   #copyright

History of nuclear weapons

2007 Schools Wikipedia Selection. Related subjects: Military History and War

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

                                                           Nuclear weapons
                                          One of the first nuclear bombs.
                                             History of nuclear weapons
                                                  Nuclear warfare
                                                 Nuclear arms race
                                              Weapon design / testing
                                                 Nuclear explosion
                                                  Delivery systems
                                                 Nuclear espionage
                                                   Proliferation
                                                                    States
                                                  Nuclear weapons states

                                              US · Russia · UK · France
                                                China · India · Pakistan
                                                     Israel · North Korea

   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.

Physics and politics in the 1930s

   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.
   Enlarge
   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.

   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.

From Los Alamos to Hiroshima

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

   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, it was
   the largest factory under one roof, and employed thousands of employees
   at its peak, most of whom had no idea what they were working on.
   Massive new physics machines were assembled at secret installations
   around the United States for the production of enriched uranium and
   plutonium.
   Enlarge
   Massive new physics machines were assembled at secret installations
   around the United States for the production of enriched uranium and
   plutonium.

   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.
   The two fission bomb assembly methods.
   Enlarge
   The two fission bomb assembly methods.

   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.
   The atomic fireball at the "Trinity" nuclear test secretly rang in the
   atomic age.
   Enlarge
   The atomic fireball at the " Trinity" nuclear test secretly rang in the
   atomic age.

   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.
   The atomic bombings of Hiroshima and Nagasaki killed tens of thousands
   of Japanese civilians.
   Enlarge
   The atomic bombings of Hiroshima and Nagasaki killed tens of thousands
   of Japanese civilians.

   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

   Soviet physicist Igor Kurchatov was in charge of analyzing the
   espionage coming in about the American nuclear project.
   Enlarge
   Soviet physicist Igor Kurchatov was in charge of analyzing the
   espionage coming in about the American nuclear 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.
   The iron hand of NKVD chief Lavrenty Beria was put in charge of the
   Russian project.
   Enlarge
   The iron hand of NKVD chief Lavrenty Beria was put in charge of the
   Russian 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 favour of ones which more closely mimicked the
   tried-and-true " Fat Man" bomb used by the U.S. against Nagasaki.
   The first Soviet bomb, "Joe-1," was tested on August 29, 1949.
   Enlarge
   The first Soviet bomb, " Joe-1," was tested on August 29, 1949.

   Working under a stubborn and scientifically ignorant administrator, the
   Soviet scientists struggled on. On August 29, 1949, the effort brought
   its results, when the USSR tested its first fission bomb, dubbed "
   Joe-1" in the U.S., years ahead of American predictions. The news of
   the first Soviet bomb was announced to the world first by the United
   States, which had detected the nuclear fallout it generated from its
   test site in Kazakhstan.

   The loss of the American monopoly on nuclear weapons marked the first
   tit-for-tat of the nuclear arms race. The response in the U.S. was one
   of apprehension, fear, and scapegoating, which would lead eventually
   into the Red-baiting tactics of McCarthyism. Before this, though,
   President Truman would announce his decision to begin a crash program
   to develop a far more powerful weapon than those which were used
   against Japan: the hydrogen bomb.

The first thermonuclear weapons

   Hungarian physicist Edward Teller toiled for years trying to discover a
   way to make a fusion bomb.
   Enlarge
   Hungarian physicist Edward Teller toiled for years trying to discover a
   way to make a fusion bomb.

   The notion of using a fission weapon to ignite a process of nuclear
   fusion can be dated back to 1942. At the first major theoretical
   conference on the development of an atomic bomb hosted by J. Robert
   Oppenheimer at the University of California, Berkeley, participant
   Edward Teller directed the majority of the discussion towards Enrico
   Fermi's idea of a "Super" bomb which would utilize the same reactions
   which powered the Sun itself. It was thought at the time that a fission
   weapon would be quite simple to develop and that perhaps work on a
   hydrogen bomb would be possible to complete before the end of the
   Second World War. However, in reality the problem of a "regular" atomic
   bomb was large enough to preoccupy the scientists for the next few
   years, much less the more speculative "Super." Only Teller continued
   working on the project—against the will of project leaders Oppenheimer
   and Hans Bethe.

   After the atomic bombings of Japan, many scientists at Los Alamos
   rebelled against the notion of creating a weapon thousands of times
   more powerful than the first atomic bombs. For the scientists the
   question was in part technical—the weapon design was still quite
   uncertain and unworkable—and in part moral: such a weapon, they argued,
   could only be used against large civilian populations, and could thus
   only be used as a weapon of genocide. Many scientists, such as Bethe,
   urged that the United States should not develop such weapons and set an
   example towards the Soviet Union. Promoters of the weapon, including
   Teller, Ernest Lawrence, and Luis Alvarez, argued that such a
   development was inevitable, and to deny such protection to the people
   of the United States—especially when the Soviet Union was likely to
   create such a weapon themselves—was itself an immoral and unwise act.

   Oppenheimer, who was now head of the General Advisory Committee of the
   successor to the Manhattan Project, the Atomic Energy Commission,
   presided over a recommendation against the development of the weapon.
   The reasons were in part because the success of the technology seemed
   limited at the time (and not worth the investment of resources to
   confirm whether this was so), and because Oppenheimer believed that the
   atomic forces of the United States would be more effective if they
   consisted of many large fission weapons (of which multiple bombs could
   be dropped on the same targets) rather than the large and unwieldy
   predictions of massive super bombs, for which there were a relatively
   limited amounts of targets of the size to warrant such a development.
   Furthermore, were such weapons developed by both the U.S. and the USSR,
   they would be more effectively used against the U.S. than by it, as the
   U.S. had far more regions of dense industrial and civilian activity
   which would serve as ideal targets for the large weapons than the
   Soviet Union did.
   The "Mike" shot in 1952 inaugurated the age of fusion weapons.
   Enlarge
   The " Mike" shot in 1952 inaugurated the age of fusion weapons.

   In the end, President Truman made the final decision, looking for a
   proper response to the first Soviet atomic bomb test in 1949. On
   January 31, 1950, Truman announced a crash program to develop the
   hydrogen (fusion) bomb. At this point, however, the exact mechanism was
   still not known: the "classical" hydrogen bomb, whereby the heat of the
   fission bomb would be used to ignite the fusion material, seemed highly
   unworkable. However, an insight by Los Alamos mathematician Stanislaw
   Ulam showed that the fission bomb and the fusion fuel could be in
   separate parts of the bomb, and that radiation of the fission bomb
   could first work in a way to compress the fusion material before
   igniting it. Teller pushed the notion further, and used the results of
   the boosted-fission "George" test (a boosted-fission device using a
   small amount of fusion fuel to boost the yield of a fission bomb) to
   confirm the fusion of heavy hydrogen elements before preparing for
   their first true multi-stage, Teller-Ulam hydrogen bomb test. Many
   scientists initially against the weapon, such as Oppenheimer and Bethe,
   changed their previous opinions, seeing the development as being
   unstoppable.

   The first fusion bomb was tested by the United States in Operation Ivy
   on November 1, 1952, on Elugelab Island in the Enewetak (or Eniwetok)
   Atoll of the Marshall Islands, code-named " Mike". "Mike" used liquid
   deuterium as its fusion fuel and a large fission weapon as its trigger.
   The device was a prototype design and not a deliverable weapon:
   standing over 20 ft (6 m) high and weighing at least 140,000 lb (64 t)
   (its refrigeration equipment added an additional 24,000 lb as well), it
   could not have been dropped from even the largest planes. Its explosion
   yielded 10.4 megatons of energy—over 450 times the power of the bomb
   dropped onto Nagasaki— and obliterated Eluegelab, leaving an underwater
   crater 6240 ft (1.9 km) wide and 164 ft (50 m) deep where the island
   had once been. Truman had initially tried to create a media blackout
   about the test—hoping it would not become an issue in the upcoming
   presidential election—but on January 7, 1953, Truman announced the
   development of the hydrogen bomb to the world as hints and speculations
   of it were already beginning to emerge in the press.
   The basics of the Teller-Ulam design for a hydrogen bomb: a fission
   bomb uses radiation to compress and heat a separate section of fusion
   fuel.
   Enlarge
   The basics of the Teller-Ulam design for a hydrogen bomb: a fission
   bomb uses radiation to compress and heat a separate section of fusion
   fuel.

   Not to be outdone, the Soviet Union exploded its first thermonuclear
   device, designed by the physicist Andrei Sakharov, on August 12, 1953,
   labeled " Joe-4" by the West. This created concern within the U.S.
   government and military, because, unlike "Mike," the Soviet device was
   a deliverable weapon, which the U.S. did not yet have. This first
   device though was arguably not a "true" hydrogen bomb, and could only
   reach explosive yields in the hundreds of kilotons (never reaching the
   megaton range of a "staged" weapon). Still, it was a powerful
   propaganda tool for the Soviet Union, and the technical differences
   were fairly oblique to the American public and politicians. Following
   the "Mike" blast by less than a year, "Joe-4" seemed to validate claims
   that the bombs were inevitable and vindicate those who had supported
   the development of the fusion program. Coming during the height of
   McCarthyism, the effect was most pronounced by the security hearings in
   early 1954 which revoked former Los Alamos director Robert Oppenheimer
   of his security clearance, on the grounds that he was unreliable, had
   not supported the American hydrogen bomb program, and had made
   long-standing, left-wing ties in the 1930s. Edward Teller participated
   in the hearing as the only major scientist to testify against
   Oppenheimer, a role which resulted in his virtual expulsion from the
   physics community.

   On February 28, 1954, the U.S. detonated its first deliverable
   thermonuclear weapon (which used isotopes of lithium as its fusion
   fuel), known as the "Shrimp" device of the " Castle Bravo" test, at
   Bikini Atoll, Marshall Islands. The device yielded 15 megatons of
   energy, over twice its expected yield, and became the worst
   radiological disaster in U.S. history. The combination of the
   unexpectedly large blast and poor weather conditions caused a cloud of
   radioactive nuclear fallout to contaminate over 7,000 square miles,
   including Marshall Island natives and the crew of a Japanese fishing
   boat, as a snow-like mist. The contaminated islands were evacuated (and
   are still uninhabitable), but the natives received enough of a
   radioactive dose that they suffered far elevated levels of cancer and
   birth defects in the years to come. The crew of the Japanese fishing
   boat, Fifth Lucky Dragon, returned to port suffering from radiation
   sickness and skin burns. Their cargo, many tons of contaminated fish,
   managed to enter into the market before the cause of their illness was
   determined. When a crew member died from the sickness and the full
   results of the contamination were made public by the U.S., Japanese
   concerns were reignited about the hazards of radiation and resulted in
   a boycott on eating fish (a main staple of the island country) for some
   weeks.
   Fallout from a large nuclear exchange would potentially blanket a
   country—perhaps even the whole world—with radioactive fission products.
   Enlarge
   Fallout from a large nuclear exchange would potentially blanket a
   country—perhaps even the whole world—with radioactive fission products.

   The hydrogen bomb age had a profound effect on the thoughts of nuclear
   war in the popular and military mind. With only fission bombs, nuclear
   war could be considered something which could easily be "limited."
   Dropped by planes and only able to destroy the most built up areas of
   major cities, it was possible to consider fission bombs simply a
   technological extension of previous wartime bombing (such as the
   extensive firebombing which took place against Japan and Germany during
   World War II), and claims that such weapons could lead to worldwide
   death or harm were easily brushed aside as grave exaggeration. Even the
   decades before the development of fission weapons there had been
   speculation about the possibility for human beings to end all life on
   the planet by either accident or purposeful maliciousness, but
   technology had never allowed for such a capacity. The far greater power
   of hydrogen bombs made this seem ever closer.

   The "Castle Bravo" incident itself raised a number of questions about
   the survivability of a nuclear war. Government scientists in both the
   U.S. and the USSR had insisted that fusion weapons, unlike fission
   weapons, were "cleaner" as fusion reactions did not result in the
   dangerously radioactive by-products as did fission reactions. While
   technically true, this hid a more gruesome point: the last stage of a
   multi-staged hydrogen bomb often used the neutrons produced by the
   fusion reactions to induce fissioning in a jacket of natural uranium,
   and provided around half of the yield of the device itself. This
   fission stage made fusion weapons considerably more "dirty" than they
   were made out to be, a fact made evident by the towering cloud of
   deadly fallout which followed the "Bravo" test. When the Soviet Union
   tested its first megaton device in 1955, the possibility of a limited
   nuclear war seemed even more remote in the public and political mind:
   even if a city or country was not the direct target of a nuclear
   attack, the clouds of fallout and harmful fission products would
   disperse along with normal weather patterns and embed themselves in the
   soil and water of non-targeted areas of the planet as well. Speculation
   began to look towards what would happen as the fallout and dust created
   by a full-scale nuclear exchange would affect the world as a whole,
   rather than just the cities and countries which had been directly
   involved. In this way, the fate of the world was now tied to the fate
   of the bomb-wielding superpowers.

Deterrence and brinkmanship

   The emergence of nuclear-tipped rockets reflected a change in both
   nuclear technology and strategy.
   Enlarge
   The emergence of nuclear-tipped rockets reflected a change in both
   nuclear technology and strategy.

   Throughout the 1950s and the early 1960s a number of trends were
   enacted between the U.S. and the USSR as they both endeavored in a
   tit-for-tat approach to disallow the other power from acquiring nuclear
   supremacy. This took form in a number of ways, both technologically and
   politically, and had massive political and cultural effects during the
   Cold War.

   The first atomic bombs dropped on Hiroshima and Nagasaki were large,
   custom-made devices, requiring highly trained personnel for their
   arming and deployment. They could be dropped only from the largest
   bomber planes—at the time the B-29 Superfortress—and each plane could
   only hold a single bomb in its hold. The first hydrogen bombs were
   similarly massive and complicated. This ratio of one plane to one bomb
   was still fairly impressive in comparison with conventional,
   non-nuclear weapons, but against other nuclear-armed countries it was
   considered to be a grave danger. In the immediate postwar years, the
   U.S. expended much effort on making the bombs "G.I.-proof"—capable of
   being used and deployed by members of the U.S. Army, rather than Nobel
   Prize–winning scientists, and in the 1950s a program of nuclear testing
   was undertaken in order to improve the nuclear arsenal.

   Starting in 1951, the Nevada Test Site (in the Nevada desert) became
   the primary location for all U.S. nuclear testing (in the USSR,
   Semipalatinsk Test Site in Kazakhstan served a similar role). Tests
   were divided into two primary categories: "weapons related" (verifying
   that a new weapon worked or looking at exactly how it worked) and
   "weapons effects" (looking at how weapons behaved under various
   conditions or how structures behaved when subjected to weapons). In the
   beginning, almost all nuclear tests were either "atmospheric"
   (conducted above ground, in the atmosphere) or "underwater" (such as
   some of the tests done in the Marshall Islands). Testing was used as a
   sign of both national and technological strength, but also raised
   questions about the safety of the tests, which released nuclear fallout
   into the atmosphere (most dramatically with the Castle Bravo test in
   1954, but in more limited amounts with almost all atmospheric nuclear
   testing).
   Hundreds of nuclear tests were conducted at the Nevada Test Site in the
   USA.
   Enlarge
   Hundreds of nuclear tests were conducted at the Nevada Test Site in the
   USA.

   Because testing was seen as a sign of technological development (the
   ability to design usable weapons without some form of testing was
   considered dubious), halts on testing were often called for as
   stand-ins for halts in the nuclear arms race itself, and many prominent
   scientists and statesmen lobbied for a ban on nuclear testing. In 1958,
   the U.S., USSR, and the United Kingdom (a new nuclear power) declared a
   temporary testing moratorium for both political and health reasons, but
   by 1961 the Soviet Union had broken the moratorium and both the USSR
   and the U.S. began testing with great frequency. As a show of political
   strength, the Soviet Union tested the largest-ever nuclear weapon in
   October 1961, the massive Tsar Bomba, which was tested in a reduced
   state with a yield of around 50 megatons—in its full state it was
   estimated to have been around 100 Mt. The weapon was largely
   impractical for actual military use, but was hot enough to induce
   third-degree burns at a distance of 62 mi (100 km) away. In its full,
   "dirty" design, it would have increased the amount of worldwide fallout
   since 1945 by 25%.

   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.

   Most tests were considerably more modest, and worked for direct
   technical purposes as well as their potential political overtones.
   Weapons improvements took on two primary forms. One was an increase in
   efficiency and power, and within only a few years fission bombs were
   being developed which were many times more powerful than the ones
   created during World War II. The other was a program of
   miniaturization, reducing the size of the nuclear weapons themselves.
   Smaller bombs meant that bombers could carry more of them, and thus
   become even more of a threat against even the most rigorous air
   defenses, and they could also be used in conjunction with the
   development in rocketry during the 1950s and 1960s. U.S. rocket efforts
   had received a large boost in the postwar years, largely from the
   acquiring of engineers who had worked on the Nazi rocketry program
   during the war, such as Wernher von Braun, who had been involved in the
   design and manufacture of the V-2 rockets which were launched across
   the English Channel. An American program, Project Paperclip, had
   endeavored to move scientists of this sort into American hands (and
   kept out of Soviet hands) and put them to work on projects for the U.S.

Weapons Improvement

   The first nuclear-tipped rockets, such as the MGR-1 Honest John, first
   deployed by the U.S. in 1953, were surface-to-surface missiles with
   relatively short ranges (around 15 mi/25 km maximum) with yields around
   twice the size of the first fission weapons. The limited range of these
   weapons meant that they could only be used in certain types of
   potential military situations—the U.S. rocket weapons could not, for
   example, threaten the city of Moscow with the threat of an immediate
   strike, and could only be used as "tactical" weapons (that is, for
   small-scale military situations).
   Long-range bomber aircraft, such as the B-52 Stratofortress, allowed
   for a wide range of "strategic" nuclear forces to be deployed.
   Enlarge
   Long-range bomber aircraft, such as the B-52 Stratofortress, allowed
   for a wide range of "strategic" nuclear forces to be deployed.

   For "strategic" weapons—weapons which would serve to threaten an entire
   country—for the time being, only long-range bombers capable of
   penetrating deep into enemy territory would work. In the U.S. this
   resulted in the creation of the Strategic Air Command in 1946, a system
   of bombers headed by General Curtis LeMay (who had previously presided
   over the firebombing of Japan during WWII), which kept a number of
   nuclear-armed planes in the sky at all times, ready to receive orders
   to attack Moscow whenever commanded.

   These technological possibilities enabled nuclear strategy to develop a
   logic considerably different than previous military thinking had
   allowed. Because the threat of nuclear warfare was so awful, it was
   first thought that it might make any war of the future impossible.
   Eisenhower's doctrine of "massive retaliation" in the early years of
   the Cold War was a message to the USSR, saying that if the Red Army
   attempted to invade the parts of Europe not given to the Eastern bloc
   during the Potsdam Conference (such as West Germany), nuclear weapons
   would be used against the Soviet troops and potentially the Soviet
   leaders.

   With the development of more rapid-response technologies (such as
   rockets and long-range bombers), this policy began to shift. If the
   Soviet Union also had nuclear weapons and a policy of "massive
   retaliation" was carried out, it was reasoned, then any Soviet forces
   not killed in the initial attack, or launched while the attack was
   ongoing, would be able to serve their own form of nuclear "retaliation"
   against the U.S. Recognizing this to be an undesirable outcome,
   military officers and game theorists at the RAND think tank developed a
   nuclear warfare strategy that would eventually become known as Mutually
   Assured Destruction (MAD).
   Submarine launched ballistic missiles made defending against nuclear
   war an impossibility.
   Enlarge
   Submarine launched ballistic missiles made defending against nuclear
   war an impossibility.

   MAD divided potential nuclear war into two stages: first strike and
   second strike. A first strike would be the first use of nuclear weapons
   by one nuclear-equipped nation against another nuclear-equipped nation.
   If the attacking nation did not prevent the attacked nation from a
   nuclear response, then a second strike could be deployed against the
   attacking nation. In this situation, whether the U.S. first attacked
   the USSR or the USSR first attacked the U.S., the end result would be
   that both nations would be damaged perhaps to the point of utter social
   collapse. According to game theory, because starting a nuclear war
   would be suicidal, no logical country would willfully enter into a
   nuclear war. However, if a country were capable of launching a first
   strike which would utterly destroy the ability of the attacked country
   to respond in kind, then the balance of power would be disturbed and
   nuclear war could then be safely undertaken.

   MAD played on two seemingly opposed modes of thought: cold logic and
   emotional fear. The phrase by which MAD was often known, "nuclear
   deterrence", was translated as "dissuasion" by the French and
   "terrorization" by the Russians. This apparent paradox of nuclear war
   was summed up by British Prime Minister Winston Churchill as "the worse
   things get, the better they are"—the greater the threat of mutual
   destruction, the safer the world would be.

   This philosophy made a number of technological and political demands on
   participating nations. For one thing, it said that it should always be
   assumed that an enemy nation may be trying to acquire "first strike
   capability," something which must always be avoided. In American
   politics this translated into demands to avoid "missile gaps" and
   "bomber gaps" where the Soviet Union could potentially "out shoot"
   American efforts (most of these supposed "gaps" proved to be political
   figments, but this hardly mattered at the time). It also encouraged the
   production of thousands of nuclear weapons by both the U.S. and the
   USSR, far more than would be needed to simply destroy the major
   civilian and military infrastructures of the opposing country.
   With early warning systems, it was thought that the strikes of nuclear
   war would come from dark rooms filled with computers, not the
   battlefield of the wars of old.
   Enlarge
   With early warning systems, it was thought that the strikes of nuclear
   war would come from dark rooms filled with computers, not the
   battlefield of the wars of old.

   The policy also encouraged the development of the first early warning
   systems. Conventional war, even at its fastest, was fought over time
   scales of days and weeks. With long-range bombers, the time from the
   start of an attack to its conclusion was reduced to mere hours. With
   rockets, it could be reduced to minutes. It was reasoned that
   conventional command and control systems could not be expected to
   adequately respond to a nuclear attack, and so great lengths were taken
   to develop the first computers which could look for enemy attacks and
   direct rapid responses. In the U.S., massive funding was poured into
   the development of SAGE, a system which would track and intercept enemy
   bomber aircraft using information from remote radar stations, and was
   the first computer system to feature real-time processing,
   multiplexing, and display devices—the first "general" computing
   machine, and a direct predecessor of modern computers.

Anti-Nuclear

   Bombers and short-range rockets were not reliable: planes could be shot
   down, and earlier nuclear missiles could cover only a limited range—
   for example, the first Soviet rockets' range limited them to targets in
   Europe. However, by the 1960s, both the United States and the Soviet
   Union had developed intercontinental ballistic missiles, which could be
   launched from extremely remote areas far away from their target; and
   submarine-launched ballistic missiles, which had less range but could
   be launched from submarines very close to the target without any radar
   warning. This made any national protection from nuclear missiles
   increasingly impractical.

   The military realities made for a precarious diplomatic situation. The
   international politics of brinkmanship led leaders to exclaim their
   willingness to participate in a nuclear war rather than concede any
   advantage to their opponents, feeding public fears that their
   generation may be the last. Civil defense programs undertaken by both
   superpowers, exemplified by the construction of fallout shelters and
   urging civilians about the "survivability" of nuclear war, did little
   to ease public concerns. A joke known by most Russians during the Cold
   War said that when one heard the air raid sirens, one should pick up a
   shovel and quietly proceed to the nearest cemetery, to dig your own
   grave. A similar joke in the U.S. recommended that one stay calm, put
   one's head between one's legs, and kiss your ass goodbye, a parody of
   the " duck and cover" routines practiced by schoolchildren across the
   country.
   U-2 photographs revealed that the Soviet Union was stationing nuclear
   missiles on the island of Cuba in 1962, beginning the Cuban Missile
   Crisis.
   Enlarge
   U-2 photographs revealed that the Soviet Union was stationing nuclear
   missiles on the island of Cuba in 1962, beginning the Cuban Missile
   Crisis.

   The climax of brinksmanship came in early 1962, when an American U-2
   spy plane photographed a series of launch sites for medium-range
   ballistic missiles being constructed on the island of Cuba, just off
   the coast of the southern United States, beginning what became known as
   the Cuban Missile Crisis. The U.S. administration of John F. Kennedy
   concluded that the Soviet Union, then led by Nikita Khrushchev, was
   planning to station Russian nuclear missiles on the island, which was
   under the control of Communist Fidel Castro. On October 22, Kennedy
   announced the discoveries in a televised address, and declared that a
   naval quarantine would be put around Cuba to turn back any Soviet
   nuclear shipments, and warned that the military was prepared "for any
   eventualities." The missiles would have a range of 2,400 miles (4,000
   km), and allow the Soviet Union to easily destroy many major American
   cities on the Eastern Seaboard if a nuclear war were started.

   The leaders of the two superpowers stood nose to nose, seemingly poised
   over the beginnings of a third world war. Khrushchev's ambitions for
   putting the weapons on the island were motivated in part by the fact
   that the U.S. had stationed similar weapons in Britain, Italy, and
   nearby Turkey, and had previously attempted to sponsor an invasion of
   Cuba the year before in the failed Bay of Pigs Invasion. On October 26,
   an offer was sent from Khrushchev to Kennedy offering to withdraw all
   missiles if Kennedy would commit to a policy of no future invasions of
   Cuba. Khrushchev worded the threat of assured destruction eloquently:

          "You and I should not now pull on the ends of the rope in which
          you have tied a knot of war, because the harder you and I pull,
          the tighter the knot will become. And a time may come when this
          knot is tied so tight that the person who tied it is no longer
          capable of untying it, and then the knot will have to be cut.
          What that would mean I need not explain to you, because you
          yourself understand perfectly what dreaded forces our two
          countries possess."

   A day later, however, the Russians put forward another offer, this time
   demanding that the U.S. remove its missiles from Turkey before any
   missiles would be withdrawn from Cuba. On the same day, a U-2 plane was
   shot down over Cuba and another was almost intercepted over Russia, and
   Soviet merchant ships were nearing the quarantine zone. Kennedy
   responded by accepting the first deal publicly, and sending his brother
   Robert to the Soviet embassy to accept the second deal in private. On
   October 28, the Soviet ships stopped at the quarantine line and, after
   some hesitation, turned back towards the Soviet Union. Khrushchev
   announced that he had ordered the removal of all missiles in Cuba, and
   U.S. Secretary of State Dean Rusk was moved to comment, "We went
   eyeball to eyeball, and the other fellow just blinked."

   The Crisis was later seen as the closest the U.S. and the USSR ever
   came to nuclear war and had been narrowly averted by last-minute
   compromise by both superpowers. Fears of communication difficulties led
   to the installment of the first hotline, a direct link between the
   superpowers which would allow them to more easily discuss future
   military activities and political maneuverings. It had been made clear
   that with their missiles, bombers, submarines, and computerized firing
   systems, the escalation of any situation to Armageddon could be done
   far easier than anybody desired.

   After stepping so close to the brink, both the U.S. and the USSR worked
   to reduce their nuclear tensions in the years immediately following.
   The most immediate culmination of this work was the signing of the
   Partial Test Ban Treaty in 1963, in which the U.S. and USSR agreed to
   no longer test nuclear weapons in the atmosphere, underwater, or in
   outer space. Testing underground continued, allowing for further
   weapons development, but the worldwide fallout risks were purposefully
   reduced, and the era of using massive nuclear tests as a form of saber
   rattling had primarily ended.

   In 1981, as U.S. President Ronald Reagan's administration pushed the
   arms race to new levels of higher tension with the USSR, one million
   people marched for nuclear disarmament and abolition in New York City.
   As the nuclear abolitionist movement grew, over 2,000 people were
   arrested in a two-day period in 1988 at the gate of the Nevada Test
   Site. Four of the significant groups organizing this renewal of
   anti-nuclear activism were Greenpeace, The American Peace Test, The
   Western Shoshone, and Nevada Desert Experience. Nevada Desert
   Experience (NDE) had kickstarted the renewal in 1982, and maintained
   annual resistance and prayer-actions for peace in Western Shoshone
   country (within Nevada) for 25 years.

Initial Proliferation

   In the fifties and sixties, three more countries joined the "nuclear
   club."

   The United Kingdom had been an integral part of the Manhattan Project
   following the Quebec Agreement in 1943. The passing of the McMahon Act
   by the United States in 1946 unilaterally broke this partnership and
   prevented the passage of any further information to the United Kingdom.
   The British Government under Clement Attlee determined that it would be
   essential for there to be a British Bomb. Because of the involvement in
   the Manhattan Project Britain had extensive knowledge in some areas,
   but not in others. An improved version of 'Fat Man' was developed, and
   on 26th February 1952, Prime Minister Winston Churchill announced that
   the United Kingdom also had an atomic bomb and a successful test took
   place on the 3rd October 1952. At first these were free-fall bombs and
   then there was a missile, Blue Steel, and a later-cancelled MRBM, Blue
   Streak. Anglo-American cooperation on Nuclear weapons was restored by
   the 1958 US-UK Mutual Defence Agreement. As a result of this and the
   Polaris Sales Agreement, the United Kingdom has bought United States
   designs for submarine missiles and fitted its own warheads. It retains
   full independent control over the use of the missiles. It no longer
   possesses any free-fall bombs.

   France had been heavily involved in nuclear research before World War
   II through the work of the Joliot-Curies. This was discontinued after
   the war because of the instability of the Fourth Republic and the lack
   of finance available . However, in the 1950's a civil nuclear research
   programme was started, a byproduct of which would be plutonium. In 1956
   a secret Committee for the Military Applications of Atomic Energy was
   formed and a development programme for delivery vehicles started. With
   the return of Charles de Gaulle to the presidency of France in 1958 the
   final decisions to build a bomb were taken, and a successful test took
   place in 1960. Since then France has developed and maintained its own
   nuclear deterrent.

   In 1951 China and the Soviet Union signed an agreement whereby China
   would supply uranium ore in exchange for technical assistance in
   producing nuclear weapons. In 1953 China had established a research
   programme under the guise of civilian nuclear energy. Throughout the
   1950's the Soviet Union provided large amounts of equipment, but as the
   relations between the two countries worsened, the amount of assistance
   was reduced, and in 1959 the donation of a bomb for copying purposes
   was refused. Despite this, rapid progress was made with the test of an
   atomic bomb on the 16th October 1964 at Lop Nur, a nuclear missile on
   25th October 1966, and of a hydrogen bomb on the 14th June 1967.
   Nuclear warheads were produced from 1968 and thermonuclear warheads
   from 1974. The Cultural Revolution slowed the pace of progress, but it
   is thought that tactical nuclear weapons have been developed. It is
   also thought that Chinese warheads have been successfully miniaturised
   from 2200kg to 700kg through the use of designs obtained by espionage
   from the United States. The current number of weapons is unknown owing
   to strict secrecy, but it is thought that up to 2000 warheads may have
   been produced, though far fewer may be available for use. China is the
   only one of the Nuclear Weapons States to have guaranteed the non-first
   use of nuclear weapons.

Cold War

   ICBMs, like the American Minuteman missile, allowed nations to deliver
   nuclear weapons thousands of miles away with relative ease.
   Enlarge
   ICBMs, like the American Minuteman missile, allowed nations to deliver
   nuclear weapons thousands of miles away with relative ease.

   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.
   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.

Further nuclear proliferation

   India's first atomic-test explosion was in 1974 with Smiling Buddha,
   which it described as a "peaceful nuclear explosion". India tested
   fission and perhaps fusion devices in 1998, and Pakistan successfully
   tested fission devices that same year, raising concerns that they would
   use nuclear weapons on each other. All of the former Soviet bloc
   countries with nuclear weapons (Belarus, Ukraine, and Kazakhstan)
   returned their warheads to Russia by 1996, though recent data has
   suggested that a clerical error may have left some warheads in Ukraine.

   In January 2004, Pakistani metallurgist and weapons scientist Abdul
   Qadeer Khan confessed to having been a part of an international
   proliferation network of materials, knowledge, and machines from
   Pakistan to Libya, Iran, and North Korea.

   South Africa also had an active program to develop uranium-based
   nuclear weapons, but dismantled its nuclear weapon program in the
   1990s. It is not believed that it actually tested such a weapon though
   it later claimed to have constructed several crude devices which it
   eventually dismantled. In the late 1970s American spy satellites
   detected a "brief, intense, double flash of light near the southern tip
   of Africa." which was speculated to have been a South African nuclear
   weapons test, though a later scientific review of the data indicated
   that it may have been caused by natural events.

   Israel is widely believed to possess an arsenal of potentially up to
   several hundred nuclear warheads, but this has never been officially
   confirmed or denied (though the existence of their Dimona nuclear
   facility was more or less confirmed by the leaks of the dissident
   Mordechai Vanunu in 1986).

   North Korea announced in 2003 that it also had several nuclear
   explosives though it has not been confirmed and the validity of this
   has been a subject of scrutiny amongst weapons experts. The first
   detonation of a nuclear weapon by the Democratic People's Republic of
   Korea was the 2006 North Korean nuclear test, conducted on October 9,
   2006.

   In Iran, Ayatollah Ali Khamenei issued a fatwa forbidding the
   production, stockpiling and use of nuclear weapons on August 9, 2005.
   The full text of the fatwa was released in an official statement at the
   meeting of the International Atomic Energy Agency (IAEA) in Vienna.
   Despite this, however, there is mounting concern in many nations about
   Iran's refusal to halt its nuclear power program, which many fear is a
   cover for weapons development. Some are especially concerned in light
   of statements by Iranian President Mahmoud Ahmadinejad indicating his
   desire to completely annihilate the nation of Israel.

   Retrieved from "
   http://en.wikipedia.org/wiki/History_of_nuclear_weapons"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
