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List of states with nuclear weapons

This is a list of states with nuclear weapons. There are currently eight states that have successfully detonated nuclear weapons. Five are considered to be "nuclear weapons states", an internationally recognized status conferred by the Nuclear Non-Proliferation Treaty (NPT). In order of acquisition of nuclear weapons these are: the United States of America, Russia (successor state to the Soviet Union), the United Kingdom, France and China. Since the formulation of the NPT, three non-signatory states of the NPT have conducted nuclear tests: India, Pakistan, and purportedly North Korea. Additionally, Israel is also strongly suspected to have an arsenal of nuclear weapons though it has refused to confirm or deny this, and there have been reports that over 200 nuclear weapons might be in its inventory. This status is not formally recognized by international bodies as none of these four countries are currently signatories to the Nuclear Non-Proliferation Treaty. Iran has been developing uranium enrichment technology and stands accused by the United States of doing so for weapons purposes. Iran insists that its intentions are limited to domestic nuclear power generation, despite plutonium traces being detected. As of February 4, 2006, the International Atomic Energy Agency referred Iran to the United Nations Security Council in response to concerns on their possible nuclear programs.

Estimated worldwide nuclear stockpiles

The following is a list of nations that have admitted the possession of nuclear weapons, the approximate number of warheads under their control in 2002, and the year they tested their first weapon. This list is informally known in global politics as the "Nuclear Club". With the exception of Russia and the United States (which have subjected their nuclear forces to independent verification under various treaties) these figures are estimates, in some cases quite unreliable estimates. Also, these figures represent total warheads possessed, rather than deployed. In particular, under the SORT treaty thousands of Russian and U.S. nuclear warheads are in inactive stockpiles awaiting processing. The fissile material contained in the warheads can then be recycled for use in nuclear reactors that drive nuclear power plants and some military submarines and warships.

From a high of 65,000 active weapons in 1985, there were about 20,000 active nuclear weapons in the world in 2002. Many of the "decommissioned" weapons were simply stored or partially dismantled, not destroyed.

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World map with nuclear weapons development status represented by color. As of October 31, 2006.
Red Five "nuclear weapons states" from the NPT
Orange Other known nuclear powers
Purple States formerly possessing nuclear weapons
Yellow States suspected of being in the process of developing nuclear weapons and/or nuclear programs
Blue States which at one point had nuclear weapons and/or nuclear weapons research programs
Pink States that claim to possess nuclear weapons

*All numbers are estimates from the Natural Resources Defense Council, published in the Bulletin of the Atomic Scientists, unless other references are given. If differences between active and total stockpile are known, they are given as two figures separated by a forward slash. If no specifics are known, only one figure is given. Stockpile number may not contain all intact warheads if a substantial amount of warheads are scheduled for but have not yet gone through dismantlement; not all "active" warheads are deployed at any given time. When a spread of weapons is given (e.g., 0-10), it generally indicates that the estimate is being made on the amount of fissile material which has likely been produced, and the amount of fissile material needed per warhead depends on estimates of a country's proficiency at nuclear weapon design.

Five "nuclear weapons states" from the NPT

The United States of America developed the first atomic weapons during World War II in co-operation with the United Kingdom and Canada, out of the fear that Nazi Germany would develop them first. It tested its first nuclear weapon in 1945 ("Trinity"), and remains the only country to have used nuclear weapons against another nation, during the atomic bombings of Hiroshima and Nagasaki (see: Manhattan Project). It was the first nation to develop the hydrogen bomb, testing it ("Ivy Mike") in 1952 and a deployable version in 1954 ("Castle Bravo").
The USSR tested its first nuclear weapon ("Joe-1") in 1949, in a crash project developed partially with espionage obtained during and after World War II (see: Soviet atomic bomb project). The direct motivation for their weapons development was the development of a balance of power during the Cold War. It tested a primitive hydrogen bomb in 1953 ("Joe-4") and a megaton-range hydrogen bomb in 1955 ("RDS-37"). The Soviet Union also tested the most powerful explosive ever detonated by humans, ("Tsar Bomba"), which had a yield of 100 megatons, but was intentionally reduced to 50. After its dissolution in 1991, its weapons entered officially into the possession of Russia.
The United Kingdom tested its first nuclear weapon ("Hurricane") in 1952, drawing largely on data gained while collaborating with the United States during the Manhattan Project. Its program was motivated to have an independent deterrent against the USSR, while also remaining relevant in Cold War Europe. It tested its first hydrogen bomb in 1957. It maintains the Trident fleet of nuclear weapon submarines.
France tested its first nuclear weapon in 1960 ("Gerboise Bleue"), based mostly on its own research aided by indirect British help[citations needed] and the experience of French scientists who had worked on the Manhattan Project namely Louis de Broglie, Pierre Auger and Frédéric Joliot. It was motivated by the will of independence vis-à-vis the United States confirmed with France's loosening of ties to NATO, and as an independent deterrent against the USSR. It was also relevant to retain great power status, along side United Kingdom, during the post-colonial Cold War (see: Force de frappe). France tested its first hydrogen bomb in 1968 ("Opération Canopus"). After the Cold War, France has disarmed 175 warheads with the reduction and modernization of its arsenal which has now evolved to a dual system based on submarine-launched ballistic missiles (SSBN) and medium-range air-to-surface missiles (Rafale bombers). However new nuclear weapons are in development and reformed nuclear squadrons were trained during Enduring Freedom operation in Afghanistan. In January 2006, president Jacques Chirac officially stated a terrorist act or the use of massive destruction weapons against France would result in a nuclear counterattack [12]. The Charles de Gaules is currently the last carrier with nuclear weapons deployed by a country.
China tested its first nuclear weapon in 1964. China was the first Asian nation to have developed and tested a nuclear weapon. The weapon was developed as a deterrent against both the United States and the USSR. It tested its first hydrogen bomb in 1967 at Lop Nur. The country is currently thought to have had a stockpile of around 130 warheads.

Other known nuclear powers

India has never been a member of the Nuclear Non-Proliferation Treaty. It tested a "peaceful nuclear device", as it was described by the Indian government, in 1974 ("Smiling Buddha"), the first test developed after the creation of the NPT, and created new questions about how civilian nuclear technology could be diverted secretly to weapons purposes (dual-use technology). It appears to have been primarily motivated as a deterrent against China. It tested weaponized nuclear warheads in 1998 ("Operation Shakti"), including a thermonuclear device (though whether the latter was fully successful is a matter of some contention). In July 2005, it was officially recognized by the United States as a "a responsible state with advanced nuclear technology" and agreed to full nuclear cooperation between the two nations. This is seen as a tacit entry into the nuclear club of the above nations. In March 2006, a civil nuclear cooperation deal was signed between President George W Bush and Prime Minister Manmohan Singh. This deal, ratified by United States Congress and United States Senate in December 2006 would pave the path for the United States and other members of the Nuclear Suppliers Group to sell civilian nuclear technology to India. The country is currently thought to have had a stockpile of around 40-50 warheads.
Pakistan is not a member of the Nuclear Non-Proliferation Treaty. Pakistan covertly developed nuclear weapons over many decades, beginning in the late 1970s. Pakistan first delved into nuclear power after the establishment of its first nuclear power plant near Karachi with equipment and materials supplied mainly by western nations in the early 1970s. After the detonation of a nuclear bomb by India, the country started its own nuclear weapons development program and established secret, mostly underground, nuclear facilities near the capital Islamabad. It is believed that Pakistan already had nuclear weapons capability by the end of the 1980s. However, this was to remain speculative until 1998 when Pakistan conducted its first nuclear tests at the Chagai Hills, a few days after India conducted its own tests.
North Korea was a member of the Nuclear Non-Proliferation Treaty, but announced a withdrawal on January 10, 2003 and did so that April. In February 2005 they claimed to possess functional nuclear weapons, though their lack of a test at the time led many experts to doubt the claim. However, in October 2006, North Korea stated that due to growing intimidation by the USA, it would conduct a nuclear test to confirm its nuclear status. North Korea reported a successful nuclear test on October 9, 2006. Most U.S. intelligence officials believe that North Korea did, in fact, test a nuclear device due to radioactive isotopes detected by U.S. aircraft; however, most agree that the test was probably only partially successful, having less than a kiloton in yield.

Suspected nuclear states

Countries believed to have at least one nuclear weapon, or programs with a realistic chance of producing a nuclear weapon in the near future:

Israel - Israel is not a member of the Nuclear Non-Proliferation Treaty and refuses to officially confirm or deny having a nuclear arsenal, or to having developed nuclear weapons, or even to having a nuclear weapons program. Although Israel claims that the Negev Nuclear Research Center near Dimona is a "research reactor," no scientific reports based on work done there have ever been published. Extensive information about the program in Dimona was also disclosed by technician Mordechai Vanunu in 1986. Imagery analysts can identify weapon bunkers, mobile missile launchers, and launch sites in satellite photographs. It is believed to possess nuclear weapons by the International Atomic Energy Agency, though unlike Iran, has never been referred to the United Nations Security Council. Israel is suspected to have tested a nuclear weapon along with South Africa in 1979, but this has never been confirmed (see Vela Incident). According to the Natural Resources Defense Council and the Federation of American Scientists, Israel possesses around 75-200 weapons.

States suspected of having clandestine nuclear programs

The question of whether individual states without nuclear weapons are trying to develop them is often a controversial one. Accusations of clandestine nuclear programs are often vehemently denied, and may be politically motivated themselves, or simply erroneous. Below are countries who have been accused by a number of governments and intergovernmental agencies as currently attempting to develop nuclear weapons technology who are not suspected as yet having developed it.

Iran - Iran signed the Nuclear Non-Proliferation Treaty and says its interest in nuclear technology, including enrichment, was for civilian purposes only (a right guaranteed under the treaty), but the United States of America's CIA and a few other western countries, mainly the United Kingdom [citation needed] suspect that this is a cover for a nuclear weapons program, claiming that Iran has little need to develop nuclear power domestically and that it has consistently chosen nuclear options which were dual-use technology rather than those which could only be used for power generation.[19] Former Iranian Foreign Minister Kamal Kharrazi stated on the intentions of his country's nuclear ambitions: "Iran will develop nuclear power abilities and these have to be recognized by the treaties." As of February 4, 2006, the International Atomic Energy Agency referred Iran to the United Nations Security Council in response to Western concerns on their possible nuclear programs. On April 11, 2006, Iran's president announced that the country had successfully enriched uranium to reactor-grade levels for the first time. On April 22, 2006, Iran's envoy to the U.N. nuclear watchdog agency stated the Islamic republic had reached a "basic deal" with the Kremlin to form a joint uranium enrichment venture on Russian territory.
Saudi Arabia - In 2003, members of the government stated that due to the worsening relations with the USA, Saudi Arabia was being forced to consider the development of nuclear weapons; however, so far they have denied that they are making any attempt to produce them.[22] It has been rumoured that Pakistan has transferred several nuclear weapons to Saudi Arabia, but this is unconfirmed. In March 2006, the German magazine Cicero reported that Saudi Arabia had since 2003 received assistance from Pakistan to acquire nuclear missiles and warheads. Satellite photos allegedly reveal an underground city and nuclear silos with Ghauri rockets south of the capital Riyadh. Pakistan has denied aiding Saudi Arabia in any nuclear ambitions.

States formerly possessing nuclear weapons

Nuclear weapons have been present in many nations, often as staging grounds under control of other powers. However, in only a few instances have nations given up nuclear weapons after being in control of them; in most cases this has been because of special political circumstances. The fall of the USSR, for example, left several former Soviet-bloc countries in possession of nuclear weapons.

South Africa – South Africa produced six nuclear weapons in the 1980s, but disassembled them in the early 1990s. In 1979 there was a putative detection of a clandestine nuclear test in the Indian Ocean, and it has long been speculated that it was potentially a test by South Africa, perhaps in collaboration with Israel, though this has never been confirmed (see Vela Incident). South Africa signed the Nuclear Non-Proliferation Treaty in 1991.

Former Soviet countries

Belarus – Belarus had 81 single warhead missiles stationed in their territory after the Soviet Union collapsed in 1991. They were all transferred to Russia by 1996. Belarus signed the Nuclear Non-Proliferation Treaty.
Kazakhstan – Kazakhstan inherited 1,400 nuclear weapons from the Soviet Union, and transferred them all to Russia by 1995. Kazakhstan has signed the Nuclear Non-Proliferation Treaty.
Ukraine - Ukraine has signed the Nuclear Non-Proliferation Treaty. Ukraine inherited about 5,000 nuclear weapons when it became independent from the USSR in 1991, making its nuclear arsenal the third-largest in the world. By 1996, Ukraine had voluntarily disposed of all nuclear weapons within its territory, transferring them to Russia.

States formerly possessing nuclear programs

These are nations known to have initiated serious nuclear weapons programs, with varying degrees of success. All of them are now regarded as currently no longer actively developing, or possessing, nuclear arms. All of the listed countries (or their descendants) signed the Nuclear Non-Proliferation Treaty.

Argentina – Argentina created its National Atomic Energy Commission (CNEA) in 1950 for developing and controlling nuclear energy for peaceful purposes in the country but conducted a nuclear weapon research program under military rule of 1978, at a time when it had signed, but not ratified, the Treaty of Tlatelolco. This program was abandoned after democratization in 1983. However, unofficial reports and U.S. intelligence postulate that Argentina continued some kind of nuclear weapons program during the 1980s (as an attempt to build a nuclear submarine), mainly because of rivalry with Brazil[32] but the program was cancelled. In the early 1990s, Argentina and Brazil established a bilateral inspection agency to verify both countries' pledges to use nuclear energy only for peaceful purposes and on February 10, 1995, Argentina acceded to the Nuclear Non-Proliferation Treaty.
Australia – Following World War II, Australian defence policy initiated joint nuclear weapons development with the United Kingdom. Australia provided uranium, land for weapons and rocket tests, and scientific and engineering expertise. Canberra was also heavily involved in the Blue Streak ballistic missile program. In 1955, a contract was signed with a British company to build the Hi-Flux Australian Reactor (HIFAR). HIFAR was considered the first step toward the construction of larger reactors capable of producing substantial volumes of plutonium for nuclear weapons. However, Australia's nuclear ambitions were abandoned by the 1960s, and the country signed the NPT in 1970 (ratified in 1973).
Brazil – Military régime conducted a nuclear weapon research program (code-named "Solimões") to acquire nuclear weapons in 1978, in spite of having ratified the Treaty of Tlatelolco in 1968. When an elected government came in to power in 1985, though, the program was ended. On July 13, 1998 President Fernando Henrique Cardoso signed and ratified both the Nuclear Non-Proliferation Treaty (NPT) and the Comprehensive Test Ban Treaty (CTBT), denying that Brazil had developed nuclear weapons.
Egypt – Had a nuclear weapon research program from 1954 to 1967. Egypt has signed the Nuclear Non-Proliferation Treaty.
Nazi Germany – During World War II, Nazi Germany researched possibilities to develop a nuclear weapon; however, for multiple reasons subject to some controversy, the project was not nearing completion at the end of the war. The research site was sabotaged by British spies and Norwegian partisans, which slowed down their research (see Norwegian heavy water sabotage). Historian Rainer Karlsch, in his 2005 book Hitlers Bombe, has suggested that the Nazis may have tested some sort of "atom bomb" in Thuringia in the last year of the war; it may have been a radiological weapon (rather than a fission weapon), though little reliable evidence of this has surfaced. Some of the German scientists involved also claimed to have sabotaged or falsely reported failures due to personal moral disagreement with Nuclear bomb development (See: German nuclear energy project).
Iraq – Iraq has signed the Nuclear Non-Proliferation Treaty. They had a nuclear weapon research program during the 1970s and 1980s. In 1981, Israel destroyed Iraqi nuclear reactor Osiraq. In 1996, the UN's Hans Blix reported that Iraq had dismantled or destroyed all of their nuclear capabilities. In 2003, a multinational coalition headed by the United States invaded Iraq based on intelligence indicating that it possessed weapons prohibited by the UN Security Council. Because of its refusal to fully cooperate with UN inspections, Iraq was strongly suspected by many UNSC members of having some form of nuclear program. However, in 2004 the Duelfer Report concluded Iraq's nuclear program was terminated in 1991.
Japan – Japan conducted research into nuclear weapons during World War II though made little headway.[38] (see Japanese atomic program). Japan signed the Nuclear Non-Proliferation Treaty. While Japan has the technological capabilities to develop nuclear weapons in a short time there is no evidence they are doing so. Although Japan's constitution does not forbid it from producing nuclear weapons, the country has been active in promoting non-proliferation treaties. There exists some suspicion that nuclear weapons may be located in US bases in Japan. Japan is also the only nation in the world against whom nuclear weapons have been used in wartime, the cities of Hiroshima and Nagasaki having been destroyed on August 6 and 9, 1945, respectively.
Libya – Signed the Nuclear Non-Proliferation Treaty. On December 19, 2003, after the U.S.-led invasion of Iraq and the October 2003 interception of Pakistani-designed centrifuge parts sent from Malaysia (as part of A. Q. Khan's proliferation ring), Libya admitted to possessing a nuclear weapon program and simultaneously announced its intention to end it and dismantle all existing weapons of mass destruction to be verified by unconditional inspections.
Poland – Nuclear research began in Poland in the early 1960s, with the first controlled nuclear fission reaction being achieved in the late 1960s. During the 1970s further research resulted in the generation of fusion neutrons through convergent shockwaves. In the 1980s research focused on the development of micro-nuclear reactions, and was under military control. Currently Poland operates the MARIA nuclear research reactor under the control of the Institute of Atomic Energy, in Świerk near Warsaw. Poland has signed the Nuclear Non-Proliferation Treaty and officially possesses no nuclear weapons.
Romania – Signed the Nuclear Non-Proliferation Treaty in 1970. In spite of this, under Nicolae Ceauşescu, in the 1980s, Romania had a secret nuclear-weapons development program that was ended after his overthrow in 1989. Now Romania runs a nuclear power plant of two reactor units (with three more under construction) built with Canadian support. It also mines and enriches its own uranium for the plant and has a research program.
South Korea began a nuclear weapons program in the early 1970s, which was believed abandoned after signing NPT in 1975. However there have been allegations that program may have been continued after this date by the military government.[42] In late 2004, the South Korean government disclosed to the IAEA that scientists in South Korea had extracted plutonium in 1982 and enriched uranium to near-weapons grade in 2000.
Sweden – During the 1950s and 1960s, Sweden seriously investigated nuclear weapons, intended to be deployed over coastal facilities of an invading enemy (the Soviet Union). A very substantial research effort of weapon design and manufacture was conducted resulting in enough knowledge to allow Sweden to manufacture nuclear weapons. A weapon research facility was to be built in Studsvik. Saab made plans for a supersonic nuclear bomber, the A36.[citation needed] However Sweden decided not to pursue a weapon production program and signed the Nuclear Non-Proliferation Treaty.
Switzerland – Between 1946 and 1969 Switzerland had a secret nuclear programme that came to light in 1995. By 1963 theoretical basics with detailed technical proposals, specific arsenals, and cost estimates for Swiss nuclear armaments were made. This program was, however, abandoned partly because of financial costs and by signing the NPT on November 27, 1969.
The Republic of China (Taiwan) – Conducted a covert nuclear weapon research program from 1964 until 1988 when it was stopped as a result of U.S. pressure. Taiwan signed the Nuclear Non-Proliferation Treaty in 1968. According to a previously classified 1974 U.S. Defense Department memorandum, Secretary of Defense James Schlesinger expressed a view during a meeting with Ambassador Leonard Unger that U.S. nuclear weapons housed in Taiwan needed to be withdrawn.


Socialist Federal Republic of Yugoslavia's nuclear ambitions began as early as 1950s when scientists considered both uranium enrichment and plutonium reprocessing. In 1956, the Vinča fuel reprocessing site was constructed, followed by research reactors in 1958 and 1959, for which the Soviets provided heavy water and enriched uranium. In 1966, plutonium reprocessing tests began in Vinča laboratories, resulting in gram quantities of reprocessed plutonium. During the 1950s and 1960s there was also cooperation in plutonium processing between Yugoslavia and Norway. In 1960 Tito froze the nuclear program for unknown reasons, but restarted it, after India's first nuclear tests, in 1974. The program continued even after Tito's death in 1980, divided into two components – for weapons design and civilian nuclear energy, until a decision to stop all nuclear weapons research was made in July 1987. The civilian nuclear program however resulted in a nuclear power plant Krško built in 1983, now co-owned by Slovenia and Croatia, and used for peaceful production of electricity.
Federal Republic of Yugoslavia inherited the Vinča laboratories and 50 kilograms of highly enriched uranium stored at the site. During the NATO bombing of Yugoslavia in 1999, Vinča was never hit because NATO was aware of the HEU. After the end of NATO bombings the U.S. government and the Nuclear Threat Initiative transported the HEU to Russia – the place from which Yugoslavia originally acquired it.

Other nuclear-capable states

Virtually any industrialized nation today has the technical capability to develop nuclear weapons within several years if the decision to do so were made. Nations already possessing substantial nuclear technology and arms industries could do so in no more than a year or two, perhaps even as fast as a few months or weeks, if they so decided to. The larger industrial nations (Japan, Germany, Italy, Australia and Canada for example) could, within several years of deciding to do so, build arsenals rivaling those of the states that already have nuclear weapons. This list below mentions some notable capabilities possessed by certain states that could potentially be turned to the development of nuclear arsenals. This list represents only strong nuclear capability, not the political will to develop weapons. All of the listed countries have signed the Nuclear Non-Proliferation Treaty.

Canada - Canada has a well developed advanced nuclear technology base, large uranium reserves and markets reactors for civilian use. Through extensive power generation and production capabilities, Canada has the technological capabilities to develop nuclear weapons, possessing large amounts of plutonium through power generation. Canada could develop nuclear weapons within a short period of time if attempted. While no nuclear weapons program existed, Canada was technically well placed to proceed with a program as early as 1945 if they wished to do so.[46] Canada has been an important contributor of both expertise and raw materials to the American program in the past, and assisted in the Manhattan Project. In 1959, NATO proposed that the RCAF assume a nuclear strike role in Europe. Thus in 1962 six Canadian CF-104 squadrons based in Europe were formed into the RCAF Nuclear Strike Force armed with B28 nuclear bombs (originally Mk 28) under the NATO nuclear weapons sharing program; the Force was disbanded in 1972 when Canada opted out of the nuclear strike role. Canada accepted having American W-40 nuclear warheads under dual key control on Canadian soil in 1963 to be used on the Canadian BOMARC missiles. The Canadian air force also maintained a stockpile of AIR-2 Genie unguided nuclear air-to-air rockets as the primary wartime weapon on the CF-101 Voodoo all-weather interceptor after 1965. Prime Minister Pierre Trudeau declared Canada would be a nuclear weapon-free country in 1971, and the last American warheads were withdrawn in 1984. Canada gave India its first research reactor, the CIRUS, in 1956 and this reactor was used to make the nuclear material used in India's first nuclear device. Canada also produces the renowned CANDU reactor and has sold the technology to several countries, including China, South Korea, India, Romania, Argentina, and Pakistan. However, there is no credible evidence that CANDU reactors were used to breed weapons grade material for either India or Pakistan. Canada nevertheless cut off nuclear trade with those two countries after they detonated nuclear weapons.
Germany - While Germany is a signatory of the NPT, it has the means to equip itself rapidly with nuclear weapons. It has an advanced nuclear industry capable of manufacturing reactors, enriching uranium, fuel fabrication, and fuel reprocessing and it operates 19 power reactors producing one third of its total electrical needs. On the other hand, Germany has since 1945 made no serious attempts of acquiring or developing its own strategic delivery systems. Considerable numbers of nuclear weapons have been stationed both in East and West Germany during the Cold War, starting as early as 1955. Under the nuclear sharing scheme, West German soldiers would in theory have been authorized to use nuclear weapons provided by the US in event of a massive Warsaw Pact attack. Several dozen such weapons reputedly remain on bases in western Germany. Since 1998, Germany has adopted a policy of eliminating nuclear power, although slow progress had been made.[47] On January 26, 2006, the former defence minister, Rupert Scholz, said that Germany may need to build its own nuclear weapons to counter terrorist threats.[48] The Treaty on the Final Settlement with Respect to Germany also specified that Germany wouldn't acquire nuclear weapons.
Japan - Japan makes extensive use of nuclear energy in nuclear reactors, generating a significant percentage of the electricity in Japan. Japan has the third largest nuclear energy production after the U.S. and France, and plans to produce over 40% of its electricity using nuclear power by 2010. Significant amounts of plutonium are created as a by-product of the energy production, and Japan had 4.7 tons of plutonium in December 1995. Japan also has its own centrifuge-based uranium enrichment program, which could also be used to create highly enriched uranium suitable for bombs. Experts believe Japan has the technology, raw materials, and the capital to produce nuclear weapons within one year if necessary, and some analysts consider it a "de facto" nuclear state for this reason. Japan has been quietly reconsidering its nuclear status because of the ongoing crisis over North Korean nuclear weapons.
Italy - Italy has operated a number of nuclear reactors, both for power and for research. The country was also a base for the Jupiter missile in the 1960s and later the GLCM nuclear-armed ground-launched variant of the Tomahawk cruise missile during the 1980s, despite strong public outcry. Several warheads are still in the NATO arsenal in Italy, mostly in form of airplane bombs. While no evidence suggests that Italy intends to develop or deploy nuclear weapons, such a capability exists - estimates from as far back as the mid-80s show that Italy could begin and complete a nuclear weapons program in as little as one year.
Lithuania - Nuclear power reactors produce 77% of Lithuania's electricity and it has 2 of the world's most powerful reactors in its territory. However, one of these reactors was recently shut down. Lithuania has the means of legally acquiring fissile materials for power plants. Lithuania also has former launch sites for Soviet Union missiles. However, there is no political will to develop nuclear weapons in Lithuania.
The Netherlands - Operates a power reactor at Borsele, producing 452 MW, which satisfies 5% of its electrical needs and has an advanced nuclear research and medical isotopes facility at Petten. Several Dutch companies are key participants in the tri-national Urenco uranium enrichment consortium. By 2000 the Netherlands had about 2 tons of separated reactor grade plutonium. Even though the capability exists, there is no evidence for nuclear weapon production in the Netherlands. Also, in the light of the fierce opposition against nuclear weapon deployment in the 1980s, it is highly unlikely that such a programme will ever exist.
Norway - Has since the 1950s operated two scientific reactors at Kjeller and Halden, and there are currently no known plans for constructing new reactors. According to environmental organization Bellona, Norway exported equipment and technology for plutonium enrichment and heavy water for use in reactors to India and Israel during the 1960s, contributing to their nuclear ambitions.[50] It is estimated Norway could complete a nuclear weapons program in a year with adequate funding, but public opposition to nuclear weapons is considerable.
Autor: Shone83 :
History of nuclear weapons

The history of nuclear weapons chronicles the development of nuclear weapons—devices of enormous destructive potential which derive their energy from nuclear fission or nuclear fusion reactions—starting with the scientific breakthroughs of the 1930s which made their development possible, continuing through the nuclear arms race and nuclear testing of the Cold War, and finally with the questions of proliferation and possible use for terrorism in the early 21st century.

The first fission weapons ("atomic bombs") were developed in the United States during World War II in what was called the Manhattan Project, at which point two were dropped on Japan. The Soviet Union started development shortly thereafter with their own atomic bomb project, and not long after that both countries developed even more powerful fusion weapons ("hydrogen bombs"). During the Cold War, these two countries each acquired nuclear weapons arsenals numbering in the thousands, placing many of them onto rockets which could hit targets anywhere in the world. Currently there are at least eight countries with functional nuclear weapons. A considerable amount of international negotiating has focused on the threat of nuclear warfare and the proliferation of nuclear weapons to new nations or groups.

There have been (at least) four major false alarms, the most recent in 1995, that almost resulted in the US or Russia launching its weapons in retaliation for a supposed attack.

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A nuclear fireball lights up the night in a United States nuclear test.

Physics and politics in the 1930s

In the first decades of the twentieth century, physics was revolutionized with developments in the understanding of the nature of atoms. In 1898, Pierre Curie and his wife Marie had discovered that present in pitchblende, an ore of uranium, was a substance which emitted large amounts of radioactivity, which they named radium. This raised the hopes of both scientists and lay people that the elements around us could contain tremendous amounts of unseen energy, waiting to be tapped.

Experiments by Ernest Rutherford in 1911 indicated that the vast majority of an atom's mass was contained in a very small nucleus at its core, made up of protons, surrounded by a web of whirring electrons. In 1932, James Chadwick discovered that the nucleus contained another fundamental particle, the neutron, and in the same year John Cockcroft and Ernest Walton "split the atom" for the first time, the first occasion on which an atomic nucleus of one element had been successfully changed to a different nucleus by artificial means.

Great changes were also mounting on the political scene. Adolf Hitler was appointed chancellor of Germany in January 1933 and, within only three months, had asserted dictatorial control over the country. As part of the anti-Semitic ideology of Nazism, all Jewish civil servants were fired from their posts, including university professors, many of whom fled to Britain and the United States, if they could find jobs.

In 1934, French physicists Irène and Frédéric Joliot-Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles, and in the same year Italian physicist Enrico Fermi reported similar results when bombarding uranium with neutrons.

In 1938, Germans Otto Hahn and Fritz Strassmann released the results of their finding proving that what Fermi had witnessed in 1934 was no less than the bursting of the uranium nucleus: nuclear fission. Immediately afterwards, Lise Meitner and Otto Robert Frisch described the theoretical mechanisms of fission and revealed that large amounts of binding energy were released in the process. Hungarian Leó Szilárd confirmed with his own experiments that along with energy, neutrons were given off in the reaction as well, creating the possibility of a nuclear chain reaction, whereby each fission created two or more other fissions, exponentially releasing energy.

As the Nazi army marched into first Czechoslovakia in 1938, and then Poland in 1939, officially beginning World War II, many of Europe's top physicists had already begun to flee from the imminent conflict. Scientists on both sides of the conflict were well aware of the possibility of utilizing nuclear fission as a weapon, but at the time no one was quite sure how it could be done. In the early years of the Second World War, physicists abruptly stopped publishing on the topic of fission, an act of self-censorship to keep the opposing side from gaining any advantages.

In nuclear fission, the nucleus of a fissile atom (in this case, enriched uranium) absorbs a thermal neutron, becomes unstable, and splits into two new atoms, releasing some energy and between one and three new neutrons, which can perpetuate the process.

From Los Alamos to Hiroshima

By the beginning of World War II, there was concern among scientists in the Allied nations that Nazi Germany might have their own project to develop fission-based weapons. Organized research first began in Britain as part of the "TUBE ALLOYS" project, and in the United States a small amount of funding was given for research into uranium weapons starting in 1939 with the Uranium Committee under Lyman James Briggs. At the urging of British scientists, though, who had made crucial calculations indicating that a fission weapon could be completed within only a few years, by 1941 the project had been wrested into better bureaucratic hands, and in 1942 came under the auspices of General Leslie Groves as the Manhattan Project. Scientifically led by the American physicist Robert Oppenheimer, the project brought together the top scientific minds of the day (many exiles from Europe) with the production power of American industry for the goal of producing fission-based explosive devices before Germany could. Britain and the U.S. agreed to pool their resources and information for the project, but the other Allied power—the Soviet Union under Joseph Stalin—was not informed.

A massive industrial and scientific undertaking, the Manhattan Project involved many of the world's great physicists in the scientific and development aspects. The United States made an unprecedented investment into wartime research for the project, which was spread across over 30 sites in the U.S. and Canada. Scientific knowledge was centralized at a secret laboratory known as Los Alamos, previously a small ranch school near Santa Fe, New Mexico.

Uranium appears in nature primarily in two isotopes: uranium-238 and uranium-235. When the nucleus of uranium-235 absorbs a neutron, it undergoes nuclear fission, splitting into two "fission products" and releasing energy and 2.5 neutrons on average. Uranium-238, on the other hand, absorbs neutrons and does not fission, effectively putting a stop to any ongoing fission reaction. It was discovered that an atomic bomb based on uranium would need to be made of almost completely pure uranium-235 (at least 80% pure), or else the presence of uranium-238 would quickly curtail the nuclear chain reaction. The team of scientists working on the Manhattan Project immediately realized that one of the largest problems they would have to solve was how to remove uranium-235 from natural uranium, which was composed of 99.3% uranium-238. Two methods were developed during the wartime project, both of which took advantage of the fact that uranium-238 has a slightly greater atomic mass than uranium-235: electromagnetic separation and gaseous diffusion—methods which separated isotopes based on their differing weights. Another secret site was erected at rural Oak Ridge, Tennessee, for the large-scale production and purification of the rare isotope. It was a massive investment: at the time, one of the Oak Ridge facilities (K-25) was the largest factory under one roof. The Oak Ridge site employed tens of thousands of employees at its peak, most of whom had no idea what they were working on.

Berkeley physicist Robert Oppenheimer led the Allied scientific effort at Los Alamos.

Though uranium-238 cannot be used inside an atomic bomb, when it absorbs a neutron it transforms first into an unstable element, uranium-239, and then decays into neptunium-239 and finally the relatively stable plutonium-239, an element which does not exist in nature. Plutonium is also fissile and can be used to create a fission reaction, and after Enrico Fermi achieved the world's first sustained and controlled nuclear chain reaction in the creation of the first "atomic pile"—a primitive nuclear reactor—in a basement at the University of Chicago, massive reactors were secretly created at what is now known as Hanford Site in the state of Washington, using the Columbia River as cooling water, to transform uranium-238 into plutonium for a bomb.

For a fission weapon to operate, there must be a critical mass—the amount needed for a self-sustaining nuclear chain reaction—of fissile material bombarded with neutrons at any one time. The simplest form of nuclear weapon would be a gun-type fission weapon, where a sub-critical mass of fissile material (such as uranium-235) would be shot at another sub-critical mass of fissile material. The result would be a super-critical mass which, when bombarded with neutrons, would undergo fission at a rapid rate and create the desired explosion.

But it was soon discovered that plutonium cannot be used in a "gun assembly," as it has too high a level of background neutron radiation; it undergoes spontaneous fission to a very small extent. If plutonium were used in a "gun assembly," the chain reaction would start in the split seconds before the critical mass was assembled, blowing the weapon apart before it would have any great effect (this is known as a fizzle). After some despair, Los Alamos scientists discovered another approach: using chemical explosives to implode a sub-critical sphere of plutonium, which would increase its density and make it into a critical mass. The difficulties with implosion were in the problem of making the chemical explosives deliver a perfectly uniform shock wave upon the plutonium sphere—if it were even slightly asymmetric, the weapon would fizzle (which would be expensive, messy, and not a very effective military device). This problem was circumvented by the use of hydrodynamic "lenses"—explosive materials of differing densities—which would focus the blast waves inside the imploding sphere, akin to the way in which an optical lens focuses light rays.

After D-Day, General Groves had ordered a team of scientists—Project Alsos—to follow eastward-moving victorious Allied troops into Europe in order to assess the status of the German nuclear program (and to prevent the westward-moving Russians from gaining any materials or scientific manpower). It was concluded that while Nazi Germany had also had an atomic bomb program, headed by Werner Heisenberg, the government had not made a significant investment in the project, and had been nowhere near success.

By the unconditional surrender of Germany on May 8, 1945, the Manhattan Project was still months away from a working weapon. That April, after the death of American President Franklin D. Roosevelt, former Vice-President Harry S. Truman was told about the secret wartime project for the first time.

Because of the difficulties in making a working plutonium bomb, it was decided that there should be a test of the weapon, and Truman wanted to know for sure if it would work before his meeting with Joseph Stalin at an upcoming conference on the future of postwar Europe. On July 16, 1945, in the desert north of Alamogordo, New Mexico, the first nuclear test took place, code-named "Trinity," using a device nicknamed "the Gadget." The test released the equivalent of 19 kilotons of TNT, far mightier than any weapon ever used before. The news of the test's success was rushed to Truman, who used it as leverage at the upcoming Potsdam Conference, held near Berlin.

After hearing arguments from scientists and military officers over the possible uses of the weapons against Japan (though some recommended using them as "demonstrations" in unpopulated areas, most recommended using them against "built up" targets, a euphemistic term for populated cities), Truman ordered the use of the weapons on Japanese cities, hoping it would send a strong message which would end in the capitulation of the Japanese leadership and avoid a lengthy invasion of the island. On August 6, 1945, a uranium-based weapon, "Little Boy", was let loose on the Japanese city of Hiroshima. Three days later, a plutonium-based weapon, "Fat Man", was dropped onto the city of Nagasaki. The atomic bombs killed at least one hundred thousand Japanese outright, most of them civilians, with the heat, radiation, and blast effects. Many tens of thousands would die later of radiation sickness and related cancers. Truman promised a "rain of ruin" if Japan did not surrender immediately, threatening to eliminate Japanese cities, one by one; Japan surrendered on August 15. Truman's threat was in fact a bluff, since the US had not completed more atomic bombs at the time.

The weapons had been developed, and their power had been demonstrated to the world. The United States held a monopoly on nuclear weapons, but nobody thought this could last forever—the principles were based in fundamental research, which could be duplicated almost anywhere. The atomic age had begun.

Soviet atomic bomb project

The Soviet Union was not invited to share in the new weapons developed by the United States and the other Allies, but they were not to be left out of the nuclear club for long. All during the war, information had been pouring in from a number of volunteer spies involved with the Manhattan Project (known in Soviet cables under the code-name of Enormoz), and the Soviet nuclear physicist Igor Kurchatov was carefully watching the Allied weapons development. As such, it came as no surprise to Stalin when Truman had informed him at the Potsdam conference that he had a "powerful new weapon." Truman was shocked at Stalin's lack of interest.

The Soviet spies in the U.S. project were all volunteers and none were Russians. One of the most valuable, Klaus Fuchs, was a German émigré theoretical physicist who had been a part in the early British nuclear efforts and had been part of the UK mission to Los Alamos during the war. Fuchs had been intimately involved in the development of the implosion weapon, and passed on detailed cross-sections of the "Trinity" device to his Soviet contacts. Other Los Alamos spies—none of whom knew each other—included Theodore Hall and David Greenglass. The information was kept but not acted upon, as Russia was still too busy fighting the war in Europe to devote resources to this new project.

In the years immediately after World War II, the issue of who should control atomic weapons became a major international point of contention. Many of the Los Alamos scientists who had built the bomb began to call for "international control of atomic energy", often calling for either control by transnational organizations or the purposeful distribution of weapons information to all superpowers, but due to a deep distrust of the intentions of the Soviet Union, both in postwar Europe and in general, the policy-makers of the United States worked to attempt to secure an American nuclear monopoly. A half-hearted plan for international control was proposed at the newly formed United Nations by Bernard Baruch ("The Baruch Plan"), but it was clear both to American commentators—and to the Soviets—that it was an attempt primarily to stymie Russian nuclear efforts. The Soviets vetoed the plan, effectively ending any immediate postwar negotiations on atomic energy, and made overtures towards banning the use of atomic weapons in general.

Soviet physicist Igor Kurchatov was in charge of analyzing the espionage coming in about the American nuclear project.

All the while, the Soviets had put their full industrial and manpower might into the development of their own atomic weapons. The initial problem for the Soviets was primarily one of resources—they had not scouted out uranium resources in the Soviet Union and the U.S. had made deals to seize monopolies over the largest known reserves in the Belgian Congo. The USSR used penal labour to mine the old deposits in Czechoslovakia—now an area under their control—and searched for other domestic deposits (which were eventually found).

Two days after the bombing of Nagasaki, the U.S. government released an official technical history of the Manhattan Project, authored by Princeton physicist Henry DeWolf Smyth, known colloquially as the Smyth Report. The sanitized summary of the wartime effort focused primarily on the production facilities and scale of investment, written in part to justify the wartime expenditure to the American public. The Soviet program, under the suspicious watch of former NKVD chief Lavrenty Beria (a participant and victor in Stalin's Great Purge of the 1930s), would use the Report as a blueprint, seeking to duplicate as much as possible the American effort. The "secret cities" used for the Soviet equivalents of Hanford and Oak Ridge literally vanished from the maps for decades to come.

At the Soviet equivalent of Los Alamos, Arzamas-16, physicist Yuli Khariton led the scientific effort to develop the weapon. Beria distrusted his scientists, however, and he distrusted the carefully collected espionage information. As such, Beria assigned multiple teams of scientists to the same task without informing each team of the other's existence. If they arrived at different conclusions, Beria would bring them together for the first time and have them debate with their newfound counterparts. Beria used the espionage information as a way to double-check the progress of his scientists, and in his effort for duplication of the American project even rejected more efficient bomb designs in favor of ones which more closely mimicked the tried-and-true "Fat Man" bomb used by the U.S. against Nagasaki.

The iron hand of NKVD chief Lavrenty Beria was put in charge of the Russian project.

Cold War

After World War II, the balance of power between the Eastern and Western blocs, resulting in the fear of global destruction, prevented the further military use of atomic bombs. This fear was even a central part of Cold War strategy, referred to as the doctrine of Mutually Assured Destruction ("MAD" for short). So important was this balance to international political stability that a treaty, the Anti-Ballistic Missile Treaty (or ABM treaty), was signed by the U.S. and the USSR in 1972 to curtail the development of defenses against nuclear weapons and the ballistic missiles which carry them. This doctrine resulted in a large increase in the number of nuclear weapons, as each side sought to ensure it possessed the firepower to destroy the opposition in all possible scenarios and against all perceived threats.

Early delivery systems for nuclear devices were primarily bombers like the United States B-29 Superfortress and Convair B-36, and later the B-52 Stratofortress. Ballistic missile systems, based on Wernher von Braun's World War II designs (specifically the V2 rocket), were developed by both United States and Soviet Union teams (in the case of the U.S., effort was directed by the German scientists and engineers). These systems, after testing, were used to launch satellites, such as Sputnik, and to propel the Space Race, but they were primarily developed to create the capability of Intercontinental Ballistic Missiles (ICBMs) with which nuclear powers could deliver that destructive force anywhere on the globe. These systems continued to be developed throughout the Cold War, although plans and treaties, beginning with the Strategic Arms Limitation Treaty (SALT I), restricted deployment of these systems until, after the fall of the Soviet Union, system development essentially halted, and many weapons were disabled and destroyed (see nuclear disarmament).

Relative sizes of a number of nuclear weapons.

There have been a number of potential nuclear disasters. Following air accidents U.S. nuclear weapons have been lost near Atlantic City, New Jersey (1957); Savannah, Georgia (1958) (see Tybee Bomb); Goldsboro, North Carolina (1961); off the coast of Okinawa (1965); in the sea near Palomares, Spain (1966); and near Thule, Greenland (1968). Most of the lost weapons were recovered, the Spanish device after three months' effort by the DSV Alvin and DSV Aluminaut. The Soviet Union was less forthcoming about such incidents, but the environmental group Greenpeace believes that there are around forty non-U.S. nuclear devices that have been lost and not recovered, compared to eleven lost by America, mostly in submarine disasters. The U.S. has tried to recover Soviet devices, notably in the 1974 Operation Jennifer using the specialist salvage vessel Hughes Glomar Explorer.

On January 27, 1967, more than 60 nations signed the Outer Space Treaty, banning nuclear weapons in space.

The end of the Cold War failed to end the threat of nuclear weapon use, although global fears of nuclear war reduced substantially.

In a major move of de-escalation, Boris Yeltsin, on January 26, 1992, announced that Russia planned to stop targeting United States cities with nuclear weapons.

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Nuclear arms race

The nuclear arms race was a competition for supremacy in nuclear weapons between the United States and Soviet Union during the Cold War. During the Cold War, in addition to the American and Soviet nuclear stockpiles, other countries also developed nuclear weapons as well, though none engaged in warhead production on the same size as the two superpowers. An additional nuclear arms race developed between India and Pakistan during the end of the 1990s.

U.S. and USSR/Russian nuclear weapons stockpiles, 1945-2006.

World War II

The first nuclear weapon was created by the American Manhattan Project during the Second World War and was developed for use against the Axis powers. Scientists in the Soviet Union, then an ally of the United States, were aware of the possibility of nuclear weapons and had been doing some work in that direction. Soviet scientists first became aware the Americans were almost certainly working on atomic weapons when all related articles disappeared from physics journals.

The Soviet Union, despite being an ally, was not informed of the American experiments until the Potsdam Conference in 1945. The Americans did not trust the Soviets to keep the information from German spies; there was also deep distrust of the Soviets and their intentions, despite the wartime partnership. Even during the war many government and military figures in the USA saw the USSR as a potential enemy in the future.

The Soviets were well aware of the program due to a spy ring operating within the American nuclear program. The atomic spies (including Klaus Fuchs [1] and Theodore Hall) kept Stalin well informed of American developments [2]. When U.S. Vice President Harry S. Truman informed Stalin of the weapons, he was surprised at how calmly Stalin took the news and thought that Stalin had not understood what he had told him. In fact Stalin had long been aware of the program. The American program had been so secret that even Truman did not know about the weapons until he became president; Stalin had thus known about the Manhattan Project before Truman himself did.

In August of 1945 Truman ordered two bombs dropped on the Japanese cities of Hiroshima and Nagasaki, by the B-29 bombers Enola Gay and Bock's Car respectively, ostensibly to quickly end the war though questions have remained about additional motivations as well (see Atomic bombings of Hiroshima and Nagasaki).

Early Cold War

The years immediately after the Second World War the Americans had a nuclear monopoly, on both specific knowledge and, most importantly, raw materials. Initially it was thought that uranium was relatively rare in the world , but this was discovered to be incorrect [3]. While American leaders hoped the monopoly would be able to win concessions out of the Soviet Union, this proved ineffective. Stalin knew that he was at a disadvantage; However, he felt that the only solution was to bluff that he was certain the Americans would not use the weapons, and wouldn't care much if they did. Stalin guessed correctly that the American policy makers would not risk another massive war over the relatively removed issues like Berlin or Czechoslovakia, and additionally many felt compelled to give the Soviets concessions for their massive sacrifices in their front against Germany.

Behind the scenes the Soviet regime was working furiously to build their own atomic weapons [4]. During the war Soviet efforts had been limited by a lack of uranium, but new supplies in Eastern Europe were taken and provided a steady supply while the Soviets developed a domestic source. Physicists were given massive funding and treated like royalty, but were also threatened with being shot if they did not make significant progress. The much feared NKVD head Lavrenty Beria was put in charge of the development process. The Soviet effort was aided by the information provided by their spies in the United States, however the information was not freely given to scientists and was instead used as an additional "check" on their progress (Beria trusted neither the scientists nor the espionage). While American thinkers had predicted that the USSR would not have nuclear weapons until the mid-1950s, the first Soviet bomb was detonated on August 29, 1949 [5], shocking the entire world. The weapon (called "Joe One" by the West) was more or less a copy of the weapon which the United States had dropped on Japan ("Fat Man").

Both governments devoted massive amounts of resources to increasing the quality and quantity of their nuclear arsenal. Both nations quickly began work on hydrogen bombs and the United States detonated the first such device on November 1, 1952 [6]. Again the Soviets surprised the Americans by exploding a deployable thermonuclear device of their own the next August, though it was not actually a "true" multi-stage hydrogen bomb (that would wait until 1954) [7]. The Soviet H-bomb was almost completely a product of domestic research, as their espionage sources in the USA had only worked on very preliminary (and incorrect) versions of the hydrogen bomb.

Delivery methods, such as the bomber fleets, were also expanded. The United States began with a considerable lead in this area, but the widespread introduction of jet powered interceptor aircraft upset this balance somewhat by reducing the effectiveness of the US bomber fleet. In 1949 Curtis LeMay was placed in command of the Strategic Air Command and started a program to update the bomber fleet to one that was all-jet. During the early 1950s the B-47 and B-52 were introduced, giving the US the ability to convincingly penetrate the USSR.

The most important development in terms of delivery in the 1950s was the introduction of ICBMs. Missiles had long been seen as the ideal platform for nuclear weapons and in 1957 on the 4th of October with the launch of Sputnik the Soviet Union showed the world that they had missiles that could hit anywhere in the world. The United States launched their own on the 31 October 1959.

The period also saw attempts begin to defend against nuclear weapons. Both powers built large radar arrays to detect incoming bombers and missiles. Fighters to use against bombers and anti-ballistic missiles to use against ICBMs were also developed. Large underground bunkers were constructed to save the leadership of the superpowers, and individuals were told to build fallout shelters and taught how to react to a nuclear attack (civil defense).

Mutually Assured Destruction (MAD)

All of these defensive measures were far from foolproof and by the 1950s both the United States and Soviet Union had the power to obliterate the other side. Both sides developed a "second-strike" capability [8], i.e. they could launch a devastating attack even after sustaining a full assault from the other side (especially by means of submarines). This policy was part of what became known as Mutually Assured Destruction: both sides knew that any attack upon the other would be suicide for themselves as well, and thus would (in theory) restrain from attacking one another.

Both Soviet and American thinkers hoped to use nuclear weapons to extract concessions from the other side, or from other powers such as China, but the risk of any use of these weapons were so large that both sides refrained from what John Foster Dulles referred to as brinkmanship. While some like General Douglas MacArthur argued nuclear weapons should be used during the Korean War both Truman and Eisenhower disagreed.

Both sides were also unaware of how their relative arsenals compared. The Americans tended to be lacking in confidence, earlier in the 1950s they believed in a non-existent "bomber gap" (aerial photography later discovered that the Soviets had been playing a sort of Potemkin village game with their bombers in their military parades, flying them in large circles to make it appear they had far more than they truly did), and the 1960 American presidential election saw accusations of a wholly spurious "missile gap" between the Soviets and the Americans. The Soviet government structure tended to exaggerate the power of Soviet weapons to the leadership and Nikita Khrushchev.

An additional controversy formed in the United States during the early-1960s over whether or not it was known if their weapons would work at all if it came down to it. All of the individual components of nuclear missiles had been tested separately (warheads, navigation systems, rockets), but it had been infeasible to test them all as a whole. Critics charged that it was not really known how a warhead would function in the gravity forces and temperature differences encountered in the upper atmosphere and outer space, and Kennedy was unwilling to run a risky test of an ICBM with a live warhead. The closest thing to an actual test, Operation Frigate Bird, which involved testing a live submarine launching a ballistic missile, was challenged by critics (including Curtis LeMay, who used doubt over missile accuracy to encourage the development of new bombers) on the grounds that it was a single test (and could therefore be an anomaly), was a lower-altitude SLBM (and therefore was subject to different conditions than an ICBM), and that significant modifications had been made to its warhead before testing (as that particular warhead was known to be potentially prone to predetonation).

Initial nuclear proliferation

In addition to the United States and the Soviet Union, three other nations, the United Kingdom [9], People's Republic of China [10], and France [11] also developed far smaller nuclear stockpiles. In 1952, the United Kingdom became the third nation to possess nuclear weapons when it detonated an atomic bomb in Operation Hurricane on October 3, 1952. During the Cold War, British nuclear deterrence revolved around the Resolution class ballistic missile submarines armed with the American-built Polaris missile and the WE.177 gravity bomb.

France became the fourth nation to possess nuclear weapons on February 13, 1960, when the atomic bomb Gerboise Bleue was detonated in Algeria, then still a French colony. During the Cold War, the French nuclear deterrent was centered around the Force de frappe, a nuclear triad consisting of Dassault Mirage IV bombers carrying such nuclear weapons as the AN-22 gravity bomb and the ASMP stand-off attack missile, Pluton and Hades ballistic missiles, and the Redoutable class submarine armed with strategic nuclear missiles.

The People's Republic of China became the fifth nuclear power on October 16, 1964, when it detonated a uranium-235 bomb in a test codenamed 596. Due to Soviet/Chinese tensions, the Chinese may have used nuclear weapons against either the United States or the Soviet Union in the event of a US/USSR nuclear war. During the Cold War, the Chinese nuclear deterrent consisting of gravity bombs carried aboard H-6 bomber aircraft and within missile systems.


Economic problems caused by the arms race in both powers, combined with China's new role and the ability to verify disarmament led to a number of arms control agreements beginning in the 1970s. This period known as Détente allowed both states to reduce their spending on weapons systems. SALT I and SALT II and all limited the size of the states arsenals. Bans on nuclear testing, anti-ballistic missile systems, and weapons in space all attempted to limit the expansion of the arms race though the Partial Test Ban Treaty.

These treaties were only partially successful. Both states continued building massive numbers of nuclear weapons, and new technologies such as MIRVs limited the effectiveness of the treaties. Both superpowers retained the ability to destroy each other many times over.

Reagan and Star Wars

Towards the end of Jimmy Carter's presidency, and continued strongly through the subsequent presidency of Ronald Reagan, the United States rejected disarmament and tried to restart the arms race through the production of new weapons and anti-weapons systems. The central part of this strategy was the Strategic Defense Initiative [12], a space based anti-ballistic missile system derided as "Star Wars" by its critics. During the second part of 1980's, the Soviet economy was teetering towards collapse and was unable to match American arms spending. Numerous negotiations by Mikhail Gorbachev attempted to come to agreements on reducing nuclear stockpiles, but the most radical were rejected by Reagan as they would also prohibit his SDI program.

Post-Cold War

With the end of the Cold War the United States, and especially Russia, cut down on nuclear weapons spending. Fewer new systems were developed and both arsenals have shrunk. But both states still maintain stocks of nuclear missiles numbering in the thousands. In the USA, stockpile stewardship programs have taken over the role of maintaining the aging arsenal.

After the Cold War ended, a large amount of resources and money which was once spent on developing nuclear weapons was then spent on repairing the environmental damage produced by the nuclear arms race, and almost all former production sites are now major cleanup sites. In the USA, the plutonium production facility at Hanford, Washington and the uranium molding facility at Rocky Flats, Colorado are among the most polluted sites.

United States policy and strategy regarding nuclear proliferation was outlined in 1995 in the document "Essentials of Post-Cold War Deterrence".

India and Pakistan

The South-Asian states of India and Pakistan have also engaged in a nuclear arms race. India detonated what it called a "peaceful nuclear device" in 1974 ("Smiling Buddha") [13] in response primarily to the development of a weapon by its neighbor China a decade before. In the last few decades of the 20th century, however, both Pakistan and India began to develop nuclear-capable rockets, and Pakistan had its own covert bomb program which extended over many years since the first Indian weapon was detonated. In 1998, both India and Pakistan tested their nuclear weapons in a tit-for-tat fashion (Operation Shakti for India), with India claiming to have tested a hydrogen bomb as well (though the validity of this is disputed). Their arms race is somewhat analogous to the US/USSR race, except that both the amount of resources which each can devote to weapons and the distances to be traversed are far less.

Milestone nuclear explosions

The following list is of milestone nuclear explosions. In addition to the atomic bombings of Hiroshima and Nagasaki, the first nuclear test of a given weapon type for a country is included, and tests which were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of TNT (see megaton).

"Deployable" refers to whether the device tested could be hypothetically used in actual combat (in contrast with a proof-of-concept device). "Staging" refers to whether it was a "true" hydrogen bomb of the so-called Teller-Ulam configuration or simply a form of a boosted fission weapon. For a more complete list of nuclear test series, see List of nuclear tests. Some exact yield estimates, such as that of the Tsar Bomba and the tests by India and Pakistan in 1998, are somewhat contested among specialists.

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Effects of nuclear explosions

A nuclear explosion occurs as a result of the rapid release of energy from an uncontrolled nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two.

Atmospheric nuclear explosions are associated with "mushroom clouds" although mushroom clouds can occur with large chemical explosions and it is possible to have an air burst nuclear explosion without these clouds. Atmospheric nuclear explosions produce large amounts of radiation and radioactive debris. In 1963, all nuclear and many non-nuclear states signed the Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. The treaty permitted underground tests.

The primary application to date has been military (i.e. nuclear weapons). However, there are other potential applications, which have not yet been explored, or have been considered all but abandoned. They include:


A nuclear explosion (nuclear detonation) has occurred on Earth twice using a nuclear weapon during war (during World War II, the atomic bombings of Hiroshima and Nagasaki), about 2,000 times during testing of nuclear weapons, and about 27 times in the U.S. and 156 in the U.S.S.R. in a series of peaceful nuclear explosions; see Operation Plowshare; and Nuclear Explosions for the National Economy

Milestone nuclear explosions

The following list is of milestone nuclear explosions. In addition to the atomic bombings of Hiroshima and Nagasaki, the first nuclear test of a given weapon type for a country is included, and tests which were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of TNT (see megaton).

"Deployable" refers to whether the device tested could be hypothetically used in actual combat (in contrast with a proof-of-concept device). "Staging" refers to whether it was a "true" hydrogen bomb of the so-called Teller-Ulam configuration or simply a form of a boosted fission weapon. For a more complete list of nuclear test series, see List of nuclear tests. Some exact yield estimates, such as that of the Tsar Bomba and the tests by India and Pakistan in 1998, are somewhat contested among specialists.

Effects of a nuclear explosion

The energy released from a nuclear weapon comes in four primary categories:

    * Blast—40-60% of total energy
    * Thermal radiation—30-50% of total energy
    * Ionizing radiation—5% of total energy
    * Residual radiation—5-10% of total energy

An American nuclear test.

However, the above values vary depending on the design of the weapon, and the environment in which it is detonated. The interaction of the X-rays and debris with the surroundings determines how much energy is produced as blast and how much as light. In general, the denser the medium around the bomb, the more it will absorb, and the more powerful the shockwave will be. Thermal radiation drops off the slowest with distance, so the larger the weapon the more important this effect becomes. Ionizing radiation is strongly absorbed by air, so it is only dangerous by itself for smaller weapons. Blast damage falls off more quickly than thermal radiation but more slowly than ionizing radiation.

The dominant effects of a nuclear weapon (the blast and thermal radiation) are the same physical damage mechanisms as conventional explosives, but the energy produced by a nuclear explosive is millions of times more per gram and the temperatures reached are in the tens of millions of degrees.

The energy of a nuclear explosive is initially released in the form of gamma rays and neutrons. When there is a surrounding material such as air, rock, or water, this radiation interacts with the material, rapidly heating it to an equilibrium temperature in about a microsecond. The hot material emits thermal radiation, mostly soft X-rays, which accounts for 75% of the energy of the explosion. In addition, the heating and vaporization of the surrounding material causes it to rapidly expand and the kinetic energy of this expansion accounts for almost all of the remaining energy.

When a nuclear detonation occurs in air near sea level, most of the soft X-rays in the primary thermal radiation are absorbed within a few feet. Some energy is reradiated in the ultraviolet, visible light and infrared spectrum, but most of the energy heats a spherical volume of air. This forms a fireball and its associated effects.

In a burst at high altitudes, where the air density is low, the soft X-rays travel long distances before they are absorbed. The energy is so diluted that the blast wave may be half as strong or less. The rest of the energy is dissipated as a more powerful thermal pulse.

In 1945 there was some initial speculation among the scientists developing the first nuclear weapons that there might be a possibility of igniting the Earth's atmosphere with a large enough nuclear explosion. This would concern a nuclear reaction of two nitrogen atoms forming a carbon and an oxygen atom, with release of energy. This energy would heat up the remaining nitrogen enough to keep the reaction going until all nitrogen atoms were consumed. This was, however, quickly shown to be unlikely enough to be considered impossible [1]. Nevertheless, the notion has persisted as a rumour for many years.

Direct effects

Blast damage

The high temperatures and pressures cause gas to move outward radially in a thin, dense shell called "the hydrodynamic front." The front acts like a piston that pushes against and compresses the surrounding medium to make a spherically expanding shock wave. At first, this shock wave is inside the surface of the developing fireball, which is created in a volume of air by the X-rays. However, within a fraction of a second the dense shock front obscures the fireball, making the characteristic double pulse of light seen from a nuclear detonation. For air bursts at or near sea-level between 50-60% of the explosion's energy goes into the blast wave, depending on the size and the yield-to-weight ratio of the bomb. As a general rule, the blast fraction is higher for low yield and/or high bomb mass. Furthermore, it decreases at high altitudes because there is less air mass to absorb radiation energy and convert it into blast. This effect is most important for altitudes above 30 km, corresponding to <1 per cent of sea-level air density.

Much of the destruction caused by a nuclear explosion is due to blast effects. Most buildings, except reinforced or blast-resistant structures, will suffer moderate to severe damage when subjected to overpressures of only 35.5 kilopascals (kPa) (5.15 pounds-force per square inch or 0.35 atm).

Overpressure ranges from 1 to 50 psi of a 1 kiloton of TNT air burst as a function of burst height. The thin black curve indicates the optimum burst height for a given ground range.

The blast wind may exceed several hundred km/h. The range for blast effects increases with the explosive yield of the weapon and also depends on the burst altitude. Contrary to what one might expect from geometry the blast range is not maximal for surface or low altitude blasts but increases with altitude up to an "optimum burst altitude" and then decreases rapidly for higher altitudes. This is due to the nonlinear behaviour of shock waves. If the blast wave reaches the ground it is reflected. Below a certain reflection angle the reflected wave and the direct wave merge and form a reinforced horizontal wave, the so-called Mach stem (named after Ernst Mach). For each goal overpressure there is a certain optimum burst height at which the blast range is maximized. In a typical air burst, where the blast range is maximized for 5 to 20 psi (35 to 140 kPa), these values of overpressure and wind velocity noted above will prevail at a range of 0.7 km for 1 kiloton (kt) of TNT yield; 3.2 km for 100 kt; and 15.0 km for 10 megatons (Mt) of TNT.

Two distinct, simultaneous phenomena are associated with the blast wave in air:

    * Static overpressure, i.e., the sharp increase in pressure exerted by the shock wave. The overpressure at any given point is directly proportional to the density of the air in the wave.
    * Dynamic pressures, i.e., drag exerted by the blast winds required to form the blast wave. These winds push, tumble and tear objects.

Most of the material damage caused by a nuclear air burst is caused by a combination of the high static overpressures and the blast winds. The long compression of the blast wave weakens structures, which are then torn apart by the blast winds. The compression, vacuum and drag phases together may last several seconds or longer, and exert forces many times greater than the strongest hurricane.

Acting on the human body, the shock waves cause pressure waves through the tissues. These waves mostly damage junctions between tissues of different densities (bone and muscle) or the interface between tissue and air. Lungs and the abdominal cavity, which contain air, are particularly injured. The damage causes severe haemorrhaging or air embolisms, either of which can be rapidly fatal. The overpressure estimated to damage lungs is about 70 kPa. Some eardrums would probably rupture around 22 kPa (0.2 atm) and half would rupture between 90 and 130 kPa (0.9 to 1.2 atm).

Blast Winds: The drag energies of the blast winds are proportional to the cubes of their velocities multiplied by the durations. These winds may reach several hundred kilometers per hour.

Thermal radiation

Nuclear weapons emit large amounts of electromagnetic radiation as visible, infrared, and ultraviolet light. The chief hazards are burns and eye injuries. On clear days, these injuries can occur well beyond blast ranges. The light is so powerful that it can start fires that spread rapidly in the debris left by a blast. The range of thermal effects increases markedly with weapon yield. Thermal radiation accounts for between 35-45% of the energy released in the explosion, depending on the yield of the device.

There are two types of eye injuries from the thermal radiation of a weapon:

Flash blindness is caused by the initial brilliant flash of light produced by the nuclear detonation. More light energy is received on the retina than can be tolerated, but less than is required for irreversible injury. The retina is particularity susceptible to visible and short wavelength infrared light, since this part of the electromagnetic spectrum is focused by the lens on the retina. The result is bleaching of the visual pigments and temporary blindness for up to 40 minutes.

On this victim of the atomic bombing of Hiroshima, the pattern of the kimono is clearly visible as burns on the skin.

A retinal burn resulting in permanent damage from scarring is also caused by the concentration of direct thermal energy on the retina by the lens. It will occur only when the fireball is actually in the individual's field of vision and would be a relatively uncommon injury. Retinal burns, however, may be sustained at considerable distances from the explosion. The apparent size of the fireball, a function of yield and range will determine the degree and extent of retinal scarring. A scar in the central visual field would be more debilitating. Generally, a limited visual field defect, which will be barely noticeable, is all that is likely to occur.

Since thermal radiation travels in straight lines from the fireball (unless scattered) any opaque object will produce a protective shadow. If fog or haze scatters the light, it will heat things from all directions and shielding will be less effective. Massive spread of radiation would also occur, which would be at the mercy of the wind.

When thermal radiation strikes an object, part will be reflected, part transmitted, and the rest absorbed. The fraction that is absorbed depends on the nature and color of the material. A thin material may transmit a lot. A light colored object may reflect much of the incident radiation and thus escape damage. The absorbed thermal radiation raises the temperature of the surface and results in scorching, charring, and burning of wood, paper, fabrics, etc. If the material is a poor thermal conductor, the heat is confined to the surface of the material.

Actual ignition of materials depends on how long the thermal pulse lasts and the thickness and moisture content of the target. Near ground zero where the light exceeds 125 J/cm², what can burn, will. Farther away, only the most easily ignited materials will flame. Incendiary effects are compounded by secondary fires started by the blast wave effects such as from upset stoves and furnaces.

In Hiroshima, a tremendous fire storm developed within 20 minutes after detonation and destroyed many more buildings and homes. A fire storm has gale force winds blowing in towards the center of the fire from all points of the compass. It is not, however, a phenomenon peculiar to nuclear explosions, having been observed frequently in large forest fires and following incendiary raids during World War II.

Indirect effects

Electromagnetic pulse

Gamma rays from a nuclear explosion produce high energy electrons through Compton scattering. These electrons are captured in the earth's magnetic field, at altitudes between twenty and forty kilometers, where they resonate. The oscillating electric current produces a coherent electromagnetic pulse (EMP) which lasts about one millisecond. Secondary effects may last for more than a second.

The pulse is powerful enough to cause long metal objects (such as cables) to act as antennae and generate high voltages when the pulse passes. These voltages, and the associated high currents, can destroy unshielded electronics and even many wires. There are no known biological effects of EMP. The ionized air also disrupts radio traffic that would normally bounce off the ionosphere.

One can shield electronics by wrapping them completely in conductive mesh, or any other form of Faraday cage. Of course radios cannot operate when shielded, because broadcast radio waves can't reach them.

The largest-yield nuclear devices are designed for this use. An air burst at the right altitude could produce

The mushroom cloud from the first "true" Soviet hydrogen bomb test in 1955.

Ionizing radiation

About 5% of the energy released in a nuclear air burst is in the form of ionizing radiation: neutrons, gamma rays, alpha particles, and electrons moving at incredible speeds, but with different speeds that can be still far away from the speed of light (alpha particles). The neutrons result almost exclusively from the fission and fusion reactions, while the initial gamma radiation includes that arising from these reactions as well as that resulting from the decay of short-lived fission products.

The intensity of initial nuclear radiation decreases rapidly with distance from the point of burst because the radiation spreads over a larger area as it travels away from the explosion. It is also reduced by atmospheric absorption and scattering.

The character of the radiation received at a given location also varies with distance from the explosion. Near the point of the explosion, the neutron intensity is greater than the gamma intensity, but with increasing distance the neutron-gamma ratio decreases. Ultimately, the neutron component of initial radiation becomes negligible in comparison with the gamma component. The range for significant levels of initial radiation does not increase markedly with weapon yield and, as a result, the initial radiation becomes less of a hazard with increasing yield. With larger weapons, above fifty kt (200 TJ), blast and thermal effects are so much greater in importance that prompt radiation effects can be ignored.

The neutron radiation serves to transmute the surrounding matter, often rendering it radioactive. When added to the dust of radioactive material released by the bomb itself, a large amount of radioactive material is released into the environment. This form of radioactive contamination is known as nuclear fallout and poses the primary risk of exposure to ionizing radiation for a large nuclear weapon.


The pressure wave from an underground explosion will propagate through the ground and cause a minor earthquake. [2] Theory suggests that a nuclear explosion could trigger fault rupture and cause a major quake at distances within a few tens of kilometers from the shot point. [3]

Summary of the effects

1) For the direct radiation effects the slant range instead of the ground range is shown here, because some effects are not given even at ground zero for some burst heights. If the effect occurs at ground zero the ground range can simply be derived from slant range and burst altitude (Pythagorean theorem).

2) "Acute radiation syndrome" corresponds here to a total dose of one gray, "lethal" to ten grays. Note that this is only a rough estimate since biological conditions are neglected here.

Other phenomena

As the fireball rises through still air, it takes on the flow pattern of a vortex ring with incandescent material in the vortex core as seen in certain photographs. At the explosion of nuclear bombs sometimes lightning discharges occur. Not related to the explosion itself, often there are smoke trails seen in photographs of nuclear explosions. These are formed from rockets emitting smoke launched before detonation. The smoke trails are used to determine the position of the shockwave, which is invisible, in the milliseconds after detonation through the refraction of light, which causes an optical break in the smoke trails as the shockwave passes. A fizzle occurs if the nuclear chain reaction is not sustained long enough to cause an explosion. This can happen if, for example, the yield of the fissile material used is too low, the compression explosives around fissile material misfire or the neutron initiator fails.


This is highly dependent on factors such as proximity to the blast and the direction of the wind carrying fallout.

There has also been controversy as to whether cockroaches would survive a nuclear blast. The answer is that they have a high degree of survivability, since they are resistant to radiation and can burrow underground for extended periods of time and avoid fallout. However, cockroaches would be instantly incinerated by the initial blast. [1]

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