Nuclear warfare (sometimes atomic warfare or thermonuclear warfare), is a military conflict or political strategy in which nuclear weaponry is used to inflict damage on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage, and in a much shorter time scale. A major nuclear exchange could have severe long-term effects, primarily from radiation release, but also from the production of high levels of atmospheric pollution leading to a "nuclear winter" that could last for decades, centuries, or even millennia after the initial attack. A large nuclear war is considered to bear existential risk for civilization on Earth.
Only 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 exploded over Nagasaki, Japan. These two bombings resulted in the deaths of approximately 200,000 Japanese people (mostly civilians) from acute injuries sustained in the detonations.
After World War II, nuclear weapons were also developed by the Soviet Union (1940s), the United Kingdom and France (1950s), and the People's Republic of China (1960's), which contributed to the state of conflict and extreme tension that became known as the Cold War. In the 1970s, India, and in the 1990s, Pakistan, two countries that were openly hostile toward each other, developed nuclear weapons. Israel (1960s) and North Korea (2000s) are also thought to have developed stocks of nuclear weapons, and have made the political decision to retain them to the present time. South Africa also manufactured several complete nuclear weapons in the 1980s, but subsequently became the first country to voluntarily destroy their domestically made weapons stocks and abandon further production (1990s).
Nuclear weapons have been detonated on over two thousand occasions for testing purposes and demonstrations.
After the collapse of the Soviet Union in 1991 and the resultant end of the Cold War, the threat of a major nuclear war between the two nuclear superpowers was generally thought to have declined. Since then, concern over nuclear weapons has shifted to the prevention of localized nuclear conflicts resulting from nuclear proliferation, and the threat of nuclear terrorism.
Types of nuclear warfare
The possibility of using nuclear weapons in war is usually divided into two subgroups, each with different effects and potentially fought with different types of nuclear armaments.
The first, a limited nuclear war (sometimes attack or exchange), refers to a small-scale use of nuclear weapons by two (or more) belligerents. A "limited nuclear war" could include targeting military facilities - either as an attempt to pre-emptively cripple the enemy's ability to attack as a defensive measure, or as a prelude to an invasion by conventional forces, as an offensive measure. This term could apply to any small-scale use of nuclear weapons that may involve military or civilian targets (or both).
The second, a full-scale nuclear war, could consist of large numbers of nuclear weapons used in an attack aimed at an entire country, including military, economic, and civilian targets. Such an attack would almost certainly destroy the entire economic, social, and military infrastructure of the target nation, and would probably have a devastating effect on Earth's biosphere.
Some Cold War strategists such as Henry Kissinger argue that a limited nuclear war could be possible between two heavily armed superpowers (such as the United States and the Soviet Union). Some predict, however, that a limited war could potentially "escalate" into a full-scale nuclear war. Others have called limited nuclear war "global nuclear holocaust in slow motion" - arguing that once such a war took place, others would be sure to follow over a period of decades, effectively rendering the planet uninhabitable in the same way that a "full-scale nuclear war" between superpowers would, only taking a much longer (and arguably more agonizing) path to the same result.
Even the most optimistic predictions of the effects of a major nuclear exchange foresee the death of many millions of victims within a very short period of time. More pessimistic predictions argue that a full-scale nuclear war could potentially bring about the extinction of the human race, or at least its near extinction, with only a relatively small number of survivors (mainly in remote areas) and a reduced quality of life and life expectancy for centuries afterward. Such a horrific catastrophe would almost certainly cause permanent damage to most complex life on the planet, its ecosystems, and the global climate - particularly if predictions about the production of a nuclear winter are accurate.
A study presented at the annual meeting of the American Geophysical Union in December 2006 asserted that even a small-scale regional nuclear war could produce as many direct fatalities as all of World War II and disrupt the global climate for a decade or more. In a regional nuclear conflict scenario in which two opposing nations in the subtropics each used 50 Hiroshima-sized nuclear weapons (ca. 15 kiloton each) on major population centers, the researchers predicted fatalities ranging from 2.6 million to 16.7 million per country. Also, they estimated that as much as five million tons of soot could be released, producing a cooling of several degrees over large areas of North America and Eurasia (including most of the grain-growing regions). The cooling would last for years and could be "catastrophic", according to the researchers.
Either a limited or full-scale nuclear exchange could occur during an accidental nuclear war, in which the use of nuclear weapons is triggered unintentionally. Postulated triggers for this scenario have included malfunctioning early warning devices and/or targeting computers, deliberate malfeasance by rogue military commanders, consequences of an accidental straying of warplanes into enemy airspace, reactions to unannounced missile tests during tense diplomatic periods, reactions to military exercises, mistranslated or misscommunicated messages, and others. A number of these scenarios actually occurred during the Cold War, though none resulted in the use of nuclear weapons. Many such scenarios have been depicted in popular culture, such as in the 1962 novel Fail-Safe (released as a film in 1964), and the film Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb, also released in 1964.
Atomic bombings of Hiroshima and Nagasaki
Mushroom cloud from the atomic explosion over Nagasaki rising 60,000 feet into the air on the morning of August 9, 1945.
During the final stages of World War II in 1945, the United States conducted two atomic bombings against the Japanese cities of Hiroshima and Nagasaki, the first on August 6, 1945, and the second on August 9, 1945. These two events are the only use of nuclear weapons in war to date.
For six months before the atomic bombings, the United States intensely fire-bombed 67 Japanese cities. Together with the United Kingdom and the Republic of China, the United States called for the unconditional surrender of Japan in the Potsdam Declaration issued July 26, 1945. The Japanese government ignored this ultimatum. By executive order of President Harry S. Truman, the U.S. employed the uranium-type nuclear weapon code named "Little Boy" on the city of Hiroshima on Monday, August 6, 1945, followed three days later by the detonation of the plutonium-type weapon code named "Fat Man" over the city of Nagasaki on August 9.
Within the first two to four months after the bombings, acute effects killed 90,000 166,000 people in Hiroshima and 60,000 80,000 in Nagasaki, with roughly half of the deaths in each city occurring in the first 24 hours. The Hiroshima prefectural health department estimates that - of the people who died on the day of the detonation - 60% died from flash or flame burns, 30% from falling or flying debris, and 10% from other causes. During the following months, large numbers died from the chronic effects of burns, radiation sickness, and other injuries, compounded by illnesses. In a U.S. estimate of the total immediate and short-term causes of death, 15 20% died from radiation sickness, 20 30% from flash burns, and 50 60% from other injuries, compounded by illnesses. In both cities, most of the dead were civilians.
Six days after the detonation over Nagasaki, on August 15, 1945, Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on September 2, 1945, officially ending the Pacific War and, therefore, World War II, as Germany had already signed its Instrument of Surrender on May 7, 1945, ending the war in Europe. The two atomic bombings led, in part, to post-war Japan's adopting of the Three Non-Nuclear Principles, which forbade the nation from developing nuclear armaments. The role of the bombings in the surrender of Japan, the ethical justification of the US for using them, as well as their strategic importance, is still hotly debated.
Immediately after the Japan bombings
Immediately after the atomic bombings of Japan, the status of atomic weapons in international and military relations was unclear. Presumably, the United States hoped atomic weapons could offset the Soviet Union's larger conventional ground forces in Eastern Europe, and possibly be used to pressure Soviet leader Joseph Stalin into making concessions. Under Stalin, the Soviet Union pursued its own atomic capabilities through a combination of scientific research and espionage directed against the American program. The Soviets believed that the Americans, with their limited nuclear arsenal, were unlikely to engage in any new world wars, while the Americans were not confident they could prevent a Soviet takeover of Europe, despite their atomic advantage.
Within the United States the authority to produce and develop nuclear weapons was removed from military control and put instead under the civilian control of the United States Atomic Energy Commission. This decision reflected an understanding that nuclear weapons had unique risks and benefits that were separate from other military technology known at the time.
For several years after World War II, the US developed and maintained a strategic force based on the Convair B-36 bomber that would be able to attack any potential enemy from bomber bases in the US. It deployed atomic bombs around the world for potential use in conflicts. Over a period of a few years, many in the US defense community became increasingly convinced of the invincibility of the United States to a nuclear attack. Indeed, it became generally believed that the threat of nuclear war would deter any strike against the United States.
Many proposals were suggested to put all US nuclear weapons under international control (by the newly formed United Nations, for example) as an effort to deter both their usage and an arms race. However, no terms could be arrived at that would be agreed upon by both the US and the USSR.
US and USSR nuclear stockpiles.
On August 29, 1949 the USSR tested its first nuclear weapon at Semipalatinsk in Kazakhstan (see also Soviet atomic bomb project). Scientists in the United States from the Manhattan Project had warned that, in time, the Soviet Union would certainly develop nuclear capabilities of its own. Nevertheless, the effect upon military thinking and planning in the US was dramatic, primarily because American military strategists had not anticipated the Soviets would "catch up" so soon. However, at this time, they had not discovered that the Russians had conducted significant nuclear espionage of the project from spies at Los Alamos, the most significant of which was done by the theoretical physicist Klaus Fuchs. The first Soviet bomb was more or less a deliberate copy of the Fat Man plutonium device.
With the monopoly over nuclear technology broken, worldwide nuclear proliferation accelerated. The United Kingdom tested its first independent atomic bomb in 1952, followed by France in 1960 and then the People's Republic of China in 1964. While much smaller than the arsenals of the US and the USSR, Western Europe's nuclear reserves were nevertheless a significant factor in strategic planning during the Cold War. A top-secret White Paper, compiled by the Royal Air Force and produced for the British Government in 1959, estimated that British atomic bombers were capable of destroying key cities and military targets in the Soviet Union, with an estimated 16 million deaths in the USSR (half of whom were estimated to be killed on impact and the rest fatally injured) before bomber aircraft from the US Strategic Air Command reached their targets.
Though the USSR had nuclear weapon capabilities in the beginning of the Cold War, the US still had an advantage in terms of bombers and weapons. In any exchange of hostilities, the US would have been capable of bombing the USSR, while the USSR would have more difficulty carrying out the reverse mission.
The widespread introduction of jet-powered interceptor aircraft upset this imbalance somewhat by reducing the effectiveness of the US bomber fleet. In 1949 Curtis LeMay was placed in command of the Strategic Air Command and instituted a program to update the bomber fleet to one that was all-jet. During the early 1950s the B-47 and B-52 were introduced, providing the ability to bomb the USSR more easily. Before the development of a capable strategic missile force in the Soviet Union, much of the war-fighting doctrine held by western nations revolved around using a large number of smaller nuclear weapons used in a tactical role. It is debatable whether such use could be considered "limited" however, because it was believed that the US would use their own strategic weapons (mainly bombers at the time) should the USSR deploy any kind of nuclear weapon against civilian targets. Douglas MacArthur, an American general, was fired by President Harry Truman, partially because he persistently requested permission to use his own discretion in deciding whether to use atomic weapons on the People's Republic of China in 1951 during the Korean War. Mao Zedong, China's communist leader, gave the impression that he would welcome a nuclear war with the capitalists because it would annihilate their imperialist system.
nuclear tests]] at the Nevada Test Site. Several scares about the increasing ability of the USSR's strategic bomber forces surfaced during the 1950s. The defensive response by the US was to deploy a fairly strong "layered defense" consisting of interceptor aircraft and anti-aircraft missiles, like the Nike, and guns, like the Skysweeper, near larger cities. However, this was a small response compared to the construction of a huge fleet of nuclear bombers. The principal nuclear strategy was to massively penetrate the USSR. Because such a large area could not be defended against this overwhelming attack in any credible way, the USSR would lose any exchange.
This logic became ingrained in US nuclear doctrine and persisted for much of the duration of the Cold War. As long as the strategic US nuclear forces could overwhelm their USSR counterparts, a Soviet preemptive strike could be averted. Moreover, the USSR could not afford to build any reasonable counterforce, as the economic output of the United States was far larger than that of the Soviets, and they would be unable to achieve "nuclear parity".
Soviet nuclear doctrine, however, did not match US nuclear doctrine. Soviet planning expected a large-scale nuclear exchange, followed by a "conventional war" which itself would involve heavy use of tactical nuclear weapons. Unfortunately, US doctrine rather assumed that Soviet doctrine was similar, with the mutual in Mutually Assured Destruction necessarily requiring that the other side see things in much the same way, rather than believing - as the Soviets did - that they could fight a large-scale, "combined nuclear and conventional" war.
A revolution in nuclear strategic thought occurred with the introduction of the intercontinental ballistic missile (ICBM), which the USSR first successfully tested in August 1957. In order to deliver a warhead to a target, a missile was much faster and more cost-effective than a bomber, and enjoyed a higher survivability due to the enormous difficulty of interception of the ICBMs (due to their high altitude and extreme speed). The USSR could now afford to achieve nuclear parity with the US in terms of raw numbers, although for a time, they appeared to have chosen not to.
Photos of Soviet missile sites set off a wave of panic in the US military, something the launch of Sputnik would do for the American public a few months later. Politicians, notably then-US Senator John F. Kennedy suggested that a "missile gap" existed between the Soviets and the US. The US military gave missile development programs the highest national priority, and several spy aircraft and reconnaissance satellites were designed and deployed to observe Soviet progress.
Early ICBMs and bombers were relatively inaccurate, which led to the concept of countervalue strikes attacks directly on the enemy population, which would theoretically lead to a collapse of the enemy's will to fight. During the Cold War the USSR invested in extensive protected civilian infrastructure, such as large "nuclear-proof" bunkers and non-perishable food stores. In the US, by comparison, smaller scale civil defense programs were instituted starting in the 1950s, where schools and other public buildings had basements stocked with non-perishable food supplies, canned water, first aid, and dosimeter and Geiger counter radiation-measuring devices. Many of the locations were given "Fallout Shelter" designation signs. Also, CONELRAD Radio information systems were adopted, whereby the commercial radio sector would broadcast on two AM frequencies in the event of a Civil Defense (CD) emergency. These two frequencies can still be seen on 1950s-vintage radios on online auction sites and museums, with many of these radios are still in use on tabletops across America. Also, the occasional backyard fallout shelter was built by private individuals.
An extensive, complicated, and worrisome situation developed in 1962, in what is called the Cuban Missile Crisis. The Soviet Union placed medium-range ballistic missiles from the US - a move considered by many as a direct response to American Jupiter missiles placed in Turkey. After intense negotiations, the Soviets ended up removing the missiles from Cuba and decided to institute a massive weapons-building program of their own. In exchange, the US dismantled its launch sites in Turkey, although this was done secretly and not publicly revealed for over two decades. Khrushchev did not even reveal this part of the agreement when he came under fire by political opponents for mishandling the crisis.
By the late 1960s, the number of ICBMs and warheads was so high on both sides that it was believed that both the US and the USSR were capable of completely destroying the infrastructure and population of the other country. Thus, a balance of power system known as mutually assured destruction (or MAD) came into being. It was thought that any full-scale exchange between the powers could not produce a victorious side, and thus neither would willingly risk initiating one.
One drawback of the MAD doctrine was the possibility of a nuclear war occurring without either side intentionally striking first. Warning system\Early Warning Systems (EWS) were notoriously error-prone. For example, on 78 occasions in 1979 alone, a "missile display conference" was called to evaluate detections that were "potentially threatening to the North American continent". Some of these were trivial errors and were spotted quickly, but several went to more serious levels. On September 26, 1983, Stanislav Petrov received convincing indications of a US first strike launch against the USSR, but positively identified the warning as a false alarm. Though it is unclear what role Petrov's actions played in preventing a nuclear war during this incident, he has been honored by the United Nations for his actions.
Similar incidents happened many times in the US, due to failed computer chips, misidentifications of large flights of geese, test programs, and bureaucratic failures to notify early warning military personnel of legitimate launches of test or weather missiles. For many years, US strategic bombers were kept airborne on a daily rotating basis "around the clock", until the number and severity of accidents persuaded policymakers it was not worthwhile.
By the late 1970s, citizens in the US and USSR (and indeed the entire world) had been living with the concept of MAD for about a decade, and it became deeply ingrained into the popular culture. Such an exchange would have killed many millions of individuals directly, and possibly induced a nuclear winter which could have led to the death of a large portion of humanity and - potentially - the collapse of global civilization.
On May 18, 1974, India conducted its first nuclear test in the Pokhran test range. The name of the operation was Smiling Buddha, and India termed the test as a "peaceful nuclear explosion".
According to the 1980 United Nations report General and Complete Disarmament: Comprehensive Study on Nuclear Weapons: Report of the Secretary-General, it was estimated that there were a total of about 40,000 nuclear warheads in existence at that time, with a potential combined explosive yield of approximately 13,000 megatons. By comparison, when the volcano Mount Tambora erupted in 1815 - turning 1816 into the Year Without A Summer due to the levels of ash expelled) - it exploded with a force of roughly 1,000 megatons. Many people believed that a full-scale nuclear war would result in the extinction of the human species, though not all analysts agreed on the assumptions required for these models.
The idea that any nuclear conflict would eventually escalate was a challenge for military strategists. This challenge was particularly severe for the United States and its NATO allies because it was believed (until the 1970s) that a Soviet tank invasion of Western Europe would quickly overwhelm NATO conventional forces, leading to the necessity of the West escalating to the use of tactical nuclear weapons.
This strategy had one major (and possibly critical) flaw, which was soon realised by military analysts but highly underplayed by the US military: conventional NATO forces in the European theatre of war were far outnumbered by similar Soviet and Warsaw Pact forces, and it was assumed that in case of a major Soviet attack (commonly envisioned as the "Red tanks rolling towards the North Sea" scenario) that NATO - in the face of quick conventional defeat - would soon have no other choice but to resort to tactical nuclear strikes against these forces. Most analysts agreed that once the first nuclear exchange had occurred, escalation to global nuclear war would likely become inevitable.
fall-out]] is indicated with the darkest considered as "lethal" to relatively fall-out free yellow zones. In the late 1970s and, particularly, during the early 1980s under US President Ronald Reagan, the US renewed its commitment to a more powerful military, which required a large increase in spending on US military programs. These programs, which were originally part of the defense budget of US President Jimmy Carter, included spending on conventional and nuclear weapons systems. Under Reagan, defensive systems like the Strategic Defense Initiative became emphasized as well.
Montage of the launch of a Trident C4 SLBM
and the paths of its reentry vehicles.
Another major shift in nuclear doctrine was the development and the improvement of the submarine-launched, nuclear-armed, ballistic missile, or SLBM. It was hailed by many military theorists as a weapon that would make nuclear war less likely. SLBMs - which can move with "stealth" (greatly lessened detectibility) virtually anywhere in the world - give a nation a "second strike" capability (i.e. after absorbing a "first strike"). Before the advent of the SLBM, thinkers feared that a nation might be tempted to initiate a first strike if it felt confident that such a strike would incapacitate the nuclear arsenal of its enemy, making retaliation impossible. With the advent of SLBMs, no nation could be certain that a first strike would incapacitate its enemy's entire nuclear arsenal. To the contrary, it would have to fear a (near certain) retaliatory second strike from SLBMs. Thus a first strike was a much less of feasible (or desirable) option, and a (deliberately initiated) nuclear war was thought to be less likely to start.
However, it was soon realized that submarines could "sneak up" close to enemy coastlines and decrease the "warning time" (the time between detection of the missile launch and the impact of the missile) from as much as half an hour to possibly under three minutes. This effect was especially significant to the United States, Britain, India and China, whose capitals all lay within of their coasts. Moscow was much more secure from this type of threat, due to its considerable distance from the sea. This greatly increased the credibility of a "surprise first strike" by one faction and (theoretically) made it possible to knock out or disrupt the chain of command of a target nation before any counterstrike could be ordered (known as a "decapitation strike". It strengthened the notion that a nuclear war could possibly be "won" - resulting not only in greatly increased tensions and increasing calls for fail-deadly control systems, but also in a dramatic increase in military spending. The submarines and their missile systems were very expensive, and one fully equipped nuclear-powered and nuclear-armed missile submarine could cost more than the entire GNP of a developing country). It was also calculated, however, that the greatest cost came in the development of both sea- and land-based anti-submarine defenses and in improving and strengthening the "chain of command", and as a result, military spending skyrocketed.
South Africa developed a nuclear weapon capability during the 1970s and early 1980s. It was operational for a brief period before being dismantled in the early 1990s.
On Sept. 1, 1983, Korean Air Lines Flight 007 was shot down by Soviet jet fighters. On the 26th, a Soviet early warning station under the command of Stanislav Petrov falsely detected 5 inbound intercontinental ballistic missiles from the US. Petrov correctly assessed the situation as a false alarm, and hence did not report his finding to his superiors. It is quite possible that his actions prevented "World War III", as the Soviet policy at that time was immediate nuclear response upon discovering inbound ballistic missiles.
The world came unusually close to nuclear war - although perhaps not as close as during the Cuban Missile Crisis - when the Soviet Union thought that the NATO military exercise Able Archer 83 was a ruse or "cover up" to begin a nuclear first strike. The Soviets responded by raising readiness and preparing their nuclear arsenal for immediate use. Soviet fears of an attack went away once the exercise concluded without incident.
Post Cold War
Although the dissolution of the Soviet Union ended the Cold War and greatly reduced tensions between the United States and the Russian Federation (the Soviet Union's formal successor state), both nations remained in a "nuclear stand-off" due to the continuing presence of a very large number of deliverable nuclear warheads in both nations. Additionally, the end of the Cold War led the United States to become increasingly concerned with the development of nuclear technology by other nations outside of the former Soviet Union. In 1995, a branch of the US Strategic Command produced an outline of forward-thinking strategies in the document "Essentials of Post Cold War Deterrence".
The former chair of the United Nations disarmament committee stated that there are more than 16,000 strategic and tactical nuclear weapons ready for deployment and another 14,000 in storage, with the U.S. having nearly 7,000 ready for use and 3,000 in storage, and Russia having about 8,500 ready for use and 11,000 in storage. In addition, China is thought to possess about 400 nuclear weapons, Britain about 200, France about 350, India about 120, and Pakistan about 90. North Korea is confirmed as having nuclear weapons, though it is not known how many, with most estimates between 1 and 10. Israel is also widely believed to possess usable nuclear weapons. NATO has stationed about 480 American nuclear weapons in Belgium, the Netherlands, Italy, Germany, and Turkey, and several other nations are thought to be in pursuit of an arsenal of their own.
A key development in nuclear warfare during the decade of the 2000s and after has been the proliferation of nuclear weapons to the developing world, with India and Pakistan both publicly testing several nuclear devices, and North Korea conducting an underground nuclear test on October 9, 2006. The US Geological Survey measured a 4.2 magnitude earthquake in the area where the North Korean test is said to have occurred. A further test was announced by the North Korean government on May 25, 2009. Iran, meanwhile, has embarked on a nuclear program which - while officially for civilian purposes - has come under close scrutiny by the United Nations and many individual states.
Recent studies undertaken by the CIA cite the enduring India-Pakistan conflict as the one "flash point" most likely to escalate into a nuclear war. During the Kargil War in 1999, Pakistan came close to using its nuclear weapons in case the conventional military situation underwent further deterioration. Pakistan's foreign minister had even warned that it would "use any weapon in our arsenal", hinting at a nuclear strike against India. The statement was condemned by the international community, with Pakistan denying it later on. This conflict remains the only war (of any sort) between two declared nuclear powers. The 2001-2002 India-Pakistan standoff again stoked fears of nuclear war between the two countries. Despite these very serious and relatively recent threats, relations between India and Pakistan have been improving somewhat over the last few years. A bus line directly linking Indian- and Pakistani-administered Kashmir has recently been established. However, with the November 26, 2008 Mumbai terror attacks, India currently will not rule out war with Pakistan.
Another potential geopolitical issue which is considered particularly worrisome by miliitary analysts is a possible conflict between the United States and the People's Republic of China over Taiwan. Although economic forces are thought to have decreased somewhat the possibility of a military conflict, there remains the worry that the increasing military buildup of (China is rapidly increasing their naval capacity, and that any move toward Taiwan independence could potentially spin out of control).
Israel is thought to possess somewhere between one hundred and four hundred nuclear warheads. It has been asserted that the submarines which Israel received from Germany have been adapted to carry missiles with nuclear warheads, so as to give Israel a second strike capability. Israel has been involved in wars with its neighbors in the Middle East (and with other "non-state actors") on numerous prior occasions, and its small geographic size and population could mean that, in the event of future wars, the Israeli military might have very little time to react to an invasion or other major threat. Such a situation could escalate to nuclear warfare very quickly in some scenarios.
In the Persian Gulf, Iran appears to many observers to be in the process of developing a nuclear weapon, which has greatly heightened fears of a nuclear conflict and arms races in the Middle East either with Israel or with one or more Arab states (a "Shia-Sunni" conflict).
The above examples envisage nuclear warfare at a strategic level, i.e. total war. However, nuclear powers have the ability to undertake more limited engagements.
"Sub-strategic use" includes the use of either "low-yield" tactical nuclear weapons, or of "scalable-yield" ("dialable-yield") strategic nuclear weapons in a very limited role, as compared to battlefield exchanges of larger-yield strategic nuclear weapons. This was described by the UK Parliamentary Defence Select Committee as "the launch of one or a limited number of missiles against an adversary as a means of conveying a political message, warning or demonstration of resolve". It is believed that all current nuclear weapons states possess tactical nuclear weapons, with the exception of the United Kingdom, which decommissioned its tactical warheads in 1998. However, the UK does possess scalable-yield strategic warheads, and this technology tends to blur the difference between "strategic", "sub-strategic", and "tactical" use or weapons. American, French and British nuclear submarines are believed to carry at least some missiles with these types of high-tech warheads for this purpose - potentially allowing a strike as low as one kiloton (or less) against a single target. Only the People's Republic of China and the Republic of India have declarative, unqualified, unconditional "no first use" nuclear weapons policies.
Commodore Tim Hare, former Director of Nuclear Policy at the British Ministry of Defence, has described "sub-strategic use" as offering the Government "an extra option in the escalatory process before it goes for an all-out strategic strike which would deliver unacceptable damage". However, this sub-strategic capacity has been criticized as potentially increasing the "acceptability" of using nuclear weapons. The related consideration of new generations of limited-yield nuclear weapons by the United States (i.e. "bunker busters") has also alarmed anti-nuclear groups, who believe it will make the use of nuclear weapons "more acceptable" or likely.
Also of note is that the United States adopted a policy in 1996 of allowing the targeting of its nuclear weapons at non-state actors armed with weapons of mass destruction.
Nuclear terrorism by non-state organizations or actors (even individuals) is a largely unknown and understudied factor in nuclear deterrence thinking, as states possessing nuclear weapons are susceptible to retaliation in kind, while sub- or trans-state actors may be less so. The collapse of the Soviet Union has given rise to the possibility that former Soviet nuclear weapons might become available on the black market (so-called 'loose nukes'). While no warheads are known to have been mislaid, it has been alleged that at least some very small or suitcase-size bombs might be unaccounted for.
A number other concerns have been expressed about the security of nuclear weapons in other, newer nuclear powers with relatively less stable governments, such as Pakistan, but in each case, the fears have been addressed to some extent by statements and evidence provided by those nations, as well as cooperative programs between nations. Worry remains, however, in many circles that a relative decrease in security of nuclear weapons has emerged in recent years, and that terrorists or others may attempt to exert control over (or use) nuclear weapons, militarily applicable technology, or nuclear materials and fuel.
Another possible nuclear terrorism threat are devices designed to disperse radioactive materials over a large area using conventional explosives, called dirty bombs. The detonation of a "dirty bomb" would not cause a nuclear explosion, nor would it release enough radiation to kill or injure a lot of people. However, it could cause severe disruption and require potentially very costly decontamination procedures and increased spending on security measures.
Post nuclear exchange:
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