation in
nuclear weapon design Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as a ...
is for the purpose of achieving different yields for different situations, and in manipulating design elements to attempt to minimize weapon size,
radiation hardness upThe international symbol for types and levels of ionizing radiation (radioactivity) that are unsafe for unshielded humans. Radiation, in general, exists throughout nature, such as in light and sound. In physics Physics (from grc ...
or requirements for special materials, especially fissile fuel or tritium.

### Tactical nuclear weapons

Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as
Tactical nuclear weapon A tactical nuclear weapon (TNW) or non-strategic nuclear weapon is a nuclear weapon A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destructive fo ...
s. The
neutron bomb A neutron bomb, officially defined as a type of enhanced radiation weapon (ERW), is a low-yield thermonuclear weapon designed to maximize lethal neutron radiation in the immediate vicinity of the blast while minimizing the physical power of the b ...
purportedly conceived by Sam Cohen is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron
radiation upThe international symbol for types and levels of ionizing radiation (radioactivity) that are unsafe for unshielded humans. Radiation, in general, exists throughout nature, such as in light and sound. In physics Physics (from grc ...

. Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in the 1980s (though not deployed in Europe, as intended, over the objections of NATO allies) for use as tactical payloads for US Army artillery shells (200 mm
W79 The W79 Artillery-Fired Atomic Projectile (AFAP), also known as the XM753 (Atomic RA) was an American nuclear artillery 320px, Video of Upshot–Knothole Grable test Nuclear artillery is a subset of limited- yield tactical nuclear weapons, in ...
and 155 mm
W82 The W82 was a low-yield tactical nuclear warhead developed by the United States and designed to be used in a 155 mm 155 mm (6.1″) is a common, NATO-standard, artillery Artillery is a class of heavy military ranged weapons built to l ...
) and forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable. A type of nuclear explosive most suitable for use by ground special forces was the
Special Atomic Demolition Munition The Special Atomic Demolition Munition (SADM) was a family of man-portable nuclear weapon A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destr ...
, or SADM, sometimes popularly known as a Suitcase nuclear device, suitcase nuke. This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". Obviously they also demand especially stringent security precautions in their storage and deployment. Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include the USAF AIR-2 Genie, the AIM-26 Falcon and US Army Nike Hercules. Missile interceptors such as the Sprint (missile), Sprint and the LIM-49 Spartan, Spartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads. Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as antisubmarine weapons. These included nuclear depth charge, depth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities.

# Weapons delivery

The system used to Nuclear weapons delivery, deliver a nuclear weapon to its target is an important factor affecting both
nuclear weapon design Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as a ...
and nuclear warfare, nuclear strategy. The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940. The simplest method for delivering a nuclear weapon is a gravity bomb dropped from aircraft; this was the method used by the United States against Japan. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both strategic bombers and tactical fighter-bombers. This method is the primary means of nuclear weapons delivery; the majority of U.S. nuclear warheads, for example, are free-fall gravity bombs, namely the B61 nuclear bomb, B61. Preferable from a strategic point of view is a nuclear weapon mounted on a missile, which can use a Ballistics, ballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for a faster and less vulnerable attack, the development of long-range intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing the chance of a successful missile defense. Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult. Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also nuclear artillery, artillery shells, nuclear land mine, land mines, and nuclear depth charges and nuclear torpedo, torpedoes for anti-submarine warfare. An atomic mortar (weapon), mortar has been tested by the United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs), such as the
Special Atomic Demolition Munition The Special Atomic Demolition Munition (SADM) was a family of man-portable nuclear weapon A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destr ...
, have been developed, although the difficulty of combining sufficient yield with portability limits their military utility.

# Nuclear strategy

Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by a nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of deterrence theory, nuclear deterrence. The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for Pre-emptive nuclear strike, first strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During the Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions. Different forms of nuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against the weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on submarines or land mobile transporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened missile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy the missiles before they land, or implementing civil defense measures using early-warning systems to evacuate citizens to safe areas before an attack. Weapons designed to threaten large populations or to deter attacks are known as ''strategic nuclear weapons, strategic weapons.'' Nuclear weapons for use on a battlefield in military situations are called ''tactical nuclear weapons, tactical weapons.'' Critics of nuclear war strategy often suggest that a nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction. This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism. Critics from the peace movement and within the military establishment have questioned the usefulness of such weapons in the current military climate. According to an International Court of Justice advisory opinion on the Legality of the Threat or Use of Nuclear Weapons, advisory opinion issued by the International Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if the survival of the state were at stake. Another deterrence theory, deterrence position is that nuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the
Cold War The Cold War was a period of tension between the and the and their respective allies, the and the , which began following . Historians do not fully agree on its starting and ending points, but the period is generally considered to span ...
between the U.S. and the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a that spanned during its existence from 1922 to 1991. It was nominally a of multiple national ; in practice and were highly until its final years. The ...
. In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle, argued in books like ''The Balance of Terror: Strategy for the Nuclear Age'' (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase Nuclear peace, international stability. Some prominent Neorealism (international relations), neo-realist scholars, such as Kenneth Waltz and John Mearsheimer, have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of total war, especially in troubled regions of the world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation, and Waltz, who was somewhat more non-interventionism (politics), interventionist.Kenneth Waltz
"The Spread of Nuclear Weapons: More May Better,"
''Adelphi Papers'', no. 171 (London: International Institute for Strategic Studies, 1981).
Interest in proliferation and the stability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese and South Korean nuclear deterrent against
North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia, constituting the northern part of the Korean Peninsula. It borders China and Russia to the north, at the Yalu River, Yalu (Amnok) and Tu ...

. The threat of potentially suicidal terrorists possessing nuclear weapons (a form of nuclear terrorism) complicates the decision process. The prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless terrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the September 11 attacks, September 11, 2001, attacks, that this complication calls for a new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War.See, for example: Feldman, Noah.
Islam, Terror and the Second Nuclear Age
," ''New York Times Magazine'' (October 29, 2006).
Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with
weapons of mass destruction A weapon of mass destruction (WMD) is a nuclear weapon, nuclear, Radiological weapon, radiological, chemical weapon, chemical, biological agent, biological, or any other weapon that can kill and bring significant harm to numerous humans or cause ...
. Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider a policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.". Graham Allison makes a similar case, arguing that the key to expanded deterrence is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin." The process is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials." According to the Pentagon's June 2019 "Doctrine for Joint Nuclear Operations" of the Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation."

# Governance, control, and law

Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by the head of government or head of state. Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage". In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The Russell–Einstein Manifesto was issued in London on July 9, 1955, by Bertrand Russell in the midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein, who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor a conference—called for in the manifesto—in Pugwash, Nova Scotia, Eaton's birthplace. This conference was to be the first of the Pugwash Conferences on Science and World Affairs, held in July 1957. By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of nuclear testing. The Partial Nuclear Test Ban Treaty (1963) restricted all nuclear testing to underground nuclear testing, to prevent contamination from nuclear fallout, whereas the
Treaty on the Non-Proliferation of Nuclear Weapons The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is an international treaty A treaty is a formal, legally binding written agreement between actors in international law Inte ...
(1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military nuclear technology to member countries without fear of proliferation. In 1957, the International Atomic Energy Agency (IAEA) was established under the mandate of the United Nations to encourage development of peaceful applications of nuclear technology, provide international safeguards against its misuse, and facilitate the application of safety measures in its use. In 1996, many nations signed the Comprehensive Nuclear-Test-Ban Treaty, which prohibits all testing of nuclear weapons. A testing ban imposes a significant hindrance to nuclear arms development by any complying country.Richelson, Jeffrey. ''Spying on the bomb: American nuclear intelligence from Nazi Germany to Iran and North Korea.'' New York: Norton, 2006. The Treaty requires the ratification by 44 specific states before it can go into force; , the ratification of eight of these states is still required.Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (2010).
Status of Signature and Ratification
". Accessed May 27, 2010. Of the "Annex 2" states whose ratification of the CTBT is required before it enters into force, China, Egypt, Iran, Israel, and the United States have signed but not ratified the Treaty. India, North Korea, and Pakistan have not signed the Treaty.
Additional treaties and agreements have governed nuclear weapons stockpiles between the countries with the two largest stockpiles, the United States and the Soviet Union, and later between the United States and Russia. These include treaties such as SALT II (never ratified), START I (expired), Intermediate-Range Nuclear Forces Treaty, INF, START II (never ratified), SORT, and New START, as well as non-binding agreements such as SALT I and the Presidential Nuclear Initiatives of 1991. Even when they did not enter into force, these agreements helped limit and later reduce the numbers and types of nuclear weapons between the United States and the Soviet Union/Russia. Nuclear weapons have also been opposed by agreements between countries. Many nations have been declared Nuclear-Weapon-Free Zones, areas where nuclear weapons production and deployment are prohibited, through the use of treaties. The Treaty of Tlatelolco (1967) prohibited any production or deployment of nuclear weapons in Latin America and the Caribbean, and the Treaty of Pelindaba (1964) prohibits nuclear weapons in many African countries. As recently as 2006 a Central Asian Nuclear Weapon Free Zone was established among the former Soviet republics of Central Asia prohibiting nuclear weapons. In 1996, the International Court of Justice, the highest court of the United Nations, issued an Advisory Opinion concerned with the "International Court of Justice advisory opinion on the Legality of the Threat or Use of Nuclear Weapons, Legality of the Threat or Use of Nuclear Weapons". The court ruled that the use or threat of use of nuclear weapons would violate various articles of international law, including the Geneva Conventions, the Hague Conventions (1899 and 1907), Hague Conventions, the UN Charter, and the Universal Declaration of Human Rights. Given the unique, destructive characteristics of nuclear weapons, the International Committee of the Red Cross calls on States to ensure that these weapons are never used, irrespective of whether they consider them lawful or not. Additionally, there have been other, specific actions meant to discourage countries from developing nuclear arms. In the wake of the tests by India and Pakistan in 1998, economic sanctions were (temporarily) levied against both countries, though neither were signatories with the Nuclear Non-Proliferation Treaty. One of the stated ''casus belli'' for the initiation of the 2003 Iraq War was an accusation by the United States that Iraq was actively pursuing nuclear arms (though this was soon discovered Niger uranium forgeries, not to be the case as the program had been discontinued). In 1981, Israel had Operation Opera, bombed a nuclear reactor being constructed in Osirak, Iraq, in what it called an attempt to halt Iraq's previous nuclear arms ambitions; in 2007, Israel Operation Orchard, bombed another reactor being constructed in Syria. In 2013, Mark Diesendorf said that governments of France, India, North Korea, Pakistan, UK, and South Africa have used nuclear power and/or research reactors to assist nuclear weapons development or to contribute to their supplies of nuclear explosives from military reactors. The two tied-for-lowest points for the Doomsday Clock have been in 1953, when the Clock was set to two minutes until midnight after the U.S. and the Soviet Union began testing hydrogen bombs, and in 2018, following the failure of world leaders to address tensions relating to nuclear weapons and climate change issues.

## Disarmament

Nuclear disarmament refers to both the act of reducing or eliminating nuclear weapons and to the end state of a nuclear-free world, in which nuclear weapons are eliminated. Beginning with the 1963 Partial Test Ban Treaty and continuing through the 1996 Comprehensive Test Ban Treaty, there have been many treaties to limit or reduce nuclear weapons testing and stockpiles. The 1968 Nuclear Non-Proliferation Treaty has as one of its explicit conditions that all signatories must "pursue negotiations in good faith" towards the long-term goal of "complete disarmament". The nuclear-weapon states have largely treated that aspect of the agreement as "decorative" and without force. Only one country—South Africa—has ever fully renounced nuclear weapons they had independently developed. The former Soviet republics of Belarus, Kazakhstan, and Ukraine returned Soviet nuclear arms stationed in their countries to Russia after the collapse of the USSR. Proponents of nuclear disarmament say that it would lessen the probability of nuclear war, especially accidentally. Critics of nuclear disarmament say that it would undermine the present nuclear peace and deterrence and would lead to increased global instability. Various American elder statesmen, who were in office during the
Cold War The Cold War was a period of tension between the and the and their respective allies, the and the , which began following . Historians do not fully agree on its starting and ending points, but the period is generally considered to span ...
period, have been advocating the elimination of nuclear weapons. These officials include Henry Kissinger, George Shultz, Sam Nunn, and William Perry. In January 2010, Lawrence M. Krauss stated that "no issue carries more importance to the long-term health and security of humanity than the effort to reduce, and perhaps one day, rid the world of nuclear weapons". In January 1986, Soviet leader Mikhail Gorbachev publicly proposed a three-stage program for abolishing the world's nuclear weapons by the end of the 20th century. In the years after the end of the Cold War, there have been numerous campaigns to urge the abolition of nuclear weapons, such as that organized by the Global Zero (campaign), Global Zero movement, and the goal of a "world without nuclear weapons" was advocated by United States President Barack Obama in an April 2009 speech in Prague. A CNN poll from April 2010 indicated that the American public was nearly evenly split on the issue. Some analysts have argued that nuclear weapons have made the world relatively safer, with peace through deterrence theory, deterrence and through the stability–instability paradox, including in south Asia. Kenneth Waltz has argued that nuclear weapons have helped keep an uneasy peace, and further nuclear weapon proliferation might even help avoid the large scale conventional wars that were so common before their invention at the end of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to 1945. It involved —including all of the great powers—forming two opposing s: the and the . In a total war directly involving m ...
. But former Secretary Henry Kissinger says there is a new danger, which cannot be addressed by deterrence: "The classical notion of deterrence was that there was some consequences before which aggressors and evildoers would recoil. In a world of suicide bombers, that calculation doesn’t operate in any comparable way". George Shultz has said, "If you think of the people who are doing suicide attacks, and people like that get a nuclear weapon, they are almost by definition not deterrable". As of early 2019, more than 90% of world's 13,865 nuclear weapons were owned by Russia and the United States.

## United Nations

The UN Office for Disarmament Affairs (UNODA) is a department of the United Nations Secretariat established in January 1998 as part of the United Nations Secretary-General Kofi Annan's plan to reform the UN as presented in his report to the United Nations General Assembly, General Assembly in July 1997. Its goal is to promote nuclear disarmament and non-proliferation and the strengthening of the disarmament regimes in respect to other weapons of mass destruction, Chemical weapons, chemical and biological weapons. It also promotes disarmament efforts in the area of conventional weapons, especially land mines and small arms, which are often the weapons of choice in contemporary conflicts.

# Controversy

## Ethics

Even before the first nuclear weapons had been developed, scientists involved with the Manhattan Project were divided over the use of the weapon. The role of the two atomic bombings of the country in Japan's surrender and the U.S.'s ethics, ethical justification for them has been the subject of scholarly and popular debate for decades. The question of whether nations should have nuclear weapons, or test them, has been continually and nearly universally controversial.Jerry Brown and Rinaldo Brutoco (1997). ''Profiles in Power: The Anti-nuclear Movement and the Dawn of the Solar Age'', Twayne Publishers, pp. 191–192.

## Notable nuclear weapons accidents

* August 21, 1945: While conducting experiments on a plutonium-gallium core at Los Alamos National Laboratory, physicist Harry Daghlian received a lethal dose of radiation when an error caused it to enter prompt criticality. He died 25 days later, on September 15, 1945, from Acute radiation syndrome, radiation poisoning. * May 21, 1946: While conducting further experiments on the same core at Los Alamos National Laboratory, physicist Louis Slotin accidentally caused the core to become briefly Critical mass, supercritical. He received a lethal dose of Gamma ray, gamma and
neutron radiation Neutron radiation is a form of ionizing radiation Ionizing radiation (ionising radiation) consists of subatomic particles or electromagnetic waves that have sufficient energy to ionization, ionize atoms or molecules by detaching electrons from the ...
, and died nine days later on May 30, 1946. After the death of Daghlian and Slotin, the mass became known as the "demon core." It was ultimately used to construct a bomb for use on the Nevada Test Range. * February 13, 1950: a 1950 British Columbia B-36 crash, Convair B-36B crashed in northern British Columbia after jettisoning a Mark 4 nuclear bomb, Mark IV atomic bomb. This was the first such United States military nuclear incident terminology, nuclear weapon loss in history. The accident was designated a "Broken Arrow (nuclear), Broken Arrow"—an accident involving a nuclear weapon but which does not present a risk of war. Experts believe that up to 50 nuclear weapons were lost during the Cold War. * May 22, 1957: a Mark 17 nuclear bomb, Mark-17 hydrogen bomb accidentally fell from a bomber near Albuquerque, New Mexico. The detonation of the device's conventional explosives destroyed it on impact and formed a crater in diameter on land owned by the University of New Mexico. According to a researcher at the Natural Resources Defense Council, it was one of the most powerful bombs made to date. * June 7, 1960: the 1960 Fort Dix IM-99 accident destroyed a Boeing CIM-10 Bomarc nuclear missile and shelter and contaminated the BOMARC Missile Accident Site in New Jersey. * January 24, 1961: the 1961 Goldsboro B-52 crash occurred near Goldsboro, North Carolina. A Boeing B-52 Stratofortress carrying two W39, Mark 39 nuclear bombs broke up in mid-air, dropping its nuclear payload in the process. * 1965 Philippine Sea A-4 crash, where a Douglas A-4 Skyhawk, Skyhawk attack aircraft with a nuclear weapon fell into the sea. The pilot, the aircraft, and the B43 nuclear bomb were never recovered. It was not until 1989 that the Pentagon revealed the loss of the one-megaton bomb. * January 17, 1966: the 1966 Palomares B-52 crash occurred when a B-52 Stratofortress, B-52G bomber of the United States Air Force, USAF collided with a KC-135 Stratotanker, KC-135 tanker during Aerial refueling, mid-air refuelling off the coast of Spain. The KC-135 was completely destroyed when its fuel load ignited, killing all four crew members. The B-52G broke apart, killing three of the seven crew members aboard. Of the four B28 nuclear bomb, Mk28 type Teller–Ulam design, hydrogen bombs the B-52G carried, three were found on land near Almería, Spain. The non-nuclear explosives in two of the weapons detonated upon impact with the ground, resulting in the contamination of a (0.78 square mile) area by
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small, dense region consisting of s and s ...

plutonium Plutonium is a radioactive decay, radioactive chemical element with the Symbol (chemistry), symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating plutoni ...

. The fourth, which fell into the Mediterranean Sea, was recovered intact after a 2½-month-long search. * January 21, 1968: the 1968 Thule Air Base B-52 crash involved a United States Air Force (USAF) B-52 Stratofortress, B-52 bomber. The aircraft was carrying four hydrogen bombs when a cabin fire forced the crew to abandon the aircraft. Six crew members ejected safely, but one who did not have an ejection seat was killed while trying to bail out. The bomber crashed onto sea ice in Greenland, causing the nuclear payload to rupture and disperse, which resulted in widespread
radioactive contamination represents two-thirds of the United States' high-level radioactive waste by volume. Nuclear reactors line the riverbank at the Hanford Site along the Columbia River in January 1960. Radioactive contamination, also called radiological contaminatio ...
. One of the bombs remains lost. * September 18–19, 1980: the 1980 Damascus, Arkansas incident, Damascus Accident, occurred in Damascus, Arkansas, where a Titan missile equipped with a nuclear warhead exploded. The accident was caused by a maintenance man who dropped a socket from a socket wrench down an shaft, puncturing a fuel tank on the rocket. Leaking fuel resulted in a hypergolic fuel explosion, jettisoning the W-53 warhead beyond the launch site.

## Nuclear testing and fallout

Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980. Radioactive fallout from nuclear weapons testing was first drawn to public attention in 1954 when the Castle Bravo hydrogen bomb test at the Pacific Proving Grounds contaminated the crew and catch of the Japanese fishing boat ''Daigo Fukuryū Maru, Lucky Dragon''. One of the fishermen died in Japan seven months later, and the fear of contaminated tuna led to a temporary boycotting of the popular staple in Japan. The incident caused widespread concern around the world, especially regarding the effects of
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast Nuclear Blast is an independent record label and mail order record distributor with subsidiaries in Germany, the United Sta ...
and atmospheric nuclear testing, and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries". As public awareness and concern mounted over the possible health hazards associated with exposure to the
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast Nuclear Blast is an independent record label and mail order record distributor with subsidiaries in Germany, the United Sta ...

# Non-weapons uses

Peaceful nuclear explosions are nuclear explosions conducted for non-military purposes, such as activities related to economic development including the creation of canals. During the 1960s and 1970s, both the United States and the Soviet Union conducted a number of PNEs. Six of the explosions by the Soviet Union are considered to have been of an applied nature, not just tests. The United States and the Soviet Union later halted their programs. Definitions and limits are covered in the Peaceful Nuclear Explosions Treaty of 1976. The stalled Comprehensive Nuclear-Test-Ban Treaty of 1996 would prohibit all nuclear explosions, regardless of whether they are for peaceful purposes or not.

# History of development

* Cobalt bomb * Cosmic bomb (phrase) * Cuban Missile Crisis * Dirty bomb * Induced gamma emission * List of nuclear close calls * List of nuclear weapons * Nth Country Experiment * Nuclear blackout * Nuclear bunker buster * Nuclear holocaust * Nuclear weapons and the United Kingdom * Nuclear weapons in popular culture * Nuclear weapons of the United States * OPANAL (Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean) * Three Non-Nuclear Principles of Japan

# References

## Bibliography

* Hans Bethe, Bethe, Hans Albrecht. ''The Road from Los Alamos''. New York: Simon and Schuster, 1991. * DeVolpi, Alexander, Minkov, Vladimir E., Simonenko, Vadim A., and Stanford, George S. ''Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry''. Fidlar Doubleday, 2004 (Two volumes, both accessible on Google Book Search) (Content of both volumes is now available in the 2009 trilogy by Alexander DeVolpi: ''Nuclear Insights: The Cold War Legacy'') * Glasstone, Samuel and Dolan, Philip J.
The Effects of Nuclear Weapons (third edition).
' Washington, D.C.: U.S. Government Printing Office, 1977
Available online (PDF).
*

'. Departments of the Army, Navy, and Air Force: Washington, D.C., 1996 * Chuck Hansen, Hansen, Chuck. ''U.S. Nuclear Weapons: The Secret History.'' Arlington, TX: Aerofax, 1988 * Hansen, Chuck,
Swords of Armageddon: U.S. nuclear weapons development since 1945
(CD-ROM & download available). PDF. 2,600 pages, Sunnyvale, California, Chucklea Publications, 1995, 2007. (2nd Ed.) * Holloway, David. ''Stalin and the Bomb''. New Haven: Yale University Press, 1994. * The Manhattan Engineer District,
The Atomic Bombings of Hiroshima and Nagasaki
(1946) * Jean-Hugues Oppel, ''Réveillez le président'', Éditions Payot et rivages, 2007 (). The book is a fiction about the Force de Frappe, nuclear weapons of France; the book also contains about ten chapters on true historical incidents involving nuclear weapons and strategy. * Henry DeWolf Smyth, Smyth, Henry DeWolf.
Atomic Energy for Military Purposes.
' Princeton, NJ: Princeton University Press, 1945. (Smyth Reportthe first declassified report by the US government on nuclear weapons) *
The Effects of Nuclear War
'. Office of Technology Assessment, May 1979. * Richard Rhodes, Rhodes, Richard. ''Dark Sun: The Making of the Hydrogen Bomb''. New York: Simon and Schuster, 1995. * Richard Rhodes, Rhodes, Richard. ''The Making of the Atomic Bomb''. New York: Simon and Schuster, 1986 * George Shultz, Shultz, George P. and Goodby, James E. ''The War that Must Never be Fought'', Hoover Press, 2015, . * Spencer Weart, Weart, Spencer R. ''Nuclear Fear: A History of Images''. Cambridge, Massachusetts: Harvard University Press, 1988. * Spencer Weart, Weart, Spencer R. ''The Rise of Nuclear Fear''. Cambridge, Massachusetts: Harvard University Press, 2012.

* Laura Grego and David Wright, "Broken Shield: Missiles designed to destroy incoming nuclear warheads fail frequently in tests and could increase global risk of mass destruction", ''Scientific American'', vol. 320, no. no. 6 (June 2019), pp. 62–67. "Current U.S. missile defense plans are being driven largely by technology, politics and fear. Missile defenses will not allow us to escape our vulnerability to nuclear weapons. Instead large-scale developments will create barriers to taking real steps toward Nuclear disarmament, reducing nuclear risks—by blocking further cuts in nuclear arsenals and potentially spurring new deployments." (p. 67.) * Michael T. Klare, "Missile Mania: The death of the INF Treaty, INF [Intermediate-Range Nuclear Forces] Treaty [of 1987] has escalated the arms race", ''The Nation'', vol. 309, no. 6 (September 23, 2019), p. 4. * Ernest J. Moniz, Moniz, Ernest J., and Sam Nunn, "The Return of Doomsday: The New Nuclear Arms Race – and How Washington and Moscow Can Stop It", ''Foreign Affairs'', vol. 98, no. 5 (September / October 2019), pp. 150–161. Former U.S. Secretary of Energy Ernest Moniz and former U.S. Senator Sam Nunn write that "the old [strategic] equilibrium" between the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in . It consists of 50 , a , five major , 326 , and some . At , it is the world's . The United States shares significan ...

and
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

has been "destabilized" by "clashing national interests, insufficient dialogue, eroding arms control structures, advanced missile systems, and new cyberweapons... Unless Washington and Moscow confront these problems now, a major international conflict or nuclear escalation is disturbingly plausible—perhaps even likely." (p. 161.) * Thomas Powers, "The Nuclear Worrier" (review of Daniel Ellsberg, ''The Doomsday Machine: Confessions of a Nuclear War Planner'', New York, Bloomsbury, 2017, , 420 pp.), ''The New York Review of Books'', vol. LXV, no. 1 (January 18, 2018), pp. 13–15. * Eric Schlosser, ''Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety'', Penguin Press, 2013, . The book became the basis for a 2-hour 2017 PBS American Experience episode, likewise titled "Command and Control". Nuclear weapons continue to be equally hazardous to their owners as to their potential targets. Under the 1970
Treaty on the Non-Proliferation of Nuclear Weapons The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is an international treaty A treaty is a formal, legally binding written agreement between actors in international law Inte ...
, nuclear-weapon states are obliged to work toward the elimination of nuclear weapons. *David Wright and Cameron Tracy, "Over-hyped: Physics dictates that hypersonic weapons cannot live up to the grand promises made on their behalf", ''Scientific American'', vol. 325, no. 2 (August 2021), pp. 64–71. Quote from p. 71: "Failure to fully assess [the potential benefits and costs of hypersonic weapons] is a recipe for wasteful spending and increased global risk."

Nuclear Weapon Archive from Carey Sublette
is a reliable source of information and has links to other sources and an informativ

* Th
Federation of American Scientists
provide solid information on weapons of mass destruction, includin
nuclear weapons
and thei

Alsos Digital Library for Nuclear Issues
– contains many resources related to nuclear weapons, including a historical and technical overview and searchable bibliography of web and print resources. * Video archive o
US, Soviet, UK, Chinese and French Nuclear Weapon Testing
a
sonicbomb.com

The National Museum of Nuclear Science & History (United States)
– located in Albuquerque, New Mexico; a Smithsonian Affiliate Museum

The Manhattan Project: Making the Atomic Bomb
at AtomicArchive.com
Los Alamos National Laboratory: History
(U.S. nuclear history)
''Race for the Superbomb''
PBS website on the history of the H-bomb
Recordings of recollections of the victims of Hiroshima and Nagasaki

The Woodrow Wilson Center's Nuclear Proliferation International History Project
or NPIHP is a global network of individuals and institutions engaged in the study of international nuclear history through archival documents, oral history interviews and other empirical sources.
NUKEMAP3D
– a 3D nuclear weapons effects simulator powered by Google Maps. {{Authority control Nuclear weapons, Weapons and ammunition introduced in 1945 American inventions Articles containing video clips Bombs Nuclear bombs