Defining Deterrence

By Jenna Higgins

On 23 August 2018, the Sir Richard Williams Foundation held a seminar on joint strike to discuss the imperative for an independent deterrent.

The aim of the seminar was to build a common understanding of the need for an independent joint strike capability to provide Australia with a powerful and potent deterrent and a means of demonstrating strategic intent.

In the lead up to the seminar, The Central Blue ran a series in order to generate discussion and enable those that cannot to attend to gain a perspective on the topic.

This is the first post of that series and Jenna Higgins focused on ways to understand and analyze the complex notion of deterrence. 

 Part 1: Defining deterrence.

In an uncertain world, the notion of being able to deter possible threats is self-evidently appealing: why risk having to fight a war when our defence policy and force structure are sufficiently robust to discourage potential aggressors before a shot is fired? Deterrence, however, is a very complex business, existing ultimately in the perceptions of the protagonists.

The intricacies and nuances of how exactly deterrence achieves its objectives has been researched by some of the finest minds within the realm of defence strategy and security. This two-part series will firstly examine the key elements of deterrence theory; and then, next week, discuss those elements in relation to Australian air power.

Generically, to deter is to discourage an action or event through instilling doubt or a creating a fear of the consequences. Ultimately, it can be distilled down into having the will and resources to achieve credible deterrence. And while this may seem simple, it is often difficult to make threats credible, or sufficiently daunting. Further, it is seldom cheap and rarely convenient. [1] Consequently, traditional deterrence has been described as a ‘sometimes thing’ as often it does not work. Deterrence, at times, makes preventing wars more difficult as it provokes resentment instead of acquiescence. Attacks are instigated, or efforts are made by opponents to design around it.[2]

Despite significant shifts in the strategic environment including a greater focus on asymmetric and urban warfare, the strategy of deterrence continues to factor in the minds of our leaders. This is mainly because of the reluctance of the developed world to initiate lethal action against diffused adversaries that might lead to unintended casualties and collateral damage. However, the unquestioned capability to carry the war to the adversary and inflict unacceptably heavy damage is also central to pursuing deterrence as a viable security strategy.[3]

Will & Perception

Before a nation can be viewed as a credible military adversary, one worthy of being avoided, the national posture or willingness to commit military action must be known. This includes the political willingness to bear the costs and risks involved in asserting its will to deter; the appetite to incur casualties or the financial imposition for instance.

To be sure, resorting to force will always involve costs of one kind or another; however, the government must be willing to convince external agencies and the domestic population that the benefits of force outweigh the costs. This idea is developed by Henry Kissinger in his 1957 book ‘Nuclear Weapons and Foreign Policy’, in which he states that:

Deterrence is greatest when military strength is coupled with the willingness to employ it. It is achieved when one side’s readiness to run risks in relation to the other is high; it is least effective when the willingness to run risks is low, however powerful the military capability.

In the case of a direct attack against the homeland, this may be easier to support than involvement in a conflict for a long term strategic outcome. Likewise, it is not just the cost of military lives which needs to be considered, but also ‘costs associated with killing non-combatants … when set against political objectives framed in terms of the defence of human rights or the elimination of terrorism.’[4]

This becomes especially pertinent when dealing with ‘rogue states’ in which the threat is the leadership rather than the people. In making a case to the constituencies for the deployment of military force, the intent to target specific threats systems and leadership, as opposed to the local population, must be clear in order to ensure domestic support and willingness for such an action.

In developing a national posture and willingness to act, communication is key. There is no scope for the adversary to perceive that a nation ‘may act’, it must be clearly communicated that a nation ‘will act’. Political will is only as good as the communication by which it is received.

There are many ways that this may be signalled including by formal statement, force deployments or the forward positioning of troops as a trip-wire.  In selecting the correct form of communication, there requires an understanding of what the adversary perceives as their vulnerabilities in order to target and message the threat appropriately.

The concept of messaging and assessing vulnerabilities is explained well by Thomas Schelling in his book Arms and Influence where he talks of the psychological nature of deterrence:

It is a tradition in military planning to attend to an enemy’s capabilities, not his intentions. But deterrence is about intentions—not just estimating enemy intentions but influencing them. The hardest part is communicating our own intentions.[5]

Capability & resources

Capability and resources must be matched to a nation’s intent to implement its political will, less the entire premise be regarded as a bluff. There is little use in clearly articulating that you will complete action X if there are no funds or insufficient numbers of personnel or equipment to support said action. Schelling expands on the concept of the bluff in stating that:

Nations have been known to bluff; they have also been known to make threats sincerely and change their minds when the chips were down. Many territories are just not worth a war, especially a war that can get out of hand. A persuasive threat of war may deter an aggressor; the problem is to make it persuasive, to keep it from sounding like a bluff.[6]

While it may be possible to bluff the adversary with big talk, ideally, ‘logistics support, serviceability, quality of command and control systems, and ability to operate and resupply in the area of operations must also be taken into account.’[7]. In all cases however, communication must remain key; this may be signaled through military exercises, show of force, or involvement in peacetime activities so presence and abilities are observed.[8]


Credibility, as an outcome of will and capability, is a product as opposed to a sum calculation. Each factor weighs heavily on the outcome, but likewise, there is undoubtedly an x-factor. The final product will be valid in some cases, but not in others.

Perhaps the product of political will, and acquiescence to high risk along with capability, is successful in defensive deterrence, but not so for offensive deterrence. Put simply, a protagonist will not risk their forces on attacking their adversary’s homeland, but will attack with their own home ground advantage.

Credibility is determined by perception. The effectiveness of a particular capability against the adversary is reliant on the adversary’s ‘perception of that capability or action vis-à-vis their own contemplated or proposed course of action.’[9] The adversary must be convinced that ‘fearsome punishment will be forthcoming; through an optimum combination of capability and the will to employ it; if any action inimical to the state’s well-being has been initiated’.[10]

Nuclear vs conventional

No conversation on deterrence theory would be complete without contemplating a nuclear option.

On nuclear deterrence: We bet our lives, our societies, our civilization (and those of everyone else) on it. The ensuing absence of outright wars among great powers strongly suggested it was working, even though deterrence to prevent lesser conflicts or nasty provocations and challenges was much less successful.

The nuclear revolution that occurred during the Cold War made the traditional assumptions regarding deterrence problematic. Where there is mutually assured destruction through nuclear weapons, defence of oneself becomes impossible. In contemplating this dilemma, coercive pressure raises the risk that the situation will escalate out of control.

Nuclear deterrence, unlike conventional deterrence, has a sole focus on punitive action which may well be so devastating that its makes the political ends irrelevant.  In a scenario where vital interests are at stake, nuclear deterrence may be a valid tactic. In other cases, punitive threats may not deter because the opponent will accept great risks, but denying that opponent a practicable vision of success may deter.


Deterrence as a successful concept is ambiguous and relies purely on perceptions. Will all protagonists share similar perceptions? Deterrence is aimed at ‘the cognitive domain of a human being and it is extremely difficult to measure its effectiveness.’[11] That said, it is generally agreed that nuclear deterrence between the USSR and USA was successful during the Cold War, in that there was no nuclear exchange, and that the two countries never came into direct conventional conflict.

Deterrence is even more complex when separating conventional and nuclear theories. A nation which can successfully deter will have considered the protagonist’s perceptions, clearly communicated its political will, demonstrated a willingness to accept risk, and signaled capability.If successful in achieving this, that nation has become a credible force.

Part 2 of this series will examine the notion of deterrence as it has been interpreted and applied by Australian air power since the second World War.

Squadron Leader Jenna Higgins is an Air Combat Officer in the Royal Australian Air Force and a co-editor at The Central Blue.

You can follow her on twitter at @jenna_ellen_.

The opinions expressed are hers alone and do not reflect those of the Royal Australian Air Force, the Australian Defence Force, or the Australian Government.

The article first appeared on Central Blue on Augusts 5, 2018 and is reprinted with the permission of The Williams Foundation.


[1] Morgan, P., 2012, The state of Deterrence in International Politics Today, Contemporary Security Policy, 33:1, pp 85 – 107

[2] ibid

[3] Kainikara, S., 2008, The Strategy of Deterrence and Air Power, Air Power Development Centre, Working Paper p27

[4] Stone, J., 2012, Conventional Deterrence and the Challenge of Credibility, Contemporary Security Policy, 33:1, p 111

[5] Cain, A., (ed)  2009, Deterrence in the Twenty first Century – Proceedings, London UK 18-19 May 2009.

[6] ibid

[7] Harvey, J., 1997, Conventional Deterrence and National Security, Air Power Development Centre

[8] ibid

[9] Op cit, Kainikara, S.

[10] ibid

[11] ibid