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A New Deterrence Playbook? Continuity and Change in the UK's Approach to Deterrence

This essay was first published in October 2021, in the second volume of the Centre for Defence Studies series on The Integrated Review in Context: Defence and Security in Focus.

The Integrated Review (IR) and the accompanying Defence Command Paper had much to say about deterrence. While there was notable change in this respect from the two previous strategic and defence reviews (2010; 2015), there was some continuity across all three, and particularly between 2015 and 2021.

This paper focuses on two core issues. First, it addresses elements of continuity and change in the UK’s approach to nuclear deterrence. It then considers the IR’s characterisation of how the UK’s approach to deterrence more broadly is already changing, and needs to evolve going forward, in order to adequately reflect the increasingly challenging and dynamic international security environment. Similar to the nuclear area, there are elements of continuity and change in the UK’s broader approach.

Nuclear Deterrence

The most unsurprising element was the continuity of the UK’s commitment to retaining a minimum, assured and credible nuclear deterrent. Like multiple prior reviews, the 2010, 2015 and 2021 iterations all made the case for The Deterrent as: ‘the ultimate means to deter the most extreme threats’ (2010); the ‘ultimate insurance policy as a nation’ (2015); and ‘the ultimate guarantee to our security, and that of our allies’ (2021).

But the IR also initiated important changes. Specifically, the UK increased its overall nuclear warhead stockpile ceiling from 225 to 260. In 2010 of course the UK had stated that it would reduce the overall number from not more than 225 to not more than 180 by the mid-2020s. The stated rationale for raising this ceiling was a ‘recognition of the evolving security environment, including the developing range of technological and doctrinal threats…’

The Integrated Review drew attention to unnamed nuclear states ‘significantly increasing and diversifying their nuclear arsenals’ and ‘investing in novel nuclear technologies and developing new ‘warfighting’ nuclear systems which they are integrating into their military strategies’. – Professor Wyn Bowen

While not specifically named this was a clear reference to Russian and Chinese programmes to modernise, expand and diversify their respective nuclear arsenals. Three decades after the end of the Cold War, then, the IR’s announcement on warhead numbers reflects a growth in the UK’s perceived utility of nuclear weapons, something that will certainly feature in debates about disarmament and non-proliferation in the context of the NPT.

Another area of continuity involved nuclear ambiguity which has long been seen by the UK and other nuclear weapon states as central to effective deterrence. The IR, like its predecessors, maintains ambiguity around the circumstances in which the UK would resort to nuclear use (the ‘when, how and what’). But there was also change here. The IR announced that the UK would add to this ambiguity by no longer providing figures on the operational warhead stockpile, including deployed warhead and missile numbers.

It is understandable why the IR was not particularly transparent on the detailed specifics underlying these nuclear changes because they are clearly designed to make the Deterrent more relevant and credible in an uncertain and more challenging world. But the relative lack of transparency opens up ample space for speculation and it poses important questions.

Some of these may be:

  • What types of scenario planning underpinned the changes?
  • Does the UK now actively contemplate potentially having to deter two or more nuclear actors simultaneously?
  • Given the 2021 assessment about the growing severity and complexity of nuclear threats, should we expect to see a return at some point to similar concepts and language as that. contained in the 1998 SDR about a ‘sub-strategic’ role for the UK’s submarine-launched ballistic missiles?
  • What is current UK thinking on the Moscow Criterion?
  • Was the decision on the new warhead ceiling influenced by dialogue with the US, and France, vis-à-vis the strategic landscape and a joined-up perspective on the collective requirements of western nuclear deterrence?
  • Was there a fiscal dimension to the ceiling decision – i.e. relying more on nuclear instead of greater investment in new and more expensive advanced conventional assets?

An Evolving Broader Approach to Deterrence

In terms of the UK’s broader approach to deterrence the IR constituted an evolution from both 2010 and 2015, but again with important aspects of continuity.– Professor Wyn Bowen

The 2010 review had placed a ‘renewed emphasis on using our conventional forces to deter potential adversaries and reassure our partners’. Notably, it heralded the return of a carrier strike capability as part of an overall force structure ‘to deter or contain threats from relatively well-equipped regional powers, as well as dealing with insurgencies and non-state actors in failing states.’ At this stage, however, Russia was not deemed to pose the direct threat to UK and western interests that it is seen to pose today, and the assertive direction of Beijing under President Xi in pursuit of Chinese economic and military dominance had not been initiated. But the investment in a new carrier strike capability in 2010, and its future implications for power projection and conventional military deterrence, were important building blocks for the IR’s approach to deterrence in 2021.

The 2015 review did mark a significant departure for the UK in terms of the need to think more broadly in terms of how to approach to deterrence. The immediate backdrop was Russia’s 2014 intervention in Crimea and eastern Ukraine, and rapidly growing concerns that in future adversaries would increasingly challenge UK interests below the traditional threshold of armed conflict, be this in Europe, the South China Sea or cyberspace. In this respect, the 2015 review announced the UK would take a full-spectrum approach to deterrence comprising military, cyber, economic, legal and covert means ‘to deter adversaries and to deny them opportunities to attack us’. While there is not much in the open source on how this has since developed, the UK’s response to the Russian nerve agent attack in Salisbury in 2018 is illustrative. The response was multi-pronged and coordinated across government and appeared designed, at least in part, to have a future deterrent effect by demonstrating, for example: attribution capability, the ability to mobilise international support and the imposition of multilateral sanctions. Indeed, the IR subsequently placed an emphasis in 2021 on ‘reinforcing our deterrence by taking a more active approach to attribution of state threats and coordinating the use of sanctions to hold state and non-state actors to account for unacceptable behaviour’. The IR further stated that the UK ‘will also make much more integrated, creative and routine use of the UK’s full spectrum of levers – our diplomatic, military, intelligence, economic, legal and strategic communications tools, and the new NCF [National Cyber Force] – to impose costs on our adversaries, deny their ability to harm UK interests, and make the UK a more difficult operating environment.’

The IR went further than 2015 in making the case that deterrence required a conceptual and practical overhaul as the strategic environment had further deteriorated.

It painted a picture of an increasingly challenging security environment with threats posed by state and non-state actors, including sub-threshold threats, across a range of domains– Professor Wyn Bowen

with the potential for significant confrontation and conflict between the UK and its allies and an array of challengers. It stated that the UK must update its ‘deterrence posture to respond to the growth in state competition below the threshold of war under international law’.

Reflecting this the IR doubled down on the importance of societal resilience for deterrence by denial. Specifically, it talked about making it ‘more difficult and costly for malign actors – both state and non-state – to achieve the effects they desire’. This was seen to be essential for ‘reducing our vulnerabilities and improving our resilience to persistent threats’. Cyber space is perhaps the clearest example here with the emphasis placed on detecting cyber threats, reducing cyber vulnerabilities and enhancing cyber resilience.

The Integrated Review emphasised the importance of presenting adversaries with ‘multiple dilemmas to enhance our deterrence posture’, and ‘more dynamically’ managing and modulating the UK’s ‘deterrent posture’ in ‘an era of persistent competition’.– Professor Wyn Bowen

Here the talk was of the UK needing ‘a new model for deterrence that takes account of the need to compete’: ‘competing below the threshold of war in order to deter war’. In this respect, the IR referenced the MOD’s Integrated Operating Concept (IOC) in 2020 which ‘introduces a fifth ‘c’ – that of competition - to the traditional deterrence model of comprehension, credibility, capability and communication’. But suggesting that competition should be elevated as a fifth ‘c’ alongside these core elements is problematic. Competition is essentially a characteristic of the current strategic landscape associated principally with China and Russia. In deterrence terms competing is a means to an end and sits within the capability element of the deterrence equation. This is not to say that competing below the threshold of war is irrelevant to deterrence today, far from it. The existing four elements are relevant to all situations where a deterrence approach is being considered, but competition is not. Indeed, there will undoubtedly be many occasions in the next few years when some challengers are not competing with the UK, but the UK will nevertheless want to deter them from doing certain things.

The IR talks about a military force structure ‘that principally deters through ‘persistent engagement’ below the threshold of war, while remaining prepared for warfighting when necessary’. This comes with the requirement of ‘deploying more of our forces overseas more often and for longer periods of time’ and importantly ‘with NATO and alongside our wider network of allies and partners’. The subsequent deployment of the multi-national, HMS Queen Elizabeth-led carrier strike group to the Indo-Pacific region is demonstrative of ‘persistent engagement’ and illustrates the importance of the IR’s ‘tilt’ in this geographical direction. The deployment demonstrates the centrality of operating with allies and partners to project power and to deter, something the IR acknowledges: the UK’s ‘network of military alliances and partnerships is at the heart of our ability to deter and defend against state adversaries’. It will also be important for the UK’s deterrence approach to work seamlessly with that of others, for example, the new U.S. concept of ‘integrated deterrence’ announced earlier in 2021 by U.S. Secretary of Defense Lloyd Austin.

The IR does not really offer deep insights in to how the ‘new model for deterrence’ is being or will be operationalised across the whole of government. With the emphasis on integrated and creative approaches to deterrence drawing on all levers of influence from across government, one must assume that deterrence planners across HMG are actively exploring the specifics. In this respect Dstl is playing an important role through its development of a new and more systematic process for building deterrence into policy and strategy approaches within government for influencing the behaviour of challengers.

It is to be expected that an important part of the overall approach will involve thinking about why and how deterrence is likely to fail and applying this to the actors and scenarios the UK is most worried about. This requires in-depth understanding of challengers be these state or non-state actors including their red-lines, their capabilities and whether they are risk adverse or acceptant and so on. It should also be noted that the most serious potential adversaries are arguably more advanced in their thinking, and even in some areas of related capability development, be this Russia’s ‘strategic deterrence’, Iran’s ‘comprehensive’ deterrence or China’s multi-instrument deterrence; each of which include aspects of compellence (coercing to change behaviour) and not just traditional deterrence with its focus on preserving the status quo. The IR’s points on strategic competition and persistent engagement are particularly relevant here of course.

Given that the world is increasingly characterised by interdependence – be it trade, dealing with climate change or cyber connectivity –

a key challenge for the UK is the question of how deterrence should fit within the broader relationship with challengers like Russia and China? – Professor Wyn Bowen

How will deterrence work alongside elements of cooperation on common challenges like the climate and inducements to encourage acceptable behaviours in other areas? Is the UK actively thinking about how to assure potential challengers that it will not deliver on deterrent threats if particular actions or behaviours are avoided? Deterrence cannot be approached in a vacuum. It will always be part of a delicate balance among different concepts and tools for managing the most challenging of international relationships.

Concluding Thoughts

The nature of deterrence will always remain a constant and it is the character of deterrence that changes over time, notably because of technological developments such as, for example, in the cyber and space domains. – Professor Wyn Bowen

The IR explicitly recognises this: ‘We will seek to deter states from aggressive acts: through the prospect of punishment– by detecting, attributing and responding accordingly; and by denying them the opportunity to act, through reducing our vulnerabilities and improving our resilience.’

The IR, the Defence Command Paper and the IOC all demonstrate that within government and the armed forces significant thought has gone into how to deter adversaries in a complex, multi-actor, multi-domain threat environment. In this respect the IR laid out a more nuanced explanation for how the UK will seek to deter challengers than the last review in 2015. But this is understandable as the world has evolved significantly during the intervening period notably with the growing assertiveness of China and Russia. The effectiveness of the UK’s evolving approach to deterrence will only become clear over time.


Professor Wyn Bowen is Head of the School of Security Studies at King’s College London. Professor Bowen was a member of the External Advisory Panel to the UK Secretary of State for Defence for the 2015 Strategic Defence and Security Review and recently co-authored a paper in Security Studies on the challenges faced by the US in seeking to deter chemical weapons use in Syria.


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Wyn Bowen

Wyn Bowen

Professor of Non-Proliferation and International Security

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