The deterioration of deterrence?

“For NATO, changed almost beyond recognition following Vladimir Putin’s latest military aggression and revitalised as a newly vibrant security body, grown both in size and financial commitment, the still vital importance attached to deterrence has been made clear at every opportunity.” – In light of Russia’s decision to go to war with its neighbour and Hamas’ attack on Israel, Professor Andrew Stewart, Head of Conflict Research (CHACR), on why the concept of deterrence has its doubters.

Read the digital document above, download a copy here or continuing reading below.

Two events during the last 18 months have raised questions about whether “the art of deterrence” has been lost. In February 2022, a visibly angry NATO Secretary General Jens Stoltenberg stood before the international media to address the recent Russian military action against Ukraine. Europe’s peace had been “shattered” and there was a continental war “on a scale and of a type we thought belong to history”. Using military power to re-establish what it argued was its sphere of influence, Russia was attacking global rules and values and creating “the new normal for our security”. For him, NATO’s instant positive response showed the principle of collective defence had survived. For others, it could be argued that deterrence, for so long the core element of NATO’s overall strategy, had failed – as it did in 2014 when it had proven insufficient to halt Russia’s initial steps to take control of its southern neighbour. The other reason to question deterrence’s continuing value has come from the October 2023 attack against Israel by the terrorist group Hamas. The most recent UK doctrine note had used the Israeli approach to suppressing the security threat posed to its borders as an example of successful restrictive deterrence. With Russia’s illegal war against Ukraine continuing and military operations by the Israeli Defence Forces still underway, a long-established and critical security concept might no longer be fit for purpose.

In this context of worsening global instability, it is perhaps surprising that there has also been a re-commitment to deterrence. For Britain, the 2021 Integrated Review had already highlighted the need for “a conceptual and practical overhaul” to reflect further deteriorations in the strategic environment. This continued a consistent theme to the reviews of the previous decade which had placed an increased emphasis on deterrence and highlighted the degree to which this underpinned thinking on security. This included the 2018 National Security Capability Review which argued the UK needed a more systematic approach across government to tackle the growing number and diversity of threats. Work continues to implement the proposed changes and more still needs to be done as evidenced in the July 2023 UK Defence Command Paper in which deterrence was the focus of one of the eight chapters and a golden thread running throughout. There was also a blunt warning that “the contested security environment requires us to become expert once again in the art of deterrence” and a good deal of work appears to currently be underway at various levels to strengthen knowledge and understanding in this area.

For NATO, changed almost beyond recognition following Vladimir Putin’s latest military aggression and revitalised as a newly vibrant security body, grown both in size and financial commitment, the still vital importance attached to deterrence has also been made clear at every opportunity. There was confirmation at the 2022 Madrid Summit of a new baseline and then at the following year’s meeting of leaders, held in Vilnius, significant measures were agreed to enhance how this was implemented across all domains. With the 75th anniversary meeting taking place in Washington DC in July 2024, NATO’s deterrence strategies will again be the most prominent item for discussion. Despite the positive language, questions have quickly been raised about the longevity of ‘the transatlantic alliance’s sense of purpose’. This is alongside more general discussion about what the future might hold for the organisation, both in response to a confusing US domestic political atmosphere but also following indications of weakening military support for Ukraine.

Against an uncertain backdrop, a recent international conference convened by the Defence Science and Technology Laboratory (Dstl) and co-hosted by the Scottish Council on Global Affairs provided an invaluable opportunity to showcase some of the important research currently underway and share important insights about deterrence’s evolving character. While the situation in eastern Europe was a frequent reference point, no more so than in a fascinating keynote which explored the argument that Russia could not have been deterred, and with numerous recent publications focusing on deterrence also to consider, there were several key discussion strands which emerged. These included:

More than just nuclear deterrence

A recurring theme was the need to decouple deterrence from nuclear weapons and ensure thinking about the concept better reflects an increasingly complex global security environment with both the conventional and asymmetric realms. An early reminder was offered that deterrence was never central to military strategy until the atomic raids which ended the Second World War, after which it has remained at the forefront of thinking. For British Cold War thinking, even before the 1957 Defence White Paper which is commonly seen as a key point, deterrence had become a core idea. Nuclear weapons were “potential war-winners” which offered “the fighting man what he has sought ever since warfare began – the possibility of achieving surprise with decisive concentration of destructive power”. Russian aggression and the Cuban missile crisis supported the decision in 1963 to order Polaris and then in 1980 the invasion of Afghanistan was followed by confirmation of the Trident missile system. The resulting independent ‘last-resort’ deterrent has endured to this day although the cost of this nuclear insurance policy has also been a source of constant debate and will likely continue to feature during any future defence review, including those which take place over the next few years.

As the discussions made clear, the conflict in Ukraine has reaffirmed the continuing importance of understanding what nuclear deterrence now means. Some fear that a lesson learnt by Putin is that in any future aggression, such as in the Baltic region, there could be an increased reliance on nuclear weapons and a potential calculation they should be used earlier to secure victory. The Russian leader has demonstrated a willingness to take risk – and with frequent miscalculation in how he goes about this – which has included signalling about coercive nuclear escalation and how he could react to any potential military defeat, an outcome which could ultimately precipitate a collapse of his regime. As one published analysis concludes, “when a conventionally superior army backs a nuclear-armed enemy against a wall, it risks nuclear war”, and this was a possibility acknowledged by speakers in the room.

Hybrid conflicts and limits to deterrence

UK doctrine states that, as with war, the nature of deterrence has remained consistent but, since the Cold War’s ending, the character has changed significantly. Threats have evolved beyond traditional state-to-state conflicts and how to respond has been a regular feature of academic and policy discussion and was another key conference theme. As early as March 2014, the House of Commons Defence Committee warned of the complexity of deterring what were then often collectively viewed as asymmetric threats. This, it was concluded, is because it is more challenging to communicate with potential adversaries who might be difficult to identify, as would interests against which a response could be legitimately threatened or targeted. Non-state actors, cyber, terrorism and hybrid threats, ever greater amounts of information combined with rapid, technology-driven change. These are factors which have challenged traditional models and complicated the deterrence landscape.

One of the most insightful presentations, which expanded on previously shared published arguments, noted that hybrid warfare represents “the foggiest form of war given the deliberate obfuscations that occur in hiding the identity of the perpetrator state”. The speaker explained that, as hybrid activity is intended to inconvenience and distract but not destroy, this makes it difficult to think how this can be deterred. At the same time, while the consequences of a major conflict escalating into a nuclear exchange might be understood by the public at large, the implications of an expanding hybrid conflict are much less so. One comment referred to opaque discussions around a contested concept and contested outcomes. Another that with capabilities such as cyber, signalling is difficult as showing what you have got – and understanding it yourself – can be challenging.

As was argued by one of the speakers, summarising her own new important work which was published concurrent to the conference, deterrence research is “not static but continues to develop in ‘waves’ – as strategies adapt and conclusions change or as the security environment evolves”. Strategies are required that encompass both military and non-military means and encompass multiple domains, including conventional military, cyber, space, economic and diplomatic measures. To better manage this, the most recent UK doctrine called for “an updated, integrated and codified approach” which both dissuades adversaries across various fronts while also strengthening the overall deterrence posture. The US has now done the same with its formal adoption of integrated deterrence as a new national security strategy concept. The conclusion from the conference remained, however, that not enough work has been done examining integration and understanding the link between hybrid threats and how deterrence is employed.

Deterrence culture

Another keenly debated theme was the vital importance of studying our adversaries to understand how they think as opposed to speculating about how we think they might react. Deterrence is seen as the strategy of preventing adversaries from taking certain actions by convincing them that the costs or risks outweigh the benefits and must be “conceived primarily as an effort to shape the thinking of a potential aggressor”. As Michael Mazarr has argued: “Any strategy to prevent aggression must begin with an assessment of the interests, motives and imperatives of the potential aggressor, including its theory of deterrence (taking into account what it values and why).” He also highlighted the significance of perceptions, being able to anticipate an opponent’s ‘red lines’ can help refine decision-making avoiding pitfalls and strengthen further how deterrence strategies are constructed. Detailed knowledge of the target society is therefore needed and a “nuanced understanding of the thought processes and strategic culture of the adversary regime”.

This led to some discussion about how deterrence links to personality and whether the psychology of certain individuals means they cannot be deterred, particularly leaders of authoritarian regimes. There remains a necessity to identify what is of the greatest concern for such individuals beyond the threat of action that could undermine their ability to retain control of power. The Russian leadership is clearly nervous about being violently removed from office and employs a range of responses from subterfuge to violence and intimidation, but this vulnerability has proven difficult to incorporate in any deterrence strategy. Elaine Bunn, a former US official working on nuclear and missile defence policy, has proposed that, with its emphasis on perceptions and “getting into the heads of others” to understand their intentions and create uncertainty, “deterrence is really the ultimate mind game”. The conclusions reached at the conference suggest that the calculations involved will likely become more complicated with the increasing ambiguity attached to many of the factors which now need to be considered.


To some degree connected to thinking about strategic culture, the current NATO enhanced Forward Presence deployments in Eastern Europe provided an intriguing case study for examining signalling and a current application of how deterrence continues to evolve. First deployed in 2017, the eight combat capable battlegroups operating in Estonia, Latvia, Lithuania and Poland are integrated into NATO’s command structure. It was commented upon earlier in the conference that NATO forgot deterrence during the first post-Cold War decade but the enhanced Forward Presence can be seen as a tangible demonstration of reinventing and rediscovering conventional deterrence. A fascinating discussion explored how intentions and resolve can be presented, what was referred to as “deterrence by flag-waving” and has been described elsewhere as “an intra-alliance solidarity performance mechanism” and “a ritualised performance of deterrence”. The argument put forward at the conference was that these demonstrate activities which “play on various symbols and senses” and that NATO summits and high-level meetings and political statements, in addition to the wargames and large scale exercises which demonstrate capability, all make the potential costs to an aggressor much more visible.

Linked to this was a marginal discussion about the enhanced Forward Presence’s actual deterrent effect based around a reported senior British officer’s comment that these forces continue to offer no more than a tripwire effect. A recently published study has also used the enhanced Forward Presence in its examination of three associated deterrence models: thin tripwires, sacrificial forces intended to trigger political and military responses; thick tripwires which are still sacrificial but force an adversary to move from hybrid to open conflict; and forward defence forces which are sufficient to fight and wait for reinforcement. While the NATO force appears to fit into the last of these and the intention is they will be reinforced by high-readiness forces until heavier follow-on forces can arrive in-theatre, the actual deterrent value they provide will remain a regular discussion point so long as Russia continues to threaten the security of the Baltic region.

This was a most valuable event organised by Dstl and suggests discussions on this subject will only expand throughout 2024. Deterrence has evolved from a primarily nuclear-focused strategy during the Cold War to a multidimensional approach that incorporates various domains, technologies and tactics. At the same time, there has remained a familiarity to the language of deterrence. By denial or by punishment, tailored, direct or extended, absolute or restricted. These discussions highlighted new thinking such as with the examination of the enhanced Forward Presence deployed across the Baltic region, an example of ‘deterrence by preparedness’ and a movement away from simply relying on ‘deterrence by reputation’. Nonetheless, it is collaborative deterrence, leveraging alliances and partnerships, most obviously through NATO, which remains of paramount importance to Britain.

There also remains the standard Cold War concern – that a reliance on nuclear deterrence could result in economising conventional forces, which carried the additional risk of preparing for the wrong kind of war. Also, the degree to which the approach that is adopted fails to achieve the desired effect. The United Kingdom became involved in both World Wars under treaty obligations which were created, at least in part, as a deterrent. They failed in both cases due to inadequate military forces, insufficient allies to make them effective and being unable to convince our adversaries of a resolve to stand and fight. Additionally, for deterrence by denial to work, the level of forces needed to effectively communicate a negative incentive would be such that it could be easily misconstrued for a build-up for offensive purposes. With this remains the potential for a destabilising spiral, security dilemma or the opponent believing that an attack would be the only way to mitigate against the threat. Any rudimentary analysis of the causes of war will highlight miscalculation and error as common factors.

As Professor Sir Lawrence Freedman has described deterrence: “[It] can be a technique, doctrine and a state of mind. In all cases it is about setting boundaries for actions and establishing risks associated with crossing these boundaries.” This has not changed, it can be argued that conventional deterrence “is rooted in the Clausewitzian logic of war” while linkages can be made to Sun Tzu and winning without fighting. Perhaps the more prescient advice to absorb, with wars being fought in Europe and the Middle East, is what was described as the most popular simile in the British Army of the Rhine: “Deterrence is like riding a bicycle. If you stop pedalling, you fall off.” No deterrence strategy is perfect and deterrence failure is much more frequent than many strategic planners would like to admit. Throughout history aggressors have only gone to war when they believed that the deterrent raised by their opponents was inadequate. The priority should therefore remain to keep upright and moving forward.