Instruct: Given a question, retrieve documents that answer the question.
Query: When were nuclear weapons first used in war?
So far, two nuclear weapons have been used in the course of warfare, both by the United States near the end of World War II. On August 6, 1945, a uranium gun-type device (code name "Little Boy") was detonated over the Japanese city of Hiroshima. Three days later, on August 9, a plutonium implosion-type device (code name "Fat Man") was detonated over the Japanese city of Nagasaki. These two bombings resulted in the deaths of approximately 120,000 people.
In the United States, where Fermi and Szilárd had both emigrated, the discovery of the nuclear chain reaction led to the creation of the first man-made reactor, the research reactor known as Chicago Pile-1, which achieved self-sustaining power/criticality on December 2, 1942. The reactor's development was part of the Manhattan Project, the Allied effort to create atomic bombs during World War II. It led to the building of larger single-purpose production reactors, such as the X-10 Pile, for the production of weapons-grade plutonium for use in the first nuclear weapons. The United States tested the first nuclear weapon in July 1945, the Trinity test, with the atomic bombings of Hiroshima and Nagasaki taking place one month later.
The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons. The design of all modern thermonuclear weapons in the United States is known as the "Teller–Ulam configuration" for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann. Similar devices were developed by the Soviet Union, United Kingdom, France, and China.
On March 1, 1954, the U.S. detonated its first practical 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, more than 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 . 239 Marshall Island natives and 28 Americans were exposed to significant amounts of radiation, resulting in elevated levels of cancer and birth defects in the years to come.
The United States Atomic Energy Commission, directed by David E. Lilienthal until 1950, was in charge of designing and building nuclear weapons. The policy was 100% civilian control. The U.S. had only 9 atomic bombs in 1946, but the stockpile grew to 650 by 1951. Lilienthal wanted to give high priority to peaceful uses, especially nuclear power plants, but coal was cheap and the power industry was not interested. Construction of the first nuclear plant would not begin until 1954. In early 1950, Truman authorized the development of thermonuclear weapons, a more powerful version of atomic bombs. Truman's decision to develop thermonuclear weapons faced opposition from many liberals and some government officials, but Truman believed that the Soviet Union would likely develop the weapons, and he was unwilling to allow the Soviets to have such an advantage. The first test of thermonuclear weaponry was conducted by the United States in 1952, and the Soviet Union performed its own thermonuclear test in August 1953.
The United States was in a Cold War Nuclear arms race with the Soviet Union to build bigger and better bombs. The next series of tests over Bikini Atoll was code named Operation Castle. The first test of that series was Castle Bravo, a new design utilizing a dry fuel thermonuclear hydrogen bomb. It was detonated at dawn on March 1, 1954.
With the basic fusion reactions confirmed, and with a feasible design in hand, there was nothing to prevent Los Alamos from testing a thermonuclear device. On 1 November 1952, the first thermonuclear explosion occurred when Ivy Mike was detonated on Enewetak Atoll, within the US Pacific Proving Grounds. This device, which used liquid deuterium as its fusion fuel, was immense and utterly unusable as a weapon. Nevertheless, its success validated the Teller–Ulam design, and stimulated intensive development of practical weapons.
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 that would use the same reactions that powered the Sun itself.
Much of the stimulus for the treaty was increasing public unease about radioactive fallout as a result of above-ground or underwater nuclear testing, particularly given the increasing power of nuclear devices, as well as concern about the general environmental damage caused by testing. In 1952–53, the US and Soviet Union detonated their first thermonuclear weapons (hydrogen bombs), far more powerful than the atomic bombs tested and deployed since 1945. In 1954, the US Castle Bravo test at Bikini Atoll (part of Operation Castle) had a yield of 15 megatons of TNT, more than doubling the expected yield. The Castle Bravo test resulted in the worst radiological event in US history as radioactive particles spread over more than , affected inhabited areas (including Rongelap Atoll and Utirik Atoll), and sickened Japanese fishermen aboard the "Lucky Dragon" upon whom "ashes of death" had rained. In the same year, a Soviet test sent radioactive particles over Japan. Around the same time, victims of the atomic bombing of Hiroshima visited the US for medical care, which attracted significant public attention. In 1961, the Soviet Union tested the Tsar Bomba, which had a yield of 50 megatons and remains the most powerful man-made explosion in history, though due to a highly efficient detonation fallout was relatively limited. Between 1951 and 1958, the US conducted 166 atmospheric tests, the Soviet Union conducted 82, and Britain conducted 21; only 22 underground tests were conducted in this period (all by the US).
On August 6, 1945, the uranium-type nuclear weapon codenamed "Little Boy" was detonated over the Japanese city of Hiroshima with an energy of about , destroying nearly 50,000 buildings (including the headquarters of the 2nd General Army and Fifth Division) and killing approximately 70,000 people, including 20,000 Japanese combatants and 20,000 Korean slave laborers. Three days later, on August 9, a plutonium-type nuclear weapon codenamed "Fat Man" was used against the Japanese city of Nagasaki, with the explosion equivalent to about , destroying 60% of the city and killing approximately 35,000 people, including 23,200–28,200 Japanese munitions workers, 2,000 Korean slave laborers, and 150 Japanese combatants. The industrial damage in Nagasaki was high, partly owing to the inadvertent targeting of the industrial zone, leaving 68–80 percent of the non-dock industrial production destroyed.
As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above , virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the Teller–Ulam design.
A thermonuclear weapon, or fusion weapon, is a second-generation nuclear weapon design which affords vastly greater destructive power than first-generation atomic bombs. Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by Uranium-235 or Plutonium-239) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason thermonuclear weapons are often colloquially called hydrogen bombs, or H-bombs.
The Cold War began in the aftermath, much like in the real world. The United States did not develop nuclear weapons for several more years (they didn't need to finish them, as Superior's early victory in the war meant the Manhattan Project was canceled late in development). However, the real arms race was in the new "Alpha" class super-humans. A handful of other "Alphas" emerged at the end of the war, and in the aftermath, and the Soviet Union was able to "create" several new Alphas, none as powerful as Superior, but still enough to challenge him. In 1949 they also detonated an atomic bomb, and the Cold War began in earnest. Even Superior was uncertain he could survive a nuclear blast. The United States quickly finished its own nuclear program, and like the real world, the fear and paranoia of the Cold War gripped the nation. Senator Joseph McCarthy held his HUAC hearings, but Superior's moral superiority eventually shamed him into closing them.
As of April 2012 there were thirty one countries that have civil nuclear power plants, of which nine have nuclear weapons, with the vast majority of these nuclear weapons states having first produced weapons, before commercial fission electricity stations.
Moreover, the re-purposing of civilian nuclear industries for military purposes would be a breach of the Non-proliferation treaty, of which 190 countries adhere to.
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of "Operation Castle". Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon. Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving Li, which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
The power of large bombs is typically measured in kilotons (kt) or megatons of TNT (Mt). The most powerful bombs ever used in combat were the two atomic bombs dropped by the United States to attack Hiroshima and Nagasaki, and the most powerful ever tested was the Tsar Bomba. The most powerful non-nuclear bomb is Russian "Father of All Bombs" (officially Aviation Thermobaric Bomb of Increased Power (ATBIP)) followed by the United States Air Force's MOAB (officially Massive Ordnance Air Blast, or more commonly known as the "Mother of All Bombs").
Only six countries—United States, Russia, United Kingdom, China, France, and India—have conducted thermonuclear weapon tests. (Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial.) North Korea claims to have tested a fusion weapon , though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it is more efficient.
In August 1939, Leo Szilard and Albert Einstein sent the Einstein–Szilárd letter to Roosevelt, warning of the possibility of a German project to develop nuclear weapons. Szilard realized that the recently discovered process of nuclear fission could be used to create a nuclear chain reaction that could be used as a weapon of mass destruction. Roosevelt feared the consequences of allowing Germany to have sole possession of the technology, and authorized preliminary research into nuclear weapons. After the attack on Pearl Harbor, the Roosevelt administration secured the funds needed to continue research and selected General Leslie Groves to oversee the Manhattan Project, which was charged with developing the first nuclear weapons. Roosevelt and Churchill agreed to jointly pursue the project, and Roosevelt helped ensure that American scientists cooperated with their British counterparts.
The thermonuclear weapons race between the United States and the Soviet Union exceeded all expectations set out before the scientists who took part. Two countries creating thermonuclear weapons with such energy yields from two different design methods proved to be the crowning achievement for science in the 1950s. Of course, the successful and promising work from both the United States and the Soviet Union only spurred each country to push for stronger weapons, as the floodgates of thermonuclear weapon potential had been opened. This was, of course, entirely the norm at the time considering that the Cold War was in full swing. It was a significant boost to Soviet morale knowing that the Soviet Union's physicists, engineers, scientist, and great minds were able to not only compete with the Americans, but also able to out perform them in some key areas of weapon and technological development.
In August 1939, Leo Szilard and Albert Einstein sent the Einstein–Szilárd letter to Roosevelt, warning of the possibility of a German project to develop nuclear weapons. Szilard realized that the recently discovered process of nuclear fission could be used to create a nuclear chain reaction that could be used as a weapon of mass destruction. Roosevelt feared the consequences of allowing Germany to have sole possession of the technology, and authorized preliminary research into nuclear weapons. After the attack on Pearl Harbor, the Roosevelt administration secured the funds needed to continue research and selected General Leslie Groves to oversee the Manhattan Project, which was charged with developing the first nuclear weapons. Roosevelt and Churchill agreed to jointly pursue the project with the Quebec Agreement, and Roosevelt helped ensure that American scientists cooperated with their British counterparts.
On July 19, 1956, AEC Chairman Lewis Strauss said that the Redwing Zuni shot clean bomb test "produced much of importance ... from a humanitarian aspect." However, less than two days after this announcement, the dirty version of Bassoon, called Bassoon Prime, with a uranium-238 tamper in place, was tested on a barge off the coast of Bikini Atoll as the Redwing Tewa shot. The Bassoon Prime produced a 5-megaton yield, of which 87% came from fission. Data obtained from this test, and others, culminated in the eventual deployment of the highest yielding US nuclear weapon known, and the highest yield-to-weight weapon ever made, a three-stage thermonuclear weapon with a maximum "dirty" yield of 25 megatons, designated as the B41 nuclear bomb, which was to be carried by U.S. Air Force bombers until it was decommissioned; this weapon was never fully tested.
Nuclear weapons brought an entirely new and terrifying possibility to warfare: a nuclear holocaust. While at first the United States held a monopoly on the production of nuclear weapons, the Soviet Union, with some assistance from espionage, managed to detonate its first weapon (dubbed "Joe-1" by the West) in August 1949. The post-war relations between the two, which had already been deteriorating, began to rapidly disintegrate. Soon the two were locked in a massive stockpiling of nuclear weapons. The United States began a crash program to develop the first hydrogen bomb in 1950, and detonated its first thermonuclear weapon in 1952. This new weapon was alone over 400 times as powerful as the weapons used against Japan. The Soviet Union detonated a primitive thermonuclear weapon in 1953 and a full-fledged one in 1955.
Another dimension to the tactical use of nuclear weapons is that of such weapons deployed at sea for use against surface and submarine vessels. Until 1992, vessels of the United States Navy (and their aircraft) deployed various such weapons as bombs, rockets (guided and unguided), torpedoes, and depth charges. Such tactical naval nuclear weapons were considered more acceptable to use early in a conflict because there would be few civilian casualties. It was feared by many planners that such use would probably quickly have escalated into large-scale nuclear war. This situation was particularly exacerbated by the fact that such weapons at sea were not constrained by the safeguards provided by the Permissive Action Link attached to U.S. Air Force and Army nuclear weapons. It is unknown if the navies of the other nuclear powers yet today deploy tactical nuclear weapons at sea.
When the Cold War ended in 1991, there were more than 500 US nuclear weapons in the UK. Of these, about 400 were bombs, 48 were Ground Launched Cruise Missiles, and approximately 100 were B57 nuclear depth bombs. The BAOR still had about 85 Lance missiles, and more than 70 W33 eight-inch and W48 155 mm nuclear artillery shells. The cruise missiles were withdrawn in 1991 under the terms of the 1987 Intermediate-Range Nuclear Forces Treaty. The United States then decided to withdraw its short-range nuclear weapons. The last US warheads, including the Mark 57 nuclear depth bombs and those used by the BAOR, were withdrawn in July 1992. The only American nuclear weapons then remaining in the UK were 110 or so B61 nuclear bombs stored at RAF Lakenheath for USAF F-15E Strike Eagles, which were withdrawn by 2008. The British WE.177 nuclear bombs used by the RAF and Royal Navy were withdrawn from service in August 1998, at which point the only remaining British nuclear weapons were the warheads on the Trident missiles of the s.
By the 1960s Okinawa was known as "The Keystone of the Pacific" to U.S. strategists and as "The Rock" to U.S. servicemen. Okinawa was critical to America's Vietnam war effort where commanders reasoned that, "without Okinawa, we cannot carry on the Vietnam war."
During U.S. involvement in the Vietnam War the use of nuclear weapons was suggested in order to "defoliate forests, destroy bridges, roads, and railroad lines." In addition, the use of nuclear weapons was suggested during the planning for the bombing of Vietnam's dikes in order to flood rice paddies, disrupt the North Vietnamese food supply, and leverage Hanoi during negotiations. Each of the cold war plans employing a U.S. launched nuclear first strike were ultimately rejected.