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1 The Nature of Deterrence

Deterrence comes in many forms. In the world of national security, the term tends to be most readily associated with nuclear threats, but even in the nuclear age most military deterrence revolves around conventional capabilities. This is often underappreciated since successful deterrence draws little attention. This chapter examines the subject of conventional deterrence, and the question of how it fits into the security landscape of the early 21st century. Defined at the brevity of a tweet, “deterrence is causing someone not to do something because they expect or fear that they will be worse off if they do it than if they do not”.Footnote 1 We practice and study deterrence in a wide variety of contexts ranging from nuclear crises to crime prevention,Footnote 2 but here the focus is on deterring interstate and similar aggression: starting wars, launching other sorts of military attacks, and expanding or escalating armed conflicts.Footnote 3

Other chapters in this volume discuss the nature and dynamics of deterrence in general, but four key points about it are worth reiterating before we delve into conventional deterrence in particular. First, deterrence (like other forms of coercion) involves making an opponent that has the ability to attack choose not to do so. Action that makes it impossible for an attack to take place, such as preventively disarming or destroying the opponent, is not deterrence, instead it is what Thomas Schelling dubbed “pure” or “brute” force.Footnote 4 Although brute force can be an effective way to deal with security threats, especially when the enemy is weak or vulnerable, coercion is usually more attractive if it can be achieved, particularly when successful deterrence means a war will not have to be fought.

Second, deterrence is not the same thing as simply making war look costly or risky but depends on making war look worse than the alternative. Deterrence tends to be relatively easy if the opponent considers the peacetime status quo to be reasonably acceptable, as most states do most of the time. However, a desperate actor may decide to attack even when starting a war appears dangerous if it expects that not doing so would be worse—Japan in 1941 is the evergreen example of a state deciding that going to war was the least bad of several unappealing options.

Third, there are a variety of ways to make aggression appear to be a bad idea compared to other options. Increasing the expected costs of aggression through threats of punishment (punitive deterrence) and making it appear unlikely that aggression will be successful in achieving its objectives (deterrence by denial), whether by military or other means, are the approaches most strongly associated with deterrence. But the prospects for successful deterrence can also be improved by making not going to war look more attractive though reassurance measures or promises of rewards. Some have aptly referred to these types of promises as “positive deterrence” but that seemingly oxymoronic label has never been widely embraced.Footnote 5 However, whether or not one defines such measures as deterrence per se, they are fundamental to the deterrence calculus and must be taken into account by good strategists and analysts.Footnote 6

Finally, and most importantly, deterrence occurs in the mind of the potential aggressor. The opponent’s choice of action depends on what it believes about the future consequences of its options—the actual costs and benefits of war and probabilities of success and failure will only affect the deterrence calculus insofar as they shape these subjective expectations. (Of course, objective reality will become very important indeed if deterrence fails and the war begins.)Footnote 7 Decision makers can misperceive reality for many reasons, and future events are often inherently difficult to predict, so many wars are started by states that would have been better off if they had decided not to attack. The most robust deterrence strategies will be those that make a case that aggression would be a bad idea which is compelling enough to overcome any potential inclination toward war resulting from such misperception.

The concept of deterrence is agnostic regarding the tools that can be used to make deterrent threats.Footnote 8 Because modern deterrence theory was developed in response to the advent and proliferation of nuclear weapons, and for several decades deterrence scholarship focused on them as both the principal tool of then-contemporary deterrence and the principal threat in need of being deterred, “deterrence” became strongly associated with nuclear strategy. Theorists today rarely suggest, as some once did, that use of the term “deterrence” should be limited exclusively to nuclear deterrence, but it is still common, for example, for “deterrent” to be U.S. doctrinal shorthand for matters involving strategic nuclear forces. But deterrence long predated the nuclear revolution, and of course non-nuclear deterrence is the only sort that many states have the ability to practice. Moreover, the long and lengthening tradition of non-use has made nuclear weapons recede into the background of many of the deterrent relationships is which they do play a role.Footnote 9

2 Unpacking Conventional Deterrence

The term “conventional deterrence” came into wide use in the 1980s, particularly associated with the work of John Mearsheimer, including his book of the same name.Footnote 10 It implies on one hand that deterrence using conventional threats is meaningfully different from nuclear deterrence, but also that they are much alike. One could define conventional deterrence as all deterrence that doesn’t involve threats to use nuclear (or other unconventional) weapons, but the non-nuclear deterrence category includes too many dissimilar elements to provide much analytical utility. Instead for this discussion we will bound it more narrowly to encompass deterrent threats to resist or to inflict costs against an aggressor using conventional military force during the resulting conflict. This is still fairly expansive, taking in measures ranging from fighting an invader on the battlefield to launching punitive military attacks against targets far removed from the scene of the aggression to irregular partisan warfare against the enemy in territory it has occupied. However, it excludes non-military threats of economic sanctions or diplomatic shaming, and any measures to inflict costs, deny benefits of conquest, or reverse the outcome of the war after hostilities end.

Within this scope exist several differentiable sub-categories of conventional deterrence, though in practice the boundaries separating them are often less than distinct. Table 4.1 portrays four ideal types in terms of the type of deterrent threat they involve and the extent to which they focus on the specific theatre of the potential enemy attack. Much of the ensuing discussion will apply to all of them, but because some are more familiar than others, we will not give each one equal attention.

Table 4.1 Conventional Deterrence Categories
Full size table

Battlefield Defeat. Proceeding anti-clockwise from the upper left quadrant of the diagram, we start with the approach that is least novel in historical terms. Threatening to defeat an enemy that attacks you has been a basic element of military strategy since before strategy, let alone deterrence, had a name.Footnote 11 The deterrent message is “if you attack me, your forces will be defeated so you will not reap the rewards you hope to achieve by your action,” or in more microeconomic terms, the probability of success is too low for attacking to be worthwhile. How convincing such a threat will be depends on the opponent’s expectations about the offensive and defensive capabilities of the respective parties, taking into account factors such as whether the attacker believes that it can employ a strategy against which the defender is unlikely to be able to defend effectively. If so, it may be hard to deter even a significantly weaker opponent—James Wirtz labels this problem of an aggressor doubting that the defender will be able to fight effectively “contestability”.Footnote 12 In general, the greater the relative capabilities of the attacker are, the harder it will tend to be for threats of battlefield defeat to carry deterrent weight. Because such threats are very familiar, we will not pay them much further attention here.

Punitive Resistance. The basic idea that a potential aggressor may be deterred by the prospect of suffering heavy losses if it goes to war is also commonsensical, but such threats lie at the heart of conventional deterrence. Here the threat is “if you attack us we cannot guarantee that you will lose, but we will inflict such heavy losses on your forces that even if they ultimately win, the cost of doing so will outweigh any benefits you may gain”. This is a natural approach to military deterrence for a weak state facing a powerful enemy that it has little hope of defeating, classically illustrated by the defensive military strategies of states such as Switzerland. The core of Mearsheimer’s argument was that it can also be a powerful enough threat among major powers to make war appear too costly to be worth fighting, citing as evidence a consistent pattern in modern history of industrialized states attacking each other only when they believed that the ensuing war would be short and relatively inexpensive, and not being willing to embark on conflicts that they expected to result in costly wars of attrition whether ultimately successful or not.Footnote 13 Punitive resistance is a more purely deterrent approach than threatening battlefield defeat in the sense that carrying out the strategy if deterrence fails may not benefit the defender very much even though it punishes the attacker, and surrendering early in a conflict will typically be less costly to the defender than fighting on only to surrender later.

Strategic Retaliation. Deterrence can also involve threats to punish an aggressor by using conventional forces to attack targets less directly related to resisting the enemy attack, a deterrent approach most famously associated with nuclear retaliation but one that was also prominent in the decades before Hiroshima once airpower evolved to the point that it could range enemy territory far beyond the vicinity of the battlefield.Footnote 14 The better part of a century ago, such threats tended to be directed against targets such as enemy cities—counter-value targets in nuclear strategy parlance—but increasingly accurate munitions including long-range missiles give strategists a wider range of targeting options today. This might be particularly promising in cases where the enemy considers heavy losses on the battlefield to be a price worth paying to achieve its objectives, but depends on being able to hold targets at risk that the adversary values more. This category also includes many threats of horizontal escalation: threatening to respond to an attack by the enemy at a time and place of its choosing by striking back somewhere else where the defender enjoys a military advantage.Footnote 15

Strategic Defeat. Finally, a deterrer can threaten “we may not be able to prevent your attack from succeeding, but that will be merely the first phase of a longer war, which we will ultimately win”. Credibly threatening to defeat the enemy in the long run depends, of course, on being able to survive the initial onslaught, so it does not lend itself to deterrence by weaker states without allies. However, it may be well-suited for extended deterrence by major powers in places that are difficult to defend—provided that the prospective aggressor believes that the deterrer will not only be able to prevail in a longer conflict, but also will be sufficiently determined to see it through.

These strategy types tend to overlap considerably in practice, of course. Fighting to defeat an attacker will also impose costs on it, retaliatory attacks against an enemy’s homeland may also weaken its military capabilities at the front, and so on. But the distinctions are worth drawing because of the differences among their characteristics, advantages, and limitations. As an illustration we can consider military strategies in each category that might be employed in the often recently-discussed case of NATO seeking to deter a potential Russian invasion of the Baltic States.Footnote 16 A battlefield defeat threat would be simple in theory though challenging in practice: preparing a defence of the Baltics potent enough to appear capable of stopping an invasion force before it reached its objectives; this would appear to require a considerably large Alliance military presence than currently exists there.Footnote 17 A threat of punitive resistance would be less ambitious and more programmatically feasible: preparing to exact sufficiently heavy costs from an invading force to make an invasion look unattractive. Strategic retaliation would focus not on the difficult problem of defending the Baltic allies, but instead threaten to impose heavy costs on the Russians elsewhere, such as by striking high-value targets in metropolitan Russia or responding with attacks against more vulnerable Russian territory or forces in other theatres. A strategic defeat approach would not devote large resources to what might be a doomed defence in the Baltics, but instead threaten to respond to an attack by mobilizing NATO’s greater military resources to mount a counteroffensive to liberate the lost territory and ultimately prevail in a prolonged war.

3 Conventional Deterrence in the 20th Century

Once, all deterrence was conventional, of course.Footnote 18 People didn’t often talk about deterrence as a distinct strategic concept because the idea that a country would defend itself if attacked, and that in general nations would not attack enemies they did not expect to be able to defeat, seemed self-evident. Several developments made conventional deterrence more interesting over the course of the 20th century. One was that the airpower revolution greatly expanded the potential to threaten retaliatory attacks against enemy nations, not just their armies and navies, without first achieving victory on the battlefield. Expectations that this would make future wars cataclysmic emerged quickly, and by the 1930s Britain and to a lesser degree other European powers turned to strategic retaliation as a core element of their grand strategies—and as a deterrent and compellent tool in colonial policing. Great Britain would also be the first great power conspicuously deterred by the same prospect, when exaggerated fears of German strategic bombing loomed large is persuading it to abandon Czechoslovakia to its fate at Munich. Harold Macmillan would later recount “We thought of [conventional] air warfare in 1938 rather as people think of nuclear warfare today.”Footnote 19

This occurred in parallel with the transformative effects that the experience of the First World War had on perceptions of how bad the costs of war on conventional battlefields could be.Footnote 20 It became much more difficult to imagine winning victories over other major powers at a cost sufficiently low to make the exercise worthwhile—and by this point the deaths of tens or hundreds or thousands of thousands of troops had itself become more significant to governments as democratization and national mobilization meant that soldiers were less easily expendable than they once were. The Second World War would see this deterrent effect undermined by new doctrines for employing mechanization and telecommunications that revived the possibility of winning fast and decisive victories against well-armed opponents—making conventional deterrence more contestable in 1940 than it had appeared to be in 1920—but only under favourable conditions and against enemies unprepared to counter them.Footnote 21

Nuclear weapons pushed conventional deterrence into the background, at least for the superpowers, for a while after 1945. Atomic and especially thermonuclear weapons’ destructive power made the severity of retaliatory deterrent threats difficult to dismiss, and the threat of tactical nuclear weapons, used in quantity, did the same for punitive resistance, for anyone not suitably impressed by the costliness of conventional warfare after the experience of World War II. The United States would briefly embrace the “New Look” strategy of relying on nuclear retaliation to deal with a wide range of conventional military threats as well as nuclear ones in the 1950s, but the loss of its nuclear monopoly soon appeared to undermine the credibility of such responses. In less than a decade conventional deterrence (though not described as such) became a matter of considerable concern and investment in U.S. and Allied planning to deal with the Soviet threat, though always backed up by nuclear capabilities.Footnote 22 Some smaller states not protected by allies’ nuclear umbrellas explicitly developed strategies for conventional deterrence against invasion through punitive resistance.Footnote 23

As the Cold War ended and the 20th century wound down, a new set of emerging military capabilities further increased the deterrent potential of conventional military force. The development and proliferation of reliable precision-guided munitions (PGMs) enabled states with advanced air forces to inflict high levels of damage against enemy military and infrastructure targets without placing their own armies at risk, while stealth aircraft and modern long-range missiles limited the ability of air defences to protect against such attacks.Footnote 24 These technologies also fostered interest in strategies to deter or compel adversary leaders by personally threatening them, although such decapitation strategies mostly failed when they were attempted.Footnote 25 PGMs could be used against civilian targets, too, but it was their ability to efficiently cripple military forces not previously vulnerable to conventional bombing that turned out to be most significant for coercion, creating new and powerful options for deterrence by denial.Footnote 26 A series of air-centric wars in the Middle East and the Balkans during and after the 1990s demonstrated the growing power of these capabilities to punish weaker adversaries and, in concert with even limited ground forces, to defeat their armed forces and depose their regimes.Footnote 27

4 Conventional Deterrence in the 21st Century

Does conventional deterrence still matter as much as it once did? The idea that conventional military threats can deter never went away, and it is clear that the concept is still meaningful. But this is not the same as saying that conventional military capabilities are worth maintaining for deterrent purposes, particularly for the United States and its Western allies. For policymakers, the question is whether they should invest resources—money, personnel, political capital, diplomatic effort—in developing or strengthening conventional deterrent capabilities. These things are limited in supply so expending them entails opportunity costs. So does choosing a strategy: focusing a state’s national security efforts against a particular adversary or type of contingency using a particular strategy also tends to mean sacrificing some measure of opportunity to prepare to deal with other threats, or the same threats in a different way.

4.1 Making the Case for Deterrence

When making costly choices in the arena of security policy, investing in deterrence can be a hard sell. Successful deterrence is usually invisible—an adversary may back down conspicuously during a confrontation in response to a deterrent threat, but the causes of crisis outcomes are often ambiguous. More significant still are the many crises that never happen in the first place, which may be due to deterrence or may not. After the 1962 Cuban Missile Crisis, the superpowers never again knowingly pushed each other to the brink of major war between them, and each side continued to invest quite heavily in both conventional and nuclear military capabilities intended to deter the other. To what extent the former was attributable to the latter is something that we still understand only imperfectly, and had little insight into at the time.

Paying for a costly defence establishment that never fights often seems problematic, even for many people well versed in national security affairs. In his 2014 critique of the U.S. Air Force, Robert Farley holds up the fact that strategic bombers such as the B-47 Stratojet and B-58 Hustler—whose sole operational role was delivering nuclear weapons against the Soviet Union—never went to war as a “disturbing” sign of institutional failure and wasted money.Footnote 28 As U.S. Ambassador to the United Nations in 1992, seasoned diplomat Madeline Albright famously queried “What’s the point of having this superb military if you can’t use it?”Footnote 29 Americans typically characterize many NATO allies’ anaemic defence spending as free riding on the U.S. military machine, far less often do they consider the role that is played by European leaders and voters who see little value in paying more for armed forces to deal with a distant power that appears to pose no more than a hypothetical threat to them.

In contrast, deterrence failures are quite visible, even though they tend to be rare. When they do occur, it can undermine faith in deterrence—conventional or otherwise—as a policy or a theory, but as with marriages, the existence of failures in execution does not imply that the principle or our theories about it are unsound, only that success is not always easy to achieve. The Russian invasion of Crimea was not the failure of NATO conventional deterrence it is often said to be (indeed it was barely a failure of Ukrainian deterrence given how little of it there was), nor does a terrorist attack prove that terrorists are in general undeterrable. Deterrence failures can occur because the aggressor does not believe that the deterrer will be able to carry out its threats (or promises) effectively, or doubts that it will actually try to do so when the time comes, or because the threatened costs or risks are insufficient to outweigh the factors that appear to argue in favour of war.Footnote 30 Good deterrence strategies will seek to avoid these pitfalls. However, any or all of these problems can become much worse if a prospective aggressor’s decision making is affected by psychological, bureaucratic, or other factors that contribute to unwarranted optimism about how easy, inexpensive, or beneficial going to war is likely to be,Footnote 31 as was illustrated by the most consequential interstate deterrence failure of the past two decades, the 2003 U.S. decision to invade Iraq.Footnote 32

4.2 Has Conventional Deterrence Become Irrelevant?

There are at least three general arguments that can be proffered in support of the idea that conventional deterrence is a relatively poor investment in the current era. One is the classic Cold War proposition that nuclear deterrence is so powerful that there is little need for nuclear-armed states or their friends to maintain substantial conventional military capabilities to deter aggression. This is logically sound, at least in contexts where the stakes are high enough to make the use of nuclear weapons plausible. Yet oddly, we see no clear examples of newer nuclear powers embracing this belief as the United States did in the 1950s. Having worked hard to acquire nuclear arsenals, we might expect Israel, India, Pakistan, or North Korea to exhibit greater confidence in the ability of nuclear weapons to protect them from attack. It is also arguably surprising that there is so little apparent sentiment within NATO in favour of trying to solve the perplexing Baltic defence problem simply by threatening nuclear strikes against Russia in the event of an invasion too substantial to fend off, as the Alliance did with respect to West Germany fifty years ago. Do nations apparently lacking faith in the deterrent power of their own nuclear arms imply that nuclear threats are not reliable deterrents?

A second, related reason for minimizing conventional deterrence investments might be that military aggression has become inherently less attractive for reasons other than conventional deterrent threats—territorial conquest appears less profitable than it once did, and international norms against aggression are stronger so attacking a neighbour entails a high political and moral price and may bring economic punishment by offended countries or frightened investors. More broadly, empire-building through conquest is rather anachronistic in the 21st century, so there simply aren’t many potential attackers for most states to worry about. Russia does not want to own the Baltic states although it might find other reasons to attack them, China does not seek ownership of any important territory other than Taiwan (which it would prefer to reclaim by means other than force), the United States has run out of seemingly weak countries it is interested in attacking. This is an argument to take seriously, for interstate aggression has indeed become increasingly rare. However, we should be wary of presuming that the popularity of aggression would have declined similarly without warfare imposing costs on invaders: the strongest case for the “obsolescence of war” thesis is more an argument for the power of conventional deterrence than for its irrelevance.Footnote 33 It is also worth noting that most conventional military capabilities take time to develop or, once demobilized, to rebuild, so if an absence of threats might be temporary, disarming in response to it carries corresponding risks.

Finally, conventional deterrence, at least as a response to traditional military aggression, might be out of step with the times in an era of novel threats. If new modes of attack such as cyber warfare, non-state terrorism, or political subversion enabled by social media represent the principal security threats to a state, it will want to recalibrate its deterrence priorities. On the other hand, if the more old-fashioned threats of territorial aggression or coercive punishment have receded because of effective conventional deterrence, maintaining that effect may still be worth the candle. Moreover, while the capabilities that are well suited to deterring conventional wars may provide little defence against cyberattacks or terrorists,Footnote 34 punitive conventional threats may be quite useful for deterring enemies from launching, sponsoring, or facilitating such attacks.Footnote 35

4.3 Conventional Military Threats in the 2020s

It is important not to exaggerate the security threats we face. In spite of frequently alarmist declarations from U.S. leaders, such as a Chairman of the Joint Chiefs of Staff declaring in 2013 that the world was then “more dangerous than it has ever been,”Footnote 36 by virtually any historically-informed measure the contemporary security environment is relatively benign for the United States and its allies. But this does not mean that deterring aggression is irrelevant—the scarcity of imminent interstate threats against key Western interests is not unrelated to the effectiveness of conventional deterrence.

To focus on the United States, in a period featuring a rapidly rising China and a relatively belligerent Russia it is noteworthy that the scenarios for potential aggression that concern Washington the most—a Russian attack somewhere on NATO’s eastern flank, a Chinese invasion of Taiwan, North Korea bombarding one of its neighbours on a major scale for some perplexing reason—do not appear to be imminent threats. However, for policymakers the problem is that if conflicts did occur in these places (and the United States were involved) the costs would likely be enormous. A war in the Baltics or over Taiwan would likely be hard to win,Footnote 37 but these are conflicts that would be much better not to fight at all. Winning a war against China or Russia would constitute a huge failure of U.S. national security policy—second only to losing one. And this is true even assuming that a conventional war did not escalate to include the use of nuclear weapons.

Among other states, some still face potential threats of attack from neighbours that well-crafted and well-resourced conventional deterrence strategies can make significantly less likely. Taiwan is arguably the most obvious example of a state with good reason to invest in being a poisonous shrimp or a porcupine, as Singaporean strategists once characterized their country;Footnote 38 it has not traditionally optimized its armed forces for conventional deterrence against China, continuing to invest resources in systems that would now have little chance of surviving very long in a conflict with the People’s Republic.Footnote 39 If Taipei embraced conventional deterrence as a priority it would also be a boon for the United States, and the same is true of other states whose vulnerability to attack by powerful neighbours creates potential flashpoints for major power war. Finally, while some states are not as safe as America, others are not safe from it. For them, conventional deterrence is something to take very seriously indeed—and in some cases this would benefit the United States as well, given that it is still suffering the aftereffects of Iraq’s failure to deter it in 2003.

4.4 The Merits and Limits of Conventional Deterrence

For states that have unresolved deterrence problems, conventional deterrence strategies often have much to offer, though their comparative advantages inevitably vary depending on the specific case. First, for many states conventional deterrence is more or less the only realistic military option, given the material and political costs of seeking security through nuclear or other unconventional means. Second, even states that possess nuclear arsenals face deterrence challenges that nuclear threats are ill-suited to address because employing such weapons would be incredible, unpalatable, or simply inconceivable. Finally, many of the tools of conventional deterrence have significant flexibility, with value for non-deterrent missions ranging from defence to security cooperation to disaster relief, something that tends to be less true for forces optimized for nuclear deterrence.

Among conventional deterrence strategies, punitive resistance is a straightforward threat that takes relatively little imagination to appreciate, though it is not as hard to dismiss as a good-sized nuclear threat. It also has the great virtue, relative to indirect conventional retaliation strategies as well as nuclear ones, of tending to be credible even when the issue at stake is not a vital interest for the deterrer that would clearly merit escalation to protect—not every army fights staunchly when attacked, but doing so is a natural response to invasion. When deterrence and defence overlap, deterrence is strengthened, and forces meant to deter can still defend if deterrence fails.

Perhaps most important, punishing an enemy on the battlefield during an invasion imposes immediate costs that are difficult for a prospective attacker to discount (except to the extent that it considers its armed forces to be expendable, which Russia, for example, does not appear to do). This relative incontestability represents an important advantage over deterrence approaches that rely on the enemy being frightened by the prospect of punishment or defeat that would occur only with considerable delay. Whether in the form of gradually cumulative economic sanctions, diplomatic shaming and isolation, sustained insurgency against an occupier, or an eventual military counterattack, a prospective aggressor has ample opportunity to imagine that it will be able to find a way to avert much or all of the eventual response. This is particularly true if the response will be costly to carry out, or will depend on maintaining the unity of an international coalition, or requires the deterrer to remain politically committed to protecting an interest that it does not hold dear.

That being said, conventional deterrence in general, and punitive resistance in particular, is not a panacea for every deterrence problem. Capable conventional military forces are expensive to build and maintain—this was the principal appeal of the New Look after all. When facing a threat from a far more powerful adversary, almost all deterrence is more difficult and punitive resistance is no exception. For powerful deterrers, security dilemma dynamics can result in defensively-motivated deterrent armament provoking attack instead of discouraging it if neighbours feel severely threatened. Finally, some non-traditional security threats simply aren’t amenable to conventional responses, an issue that is addressed elsewhere in this volume.

Looking forward, there appears to be little reason to expect conventional deterrence to wane in importance relative to other elements of national security policy in the near future. Technological changes such as expanding capabilities and applications for remotely-operated and autonomous weapons systems are likely to alter specific security threats and options for punitive resistance and retaliation, although it remains to be seen whether this will tend to narrow or expand the capability gap between large and small states, or rich and poor ones. Continuing expectations in the West that wars can and should involve few casualties, especially but not only for our own forces, may enhance the potential of punitive resistance strategies. If we are in the early days of a new era of great power strategic competition, as prophesied by recent U.S. strategy statements,Footnote 40 conventional deterrence certainly stands to be a growth industry, as does its nuclear counterpart, and the importance of making sound conventional deterrence strategy will be all the greater given the potentially enormous costs of escalation in conflicts among states with vast resources and large nuclear arsenals. There is no prima facie reason to assume that any of these factors will make wars more frequent given their declining incidence in the recent past, but as with nuclear weapons, a scarcity of conventional conflict does not imply the absence of conventional deterrence, and is often a sign of its potency. The fact that people don’t see you using your “superb military” does not necessarily mean that there is no point in having it.

5 Principles for Conventional Deterrence

  • Every deterrence situation is different, so offering generalizations is often perilous, but there are some prescriptions that tend to apply in most cases, and make a good starting point for deterrence strategy:

  • Plan against a range of specific threats. We are often told that the world is unpredictable and threats are difficult to anticipate. Nevertheless, deterrence strategy should take case-specific considerations into account because the differences among adversaries matter. One size does not fit all. However, it is also important not to design deterrence strategy so narrowly that it becomes brittle when reality fails to match one’s planning scenarios, as it almost always will.

  • Design forces to deter. One of the selling points of conventional deterrence is that the forces involved usually have a variety of uses. However, if deterrence is their most important function even if it is often invisible, maximizing their deterrent value—in terms of capabilities, readiness, basing, interoperability, and other factors—should be prioritized accordingly.

  • Expect misperception and try to minimize it. The effects of deterrent threats depend on how they are perceived, and perceptions will be affected by cognitive and motivated biases, intelligence errors, and communications failures. When a threat needs to be understood, take pains to make it hard to misunderstand. This may involve trade-offs with military secrecy and maintaining freedom of action.

  • Threaten to tear an arm off the enemy, as de Gaulle described the purpose of the Force de frappe. This principle applies to threats of conventional punishment as well as nuclear ones, and arguably even more so: to carry deterrent weight, a punitive threat should target something the enemy values. In many cases, heavy losses to armed forces fit this bill, but this is not universally the case. What the enemy values most may not be physical, but that need not preclude threatening it.

  • Make threats that are hard to discount. As discussed in the main text, the effects of threats that depend upon favourable conditions or on sustained commitment, action, or unity of effort over a prolonged period are easier for adversary decision makers to imagine being able to avoid than threats that have immediate and relatively automatic consequences.

  • Make optimism about aggression impossible, or at least as difficult as possible. Because deterrence occurs in the mind of the adversary, its goals are best served not simply by making war a bad idea, but by making it impossible for enemy leaders to imagine or convince themselves that war is a good idea. The latter is almost always more difficult. Conventional deterrence failures are most likely when a Guderian or a Yamamoto or someone less clever but with the ear of the leader can present a convincing theory of how aggression will be successful at an enticingly affordable cost. The challenge the conventional deterrence strategist faces is to prevent this narrative from being created and believed.