145-550: RDS-3 was the third atomic bomb developed by the Soviet Union in 1951, after the RDS-1 and RDS-2 . It was called Marya in the military. The bomb had a composite design with a plutonium core inside a uranium shell, providing an explosive power of 41.2 kilotons. The RDS-3T was a modernized version and the first mass-produced nuclear weapon by the Soviet Union . It was assigned to Long Range Aviation in 1953. RDS-3
290-569: A conventional bomb can devastate an entire city by blast, fire, and radiation . Since they are weapons of mass destruction , the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been deployed twice in war , both by the United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II . Nuclear weapons have only twice been used in warfare, both times by
435-559: A Fat Man was dropped on Nagasaki. Over the next two to four months, the effects of the atomic bombings killed 90,000 to 166,000 people in Hiroshima and 60,000 to 80,000 people in Nagasaki; roughly half occurred on the first day. For months afterward, many people continued to die from the effects of burns, radiation sickness , and other injuries, compounded by illness and malnutrition. Despite Hiroshima's sizable military garrison, most of
580-696: A conference—called for in the manifesto—in Pugwash, Nova Scotia , Eaton's birthplace. This conference was to be the first of the Pugwash Conferences on Science and World Affairs , held in July 1957. By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of nuclear testing . The Partial Nuclear Test Ban Treaty (1963) restricted all nuclear testing to underground nuclear testing , to prevent contamination from nuclear fallout, whereas
725-458: A faster and less vulnerable attack, the development of long-range intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing
870-656: A fission ("atomic") bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ ). The first thermonuclear ("hydrogen") bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). Nuclear bombs have had yields between 10 tons TNT (the W54 ) and 50 megatons for the Tsar Bomba (see TNT equivalent ). A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ). A nuclear device no larger than
1015-492: A fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the United States Department of Energy divulged that the United States had, "...made
1160-421: A fusion weapon as of January 2016 , 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 results in an explosion hundreds of times stronger than that of a fission bomb of similar weight. Thermonuclear bombs work by using
1305-646: A greater loss of life; according to critics, the bombings were unnecessary for the war's end and were a war crime , raising moral and ethical implications. In 1945, the Pacific War between the Empire of Japan and the Allies entered its fourth year. Most Japanese military units fought fiercely, ensuring that the Allied victory would come at an enormous cost. The 1.25 million battle casualties incurred in total by
1450-399: A large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs ). This has long been noted as something of a misnomer , as their energy comes from the nucleus of
1595-494: A large fraction of the city may be destroyed. The Emperor's palace in Tokyo has a greater fame than any other target but is of least strategic value." Edwin O. Reischauer , a Japan expert for the U.S. Army Intelligence Service , was incorrectly said to have prevented the bombing of Kyoto. In his autobiography, Reischauer specifically refuted this claim: ... the only person deserving credit for saving Kyoto from destruction
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#17327807934961740-423: A large war industry, manufacturing parts for planes and boats, for bombs, rifles, and handguns. The center of the city contained several reinforced concrete buildings. Outside the center, the area was congested by a dense collection of small timber workshops set among Japanese houses. A few larger industrial plants lay near the outskirts of the city. The houses were constructed of timber with tile roofs, and many of
1885-698: A leaflet listing 11 or 12 cities targeted for firebombing; a total of 33 cities listed. With the text of this leaflet reading in Japanese "... we cannot promise that only these cities will be among those attacked ..." Hiroshima was not listed. In 1943, the United States and the United Kingdom signed the Quebec Agreement , which stipulated that nuclear weapons would not be used against another country without mutual consent. Stimson therefore had to obtain British permission. A meeting of
2030-558: A leaflet. Leaflet texts were prepared by recent Japanese prisoners of war because they were thought to be the best choice "to appeal to their compatriots". In preparation for dropping an atomic bomb on Hiroshima, the Oppenheimer-led Scientific Panel of the Interim Committee decided against a demonstration bomb and against a special leaflet warning. Those decisions were implemented because of
2175-530: A meeting with the President and commanders on 18 June 1945, General George C. Marshall stated that "there was reason to believe" casualties for the first 30 days would not exceed the price paid for Luzon . Additionally, with the Japanese position rendered "hopeless" by an invasion of their mainland, Marshall speculated that Soviet entry into the war might be "the decisive action" needed to finally "[leverage] them into capitulation." Marshall began contemplating
2320-472: A nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area. Research has been done into the possibility of pure fusion bombs : nuclear weapons that consist of fusion reactions without requiring
2465-537: A new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War. Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction . Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider
2610-425: A nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction . This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism. Critics from the peace movement and within
2755-411: A nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of nuclear deterrence . The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for first strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During
2900-527: A nuclear weapon is a gravity bomb dropped from aircraft ; this was the method used by the United States against Japan in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both strategic bombers and tactical fighter-bombers . This method
3045-409: A nuclear weapon to its target is an important factor affecting both nuclear weapon design and nuclear strategy . The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940. The simplest method for delivering
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#17327807934963190-433: A nuclear weapon with suitable materials (such as cobalt or gold ) creates a weapon known as a salted bomb . This device can produce exceptionally large quantities of long-lived radioactive contamination . It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around
3335-553: A peak of over 381,000 earlier in the war but prior to the atomic bombing, the population had steadily decreased because of a systematic evacuation ordered by the Japanese government . At the time of the attack, the population was approximately 340,000–350,000. Residents wondered why Hiroshima had been spared destruction by firebombing. Some speculated that the city was to be saved for U.S. occupation headquarters, others thought perhaps their relatives in Hawaii and California had petitioned
3480-421: A policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.". Graham Allison makes a similar case, arguing that the key to expanded deterrence
3625-590: A press conference that the Potsdam Declaration was no more than a rehash ( yakinaoshi ) of the Cairo Declaration , that the government intended to ignore it ( mokusatsu , "kill by silence"), and that Japan would fight to the end. The statement was taken by both Japanese and foreign papers as a clear rejection of the declaration. Emperor Hirohito, who was waiting for a Soviet reply to non-committal Japanese peace feelers, made no move to change
3770-506: A request from Winston Churchill that Britain be represented when the atomic bomb was dropped. William Penney and Group Captain Leonard Cheshire were sent to Tinian, but LeMay would not let them accompany the mission. The Little Boy bomb, except for the uranium payload, was ready at the beginning of May 1945. There were two uranium-235 components, a hollow cylindrical projectile and a cylindrical target insert. The projectile
3915-544: A series of landings by the U.S. Sixth Army intended to capture the southern third of the southernmost main Japanese island, Kyūshū . This was to be followed in March 1946 by Operation Coronet , the capture of the Kantō Plain , near Tokyo on the main Japanese island of Honshū by the U.S. First , Eighth and Tenth Armies, as well as a Commonwealth Corps made up of Australian, British and Canadian divisions. The target date
4060-465: A series of raids on strategic targets in Japan. This effort failed to achieve the strategic objectives that its planners had intended, largely because of logistical problems, the bomber's mechanical difficulties, the vulnerability of Chinese staging bases, and the extreme range required to reach key Japanese cities. Brigadier General Haywood S. Hansell determined that Guam , Tinian , and Saipan in
4205-510: A significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions. Only six countries—the United States , Russia , the 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
4350-691: A study by the Joint War Plans Committee, drawing on the experience of the Battle of Leyte , estimated that Downfall would result in 132,500 to 220,000 U.S. casualties, with U.S. dead and missing in the range from 27,500 to 50,000. Secretary of War Henry L. Stimson commissioned his own study by Quincy Wright and William Shockley , who estimated the invading Allies would suffer between 1.7 and 4 million casualties, of whom between 400,000 and 800,000 would be dead, while Japanese fatalities would have been around 5 to 10 million. In
4495-550: A substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment". Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurring isotopes ( Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in
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4640-627: Is Henry L. Stimson, the Secretary of War at the time, who had known and admired Kyoto ever since his honeymoon there several decades earlier. Extant sources show that while Stimson was personally familiar with Kyoto, this was the result of a visit decades after his marriage, not because he honeymooned there. On 30 May, Stimson asked Groves to remove Kyoto from the target list due to its historical, religious and cultural significance, but Groves pointed to its military and industrial significance. Stimson then approached President Harry S. Truman about
4785-444: Is a stub . You can help Misplaced Pages by expanding it . Atomic bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions , either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb ), producing a nuclear explosion . Both bomb types release large quantities of energy from relatively small amounts of matter . The first test of
4930-420: Is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron radiation . Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in
5075-456: Is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials." According to the Pentagon's June 2019 " Doctrine for Joint Nuclear Operations " of
5220-403: Is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin." The process
5365-481: Is for the purpose of achieving different yields for different situations , and in manipulating design elements to attempt to minimize weapon size, radiation hardness or requirements for special materials, especially fissile fuel or tritium. Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as tactical nuclear weapons . The neutron bomb purportedly conceived by Sam Cohen
5510-503: Is no evidence that it is feasible beyond the military domain. However, the U.S. Air Force funded studies of the physics of antimatter in the Cold War , and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion . Most variation in nuclear weapon design
5655-409: Is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of
5800-490: Is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute. The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs ), as they rely on fusion reactions between isotopes of hydrogen ( deuterium and tritium ). All such weapons derive
5945-416: Is such a size that a large part of the city could be extensively damaged. There are adjacent hills which are likely to produce a focusing effect which would considerably increase the blast damage. Due to rivers it is not a good incendiary target." The Target Committee stated that "It was agreed that psychological factors in the target selection were of great importance. Two aspects of this are (1) obtaining
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6090-558: Is the only country to have independently developed and then renounced and dismantled its nuclear weapons. The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but there are different views of its effectiveness. There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, and those that use fission reactions to begin nuclear fusion reactions that produce
6235-454: Is the primary means of nuclear weapons delivery; the majority of U.S. nuclear warheads, for example, are free-fall gravity bombs, namely the B61 , which is being improved upon to this day. Preferable from a strategic point of view is a nuclear weapon mounted on a missile , which can use a ballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for
6380-688: The Boeing B-29 Superfortress , and deployed to Tinian in the Mariana Islands . The Allies called for the unconditional surrender of the Imperial Japanese armed forces in the Potsdam Declaration on 26 July 1945, the alternative being "prompt and utter destruction". The Japanese government ignored the ultimatum. The consent of the United Kingdom was obtained for the bombing, as was required by
6525-572: The Combined Policy Committee , which included one Canadian representative, was held at the Pentagon on 4 July 1945. Field Marshal Sir Henry Maitland Wilson announced that the British government concurred with the use of nuclear weapons against Japan, which would be officially recorded as a decision of the Combined Policy Committee. As the release of information to third parties was also controlled by
6670-544: The Einstein–Szilard letter to Roosevelt in 1939. This prompted preliminary research in the United States in late 1939. Progress was slow until the arrival of the British MAUD Committee report in late 1941, which indicated that only 5 to 10 kilograms of isotopically -pure uranium-235 were needed for a bomb instead of tons of natural uranium and a neutron moderator like heavy water . Consequently,
6815-560: The Interim Committee was created by Stimson at the urging of leaders of the Manhattan Project and with the approval of Truman to advise on matters pertaining to nuclear technology . They agreed that the atomic bomb was to be used (1) against Japan at the earliest opportunity, (2) without special warning, and (3) on a "dual target" of military installation surrounded by other buildings susceptible to damage. During
6960-522: The Mariana Islands would better serve as B-29 bases, but they were in Japanese hands. Strategies were shifted to accommodate the air war, and the islands were captured between June and August 1944. Air bases were developed, and B-29 operations commenced from the Marianas in October 1944. The XXI Bomber Command began missions against Japan on 18 November 1944. The early attempts to bomb Japan from
7105-475: The Quebec Agreement , and orders were issued on 25 July by General Thomas Handy , the acting chief of staff of the United States Army , for atomic bombs to be used against Hiroshima, Kokura , Niigata , and Nagasaki. These targets were chosen because they were large urban areas that also held militarily significant facilities. On 6v August, a Little Boy was dropped on Hiroshima. Three days later,
7250-695: The Starfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called a nuclear electromagnetic pulse . This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling
7395-499: The Treaty on the Non-Proliferation of Nuclear Weapons (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military nuclear technology to member countries without fear of proliferation. Atomic bombings of Hiroshima and Nagasaki Second Sino-Japanese War On 6 and 9 August 1945, the United States detonated two atomic bombs over
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#17327807934967540-676: The Tsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210 PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements. In the early 1950s the Livermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon and Sundial , 1 gigaton of TNT and 10 gigatons of TNT respectively. Fusion reactions do not create fission products, and thus contribute far less to
7685-575: The United States against Japan at the end of World War II . On August 6, 1945, the United States Army Air Forces (USAAF) detonated a uranium gun-type fission bomb nicknamed " Little Boy " over the Japanese city of Hiroshima ; three days later, on August 9, the USAAF detonated a plutonium implosion-type fission bomb nicknamed " Fat Man " over the Japanese city of Nagasaki . These bombings caused injuries that resulted in
7830-485: The United States , the Soviet Union (succeeded as a nuclear power by Russia ), the United Kingdom , France , China , India , Pakistan , and North Korea . Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity , it does not acknowledge having them. Germany , Italy , Turkey , Belgium , the Netherlands , and Belarus are nuclear weapons sharing states. South Africa
7975-424: The hafnium controversy ) have been proposed as possible triggers for conventional thermonuclear reactions. Antimatter , which consists of particles resembling ordinary matter particles in most of their properties but having opposite electric charge , has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there
8120-614: The head of government or head of state . Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage". In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The Russell–Einstein Manifesto was issued in London on July 9, 1955, by Bertrand Russell in
8265-486: The instrument of surrender on 2 September, effectively ending the war . In the final year of World War II , the Allies prepared for a costly invasion of the Japanese mainland . This undertaking was preceded by a conventional bombing and firebombing campaign that devastated 64 Japanese cities, including an operation on Tokyo . The war in the European theatre concluded when Germany surrendered on 8 May 1945, and
8410-436: The tropopause into the stratosphere , where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion. There are other types of nuclear weapons as well. For example, a boosted fission weapon is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it
8555-537: The "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 kilotons ) of TNT (4.2 to 2.1 × 10 GJ). All fission reactions generate fission products ,
8700-586: The 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200 mm W79 and 155 mm W82 ) and short range missile forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable. A type of nuclear explosive most suitable for use by ground special forces
8845-399: The 393d Bombardment Squadron plus one from the 216th Army Air Force Base Unit, and transported to North Field, arriving on 2 August. At the time of its bombing, Hiroshima was a city of industrial and military significance. A number of military units were located nearby, the most important of which was the headquarters of Field Marshal Shunroku Hata 's Second General Army , which commanded
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#17327807934968990-422: The 3rd Anti-Aircraft Division, including units from the 121st and 122nd Anti-Aircraft Regiments and the 22nd and 45th Separate Anti-Aircraft Battalions. In total, an estimated 40,000 Japanese military personnel were stationed in the city. Hiroshima was a supply and logistics base for the Japanese military. The city was a communications center, a key port for shipping, and an assembly area for troops. It supported
9135-481: The 509th Composite Group about the possibility of a B-29 crashing on takeoff, Birch had modified the Little Boy design to incorporate a removable breech plug that would permit the bomb to be armed in flight. The first plutonium core , along with its polonium - beryllium urchin initiator , was transported in the custody of Project Alberta courier Raemer Schreiber in a magnesium field carrying case designed for
9280-538: The 509th Composite Group moved by rail on 26 April 1945, to its port of embarkation at Seattle , Washington. On 6 May the support elements sailed on the SS Cape Victory for the Marianas, while group materiel was shipped on the SS Emile Berliner . The Cape Victory made brief port calls at Honolulu and Eniwetok but the passengers were not permitted to leave the dock area. An advance party of
9425-523: The 509th had attached to it on Tinian 51 civilian and military personnel from Project Alberta , known as the 1st Technical Detachment. The 509th Composite Group's 393d Bombardment Squadron was equipped with 15 Silverplate B-29s. These aircraft were specially adapted to carry nuclear weapons, and were equipped with fuel-injected engines, Curtiss Electric reversible-pitch propellers , pneumatic actuators for rapid opening and closing of bomb bay doors and other improvements. The ground support echelon of
9570-509: The Allies advanced towards Japan, conditions became steadily worse for the Japanese people. Japan's merchant fleet declined from 5,250,000 gross register tons in 1941 to 1,560,000 tons in March 1945, and 557,000 tons in August 1945. The lack of raw materials forced the Japanese war economy into a steep decline after the middle of 1944. The civilian economy, which had slowly deteriorated throughout
9715-413: The Allies turned their full attention to the Pacific War . By July 1945, the Allies' Manhattan Project had produced two types of atomic bombs: " Little Boy ", an enriched uranium gun-type fission weapon , and " Fat Man ", a plutonium implosion-type nuclear weapon . The 509th Composite Group of the United States Army Air Forces was trained and equipped with the specialized Silverplate version of
9860-425: The Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions. Different forms of nuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against
10005-437: The Japanese cities of Hiroshima and Nagasaki , respectively. The bombings killed between 150,000 and 246,000 people, most of whom were civilians, and remain the only use of nuclear weapons in an armed conflict. Japan surrendered to the Allies on 15 August, six days after the bombing of Nagasaki and the Soviet Union's declaration of war against Japan and invasion of Japanese-occupied Manchuria . The Japanese government signed
10150-494: The Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation." Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by
10295-468: The Manhattan Project took place at dozens of sites across the United States, and even some outside of its borders. It would ultimately cost over US$ 2 billion (equivalent to about $ 27 billion in 2023) and employ over 125,000 people simultaneously at its peak. Groves appointed J. Robert Oppenheimer to organize and head the project's Los Alamos Laboratory in New Mexico , where bomb design work
10440-719: The Marianas proved just as ineffective as the China-based B-29s had been. Hansell continued the practice of conducting so-called high-altitude precision bombing , aimed at key industries and transportation networks, even after these tactics had not produced acceptable results. These efforts proved unsuccessful due to logistical difficulties with the remote location, technical problems with the new and advanced aircraft, unfavorable weather conditions, and enemy action. Hansell's successor, Major General Curtis LeMay , assumed command in January 1945 and initially continued to use
10585-503: The Nuclear Age (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase international stability . Some prominent neo-realist scholars, such as Kenneth Waltz and John Mearsheimer , have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of total war , especially in troubled regions of
10730-578: The Pacific, the Allies returned to the Philippines , recaptured Burma , and invaded Borneo . Offensives were undertaken to reduce the Japanese forces remaining in Bougainville , New Guinea and the Philippines. In April 1945, American forces landed on Okinawa , where heavy fighting continued until June. Along the way, the ratio of Japanese to American casualties dropped from five to one in
10875-465: The Philippines to two to one on Okinawa. Although some Japanese soldiers were taken prisoner , most fought until they were killed or committed suicide . Nearly 99 percent of the 21,000 defenders of Iwo Jima were killed. Of the 117,000 Okinawan and Japanese troops defending Okinawa in April to June 1945, 94 percent were killed; 7,401 Japanese soldiers surrendered, an unprecedentedly large number. As
11020-509: The Quebec Agreement, discussion then turned to what scientific details would be revealed in the press announcement of the bombing. The meeting also considered what Truman could reveal to Joseph Stalin , the leader of the Soviet Union , at the upcoming Potsdam Conference , as this also required British concurrence. Orders for the attack were issued to General Carl Spaatz on 25 July under the signature of General Thomas T. Handy ,
11165-590: The USAAF; and scientists John von Neumann , Robert R. Wilson and William Penney from the Manhattan Project. The Target Committee met in Washington on 27 April; at Los Alamos on 10 May, where it was able to talk to the scientists and technicians there; and finally in Washington on 28 May, where it was briefed by Tibbets and Commander Frederick Ashworth from Project Alberta, and the Manhattan Project's scientific advisor, Richard C. Tolman . The Target Committee nominated five targets: Kokura (now Kitakyushu ),
11310-777: The USAF AIR-2 Genie , the AIM-26 Falcon and US Army Nike Hercules . Missile interceptors such as the Sprint and the Spartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads. Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as antisubmarine weapons. These included nuclear depth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities. The system used to deliver
11455-558: The United States in World War II included both military personnel killed in action and wounded in action . Nearly one million of the casualties occurred during the last year of the war, from June 1944 to June 1945. In December 1944, American battle casualties hit an all-time monthly high of 88,000 as a result of the German Ardennes Offensive . Worried by the losses sustained, President Roosevelt suggested
11600-526: The United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs ), such as the Special Atomic Demolition Munition , have been developed, although the difficulty of combining sufficient yield with portability limits their military utility. Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by
11745-608: The acting chief of staff, since Marshall was at the Potsdam Conference with Truman. It read in part: That day, Truman noted in his diary that: This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as
11890-478: The air echelon, consisting of 29 officers and 61 enlisted men, flew by C-54 to North Field on Tinian, between 15 and 22 May. There were also two representatives from Washington, D.C., Brigadier General Thomas Farrell , the deputy commander of the Manhattan Project, and Rear Admiral William R. Purnell of the Military Policy Committee, who were on hand to decide higher policy matters on
12035-452: The air raids to preserve fighter aircraft to counter the expected invasion. By mid-1945 the Japanese only occasionally scrambled aircraft to intercept individual B-29s conducting reconnaissance sorties over the country, to conserve supplies of fuel. In July 1945, the Japanese had 137,800,000 litres (1,156,000 US bbl) of avgas stockpiled for the invasion of Japan. About 72,000,000 litres (604,000 US bbl) had been consumed in
12180-455: The atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material ( enriched uranium or plutonium ) is forced into supercriticality —allowing an exponential growth of nuclear chain reactions —either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled explosive lenses . The latter approach,
12325-490: The atomic attack, and the Japanese could deny the atomic bomb was lethal, making the mission less likely to produce surrender. Allied prisoners of war might be moved to the demonstration site and be killed by the bomb. They also worried that the bomb might be a failure, as the Trinity test was that of a stationary device, not an air-dropped bomb. In addition, although more bombs were in production, only two would be available at
12470-477: The bombing campaign to be further escalated. Aircraft flying from Allied aircraft carriers and the Ryukyu Islands also regularly struck targets in Japan during 1945 in preparation for Operation Downfall. Firebombing switched to smaller cities, with populations ranging from 60,000 to 350,000. According to Yuki Tanaka , the U.S. fire-bombed over a hundred Japanese towns and cities. The Japanese military
12615-485: The chance of a successful missile defense . Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult. Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines , and nuclear depth charges and torpedoes for anti-submarine warfare . An atomic mortar has been tested by
12760-442: The chance that one of them might be a dud. If the test were made on some neutral territory, it was hard to believe that Japan's determined and fanatical military men would be impressed. If such an open test were made first and failed to bring surrender, the chance would be gone to give the shock of surprise that proved so effective. On the contrary, it would make the Japanese ready to interfere with an atomic attack if they could. Though
12905-426: The city and 267,000 buildings in a single night. It was the deadliest bombing raid of the war, at a cost of 20 B-29s shot down by flak and fighters. By May, 75 percent of bombs dropped were incendiaries designed to burn down Japan's "paper cities". By mid-June, Japan's six largest cities had been devastated. The end of the fighting on Okinawa that month provided airfields even closer to the Japanese mainland, allowing
13050-435: The creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past
13195-411: The dead were civilians. Scholars have extensively studied the effects of the bombings on the social and political character of subsequent world history and popular culture , and there is still much debate concerning the ethical and legal justification for the bombings. According to supporters, the atomic bombings were necessary to bring an end to the war with minimal casualties and ultimately prevented
13340-591: The deaths of approximately 200,000 civilians and military personnel . The ethics of these bombings and their role in Japan's surrender are to this day, still subjects of debate . Since the atomic bombings of Hiroshima and Nagasaki , nuclear weapons have been detonated over 2,000 times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test)
13485-455: The decision process. The prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless terrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the September 11, 2001, attacks , that this complication calls for
13630-527: The defense of all of southern Japan, and was located in Hiroshima Castle . Hata's command consisted of some 400,000 men, most of whom were on Kyushu where an Allied invasion was correctly anticipated. Also present in Hiroshima were the headquarters of the 59th Army , the 5th Division and the 224th Division , a recently formed mobile unit. The city was defended by five batteries of 70 mm and 80 mm (2.8 and 3.1 inch) anti-aircraft guns of
13775-469: The energy of a fission bomb to compress and heat fusion fuel. In the Teller-Ulam design , which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel ( tritium , deuterium , or lithium deuteride ) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, gamma rays and X-rays emitted first compress
13920-470: The entire war. In February 1945, Prince Fumimaro Konoe advised Emperor Hirohito that defeat was inevitable, and urged him to abdicate. Even before the surrender of Nazi Germany on 8 May 1945, plans were underway for the largest operation of the Pacific War, Operation Downfall , the Allied invasion of Japan. The operation had two parts: set to begin in October 1945, Operation Olympic involved
14065-429: The final adjustments of the bomb the Japanese defenders should attack, a faulty move might easily result in some kind of failure. Such an end to an advertised demonstration of power would be much worse than if the attempt had not been made. It was now evident that when the time came for the bombs to be used we should have only one of them available, followed afterwards by others at all-too-long intervals. We could not afford
14210-455: The fission bomb core. The external method of boosting enabled the USSR to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles. The detonation of any nuclear weapon is accompanied by a blast of neutron radiation . Surrounding
14355-420: The fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed neutrons , which can then induce fission in materials not normally prone to it, such as depleted uranium . Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of
14500-535: The globe, would make all life on the planet extinct. In connection with the Strategic Defense Initiative , research into the nuclear pumped laser was conducted under the DOD program Project Excalibur but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target. During
14645-579: The government position. Japan's willingness to surrender remained conditional on the preservation of the kokutai (Imperial institution and national polity ), assumption by the Imperial Headquarters of responsibility for disarmament and demobilization, no occupation of the Japanese Home Islands , Korea or Formosa , and delegation of the punishment of war criminals to the Japanese government. At Potsdam, Truman agreed to
14790-454: The greatest psychological effect against Japan and (2) making the initial use sufficiently spectacular for the importance of the weapon to be internationally recognized when publicity on it is released. ... Kyoto has the advantage of the people being more highly intelligent and hence better able to appreciate the significance of the weapon. Hiroshima has the advantage of being such a size and with possible focussing from nearby mountains that
14935-565: The home islands area in April, May and June 1945. While the Japanese military decided to resume attacks on Allied bombers from late June, by this time there were too few operational fighters available for this change of tactics to hinder the Allied air raids. The discovery of nuclear fission in 1938 made the development of an atomic bomb a theoretical possibility. Fears that a German atomic bomb project would develop atomic weapons first, especially among scientists who were refugees from Nazi Germany and other fascist countries, were expressed in
15080-498: The home islands, backed by a civilian militia of 28 million. Casualty predictions varied widely, but were extremely high. The Vice Chief of the Imperial Japanese Navy General Staff , Vice Admiral Takijirō Ōnishi , predicted up to 20 million Japanese deaths. The Americans were alarmed by the Japanese buildup, which was accurately tracked through Ultra intelligence. On 15 June 1945,
15225-549: The industrial buildings were also built around timber frames. The city as a whole was highly susceptible to fire damage. It was the second largest city in Japan after Kyoto that was still undamaged by air raids, primarily because it lacked the aircraft manufacturing industry that was the XXI Bomber Command's priority target. On 3 July, the Joint Chiefs of Staff placed it off limits to bombers, along with Kokura, Niigata and Kyoto. The population of Hiroshima had reached
15370-472: The leader of the world for the common welfare cannot drop that terrible bomb on the old capital [Kyoto] or the new [Tokyo]. He and I are in accord. The target will be a purely military one. The 16 July success of the Trinity Test in the New Mexico desert exceeded expectations. On 26 July, Allied leaders issued the Potsdam Declaration , which outlined the terms of surrender for Japan. The declaration
15515-412: The matter. Truman agreed with Stimson, and Kyoto was temporarily removed from the target list. Groves attempted to restore Kyoto to the target list in July, but Stimson remained adamant. On 25 July, Nagasaki was put on the target list in place of Kyoto. It was a major military port, one of Japan's largest shipbuilding and repair centers, and an important producer of naval ordnance. In early May 1945,
15660-470: The meetings on 31 May and 1 June, scientist Ernest Lawrence had suggested giving the Japanese a non-combat demonstration. Arthur Compton later recalled that: It was evident that everyone would suspect trickery. If a bomb were exploded in Japan with previous notice, the Japanese air power was still adequate to give serious interference. An atomic bomb was an intricate device, still in the developmental stage. Its operation would be far from routine. If during
15805-407: The midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein , who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor
15950-545: The military establishment have questioned the usefulness of such weapons in the current military climate. According to an advisory opinion issued by the International Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if
16095-408: The missiles before they land or implementing civil defense measures using early-warning systems to evacuate citizens to safe areas before an attack. Weapons designed to threaten large populations or to deter attacks are known as strategic weapons . Nuclear weapons for use on a battlefield in military situations are called tactical weapons . Critics of nuclear war strategy often suggest that
16240-421: The missions over Japan were flown by single unescorted bombers with a single payload to accustom the Japanese to this pattern. They also simulated actual atomic bombing runs, including the directions of ingress and egress with respect to the wind. Tibbets himself was barred from flying most missions over Japan for fear that he might be captured and interrogated. On 5 April 1945, the code name Operation Centerboard
16385-615: The only way to destroy their production capabilities, shifting from precision bombing to area bombardment with incendiaries. Like most strategic bombing during World War II , the aim of the air offensive against Japan was to destroy the enemy's war industries, kill or disable civilian employees of these industries, and undermine civilian morale . Over the next six months, the XXI Bomber Command under LeMay firebombed 64 Japanese cities. The firebombing of Tokyo , codenamed Operation Meetinghouse , on 9–10 March, killed an estimated 100,000 people and destroyed 41 km (16 sq mi) of
16530-605: The possibility of a demonstration that would not destroy human lives was attractive, no one could suggest a way in which it could be made so convincing that it would be likely to stop the war. The possibility of a demonstration was raised again in the Franck Report issued by physicist James Franck on 11 June and the Scientific Advisory Panel rejected his report on 16 June, saying that "we can propose no technical demonstration likely to bring an end to
16675-400: The psychological impact of bombing, and reduce the international stigma of area-bombing cities. Even with the warnings, Japanese opposition to the war remained ineffective. In general, the Japanese regarded the leaflet messages as truthful, with many Japanese choosing to leave major cities. The leaflets caused such concern that the government ordered the arrest of anyone caught in possession of
16820-433: The purpose by Philip Morrison . Magnesium was chosen because it does not act as a neutron reflector . The core departed from Kirtland Army Air Field on a C-54 transport aircraft of the 509th Composite Group's 320th Troop Carrier Squadron on 26 July, and arrived at North Field 28 July. Three Fat Man high-explosive pre-assemblies, designated F31, F32, and F33, were picked up at Kirtland on 28 July by three B-29s, two from
16965-428: The remains of the split atomic nuclei. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of radioactive contamination . Fission products are the principal radioactive component of nuclear fallout . Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in
17110-416: The same precision bombing tactics, with equally unsatisfactory results. The attacks initially targeted key industrial facilities but much of the Japanese manufacturing process was carried out in small workshops and private homes. Under pressure from United States Army Air Forces (USAAF) headquarters in Washington, LeMay changed tactics and decided that low-level incendiary raids against Japanese cities were
17255-439: The site of one of Japan's largest munitions plants; Hiroshima , an embarkation port and industrial center that was the site of a major military headquarters; Yokohama , an urban center for aircraft manufacture, machine tools, docks, electrical equipment and oil refineries; Niigata , a port with industrial facilities including steel and aluminum plants and an oil refinery; and Kyoto , a major industrial center. The target selection
17400-483: The spot. Along with Captain William S. Parsons , the commander of Project Alberta, they became known as the "Tinian Joint Chiefs". In April 1945, Marshall asked Groves to nominate specific targets for bombing for final approval by himself and Stimson. Groves formed a Target Committee, chaired by himself, that included Farrell, Major John A. Derry, Colonel William P. Fisher, Joyce C. Stearns and David M. Dennison from
17545-400: The start of August, and they cost billions of dollars, so using one for a demonstration would be expensive. For several months, the U.S. had warned civilians of potential air raids by dropping more than 63 million leaflets across Japan. Many Japanese cities suffered terrible damage from aerial bombings; some were as much as 97 percent destroyed. LeMay thought that leaflets would increase
17690-402: The surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most commonly used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239 . Less commonly used has been uranium-233 . Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it
17835-498: The survival of the state were at stake. Another deterrence position is that nuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the Cold War between the U.S. and the Soviet Union . In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle , argued in books like The Balance of Terror: Strategy for
17980-425: The uncertainty of a successful detonation and also because of the wish to maximize shock in the leadership . No warning was given to Hiroshima that a new and much more destructive bomb was going to be dropped. Various sources gave conflicting information about when the last leaflets were dropped on Hiroshima prior to the atomic bomb. Robert Jay Lifton wrote that it was 27 July, and Theodore H. McNelly wrote that it
18125-519: The use of a weapon that was "readily available and which assuredly can decrease the cost in American lives": poison gas . Quantities of phosgene , mustard gas , tear gas and cyanogen chloride were moved to Luzon from stockpiles in Australia and New Guinea in preparation for Operation Olympic, and MacArthur ensured that Chemical Warfare Service units were trained in their use. Consideration
18270-408: The use of atomic bombs on Germany as soon as possible, but was informed the first usable atomic weapons were still months away. America's reserves of manpower were running out. Deferments for groups such as agricultural workers were tightened, and there was consideration of drafting women. At the same time, the public was becoming war-weary, and demanding that long-serving servicemen be sent home. In
18415-433: The war, reached disastrous levels by the middle of 1945. The loss of shipping also affected the fishing fleet, and the 1945 catch was only 22 percent of that in 1941. The 1945 rice harvest was the worst since 1909, and hunger and malnutrition became widespread. U.S. industrial production was overwhelmingly superior to Japan's. By 1943, the U.S. produced almost 100,000 aircraft a year, compared to Japan's production of 70,000 for
18560-405: The war; we see no acceptable alternative to direct military use." Franck then took the report to Washington, D.C., where the Interim Committee met on 21 June to re-examine its earlier conclusions; but it reaffirmed that there was no alternative to the use of the bomb on a military target. Like Compton, many U.S. officials and scientists argued that a demonstration would sacrifice the shock value of
18705-446: The weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on submarines or land mobile transporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened missile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy
18850-536: The work was accelerated, first as a pilot program, and finally in the agreement by Roosevelt to turn the work over to the U.S. Army Corps of Engineers to construct the production facilities necessary to produce uranium-235 and plutonium-239 . This work was consolidated within the newly created Manhattan Engineer District, which became better known as the Manhattan Project , eventually under the direction of Major General Leslie R. Groves, Jr. . The work of
18995-631: The world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation, and Waltz, who was somewhat more non- interventionist . Interest in proliferation and the stability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese and South Korean nuclear deterrent against North Korea . The threat of potentially suicidal terrorists possessing nuclear weapons (a form of nuclear terrorism ) complicates
19140-624: The yield comes from the final fissioning of depleted uranium. Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to criticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated,
19285-427: Was 30 July. The USAAF history noted that eleven cities were targeted with leaflets on 27 July, but Hiroshima was not one of them, and there were no leaflet sorties on 30 July. Leaflet sorties were undertaken on 1 and 4 August. Hiroshima may have been leafleted in late July or early August, as survivor accounts talk about a delivery of leaflets a few days before the atomic bomb was dropped. Three versions were printed of
19430-533: Was also given to using biological weapons . While the United States had developed plans for an air campaign against Japan prior to the Pacific War, the capture of Allied bases in the western Pacific in the first weeks of the conflict meant that this offensive did not begin until mid-1944 when the long-ranged Boeing B-29 Superfortress became ready for use in combat. Operation Matterhorn involved India-based B-29s staging through bases around Chengdu in China to make
19575-499: Was assigned. The officer responsible for its allocation in the War Department 's Operations Division was not cleared to know any details of it. The first bombing was later codenamed Operation Centerboard I, and the second, Operation Centerboard II. The 509th Composite Group had an authorized strength of 225 officers and 1,542 enlisted men, almost all of whom eventually deployed to Tinian. In addition to its authorized strength,
19720-467: Was carried out. Two different types of bombs were eventually developed: a gun-type fission weapon that used uranium-235, called Little Boy , and a more complex implosion-type nuclear weapon that used plutonium-239, called Fat Man . There was a Japanese nuclear weapon program , but it lacked the human, mineral, and financial resources of the Manhattan Project, and never made much progress towards developing an atomic bomb. The 509th Composite Group
19865-556: Was chosen to allow for Olympic to complete its objectives, for troops to be redeployed from Europe, and the Japanese winter to pass. Japan's geography made this invasion plan obvious to the Japanese; they were able to predict the Allied invasion plans accurately and thus adjust their defensive plan, Operation Ketsugō , accordingly. The Japanese planned an all-out defense of Kyūshū, with little left in reserve. In all, there were 2.3 million Japanese Army troops prepared to defend
20010-468: Was completed on 15 June, and the target insert on 24 July. The projectile and eight bomb pre-assemblies (partly assembled bombs without the powder charge and fissile components) left Hunters Point Naval Shipyard , California, on 16 July aboard the cruiser USS Indianapolis , and arrived on Tinian on 26 July. The target insert followed by air on 30 July, accompanied by Commander Francis Birch from Project Alberta. Responding to concerns expressed by
20155-454: Was constituted on 9 December 1944, and activated on 17 December 1944, at Wendover Army Air Field , Utah, commanded by Colonel Paul Tibbets . Tibbets was assigned to organize and command a combat group to develop the means of delivering an atomic weapon against targets in Germany and Japan. Because the flying squadrons of the group consisted of both bomber and transport aircraft, the group
20300-460: Was designated as a "composite" rather than a "bombardment" unit. Due to its remoteness, Tibbets selected Wendover for his training base over Great Bend, Kansas and Mountain Home, Idaho . Each bombardier completed at least 50 practice drops of inert or conventional explosive pumpkin bombs , targeting islands around Tinian and later the Japanese home islands, until as late as 14 August 1945. Some of
20445-476: Was presented as an ultimatum and stated that without a surrender, the Allies would attack Japan, resulting in "the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland". The atomic bomb was not mentioned in the communiqué. On 28 July, Japanese papers reported that the declaration had been rejected by the Japanese government. That afternoon, Prime Minister Kantarō Suzuki declared at
20590-471: Was subject to the following criteria: These cities were largely untouched during the nightly bombing raids, and the Army Air Forces agreed to leave them off the target list so accurate assessment of the damage caused by the atomic bombs could be made. Hiroshima was described as "an important army depot and port of embarkation in the middle of an urban industrial area. It is a good radar target and it
20735-576: Was tested on October 18, 1951, being air-dropped from Tupolev Tu-4 . It was the first such test of a nuclear device by the Soviets, known as Joe-3 in the West. It was detonated at an altitude of four hundred meters. The resulting flash could be seen from 170 kilometers away, and the sound heard from around the same distance. The footage of the test was filmed by an instrument tower 7.5 kilometers from ground zero. This article related to nuclear weaponry
20880-744: Was the Special Atomic Demolition Munition , or SADM, sometimes popularly known as a suitcase nuke . This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment. Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include
21025-537: Was unable to stop the Allied attacks and the country's civil defense preparations proved inadequate. Japanese fighters and anti-aircraft guns had difficulty engaging bombers flying at high altitude. From April 1945, the Japanese interceptors also had to face American fighter escorts based on Iwo Jima and Okinawa. That month, the Imperial Japanese Army Air Service and Imperial Japanese Navy Air Service stopped attempting to intercept
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