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Weapons of Mass Debate - Integrating the UK Into the European Discussion

Weapons of Mass Debate - Integrating the UK Into the European Discussion
 Malcolm Chalmers
Deputy Director-General of RUSI

Since the August 1945 nuclear attacks on Hiroshima and Nagasaki that led to Japan’s unconditional surrender and ultimately kicked off the Cold War, nuclear weapons have changed the face of warfare and international relations. They laid a shadow on the international stage with the start of a nuclear arms race, and introduced deterrence as a new form of diplomacy. In the midst of all this, as the European Union continued its process of integration, security and strategic matters led European leaders to ponder the nuclear question. In February 2020, French President Emmanuel Macron invited his European partners to launch a strategic dialogue on the role the French nuclear deterrence can play to safeguard European collective security. Although this call has so far remained without any real response, the evolution of the strategic context - including the resurgence of military powers, the new US administration, the redefinition of NATO’s strategic concept, the publication of the British Integrated Review and the upcoming federal elections in Germany - has put this issue on the agenda once again. 

This new environment has led Bruno Tertrais, Senior Fellow for Strategic Affairs, and Mahaut de Fougières, Policy Officer for International Affairs, at Institut Montaigne to launch a discussion on the role of nuclear weapons in Europe. "Weapons of Mass Debate" aims at giving a voice to European experts in order to shed light on the state of the debate on nuclear weapons in their country. In this first episode, Malcolm Chalmers, Deputy Director-General of the Royal United Services Institute (RUSI), shares his analysis of the UK’s evolving vision on nuclear weapons and their role for European security, after Brexit and the publication of its Integrated Review.

The UK's nuclear force has been a central feature of its defense policy since the 1950s. As long as nuclear weapons exist in the possession of potential adversaries, it will continue to be seen as having a key role as the ultimate guarantor of national security. 

While the UK has much in common with France in this commitment, there are two characteristics of its nuclear posture that distinguish it from that of its strongest European ally. 

First, the UK’s deterrent force is closely linked to US nuclear capabilities, both through deep programmatic cooperation and through its integration into NATO nuclear planning. The submarine force is equipped with the US’s Trident long-range missiles, and the new countries are cooperating on the production of new generations of missile submarines. The warhead complex maintains close cooperation with its US counterparts on warhead design and relies on the US for key (non-fissile) warhead components. This arrangement has had the added benefit that it has been significantly less expensive than a national procurement option. 

Second, there has always been a vigorous domestic political debate on the wisdom of maintaining that force, and on the morality of nuclear deterrence more broadly. While unilateral nuclear disarmament has never commanded majority support, successive governments have felt obliged to respond to this debate by emphasizing their strong commitment to disarmament as an accompanying pillar to deterrence. In addition to the key role which the UK has played in establishing, and then strengthening the NPT, post-1990 governments have also sought to emphasize that the UK is the most disarmament-oriented of NATO’s nuclear states.

These key features have not been fundamentally changed as a result of the Integrated Review of Defense, Security, Development and Foreign Policy (IR), published in March 2021.

The UK nuclear posture could be seen as having become more like that of France.

Even so, there has been a significant shift in emphasis, with the removal of restraint and transparency measures announced in previous reviews used to emphasize the increased importance now being given to deterrent credibility. In this regard, the UK nuclear posture could be seen as having become more like that of France.

The UK as Disarmament Leader

The IR has maintained the recent practice of using national defense reviews to publish updates on nuclear weapons policy. It is the fifth such document since 1998. In each case, the Government has made statements on deterrent doctrine and disarmament commitments, together with updates on national declaratory policy and the UK's nuclear commitments to NATO. 

One of the central features of the first three of these reviews - in 1998, 2007 and 2010 - was a commitment to visibly reduce the nuclear arsenal to the lowest level possible, demonstrating that the UK was a strong supporter of disarmament. Most recently, the 2010 Strategic Defence and Security Review (SDSR) cut the number of warheads and operational missiles on each submarine to 40 and 8 respectively. It also declared that the overall stockpile would be cut from "not more than 225" to "not more than 180" warheads by the mid-2020s.

All three of these reviews took place against the background of a strategic environment in which concerns about Russia remained in recess. By the time of the next SDSR in November 2015, however, this had changed. The SDSR announced no new initiatives in relation to the nuclear stockpile, while reaffirming the commitments made in 2010. In a nod to growing concerns over possible future developments, moreover, it made clear that "we will continue to keep our nuclear posture under constant review in the light of the international security environment and the actions of potential adversaries".

The Integrated Review 

By the time that the IR process began in 2020, the concerns about Russia expressed in the 2015 Review had deepened and widened. The aggression in Ukraine was now seen as part of a wider pattern of assertive behaviour. The use of chemical weapons on UK soil in 2018 had an especially profound impact on political attitudes, reinforcing the belief that Russia’s leadership was increasingly willing to breach international norms in relation to weapons of mass destruction.

This shift in perceptions of Russia’s behaviour was magnified by heightened concerns over its technological capabilities and nuclear doctrine. Together, these factors led to a reversal of most of the disarmament steps that had been inherited from previous reviews:

  • First, the IR abandoned the commitment to reduce the total nuclear stockpile to no more than 180. Instead, in recognition of the new security environment and new technological threats outlined above, it increased the ceiling on the overall stockpile to no more than 260 warheads. This is still lower in size than France’s total arsenal of less than 300 warheads. But the gap has narrowed. 
  • Second, the Government reversed the additional transparency measures adopted in its 2010 Review. Henceforth, it will be able to vary the number of warheads and missiles deployed on each boat above the previous ceilings. The UK no longer provides separate figures for its operationally-available arsenal. Whereas the UK was previously the most transparent of the five recognized nuclear-weapon states, its level of transparency is now roughly comparable to that of France, although still much more transparent than Russia or China. 

The primary explanation for these two changes is the changing assessment of the threat from Russia. At the heart of UK nuclear doctrine since the 1950s has been the ‘Moscow criterion’, the requirement to pose a credible threat of unacceptable damage to the most valuable assets of a potential adversary. The decisions announced in the Review - and in particular the increase in the stockpile ceiling - reflected an assessment that it is getting harder to maintain this strategic threat in the face of new Russian defensive countermeasures, including its missile defences. 

The conclusions of the IR also reflect the importance that the UK attaches to maintaining credible sub-strategic nuclear options.

The conclusions of the IR also reflect the importance that the UK attaches to maintaining credible sub-strategic nuclear options. Unlike France, the UK has no nuclear-armed bomber aircraft. It therefore has fewer options for nuclear signalling during a crisis. When it gave up its air leg in 1998, however, the MoD made clear that its Trident force was capable of "retaining an option for a limited strike that would not automatically lead to a full scale nuclear exchange". This remains the case. Unlike France, the UK has not limited its flexibility in this regard by committing to a "unique and one-time-only nuclear warning". The Government has made clear that it sees no role for nuclear weapons in a tactical role. But it does see value in maintaining ambiguity as to whether and how it might consider escalation, including after a first exchange of warning shots. Increased Russian interest in its own sub-strategic options, together with the deployment of new INF-range missiles capable of reaching much of NATO Europe, have been added factors in the UK's reappraisal.

The dual requirement for maintaining credible strategic and sub-strategic forces, in the face of plausible improvements in Russian defensive capabilities, helps explain why the MoD has now reversed the 2010 decisions on transparency on deployed warhead and missile numbers. Even if an opponent in a crisis would be unlikely to take unverifiable declarations at face value, they do limit the flexibility which UK forces can exercise in planning and deploying the force in peacetime. As a result of this change, the Royal Navy can now vary the loadings of submarines without public notice, increasing the uncertainty that faces a potential adversary. 

Beyond the Integrated Review

While the main force driver for the UK deterrent remains a potential threat from Russia, it could also be relevant to future threats from other states, for example from the Middle East. In some scenarios, China might also one day become a more significant driver of the UK's nuclear capabilities and deployments. But that is an issue for a future Review.

There has not been any suggestion that the UK should re-invest in an air-based component to its deterrent force. Although it is the only nuclear-armed state with a single delivery system, the UK's nuclear planners have enough on their plate to sustain a credible submarine-based force.


The Polaris ballistic missile system purchased from the US in the 1960s proved to be a remarkable bargain. Since that period, however, the nuclear force has taken a growing share of a total defense budget which, for much of the period, has been relatively stagnant in real terms. Over the last decade, substantial new resources have had to be spent on recapitalizing the nuclear warhead complex, as well as on the development of a new generation of submarines. Even before the Integrated Review, ten-year projections showed some 25% of total equipment spending being devoted to nuclear and submarine capabilities. The IR is likely to have increased this proportion, with confirmation of the plan for a new warhead, increased costs associated with keeping the existing submarines in service, as well as growing costs for the new class of Dreadnought submarines. Whatever it costs, however, any future government is likely to prioritize the maintenance of a credible nuclear deterrent force, if necessary at the expense of conventional capabilities. 

The Alliance Dimension

The UK has always assigned its entire nuclear capability to NATO’s collective efforts, as well as maintaining an active membership in the alliance’s Nuclear Planning Group (NPG). In addition, the IR has signalled an increased policy focus on the UK’s support for NATO’s other nuclear missions. 


The IR has signalled an increased policy focus on the UK’s support for NATO’s other nuclear missions.

In a new passage that was not included in the 2015 review, the IR states that the UK "will work with Allies to ensure that NATO’s nuclear deterrent capabilities remain safe, secure and effective". This refers to UK efforts to improve awareness of the requirements of a credible nuclear posture, including practical help to allies designed to improve the security and survivability of their DCA assets.

The UK's reaction to President Macron’s proposal for a "strategic dialogue" on the role of France’s nuclear force in European collective security has largely been one of puzzlement. From a UK point of view, mechanisms already exist - through the NPG - for European NATO members to pursue such a dialogue. 

The experience of the Trump presidency has led to some reflections on the importance of an independent deterrent as a hedge against the possibility that the US might not be seen as fully reliable in a future crisis. For the UK, this means that the case is as strong as ever for maintaining a capability which can both serve as a separate nuclear centre for decision-making and can also deter the most extreme threats to the UK if it were to stand alone. 

The UK and European Security

Brexit has made no difference to the strength of the UK’s commitment to NATO. As in France, there has been a marked "Indo-Pacific tilt" in foreign policy, especially evident in trade policy and maritime deployments. But the IR has confirmed that the UK’s most vital security interests are in Europe and that NATO remains central to its defense and security priorities.  

The IR makes clear that France retains its position as the UK’s most important European security partner, reaffirms the commitments made in the 2010 Lancaster House Treaty, and praises the achievements of the Combined Joint Expeditionary Force (CJEF). Importantly, it also emphasizes that, since 1995, the two countries have stated that "they can imagine no circumstances under which a threat to the vital interests of one would not constitute a threat to the vital interests of the other". This is the political context for the 2010 Teutates Treaty, under which both countries work together to manage their joint hydrodynamic testing facility in France. 

Where the IR is much less clear is on the future of its foreign and security policy relationship with the European Union. At the UK’s insistence, this was excluded from negotiation of the final Trade and Cooperation Agreement. In time, new arrangements in this area might well be developed, for example in relation to defence industrial cooperation. At least from the perspective of London, however, it is hard to see any role for the EU - or for UK/EU cooperation - in relation to nuclear deterrence or capabilities. 

In the last analysis, the UK’s commitment to the security of its European allies, and vice versa, is political and cultural, more than it is legal. And the last decade has shown that we ignore the consequences for the Western alliance of major political ruptures within member states at our peril. The UK will therefore take a keen interest in how the defense and nuclear policies of its most important neighbours evolve as they enter their own national elections. However these turn out, the twin pillars of UK defense policy seem likely to remain its deep commitments to collective defense through NATO and to the maintenance of a credible minimum nuclear deterrent. 



Copyright: Andy Buchanan / AFP

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