Britain’s Extended Deterrence Dilemma

As the trans-Atlantic alliance is under stress due to President Trump’s unpredictable policies, the waning of credibility of extended deterrence assurances by the U.S. has created an opening for the UK to take a more assertive role in the European security architecture. Within the European deterrence framework, the UK enjoys a very unique position due to its possession of nuclear weapons and participation in the alliance as a trusted partner, while having dependencies on the U.S. as a nuclear power. The European countries are mulling over new options for overcoming dependencies on the U.S. Merely by virtue of the fact that the UK possesses nuclear weapons, it cannot present itself as an alternative to the U.S. unless it exhibits strategic autonomy, bolsters conventional capabilities, and explicitly outlines its extended deterrence commitments.

The Royal Navy has maintained a Continuous at Sea Deterrence (CASD) since 1969, reiterating the credibility and capability of the British nuclear forces. Furthermore, the declaratory policy of the UK explicitly mentions that it will use nuclear weapons in extreme circumstances for the self as well as allies‘ defense. The British nuclear forces comprise Vanguard-class SSBNs, Trident II D5 SLBMs, and MK4A warheads deployed on these missiles. The UK is also modernizing its SSBNs and warheads and planning to acquire F-35A aircraft, capable of delivering nuclear weapons. Although the modernization of British nuclear forces heavily relies on its cooperation with the U.S. This article will examine the British nuclear declaratory policy, the potency of its nuclear forces, and the effectiveness of its nuclear signaling for the extended deterrence commitments.

The explicit provisions of the use of nuclear weapons in extreme conditions for the defense of allies in the British nuclear declaratory policy strengthen its case for offering extended deterrence commitments to other European states. The existence of such doctrinal provisions will further build trust between the UK and the rest. Furthermore, the UK also participates in NATO’s Nuclear Planning Group (NPG) as the only European nuclear power. However, from an ally’s perspective, many questions need to be addressed, including: Firstly, if the US is unwilling to use nuclear weapons in a situation, will the UK do so? Secondly, what will be the difference in the threshold of use of nuclear weapons by the US and the UK? It seems likely that a decision to use the nuclear weapons by the UK will be highly dependent on the situation, not on a prescribed formula. With this, it will be misleading to assume that the UK will use nuclear weapons for allies’ defense in a situation. The U.S. is unwilling to do so.

Another factor complicating the efficacy of the UK’s extended deterrence is the difference between the doctrinal thinking of the former and the US on concepts of escalation management and re-establishment of deterrence by the use of nuclear weapons. The U.S. nuclear doctrine rejects the No First Use (NFU) policy and considers the use of nuclear weapons for European defense, thus ensuring deterrence. However, the UK envisions the use of nuclear weapons as a last resort, not a war-fighting option. These doctrinal inconsistencies will further make the European allies skeptical about the credibility of the UK’s extended deterrence commitments.

However, the UK, as the only European country in NATO’s NPG, can take a lead in engaging with other allies for debating the various concepts anchoring the alliance’s nuclear policy. This debate will ensure that the perspective of those European countries on the deterrence expectations, who do not sit in NPG, is listened to and maybe accommodated by the concerned.        

The geographical reality that the UK offers a target-rich environment to Russia presents another challenge to its extended deterrence commitments, as there is a likelihood of Russia’s coercion succeeding against it. The European allies must engage in a dialogue with the UK to understand what deterrence effects the UK intends to achieve and how. What will it actually contribute to strengthen the European deterrence?

The size and composition of the UK’s nuclear forces are another constraint for offering extended deterrence commitments. With fewer warheads and only sea-based deterrence, the capability was designed to deter threats against the homeland. Thus, it will become difficult for the UK to manage escalation in high-intensity conflicts due to the unavailability of flexible options in evolving situations. Furthermore, the nuclear signaling will become problematic, as the UK has only submarines, and exposing them will raise serious doubts on the effectiveness and credibility of the Assured Second-Strike Capability (ASSC). The UK is modernizing its nuclear arsenal; however, financial constraints and dependence on the US will limit the prospects for executing strategic autonomy.

With the existing nuclear forces, it is unlikely that the UK can provide an effective and credible nuclear deterrent to its allies without the U.S. nuclear umbrella.

The development of robust conventional capabilities by the British will relieve some pressure from its nuclear forces. If the UK deploys conventional forces in large numbers on the eastern flank, it will raise the cost for Russia to pursue any misadventure. The way forward for the UK lies in the modernization of its nuclear arsenal while decoupling itself from the U.S. and revisiting its doctrinal positions for responding in evolving situations. The UK must continue to engage with the other non-nuclear European allies on the concepts related to extended deterrence for harmonizing the understandings about it. At the declaratory level, the UK must enunciate what it means from the extended deterrence commitments and how it will achieve it.

The UK has an important role in the European security architecture; however, it is yet to be seen what it can offer to the European allies in terms of extended deterrence commitments without the U.S. nuclear umbrella.