British Grand Strategy and Hedging in Europe: The Case for Nuclear Arming
Introduction
Britain faces the most turbulent geopolitical landscape since the early Cold War. An emboldened Russia is adapting to drone-based warfare in Ukraine, mounting covert operations across North Atlantic Treaty Organization (NATO) territory, and helping Beijing prepare to absorb Taiwan. European militaries, for their part, are under-equipped and unable to rapidly deploy eastward in force.
At the same time, U.S. foreign policy is in flux. America has been tied to Europe since the early Cold War by intertwined economic, ideological and strategic imperatives. Compared to its post-World War II predecessors, however, the second Trump administration takes a minimalist view of U.S. interests on the continent. While outright NATO withdrawal remains unlikely in the short-term, de facto disengagement is underway.
In Britain, most commentators favor higher spending on military forces as a share of national income, but how increased spending would enhance the country’s security is often left vague or implicit. Explicit means-ends reasoning is crucial for grand-strategic analysis, however. In Joshua Rovner’s words, “Grand strategies that cannot describe the logical link between national effort and national security are vacuous.” Many explicit arguments suggest allocating scarce resources to conventional forces, especially ground forces. From this perspective, the nuclear deterrent remains adequate, given its potency and invulnerability, but the UK’s inability to sustain a full-scale conventional war against a peer competitor—namely Russia—requires urgent redress.
I argue that the standard view misconstrues Britain’s threat environment. While its strategic nuclear deterrent remains largely secure, vulnerabilities exist and may increase, growing in salience as America disengages. Moreover, the strategic deterrent is ill-suited to crises with less-than-existential stakes. Short of large-scale attacks on the UK mainland, Russian leaders might well discount British nuclear threats. To minimise its strategic vulnerability, Britain must operate at least one additional submarine; to maintain deterrence in Europe, it should reacquire tactical nuclear weapons. Although both measures are commonly portrayed as prohibitively costly, London should prioritise nuclear arming over a broad conventional buildup.
The relevance of grand strategy
“Grand strategy” is discussed much less often in the British than in the American, Russian or Chinese contexts. Senior British officials have stated publicly that the country either cannot formulate or does not require a grand strategy, in light of the relative tranquility, or later “complexity,” of the post-Cold War environment.
For many commentators on both left and right, the discussion itself appears naïve or quaint, given the country’s role as a satellite or client of the American empire. “The hidden fist of the US empire,” writes Matt Kennard, “which I’d seen deployed all over the developing world – the massive American military – [is] also occupying Britain” in the form of U.S. air force installations. Neema Parvini similarly dismisses “the fiction that Liz Truss or Boris Johnson... have been leaders of the autonomous Government of the United Kingdom rather than a supine regional vassal state.”
Properly understood, however, “grand strategy” is not the exclusive preserve of great powers or a vestige of a simpler era, but refers to a state’s theory of security. Client states naturally lack independent theories of security, but Britain is not a U.S. client. While the global distribution of military power remains unipolar, the current international system—including the institutionally integrated “liberal international order” sub-system—remains a balance-of-power order composed of domestically ruled nation-states.
U.S. power preponderance does provide Washington with extensive leverage, but that leverage is bounded, for two basic reasons. First, although a larger power advantage makes a given threat more credible, potential targets will also be less inclined to consider the threat in isolation and more likely to anticipate expansive future demands. Compliance makes less sense when the resulting reprieve is temporary. Second, the balance of military power is distinct from the distribution of usable military capabilities. Despite unparalleled power-projection tools, for example, Washington cannot plausibly threaten the territorial integrity of—nor therefore powerfully coerce—states that maintain or could rapidly deploy survivable nuclear forces.
To be sure, imperial ties can be concealed beneath ostensibly interstate relations. A state might rule another indirectly, by elevating like-minded or pliable elites through regime-level security guarantees, conditional aid, or manipulating elections, to produce desired policy outcomes. During the early Cold War, Washington molded West European politics by employing these and other methods to bolster anti-Soviet domestic factions.
In Britain, however, the postwar Labour Party’s anti-Soviet posture gave the U.S. neither a strong incentive nor a viable means to exert influence. “The United States did not attempt to manipulate Britain’s internal politics and allowed autonomous political processes to unfold,” notes David Lake, “for two critical reasons. First, United States and British policy preferences were more closely aligned than elsewhere... Second, the similarity in the foreign policy preferences of the two major political parties in Britain—Labour and Conservative—limited the ability of the United States to impose indirect rule,” since “[t]ipping the balance of political power in one direction or the other would have produced little difference in Britain’s foreign policy.”
More broadly, while the American military retains most of its Cold War-era overseas bases, their presence does not in itself imply indirect rule. Overall, U.S. strategy in the unipolar era has been less “imperial” than it was prior to 1989, as Washington has less often exerted major pressure on host states and allies. And as William James concludes, although Anglo-American relations have stayed close since World War II, “the extent of American influence over British grand strategy has been greatly exaggerated.”
A more basic objection to “British grand strategy” talk emphasises the long-term decline in the UK’s relative power, its anemic productivity growth following the 2008 financial crisis and the chastening stability operations in Afghanistan and Iraq. Grand-strategic debates, in this view, are a distraction from the more piecemeal approach befitting a formerly great power.
Britain’s military potential is indeed limited. While power cannot be measured precisely, arguably the most useful definition is relative net resources, which can be proxied by comparing the products of states’ total economic output and output per capita. These figures account for variation in states’ welfare and security costs, and their efficiency at converting resources into military capabilities. In terms of net resources, Russia’s power advantage over Britain was around 5:4 in 2024, China held a nearly 4:1 advantage, and America’s stood at more than 9:1.
Declining power does not reduce the need to carefully formulate grand strategy, however. On the contrary, less capable states operate in a more dangerous environment, leaving their security more rather than less sensitive to suboptimal military policies. Moreover, the security a state derives from its power in a specific context is mediated by the offence-defence balance, or the relative cost of the forces required to overcome a given defending force. When a state is surrounded by water, for example, or acquires nuclear weapons, even far more powerful rivals cannot necessarily translate their advantage in military assets into operational success or coercive leverage. Accordingly, modern realist theories of international relations focus on military capabilities rather than power.
U.S. withdrawal from NATO is plausible
Beyond power and offence-defence variables, a grand strategy should make judgements about a state’s potential allies. In any serious military contingency since the Second World War, Britain would almost certainly have acted alongside the U.S. This insulated the country’s security from changes in its sovereign military capabilities.
Today, however, the British government should plan as though Europe’s post-World War II security arrangements are no longer in place. While predicting even near-term U.S. strategy is now far from straightforward, when uncertainty is high decision-makers should rationally focus on the plausible worst-case, and de facto American withdrawal from NATO should be viewed as eminently plausible, for several reasons.
Most obviously, Trump’s longstanding worldview sits uneasily beside the NATO commitment. Unlike in his first term, however, senior officials in his administration are also genuinely skeptical of its overall benefits. A useful simplification would divide officials into four factions.
First, the Atlanticist old guard (“neocons” in common parlance), composed of Republican elder statesmen, assorted hawks and liberal interventionists who favor deep and open-ended military engagement in Europe. In their view, U.S. primacy is crucial for suppressing regional security dilemmas, sustaining democratic governance and open trade, and deterring potential predators. The Atlanticists narrowly averted fundamental revisions in U.S. global strategy during Trump’s first term, but are now largely absent from senior policy roles.
The second is comprised of conservative nationalists, paleoconservatives, and libertarian anti-interventionists who harbour a minimal conception of America’s overseas security interests and a highly skeptical view of aid to Ukraine. Though ideologically diverse, this faction cleanly rejects the premises of U.S. international primacy. Its most influential voice inside the White House is Vice President JD Vance, whose personal indifference to the outcome in Ukraine and private contempt for allied dependence on the U.S. military have visibly unnerved European elites.
A third grouping is a cohort of self-described realists. In a military policy context, the realist moniker commonly signifies “restraint,” i.e. a preference for “offshore balancing” over forward-deployments and a relative uninterest in non-security goals, often coupled with the presumption that other major powers’ aggressive behaviours are motivated mostly by insecurity. The last assumption, which Trump sometimes seems to share, would give officials little reason to expect Russian aggression in Europe beyond Ukraine, while offshore balancing and a security-only focus would provide no immediate reason to intervene.
Lastly, more hawkish policy realists within the administration also deemphasise non-security goals, but interpret Moscow and Beijing’s aims as less defensive, and therefore less responsive to reassurance about U.S. intentions. Still, given China’s much greater latent and military power, these officials prioritise raising American warfighting capability in East Asia at the expense of the U.S. footprint in Europe. As the Pentagon’s lead policy official Elbridge Colby has written, “the US interest in Europe must be shaped by the requirements for ensuring that China does not establish predominance in Asia.”
These factions’ actual influence on current policy in the face of organizational inertia and Trump’s mercurial temperament is open for debate. European policymakers, however, would be wise to note that most GOP voters have an “unfavorable” view of NATO; many influential right-wing commentators endorse U.S. withdrawal, and more fervent nationalist elements may dominate the 2028 Republican primary. Needless to say, the grand strategies of U.S. allies should not hinge on the Democratic Party’s electoral success.
Beyond the current administration’s composition, Europeans should also recognise the looseness of the security guarantee embedded in the North Atlantic Treaty. “Guarantee” is of course a misnomer; states will take costly actions, such as military interventions, only inasmuch as they serve their current interests. But Article 5 of the Treaty fails to even notionally commit the U.S. to defend a co-signatory. Instead, parties merely “agree that, if such an armed attack occurs, each of them... will assist the Party or Parties so attacked by taking forthwith… such action as it deems necessary [emphasis added], including the use of armed force, to restore and maintain the security of the North Atlantic area.”
The treaty language was kept vague in part to mollify longstanding congressional and popular desire to avoid foreign entanglements. The Truman administration sold it to Congress emphasizing the noncommittal letter of Article 5 over its eventual spirit, while a large share of the American public knew the treaty contained no ironclad pledge and conditioned their support on its absence.
Also weighing against a clear security pledge, however, was the lack of a consensus rationale for intervention even among top officials. Traditional accounts of why the U.S. committed to Europe emphasise the imperative of preventing a single power from dominating Eurasia, a supercontinent endowed with sufficient resources for a hegemon to eventually conquer North America. But that hypothesis rested on the questionable assumption that large invasion forces could still be transported across wide, contested oceans in a world of mass airpower and nuclear weapons. In fact, many on either side of the treaty debate agreed that a Soviet takeover of Europe would not necessarily spell doom. Nonetheless, the survival of non-communist Europe was seen as extremely important for many reasons, not all material. “With a totalitarian Europe which would have no regard for individual freedom,” noted one government committee, “our spiritual loss would be incalculable.”
By the early 1960s, a de facto security commitment had emerged, underwritten by large deployments of U.S. conventional and tactical nuclear forces. Many American officials wanted a Europe capable of protecting itself, but they disagreed on the German nuclear question. The basic problem was that to balance Warsaw Pact military power, Britain and France needed West Germany, but for Bonn, playing that role meant acquiring formidable nuclear capabilities. The West Germans were eager, yet for obvious reasons Moscow was fiercely opposed, and initiated crises over Berlin in the late 1950s and early 1960s in order to convince Washington to keep nuclear weapons permanently out of German hands.
The Eisenhower administration, intent on reducing the fiscal burden imposed by deterrence in Europe, eagerly supported West German proliferation and ceded de facto control of some forward-deployed nuclear weapons to the Bundeswehr. The Kennedy administration, by contrast, aimed to reduce tensions with Moscow by blocking German nuclear ambitions and to preserve America’s preeminence within the collective West. To these ends, it reasserted sovereign control over all deployed nuclear weapons and threatened to withdraw U.S. forces from the continent before the Germans would have time to acquire their own arsenal. Bonn acquiesced, burying the most serious source of tension in postwar Europe and solidifying transatlantic dependence for the remainder of the Cold War. That dependence gave Washington leverage in keeping core U.S. allies economically open, politically liberal and geopolitically subordinate, while NATO’s reliance on tactical nuclear forces to offset Soviet conventional superiority limited the ensuing fiscal burden. Not coincidentally, this compact set the stage for the unipolar era that took shape after 1989.
Today, Moscow cannot plausibly aspire to dominate all of Europe, much less Eurasia, but the German nuclear question still looms. “The heart of the problem” for America and Europe, writes Marc Trachtenberg, “concerns not Ukraine but Germany, especially the question of whether that country should possess nuclear forces… Few people, either in Germany or the other Western countries, are comfortable dealing with that issue openly,” but the depth of opposition to German nuclearization largely explains why “Europe never developed the capability to stand on its own militarily during the Cold War, and indeed, why the NATO system remained intact” after it.
In Washington, uncertainty around the long-term consequences of disengagement might continue to prevail over the domestic and strategic pressures to pull back, but European states would be reckless to assume it will.
Grand-strategic independence
As the U.S. commitment has frayed, recent British governments have set increasingly ambitious targets for defence spending. Yet spending alone, untethered to specific scenarios, can be a poor proxy for military capability.
To hedge against American disengagement, Britain would need to adopt a much more independent grand strategy. Grand-strategic independence does not imply relinquishing commitments in Europe or abandoning non-security goals. The security value of maintaining NATO states’ territorial integrity or Ukraine’s survival would be a matter of debate, and London could continue to pursue broad aims.
An independent grand strategy, however, requires sovereign military forces capable of deterring or defeating large-scale threats to the homeland, and of resisting coercion by hostile powers without support from allies. For Britain, military self-sufficiency would be a departure from post-World War II grand strategy, but historically, capable states have been reluctant to rely on others’ support.
Military policy implications of U.S. disengagement
In Britain, many commentators and former officials have called for large increases in military spending, primarily on conventional forces, as a hedge against U.S. disengagement. On the nuclear side, many also contend that Britain’s forces remain adequate, given their capacity to inflict unacceptable damage on Russia.
This view misconstrues the UK’s military weaknesses. Currently, Britain can reliably deter existential threats with its secure second-strike capability. However, this “minimal” deterrent could become increasingly vulnerable, or at least perceived as such. At the same time, Britain’s ability to bargain over important but less-than-vital interests is restricted by its lack of limited nuclear options; in an escalating crisis, Britain would struggle to credibly threaten limited use, either initially or in response.
Note that the analysis does not predict the overall outcome of U.S. disengagement or the probable impact on Britain’s existing priorities, and does not evaluate those priorities. Instead, I take London’s basic strategic aims as given, focusing on the narrow military policy implications of U.S. disengagement.
Strategic background: The Anglo-Russian security dilemma
To gauge the threat posed by a rival, a state must assess both the military balance and the rival’s aims; in particular, whether it harbours non-security or “greedy” goals with respect to the state’s interests.
Assessing motives can be crucial, because although deterring a greedy rival requires competitive policies, satisfying an insecure rival means reassuring them about their own security. At first glance, simply competing might initially seem the most prudent policy. But states often face a security dilemma, wherein measures designed to enhance their own security decrease the security of others. Consequently, while policies that can reassure an apparently insecure rival that is actually greedy would erode deterrence, the flip side is that treating an insecure rival as though it were greedy can inadvertently pressure it into an arms buildup to restore its defences, diplomatic belligerence to signal resolve, and as a last resort, preventive war.
Russia is generally viewed as Britain’s principal state adversary, but President Vladimir Putin’s motives and threat perceptions remain widely debated. Some observers view his decision to invade Ukraine as a desperate effort to preserve a wide buffer zone against future Western conventional aggression or the close-in deployment of nuclear forces; others see this stated rationale as a pretext for a decision driven by an ambition to restore Russia’s great-power status or to neutralise a threat to the Russian regime’s domestic legitimacy.
Fortunately, the case for the policies discussed here is not highly sensitive to assumptions about Russian motives. If Putin’s actions in Ukraine are driven by perceived insecurity, Britain’s nuclear security dilemma is not severe, since its nuclear capabilities fall well short of threatening Russia’s second-strike. Moreover, if Russian officials do grow concerned, they would be unlikely to resort to the dangerous policies associated with a severe security dilemma, as those policies would be ineffective. As Brendan Green summarises, “in a world where bargaining occurs through nuclear risk-taking, an insecure adversary cannot affect the military balance by conquering territory, adding strategic depth, or conventionally punishing the adversary army... if insecure states fear the future military balance, their only choice is redoubled nuclear competition.”
The prospects for nuclear arms control
Arms control can play an important role in grand strategy. Although Britain has not been party to any bilateral nuclear arms limitations and Anglo-Russian diplomacy remains frozen, opportunities might arise. If so, London’s approach ought to be guided by a clear view of the purpose of arms control among rival powers, which is often misunderstood by both dovish and hawkish commentators.
In most dovish commentary, arms agreements represent off-ramps from dangerous and futile arms racing. When international tensions stem from a fundamental conflict of interest, however, states are likely to compete for military advantage. Arms negotiations may be feasible and useful, but as an element of the competitive process, not an alternative to it. By agreeing to limits on particular weapon systems, rivals can formalise bets about those weapons’ strategic value. In the early 1970s, for example, the Strategic Arms Limitation Talks froze the ICBM buildup, locking in Moscow’s quantitative superiority but allowing Washington to focus on improving its arsenal’s lethality against hardened silos, an effort that bore fruit in the 1980s. Thus, in competitive negotiations, incentivizing agreement and disincentivising subsequent defection means pursuing (and credibly threatening to pursue) policies that effectively threaten the adversary’s military position.
Hawks also tend to equate arms control with détente. According to many, agreements are only desirable to the extent that they transform all or many of the adversary’s unwanted behaviors. Critics of the Iran Nuclear Deal, for instance, often argued that Tehran’s persistent support for hostile paramilitary groups betrayed its disinterest in genuine cooperation. In future Anglo-Russian talks, analysts may likewise highlight Moscow’s intransigence on Ukraine or covert action in Europe as precluding or sinking an arms agreement. However, such concessions would be irrelevant; instead, arms agreements should be graded in terms of their impact on a state’s military capabilities. As long as fundamental conflicts of interest persist, British officials should keep in mind that arms agreements require, and serve as a component of, effective military competition.
Entrenching MAD: The case for multiple submarine patrols
Britain’s strategic nuclear posture was formulated, and only remains adequate, under the assumption of close U.S. alignment. The country relies on a fleet of four Vanguard-class nuclear ballistic missile submarines (SSBNs), with one on constant patrol to uphold a continuous-at-sea deterrent (CASD) posture.
Russia’s nuclear stockpile dwarfs Britain’s arsenal, enabling it to strike the UK mainland with many more warheads. Unequal force size, however, matters only inasmuch as it produces a politically salient difference in vulnerability. “Countervalue” capabilities exhibit sharp diminishing returns; when both side’s major cities are highly vulnerable, as in the Anglo-Russian case, “mutual assured destruction” (MAD) effectively holds, so that even a large imbalance in deliverable warheads will not translate into lopsided leverage. In principle, even a single surviving SSBN—carrying eight Trident II submarine-launched ballistic missiles (SLBMs) each typically armed with five 100-kiloton Holbrook thermonuclear warheads—is probably sufficient to destroy Russia as a political entity.
CASD is also the appropriate posture. Constructing silo fields, as one government report noted, “is entirely impractical in the UK.” The three fields in the U.S. currently hosting America’s Minuteman ICBM force, for comparison, span the equivalent of 43% of Britain’s landmass. The UK would not require as large an arsenal, but fixed ICBMs are increasingly vulnerable. SSBNs, in contrast, remain highly survivable; like their American Ohio-class counterparts, Britain’s SSBNs operate in deep waters far from major shipping lanes, and are quieter than Russian and Chinese submarines.
Relevant technologies are advancing rapidly. The UK’s reliance on small undersea nuclear forces leaves its security highly sensitive to technological innovation. In Tom Layhe’s words, “the UK is the only nuclear power where developments in the anti-submarine warfare (ASW) domain concern its entire deterrence delivery capability.”
Fortunately, although SSBNs face a growing array of potential threats, for the foreseeable future these threats can be addressed. As in the Cold War, threats to submarines will centre around acoustic detection and tracking at sea, and as before, both passive and active sonars face major obstacles. British and U.S. SSBNs remain extremely quiet, and the inherent trade-off between passive sonar sensitivity and false-alarm rates should prevent SSBN hunters from keeping pace, especially given the rise in ambient noise from commercial shipping. Active sonars, on the other hand, can be highly effective at close range, but emitters reveal their presence to a target much further out than vice versa, allowing SSBNs to evade or to maneuver near friendly naval assets to “delouse” potential trackers.
Other threats to SSBNs also seem limited. The simplest scenario would involve a locatable “tag” being covertly placed on a vessel while in port or attached while en route to its dive site. However, tight security measures inside Faslane as well as thick surrounding air, surface and undersea coverage make successful tagging extremely improbable. More speculatively, innovation in uncrewed underwater vehicle (UUVs) will boost “anti-SSBN” operations, yet there is no obvious way to overcome the cross-cutting challenges of endurance, speed, communication and quieting. At the same time, more advanced UUVs can serve as more effective pro-SSBN decoys and minehunters. Progress in artificial intelligence (AI) is highly uncertain, but at this stage seems unlikely to asymmetrically bolster anti-SSBN forces in the near term. Overall, trends suggest that Russia and China will not be able to jeopardise Britain’s CASD in the foreseeable future.
Still, there are four important caveats to this optimistic conclusion. First, it describes the likely outcome of optimal or near-optimal policies that enable both sides to operate close to the technological limit. It suggests that British SSBNs can remain survivable, not that they will automatically. Extensive and continuous research, testing and maintenance will be needed to anticipate and address looming ASW threats. For the U.S. government to protect its much larger SSBN fleet, Tom Stefanick concludes, it must ensure “strong support for research in oceanography, sensors, and signal processing, as well as [for] SSBNs and their crews.”
Second, conclusions about technological trends are inherently uncertain and subject to rapid revision. While not the most likely outcome, rapid progress in AI or undersea drone technology could decisively empower anti-SSBN operations. Nuclear competitions have always been plagued by technological uncertainty. In the Cold War, Washington and Moscow both knew the other might limit its own vulnerability, a fear which drove the construction of seemingly redundant forces to insulate their deterrents from technological shocks. Underlying fragilities in the nuclear balance became visible soon after the Soviet collapse; by the mid-2000s, the decay of Russia’s forces and warning systems and advances in U.S. counterforce combined to effectively dissolve MAD. For a number of years, Washington could have plausibly destroyed Moscow’s entire long-range arsenal in a “bolt-from-the-blue” attack, while Beijing might have been disarmed even if fully alerted.
Third, note that Russia’s willingness to risk nuclear war will depend on the perceived rather than the actual costs of war. This means that, from a bargaining perspective, the key variable for British decisionmakers is whether the Russian government believes it can limit damage. If British officials think Moscow believes it can neutralise the UK’s sole patrolling SSBN, then in the short run they should behave as though MAD no longer holds, i.e. make larger concessions to avoid or restrain crises, even when certain it still does. Britain’s requirements for sustaining nuclear stalemate are thus more onerous—and Russia’s for undermining it are less onerous—than implied by analyses that cast beliefs about the military balance as necessarily accurate or symmetrical.
Fourth, reliance on a single patrolling submarine gives Britain’s national security a single point of failure, and although they remain extremely hard to track, a Vanguard-class submarine could be disabled by an accident or malfunction. Between 1988 and 2011, the Ministry of Defence recorded 14 collisions, mostly groundings, involving British SBNNs, along with 20 significant onboard fires. In 2009, the HMS Vanguard collided with a French SSBN in the Atlantic; while neither was disabled, both suffered substantial damage. In 2023, the primary depth gauge on a Vanguard-class SSBN failed during a dive.
While unlikely, a severe incident could occur coincidentally during an intense crisis. London would not disclose its impaired status, of course, but if it was revealed inadvertently, Moscow would perceive a fleeting first-strike capability. If Russian officials are already pessimistic about the course of the crisis, they might risk striking before the UK could “flush” an extra SSBN from Faslane. The flushing process might take several days even in an emergency, and the frenetic activity observable around the port could raise or confirm Moscow’s suspicions.
Minimizing these risks is straightforward. Ideally, Britain would switch to dual patrols by constructing more than the four planned Dreadnought-class submarines. A fifth boat, as Andrew Futter emphasises, “would be relatively cost-effective given the economies of scale and sunk costs.” At a minimum, however, London should be able to rapidly flush a second boat in a crisis. The latter option is currently uncertain, and lengthening patrol times suggest growing strain across the overall maintenance cycle.
In terms of maintenance and testing, Britain’s deterrent is highly reliant on cooperation with the U.S. The UK’s Trident missiles do not require any foreign launch authorization, but they are drawn from a joint U.S.-UK missile pool located in the U.S. state of Georgia. The decision to share missiles was taken in the 1980s under Margaret Thatcher, whose cabinet secretary described the prospect of Washington refusing to support the UK’s deterrent in the future as “inconceivable.” Cooperation rests on the 1958 Mutual Defence Agreement, which was previously renewed each decade but then extended indefinitely in November 2024. Though certainly desirable, gaining full technological autonomy in strategic forces is not a top priority; no U.S. administration would exit the MDA short of a complete breakdown in Anglo-American relations.
Sub-strategic deterrence: The case for sovereign tactical nuclear forces
Given that nuclear stalemate remains in place, Britain has a range of options to enhance its military power in a post-American Europe.
Many analysts argue that a buildup of conventional forces sufficient to deny Russia any ability to invade is an essential requirement. As Chatham House’s Marion Messmer writes, “a visible and understood ability to be able to fight and win using conventional weapons is a vital piece of any deterrence strategy.”
However, a favorable local or global conventional balance is neither necessary nor sufficient to deter or prevail in crises among nuclear-armed states. Under MAD, stronger conventional forces can provide useful options at the lower end of escalation and prevent faits accomplis, as discussed below. But when neither state can defend itself from the other, crisis outcomes are ultimately decided by their comparative willingness to escalate.
Russia’s leadership is under no illusions. As Michael Kofman and Anya Fink note, while “it does not write of nuclear escalation in recklessly optimistic terms,” the Russian military “expects a great-power war between nuclear peers to eventually involve nuclear weapons, and is comfortable with this reality... see[ing] escalation management as possible up to larger-scale employment.” Analysts generally agree; as Kofman emphasised in 2016, “Most Russian experts I know in the military analysis community, including those in Russia, don’t see much of a chance for conventional battle with NATO to stay conventional... [which] makes the [Western] debate over how many brigades to stick into the Baltics somewhat moot.” Such views do not appear confined to Russia’s uniformed military or analytic communities. Asked in 2018 whether Russian security is threatened by the behavior of other states, Putin averred that “we live in a world where security relies on nuclear capability. Russia is one of the largest nuclear powers… In this sense, we feel confident and calm.”
Although Russia’s nuclear-centric strategy is often regarded as a leap into the Strangelovian unknown, it rests on the same approach as NATO’s earlier posture. During the Cold War, NATO conventional forces were widely seen as unable to withstand a full-scale invasion of Western Europe by Warsaw Pact forces. Rather, conventional deterrence was primarily based on the threat to escalate a conventional war to the nuclear level. While an all-out nuclear response was not credible under MAD, the strategy held that limited nuclear options (LNOs) could generate risks of further escalation that would exceed any potential gains Moscow could envisage, thereby deterring or halting a conventional attack.
The key variable in competitive risk-taking is a state’s relative “resolve” or willingness to escalate, which is a function of the perceived interests at stake. I make the strong assumption that the British government values preserving the territorial status quo in Eastern Europe more than Moscow values revising it. However, what matters in practice is not a state’s hypothetical willingness to escalate—a more or less pure function of perceived interests—but its willingness and unilateral ability to do so. For an escalatory action to be rational, its expected costs cannot exceed the costs of backing down. Consequently, even a highly resolute nuclear power that lacks limited options could face a “resolve-capability gap,” forcing it to back down rather than over-escalate. Under MAD, the basic purpose of tactical nuclear weapons, and of conventional forces in lower-stakes crises, is to close gaps in a state’s deterrence posture.
Moscow currently maintains a tactical nuclear arsenal of around 2000 warheads arrayed on air, ground, and sea-based platforms. It likely includes both reduced-fallout and “ultra low-yield” devices of around 10 tons of TNT-equivalent, comparable to the U.S. GBU-43/B conventional munition employed against Islamic State tunnels in Afghanistan in 2017. In contrast, Britain has few viable LNOs. Its low-yield weapons were decommissioned after the Cold War, and while Trident SLBMs can of course be fired individually, any launch would reveal the SSBN’s location. An adversary would struggle to promptly destroy it, given that a rapid dive would sharply dampen the effect of surface nuclear strikes, but London’s uncertainty about the boat’s immunity from tracking could still markedly increase.
To credibly translate its resolve into coercive leverage, Britain would require more than a “minimum” deterrent, as government policy documents term it. As Keir Lieber and Daryl Press emphasise, nuclear arsenals geared toward bargaining and conventional deterrence should be large, survivable both in peacetime and across an ongoing conventional war, and flexible enough to facilitate selective use. That is, the ultimate countervalue threat ought to be technically feasible, while lower-level options should vary—in terms of provocation and costs imposed—from initial demonstrative use up to significant attacks. Such attacks would avoid striking the adversary’s core population centers and thus leave its incentives for restraint partially intact. Overall, as Kofman and Anya Fink write of the U.S., Britain “needs to develop its own strategy for escalation management, and a stronger comfort level with the realities of nuclear war.”
Critics of tactical acquisition often dismiss the move as self-defeating, since an adversary would respond with an offsetting buildup. A Liberal Democrats’ policy document, for example, argues for ruling out tactical nuclear acquisition, which it describes as “primarily designed to provide for battlefield advantage as opposed to having a deterrence purpose,” in light of “the potential for a tactical nuclear weapon arms race.”
However, because Russia already maintains a large tactical arsenal, a British buildup should not provoke countervailing arming. Tactical weapons are not designed to shift the overall military balance, which remains stalemated under MAD, but to provide options for limited use. Consequently, relative force size becomes essentially irrelevant beyond low levels. On the flip side, if Russia did respond by expanding its tactical arsenal, the deterrent benefit of the initial buildup would remain and Britain’s security would not be threatened, assuming it maintains an assured-destruction capability.
Some senior officials acknowledge the need for tactical forces. Recently retired armed forces chief Admiral Tony Radakin apparently considers it Britain’s top military policy priority, while the former head of the Civil Service, Simon Case, is a convinced proponent. But a major decision on acquisition has yet to be taken.
At the 2025 NATO Summit, Prime Minister Keir Starmer announced the planned purchase of twelve American F-35A fighters capable of carrying B-61 Mk. 12 nuclear bombs with a yield that can be adjusted from 0.3kt—less than the force of the 2020 Beirut explosion—up to 50kt. The move will allow Britain to participate in NATO’s “nuclear sharing” of American B-61s. An official press release described it as “the biggest strengthening of the UK’s nuclear posture in a generation,” one that “reintroduces a nuclear role for the Royal Air Force for the first time since the UK retired its sovereign air-launched nuclear weapons following the end of the Cold War,” thus “strengthening NATO’s nuclear deterrence posture.” A Wall Street Journal article referred to the move as an “overhaul of Britain’s nuclear policy.”
Britain’s participation in nuclear sharing cannot provide effective LNOs, however, or plausibly enhance NATO’s tactical deterrent. B61-12s are inert without American authorization, and while Washington might plausibly greenlight tactical use in a future crisis, it would be an American decision, and perceived as an American decision, taken whether or not a portion of its arsenal were carried by European rather than U.S. aircraft. Accordingly, despite the language of the press release, Defence Procurement minister Maria Eagle later clarified that the government was “not seeking to widen our range of nuclear capability” and the F-35A “is not some kind of stepping stone to acquiring tactical nuclear weapons.”
The proper “stepping stone” might be developing warheads for an air-launched cruise missile (ALCM), either new, or an existing system such as Storm Shadow. Though costly, this should be treated as a high priority program and, if necessary, come at the expense of broad investments in conventional forces. Fortunately, an important enabler for tactical options—the ability to suppress and destroy Russian integrated air defence systems (IADS)—would also be a high-return conventional investment. Russian IADS have gained extensive experience against Western weapons since 2022. In a conventional conflict, they could shield ground forces from oncoming fires, largely neutralising Europe’s advantage in tactical air power. Then, following escalation to the nuclear level, Russia’s air defence bubble could prevent limited use by a NATO state.
Other conventional capabilities also matter. Most importantly, the local conventional balance should not be so skewed in Russia’s favor as to enable it to present Western powers with a fait accompli. That is, if Russian forces could seize territory covered by Article 5 without encountering major resistance, the onus for triggering a large-scale conventional conflict that might go nuclear would shift onto European capitals. Rather than take that risk, NATO might accept the loss of territory. Russia’s essentially bloodless seizure of Crimea in 2014 is a classic example, and similar scenarios were discussed by Western analysts during the Cold War, when NATO forces, though seen as unable to withstand a full-scale invasion, were designed to defeat smaller scale, fait accompli-style aggression.
Fortunately, raising a “thick tripwire” against Russian faits accomplis is unlikely to require massive conventional balancing by European powers. In combination, British, French, German and Polish forces are probably capable of blunting a Russian ground attack, although they lack the mobility to surge eastward at pace. Force requirements are of course relative; following a ceasefire in Ukraine, Russia could seek to build up much larger peacetime conventional forces, so that preserving a safe imbalance would require a proportionally greater buildup by NATO states. Given the conventional capabilities that satisfied Moscow before its invasion of Ukraine, however, this would entail a marked shift in either its aims or its threat perceptions.
Conclusion
This essay has outlined the main military preconditions for Britain to shift to a much more independent grand strategy, given looming U.S. disengagement. Ultimately, however, the country’s overall military requirements (especially conventional) depend on what is judged necessary to protect British security beyond deterring major attacks on the mainland, which non-security interests are worth defending without an American security umbrella, and how much risk the country should tolerate to protect its interests from predation in a less stable world.
Alex Hughes