Deterrence theory is the idea that an inferior force, by virtue of the destructive power of the force's weapons, could deter a more powerful adversary, provided that this force could be protected against destruction by a surprise attack. This doctrine gained increased prominence as a military strategy during the Cold War with regard to the use of nuclear weapons and is related to, but distinct from, the concept of Mutual assured destruction, which models the preventative nature of full-scale nuclear attack that would devastate both parties in a nuclear war. Deterrence is a strategy intended to dissuade an adversary from taking an action not yet started by means of threat of reprisal, or to prevent them from doing something that another state desires. The strategy is based on the psychological concept of the same name. A credible nuclear deterrent, Bernard Brodie wrote in 1959, must be always at the ready, yet never used.[a]
In Thomas Schelling's (1966) classic work on deterrence, the concept that military strategy can no longer be defined as the science of military victory is presented. Instead, it is argued that military strategy was now equally, if not more, the art of coercion, of intimidation and deterrence. Schelling says the capacity to harm another state is now used as a motivating factor for other states to avoid it and influence another state's behavior. To be coercive or deter another state, violence must be anticipated and avoidable by accommodation. It can therefore be summarized that the use of the power to hurt as bargaining power is the foundation of deterrence theory, and is most successful when it is held in reserve.
In 2004 Frank C. Zagare made the case that deterrence theory is logically inconsistent, not empirically accurate, and that it is deficient as a theory. In place of classical deterrence, rational choice scholars have argued for perfect deterrence, which assumes that states may vary in their internal characteristics and especially in the credibility of their threats of retaliation.
In a January 2007 article in the Wall Street Journal, veteran cold-war policy makers Henry Kissinger, Bill Perry, George Shultz, and Sam Nunn reversed their previous position and asserted that far from making the world safer, nuclear weapons had become a source of extreme risk. Their rationale and conclusion was not based on the old world with only a few nuclear players, but on the instability in many states possessing the technologies and the lack of wherewithal to properly maintain and upgrade existing weapons in many states:
The risk of accidents, misjudgments or unauthorised launches, they argued, was growing more acute in a world of rivalries between relatively new nuclear states that lacked the security safeguards developed over many years by America and the Soviet Union. The emergence of pariah states, such as North Korea (possibly soon to be joined by Iran), armed with nuclear weapons was adding to the fear as was the declared ambition of terrorists to steal, buy or build a nuclear device.-- The Economist, June 16, 2011
According to The Economist, "Senior European statesmen and women" called for further action in 2010 in addressing problems of nuclear weapons proliferation. They said: "Nuclear deterrence is a far less persuasive strategic response to a world of potential regional nuclear arms races and nuclear terrorism than it was to the cold war".
The use of military threats as a means to deter international crises and war has been a central topic of international security research for at least 200 years. Research has predominantly focused on the theory of rational deterrence to analyze the conditions under which conventional deterrence is likely to succeed or fail. Alternative theories however have challenged the rational deterrence theory and have focused on organizational theory and cognitive psychology.
The concept of deterrence can be defined as the use of threats by one party to convince another party to refrain from initiating some course of action. A threat serves as a deterrent to the extent that it convinces its target not to carry out the intended action because of the costs and losses that target would incur. In international security, a policy of deterrence generally refers to threats of military retaliation directed by the leaders of one state to the leaders of another in an attempt to prevent the other state from resorting to the threat of use of military force in pursuit of its foreign policy goals.
As outlined by Huth, a policy of deterrence can fit into two broad categories being (i) preventing an armed attack against a state's own territory (known as direct deterrence); or (ii) preventing an armed attack against another state (known as extended deterrence). Situations of direct deterrence often occur when there is a territorial dispute between neighboring states in which major powers like the United States do not directly intervene. On the other hand, situations of extended deterrence often occur when a great power becomes involved. It is the latter that has generated the majority of interest in academic literature. Building on these two broad categories, Huth goes on to outline that deterrence policies may be implemented in response to a pressing short-term threat (known as immediate deterrence) or as strategy to prevent a military conflict or short term threat from arising (known as general deterrence).
A successful deterrence policy must be considered in not only military terms, but also in political terms; specifically International Relations (IR), foreign policy and diplomacy. In military terms, deterrence success refers to preventing state leaders from issuing military threats and actions that escalate peacetime diplomatic and military cooperation into a crisis or militarized confrontation which threatens armed conflict and possibly war. The prevention of crises of wars however is not the only aim of deterrence. In addition, defending states must be able to resist the political and military demands of a potential attacking nation. If armed conflict is avoided at the price of diplomatic concessions to the maximum demands of the potential attacking nation under the threat of war, then it cannot be claimed that deterrence has succeeded.
Furthermore, as Jentleson et al. argue, two key sets of factors for successful deterrence are important being (i) a defending state strategy that firstly balances credible coercion and deft diplomacy consistent with the three criteria of proportionality, reciprocity, and coercive credibility, and secondly minimizes international and domestic constraints; and (ii) the extent of an attacking state's vulnerability as shaped by its domestic political and economic conditions. In broad terms, a state wishing to implement a strategy of deterrence is most likely to succeed if the costs of non-compliance it can impose on, and the benefits of compliance it can offer to, another state are greater than the benefits of noncompliance and the costs of compliance.
Deterrence theory holds that nuclear weapons are intended to deter other states from attacking with their nuclear weapons, through the promise of retaliation and possibly mutually assured destruction (MAD). Nuclear deterrence can also be applied to an attack by conventional forces; for example, the doctrine of massive retaliation threatened to launch US nuclear weapons in response to Soviet attacks.
A successful nuclear deterrent requires that a country preserve its ability to retaliate, either by responding before its own weapons are destroyed or by ensuring a second strike capability. A nuclear deterrent is sometimes composed of a nuclear triad, as in the case of the nuclear weapons owned by the United States, Russia, the People's Republic of China and India. Other countries, such as the United Kingdom and France, have only sea- and air-based nuclear weapons.
Jentleson et al. provide further detail in relation to these factors. Firstly, proportionality refers to the relationship between the defending state's scope and nature of the objectives being pursued, and the instruments available for use to pursue this. The more the defending state demands of another state, the higher that state's costs of compliance and the greater need for the defending state's strategy to increase the costs of noncompliance and the benefits of compliance. This is a challenge, as deterrence is, by definition, a strategy of limited means. George (1991) goes on to explain that deterrence may, but is not required to, go beyond threats to the actual use of military force; but if force is actually used, it must be limited and fall short of full-scale use or war otherwise it fails. The main source of disproportionality is an objective that goes beyond policy change to regime change. This has been seen in the cases of Libya, Iraq, and North Korea where defending states have sought to change the leadership of a state in addition to policy changes relating primarily to their nuclear weapons programs.
Secondly, Jentleson et al. outline that reciprocity involves an explicit understanding of linkage between the defending state's carrots and the attacking state's concessions. The balance lies neither in offering too little too late or for too much in return, not offering too much too soon or for too little return.
Finally, coercive credibility requires that, in addition to calculations about costs and benefits of cooperation, the defending state convincingly conveys to the attacking state that non-cooperation has consequences. Threats, uses of force, and other coercive instruments such as economic sanctions must be sufficiently credible to raise the attacking state's perceived costs of noncompliance. A defending state having a superior military capability or economic strength in itself is not enough to ensure credibility. Indeed, all three elements of a balanced deterrence strategy are more likely to be achieved if other major international actors like the United Nations or NATO are supportive and if opposition within the defending state's domestic politics is limited.
The other important consideration outlined by Jentleson et al. that must be taken into consideration is the domestic political and economic conditions within the attacking state affecting its vulnerability to deterrence policies, and the attacking state's ability to compensate unfavourable power balances. The first factor is whether internal political support and regime security are better served by defiance, or if there are domestic political gains to be made from improving relations with the defending state. The second factor is an economic calculation of the costs that military force, sanctions, and other coercive instruments can impose, and the benefits that trade and other economic incentives may carry. This in part is a function of the strength and flexibility of the attacking state's domestic economy and its capacity to absorb or counter the costs being imposed. The third factor is the role of elites and other key domestic political figures within the attacking state. To the extent these actors' interests are threatened with the defending state's demands, they act to prevent or block the defending state's demands.
The predominant approach to theorizing about deterrence has entailed the use of rational choice and game-theoretic models of decision making (see game theory). Deterrence theorists have consistently argued that deterrence success is more likely if a defending state's deterrent threat is credible to an attacking state. Huth outlines that a threat is considered credible if the defending state possesses both the military capabilities to inflict substantial costs on an attacking state in an armed conflict, and if the attacking state believes that the defending state is resolved to use its available military forces. Huth goes on to explain the four key factors for consideration under rational deterrence theory being (i) the military balance; (ii) signaling and bargaining power; (iii) reputations for resolve; and (iv) interests at stake.
Deterrence is often directed against state leaders who have specific territorial goals that they seek to attain either by seizing disputed territory in a limited military attack or by occupying disputed territory after the decisive defeat of the adversary's armed forces. In either case, the strategic orientation of potential attacking states is generally short term and driven by concerns about military cost and effectiveness. For successful deterrence, defending states need the military capacity to respond quickly and in strength to a range of contingencies. Where deterrence often fails is when either a defending state or an attacking state under or overestimate the others' ability to undertake a particular course of action.
The central problem for a state that seeks to communicate a credible deterrent threat through diplomatic or military actions is that all defending states have an incentive to act as if they are determined to resist an attack, in the hope that the attacking state will back away from military conflict with a seemingly resolved adversary. If all defending states have such incentives, then potential attacking states may discount statements made by defending states along with any movement of military forces as merely bluffs. In this regards, rational deterrence theorists have argued that costly signals are required to communicate the credibility of a defending state's resolve. Costly signals are those actions and statements that clearly increase the risk of a military conflict and also increase the costs of backing down from a deterrent threat. States that are bluffing are unwilling to cross a certain threshold of threat and military action for fear of committing themselves to an armed conflict.
There are three different arguments that have been developed in relation to the role of reputations in influencing deterrence outcomes. The first argument focuses on a defending state's past behaviour in international disputes and crises, which creates strong beliefs in a potential attacking state about the defending state's expected behaviour in future conflicts. The credibilities of a defending state's policies are arguably linked over time, and reputations for resolve have a powerful causal impact on an attacking state's decision whether to challenge either general or immediate deterrence. The second approach argues that reputations have a limited impact on deterrence outcomes because the credibility of deterrence is heavily determined by the specific configuration of military capabilities, interests at stake, and political constraints faced by a defending state in a given situation of attempted deterrence. The argument of this school of thought is that potential attacking states are not likely to draw strong inferences about a defending states resolve from prior conflicts because potential attacking states do not believe that a defending state's past behaviour is a reliable predictor of future behaviour. The third approach is a middle ground between the first two approaches. It argues that potential attacking states are likely to draw reputational inferences about resolve from the past behaviour of defending states only under certain conditions. The insight is the expectation that decision makers will use only certain types of information when drawing inferences about reputations, and an attacking state updates and revises its beliefs when the unanticipated behaviour of a defending state cannot be explained by case-specific variables. An example both shows that the problem extends to the perception of the third parties as well as main adversaries and underlies the way in which attempts at deterrence can not only fail but backfire if the assumptions about the others' perceptions are incorrect.
Although costly signaling and bargaining power are more well established arguments in rational deterrence theory, the interests of defending states are not as well known, and attacking states may look beyond the short term bargaining tactics of a defending state and seek to determine what interests are at stake for the defending state that would justify the risks of a military conflict. The argument here is that defending states that have greater interests at stake in a dispute are more resolved to use force and be more willing to endure military losses to secure those interests. Even less well established arguments are the specific interests that are more salient to state leaders such as military interests versus economic interests.
Furthermore, Huth argues that both supporters and critics of rational deterrence theory agree that an unfavourable assessment of the domestic and international status quo by state leaders can undermine or severely test the success of deterrence. In a rational choice approach, if the expected utility of not using force is reduced by a declining status quo position, then deterrence failure is more likely, since the alternative option of using force becomes relatively more attractive.
In 1966 Schelling is prescriptive in outlining the impact of the development of nuclear weapons in the analysis of military power and deterrence. In his 1966 analysis, before the widespread use of assured second strike capability, or immediate reprisal, in the form of SSBN submarines, Schelling argues that nuclear weapons give nations the potential to not only destroy their enemies but humanity itself without drawing immediate reprisal because of the lack of a conceivable defense system and the speed with which nuclear weapons can be deployed. A nation's credible threat of such severe damage empowers their deterrence policies and fuels political coercion and military deadlock, which in turn can produce proxy warfare.
Historical analysis of nuclear weapons deterrent capabilities has led modern researchers to the concept of the stability-instability paradox, whereby nuclear weapons confer large scale stability between nuclear weapon states, as in over 60 years none have engaged in large direct warfare due primarily to nuclear weapons deterrence capabilities, but instead are forced into pursuing political aims by military means in the form of comparatively smaller scale acts of instability, such as proxy wars and minor conflicts.
The US policy of deterrence during the Cold War underwent significant variations.
The early stages of the Cold War were generally characterized by containment of communism, an aggressive stance on behalf of the US especially on developing nations under its sphere of influence. This period was characterized by numerous proxy wars throughout most of the globe, particularly Africa, Asia, Central America, and South America. A notable such conflict was the Korean War. George F. Kennan, who is taken to be the founder of this ideology in his Long Telegram, asserted that he never advocated military intervention, merely economic support; and that his ideas were misinterpreted when espoused by the general public.
With the U.S. drawdown from Vietnam, the normalization of U.S. relations with China, and the Sino-Soviet Split, the policy of Containment was abandoned and a new policy of détente was established, whereby peaceful coexistence was sought between the United States and the Soviet Union. Although all factors listed above contributed to this shift, the most important factor was probably the rough parity achieved in stockpiling nuclear weapons with the clear capability of Mutual Assured Destruction (MAD). Therefore, the period of détente was characterized by a general reduction in the tension between the Soviet Union and the United States and a thawing of the Cold War, lasting from the late 1960s until the start of the 1980s. The doctrine of mutual nuclear deterrence characterized relations between the United States and the Soviet Union during this period, and relations with Russia until the onset of the New Cold War in the early 2010s. Since then, the relations have been less clear.
A third shift occurred with President Ronald Reagan's arms build-up during the 1980s. Reagan attempted to justify this policy in part due to concerns of growing Soviet influence in Latin America and the new republic of Iran, established after the Iranian Revolution of 1979. Similar to the old policy of containment, the United States funded several proxy wars, including support for Saddam Hussein of Iraq during the Iran-Iraq War, support for the mujahideen in Afghanistan, who were fighting for independence from the Soviet Union, and several anti-communist movements in Latin America such as the overthrow of the Sandinista government in Nicaragua. The funding of the Contras in Nicaragua led to the Iran-Contra Affair, while overt support led to a ruling from the International Court of Justice against the United States in Nicaragua v. United States.
While the army was dealing with the breakup of the Soviet Union and the spread of nuclear technology to other nations beyond the United States and Russia, the concept of deterrence took on a broader multinational dimension. The U.S. policy on post-Cold War deterrence was outlined in 1995 in a document called "Essentials of Post-Cold War Deterrence". This document explains that while relations with Russia continue to follow the traditional characteristics of Mutual Nuclear Deterrence, due to both nations continuing MAD, U.S. policy of deterrence towards nations with minor nuclear capabilities should ensure through threats of immense retaliation (or even preemptive action) that they do not threaten the United States, its interests, or allies. The document explains that such threats must also be used to ensure that nations without nuclear technology refrain from developing nuclear weapons and that a universal ban precludes any nation from maintaining chemical or biological weapons. The current tensions with Iran and North Korea over their nuclear programs are due in part to the continuation of this policy of deterrence.
Modern Deterrence is the application of deterrence theory to non-nuclear and post-nuclear challenges, including hybrid warfare. As with nuclear deterrence, the aim of modern deterrence is to "dissuade an adversary from taking aggressive action by persuading that actor that the costs would outweigh the potential gains." However, the unattributable nature of some new forms of attacks, including propaganda and cyber attacks, and the fact that they may be below the threshold of an armed response pose a particular challenge for deterrence. The Center for Strategic and International Studies concluded that modern deterrence is made most effective at reducing the threat of non-nuclear attacks by:
Deterrence theory is criticized for its assumptions about opponent rationales.
First, it is argued that suicidal or psychotic opponents may not be deterred by either forms of deterrence. Second, if two enemy states both possess nuclear weapons, Country X may try to gain a first-strike advantage by suddenly launching weapons at Country Y, with a view to destroying its enemy's nuclear launch silos thereby rendering Country Y incapable of a response. Third, diplomatic misunderstandings and/or opposing political ideologies may lead to escalating mutual perceptions of threat, and a subsequent arms race that elevates the risk of actual war, a scenario illustrated in the movies WarGames (1983) and Dr. Strangelove (1964). An arms race is inefficient in its optimal output, as all countries involved expend resources on armaments that would not have been created if the others had not expended resources, a form of positive feedback. Fourth, escalation of perceived threat can make it easier for certain measures to be inflicted on a population by its government, such as restrictions on civil liberties, the creation of a military-industrial complex, and military expenditures resulting in higher taxes and increasing budget deficits.
In recent years, many mainstream politicians, academic analysts, and retired military leaders have also criticized deterrence and advocated nuclear disarmament. Sam Nunn, William Perry, Henry Kissinger, and George Shultz have all called upon governments to embrace the vision of a world free of nuclear weapons, and in three Wall Street Journal op-eds proposed an ambitious program of urgent steps to that end. The four have created the Nuclear Security Project to advance this agenda. Organisations such as Global Zero, an international non-partisan group of 300 world leaders dedicated to achieving nuclear disarmament, have also been established. In 2010, the four were featured in a documentary film entitled Nuclear Tipping Point. The film is a visual and historical depiction of the ideas laid forth in the Wall Street Journal op-eds and reinforces their commitment to a world without nuclear weapons and the steps that can be taken to reach that goal.
Former Secretary Kissinger puts the new danger, which cannot be addressed by deterrence, this way: "The classical notion of deterrence was that there was some consequences before which aggressors and evildoers would recoil. In a world of suicide bombers, that calculation doesn't operate in any comparable way." Shultz has said, "If you think of the people who are doing suicide attacks, and people like that get a nuclear weapon, they are almost by definition not deterrable".
As opposed to the extreme mutually assured destruction form of deterrence, the concept of minimum deterrence in which a state possesses no more nuclear weapons than is necessary to deter an adversary from attacking is presently the most common form of deterrence practiced by nuclear weapon states, such as China, India, Pakistan, Britain, and France. Pursuing minimal deterrence during arms negotiations between United States and Russia allows each state to make nuclear stockpile reductions without the state becoming vulnerable, however it has been noted that there comes a point where further reductions may be undesirable, once minimal deterrence is reached, as further reductions beyond this point increase a state's vulnerability and provide an incentive for an adversary to secretly expand its nuclear arsenal.
"Senior European statesmen and women" called for further action in addressing problems of nuclear weapons proliferation in 2010. They said: "Nuclear deterrence is a far less persuasive strategic response to a world of potential regional nuclear arms races and nuclear terrorism than it was to the cold war".
Paul Virilio has criticized nuclear deterrence as anachronistic in the age of information warfare since disinformation and kompromat are the current threats to suggestible populations. The wound inflicted on unsuspecting populations he calls an "integral accident":
Former deputy defense secretary and strategic arms treaty negotiator Paul Nitze stated in a Washington Post op-ed in 1994 that nuclear weapons were obsolete in the "new world disorder" following the dissolution of the Soviet Union, and advocated reliance on precision guided munitions to secure a permanent military advantage over future adversaries.