What is Deterrence?
According to the Oxford Online Dictionary, deterrence is defined as: ‘The action of discouraging an action or event through instilling doubt or fear of the consequences.’1 This is similar to the NATO Terminology Database definition: ‘The convincing of a potential aggressor that the consequences of coercion or armed conflict would outweigh the potential gains.’2 These definitions are very general, and rightfully so. There is no universal formula on how to deter a potential adversary but, by practical definition, it can be assumed that deterrence has failed when missiles fly.
The following two statements by Glenn Snyder ‘Deterrence works on the enemy’s intentions, while defence reduces its capabilities’, and ‘Deterrence is by definition a peacetime objective, while defence is a wartime value’ seem to support this.3 However, how BMD, as a defensive capability, can contribute in times of deterrence still needs to be analysed. Normally, the need for deterrence is perceived if a nation’s vital interests are threatened. To deter successfully, it is important to have the right capabilities, sufficient capacity and credibility, and the means to communicate intent. However, it is key to recognize and identify threats correctly; otherwise, an action intended as a stabilizing deterrent might be perceived as an unfounded threat itself, which could have an escalating effect. This has been termed ‘the security dilemma’ by academia.4 Also, it is vital to understand the adversary’s value system and definitions of success/victory to compose a functioning set of deterring measures.5
An adversary can be deterred by threatening his ambitions and value systems or by increasing the cost and risk of pursuing his goals. A credible threat requires the combination of capability and intent, and the capability must be able to deliver a credible combination of risk and cost.
Overall, there are numerous forms of deterrence. From a chronological perspective there are ‘general deterrence’ and ‘immediate deterrence’, and from a political and military effects perspective, there are ‘deterrence by punishment’ and ‘deterrence by denial’.6 Comprehensively there are also other, non-military measures to deter potential adversaries, such as economic sanctions, strategic treaties, or humanitarian aid, but these are not the focus of this article.
If deterrence measures are being employed but are not challenged by a potential adversary, it is called general deterrence. When the general deterrent is being challenged, but the challenger is dissuaded from using force, it is called immediate deterrence.7 Since in both phases ballistic missiles can be used to threaten friendly interests, BMD can also be used as a deterrent in both. Deterrence by punishment, like the Cold War concept of Mutually Assured Destruction (MAD)8, deters by threatening to impose unacceptable costs on the adversary, outweighing his potential benefits of his contemplated action(s). Deterrence by denial, in comparison, is denying the opponent his war aims9.
Because BMD is a purely defensive weapon, it is part of the deterrence by denial portfolio, but can increase cost and risk for the opponent, which will be shown below. The advancements of BMD technology since the end of World War II are remarkable, from the first conceptual US studies of possibilities of intercepting ballistic missiles such as the German V2 in the ‘Wizard Program’10, through the idea of intercepting incoming missiles with nuclear warheads (e.g. Nike Zeus), to modern-day hit-to-kill technology, which uses kinetic energy to destroy warheads in the exo-atmospheric midcourse phase of a ballistic missile’s flight path. The achieved technical feasibility, combined with the significantly increased probability of successfully intercepting ballistic missiles, opens up new ways of employing current BMD means.
To understand how BMD can contribute to deterrence, we need to understand why ballistic missiles threats are so special. There are numerous classes of ballistic missiles, initially categorized by their range from Short Range Ballistic Missile (SRBM; up to 100 km) to Intercontinental Ballistic Missile (ICBM; greater than 5,500 km). Furthermore, they can vary in number and type of warheads (e.g. regular re-entry vehicles, manoeuvring re-entry vehicles, or hypersonic glide vehicles), different payloads (e.g. conventional, biological, chemical or nuclear), propellant (liquid or solid), launch platform (e.g. fixed site, mobile launcher, submarine or even air-launched), or potential BMD countermeasures (e.g. manoeuvrability or decoys). Ballistic missiles are attractive to a lot of state and non-state actors because their range, speed and high trajectories give them a unique reach, and make them much more challenging for defences to intercept than do other delivery systems, such as manned aircraft or cruise missiles.11 In asymmetric conflicts with non-peer opponents, they can be used as a tool for coercion, due to elevated chances of successful effect delivery.
Benefits of BMD to Deterrence12
As stated above, deterrence works on adversary intentions. Hence, deterrent intent must be communicated carefully and correctly to have the intended effect. Since BMD is generally used in a defensive context, it provides a non-escalating means within the pool of deterring capabilities. By employing BMD, the likelihood of hostile ballistic missiles achieving the adversary’s desired effect is reduced. This not only potentially saves many lives but may also deter the adversary from using ballistic missiles at all, since the intended effect becomes unreliable. The adversary’s increased uncertainty of reaching their political or military goals with ballistic missiles also reduces the credibility of this threat.
Therefore, ballistic missiles, as a tool of political coercion, might not be used against nations with adequate BMD in the first place. This helps in managing escalation (intended or unintended) of a potential crisis, buys time for diplomacy, and consequently decreases the pressure to take pre-emptive, preventive or anticipatory self-defence actions. Also, since ballistic missiles may have less effectiveness in a BMD environment, the adversary has to decide to either procure a significantly larger stockpile of ballistic missiles (which increases cost) or to reduce his stock and employ fewer missiles in favour of other means. As such, BMD raises the cost of the adversary’s offensive capability, which has a deterrent effect of its own.
In general, the credibility of a military capability significantly rises when it is successfully demonstrated. Therefore, public ballistic missile tests are often used by an adversary to emphasize the relevance of a nation’s capabilities and to increase public pressure on a political level. BMD can be used to mitigate this effect as well.
When switching from general deterrence to immediate or extended immediate deterrence (cooperative sharing of deterrent capabilities to a third party), and once forces start to deploy, BMD has several supporting effects. BMD has proven to contribute to warfighting success by allowing a higher level of freedom of movement and through protection of the deployed forces. This could complicate planning for the adversary, increase his resource demands, and might cause higher attrition rates. Depending on the level of risk aversion or tolerance of the opponent, this may delay or suppress escalation and therefore create a deterrent effect.
The lack of pinpoint accuracy in most ballistic missiles often stimulates the use of Weapons of Mass Destruction (WMD) to ensure a compelling effect is achievable. In other words, employing WMD ensures that near misses can still affect the target, an important consideration, especially for non-peer adversaries. However, effective BMD systems reduce the likelihood of even near misses, thereby reducing the credibility of the threat. This might deter nations from pursuing costly delivery systems and weapons, including WMD. If WMD capabilities are already available to a state, effective BMD raises the threshold of using them, especially in limited attacks, due to decreased odds of success and could cause the opponent to deescalate due to increased risk. In short, the better the defences against ballistic missiles, the less credible the adversary’s threats become, and the more risk-accepting and potentially aggressive the BMD owning nation may appear. This perception may serve as a deterrent but might also have unforeseen negative effects.
Drawbacks of BMD13
Although technological advancements have made BMD systems very reliable, they cannot guarantee a 100% intercept rate. Based on technical limitations, the number of available BMD assets and/or sheer numbers of incoming threat missiles, current BMD systems are not able to create a perfect defence. The possibility of hostile missiles carrying WMD and leaking through defences raises the question of whether the remaining risk of a successful ballistic missile attack, and the extreme consequences thereof, render the high cost of the defence system unacceptable. This also creates political questions about the utility of BMD and undermines its deterrent effect. One can say that the deterrence by denial effect of BMD could trigger, rather than deter, a conflict. This was predicted during the Cold War and led to the Anti-Ballistic Missile Treaty14 of 1972 between the USA and the Soviet Union.
Also, the better our BMD systems get, the more likely it is that potential adversaries will develop new and better countermeasures which will exploit BMD limitations. Ballistic missiles with multiple warheads, high altitude electromagnetic pulse warheads, faster re-entry vehicles or manoeuvrable ones with less predictable flight paths that reduce intercept probabilities all enhance the chance of successfully delivering the threatened effect. A good example is the UK’s Polaris upgrade in the 1960s which was used to counter the BMD shield around Moscow.
If the opponent relies heavily on ballistic missile effects but perceives friendly BMD effective, chances are increased that he will pursue the development or procurement of nuclear weapons to maintain a credible threat. In other words, BMD could contribute to increased WMD proliferation, especially for non-peer competitors. Furthermore, an adversary’s proliferation of ballistic missiles or ballistic missile technology to other state and non-state actors might be intentionally increased to ensure an overall advantage against a common opponent.
Successful BMD unbalances the playing field, giving the owner the ability to engage in conflict without fear of BM retaliation. This could be perceived as setting the stage for impending aggressive action, and in the case of a peer or near peer competitor, could lead to a preventive, pre-emptive or anticipatory self-defence first strike, possibly emphasizing asymmetric means that circumvent the BMD capability and maintain a credible threat. Also, this perceived ‘aggressive posture’ might be misperceived by other potential adversaries, causing an unrelated situation to escalate as well.
In the case of extended deterrence, such as the US employs with partners in the Asia-Pacific region against North Korea, a strong domestic BMD posture might make the primary defender more risk tolerant than the third party itself. This could be a stressor within coalitions on agreeing on the right deterrent when risk perception is inhomogeneous.
BMD has great potential as a contributor to deterrence strategy. It can communicate a defensive posture, increase the time for diplomacy, deny adversaries benefits and impose costs the opponent is unwilling or unable to accept. By limiting the threat through reduction of risk, stimulating adversary restraint in pursuing WMD, and increasing the time for diplomatic solutions, BMD can be a very valuable political tool.
However, since an opponent will seek to maintain his potential level of threat, be it as means of coercion or maybe as a deterrent itself, there can be negative consequences for employing BMD. Therefore, BMD has to be used wisely, and the intent for use needs to be communicated carefully. Also, BMD has to be part of an overall deterrence strategy to de-escalate possible crises. Unless we can employ a perfect and unlimited defence, deterrence cannot be based solely on defensive capabilities. However, even limited defensive capabilities can enhance the deterrent effect of strong offensive capabilities by shifting the balance between opponents. Effective deterrence must present a viable threat through a comprehensive approach which includes offensive military capabilities, to ensure effective levels of cost and risk to the opponent.
Considering present BMD capabilities and the remaining risks and costs of WMD-armed ballistic missile attacks by peer states, BMD is currently not a convincing threat to the deterrence paradigm of MAD. Lastly, BMD systems are very costly (even in small numbers), and they need to be kept up-to-date. Otherwise, they will lose their deterring potential. This can potentially be very costly in the long run and needs to be considered when basing parts of the deterrence strategy on BMD capabilities.
Overall, a robust BMD posture against limited, miscalculated or accidental attacks supports general deterrence; and when coupled with enough additional BMD means to secure vital assets and deployed forces during crises, promises to be an excellent medium to deliver effective political and military deterrent effects in our current security environment.