Europe faces a strategic reckoning. Russia’s war in Ukraine has brought conflict to the continent’s doorstep, while the return of Donald Trump to the White House has made the transatlantic alliance uncertain. At the center of this crisis sits Britain: militarily essential to NATO, cautiously re-engaging with the EU, yet constrained by domestic politics and the legacy of Brexit.
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Europe faces a strategic reckoning. Russia’s war in Ukraine has brought conflict to the continent’s doorstep, while the return of Donald Trump to the White House has made the transatlantic alliance uncertain. At the center of this crisis sits Britain: militarily essential to NATO, cautiously re-engaging with the EU, yet constrained by domestic politics and the legacy of Brexit. How London navigates between Washington and Brussels will shape both its own role and Europe’s future security order.
NATO can no longer be assumed a guaranteed shield. Its strength has always relied as much on political reliability as military capability, and Trump’s unpredictability has forced European governments to confront a stark reality: their security cannot be fully outsourced across the Atlantic. Defense budgets are being reconsidered, troop deployments recalculated, and strategic plans rewritten in real time.
Britain feels this tremor acutely. Prime Minister Keir Starmer, a staunch defender of the liberal world order, seeks to reassure the United States of Britain’s commitment while signaling to Brussels a readiness for practical cooperation. Yet Europe’s leaders are watching closely: London must now navigate between an increasingly unreliable ally across the Atlantic and a European partner whose importance is rising, shaping both Britain’s role and the continent’s emerging security order.
For now, NATO remains Europe’s framework sine qua non, yet the war in Ukraine has exposed both its strengths and limits. In absolute terms, the United States dwarfs its NATO allies, spending $935 billion (€787 billion) on defense in 2024—3.2 percent of GDP and nearly twice the combined defense budgets of the rest of the alliance. Yet, the war in Ukraine has revealed a hard truth: reliance on Washington alone is no longer enough. Europe now confronts a paradox: it must rely on NATO while simultaneously preparing to defend itself if the alliance falters.
Across Europe, the numbers tell a story of urgency, particularly when it comes to the tandem of France and Germany. In Berlin, Chancellor Friedrich Merz has broken a decades-old taboo by loosening fiscal restraints, using special funds to push defense spending beyond the country’s constitutional debt brake and pledging to create the continent’s strongest military by investing €649 billion over the next five years.
In tandem, Merz and President Macron have jointly declared the ambition to raise core defense investment to 3.5 percent of GDP over the next years — far above the current NATO baseline. France, the only EU state with independent nuclear deterrence and the most integrated defense industrial model, is ramping up defense spending from €59 billion in 2024 to €67 billion by 2030 under its Military Programming Law. Against this backdrop, Britain’s strategic posture must be measured not in abstraction but relative to Paris’s market-centric sovereignty and Berlin’s renewed industrial and fiscal vigor — and it shows.
Britain’s strategic posture must be measured not in abstraction but relative to Paris’s market-centric sovereignty and Berlin’s renewed industrial and fiscal vigor
London has committed to raise defense investment to 2.5 percent of GDP by 2027 with the ambition to reach 3 percent by 2034 alongside ambitious plans to add a dozen nuclear-powered attack submarines under AUKUS, a trilateral security partnership between Australia, the United Kingdom, and the United States. In the East, the trend is even starker: Poland and the Baltic states spend well above NATO’s threshold, convinced that geography leaves them no choice. Taken together, the shift is unprecedented. Ten European members of NATO increased their defense budgets by more than 20 percent last year alone—a scale of rearmament not seen since the Cold War. What once seemed unimaginable in peacetime Europe has become, almost overnight, a new orthodoxy.
The European Union, long a marginal actor in defense, is following suit. With its ReArm Europe plan, the European Commission has authorized up to €800 billion in new defense spending and more than half of the bloc’s governments now intend to exceed the spending limits that once defined the Union’s economic discipline. Initiatives such as the €150 billion SAFE (Strategic European Facility for Armaments) mechanism signal a willingness to combine financial and industrial power with strategic ambition.
Yet, ambition alone is insufficient; without the factories, supply chains, and industrial coordination to match it, European autonomy remains an aspiration, not a reality. This is where the SAFE instrument—and Britain’s role within it—becomes decisive particularly since the EU and the UK signed a new defense and security partnership in May 2025 that will formalize security cooperation.
The agreement resets the relationship in four ways. First, it creates regular consultation mechanisms: the EU’s High Representative will now meet systematically with Britain’s foreign and defense ministers, and senior officials on both sides will institutionalize cooperation. Second, it opens the door for British participation in EU joint procurement — even though Britain is outside the single market. Details still need to be worked out, especially on whether British defense firms will count toward SAFE’s requirement that 65 percent of procurement flow to European companies.
Third, it lays out intent to expand cooperation further: Britain could take part in EU civilian and military missions, collaborate with the European Defense Agency, and exchange personnel for joint exercises. Fourth, it identifies a wide agenda for deeper engagement — from Ukraine, the Western Balkans, and the Arctic to sanctions coordination, cyber defense, maritime security, and even climate-linked security challenges. For London, this evolution poses both opportunity and challenge. Brexit formally cut London out of European defense decision-making, leaving it dependent on NATO channels and ad hoc cooperation.
If there is one lesson Europe should have drawn from the first three years of the war in Ukraine, it is that military alliances cannot succeed without industrial depth. But Europe is hardly starting from scratch. The continent hosts five of the world’s twenty largest defense firms and many have already expanded production since Russia’s invasion. Their capacity exists; what has been missing until now are the orders that would force those factories into full gear.
This is where the new European initiative enters the conversation. On paper, SAFE is an ambitious mechanism designed to fix the structural weakness that has plagued the European defense project for decades: fragmented procurement, duplication of capabilities, and chronic underinvestment. SAFE aims to channel EU funds into scaling up ammunition production, streamlining orders across member states, and nudging Europe toward something resembling the industrial resilience the United States has long possessed.
And here the United Kingdom’s role becomes unavoidable. Despite Brexit, Britain’s defense sector remains woven into the fabric of European supply chains. British aerospace giants’ supply components for Franco-German fighter programs; British contractors still collaborate with continental firms on shipbuilding and missile systems; even post-Brexit regulatory divergence has not severed the industrial web created over decades of cooperation. To exclude Britain from SAFE would therefore not merely be a political choice but an act of economic self-sabotage for Europe’s rearmament effort.
Yet, inclusion is politically fraught. The European Commission has hinted that London could tap into SAFE, but Brussels is in no hurry to offer Britain a free pass. British participation will likely come with strings attached; perhaps direct financial contributions and restrictions on decision-making authority. The irony is that Europe itself stands to gain the most from Britain’s participation. Britain’s industrial weight, given its skilled labor force, advanced technologies, and export markets, could multiply the instrument’s impact. Without it, SAFE risks becoming another well-intentioned but underpowered EU scheme.
Britain’s industrial weight could multiply the impact of European SAFE initiative. Without it, SAFE risks becoming another well-intentioned but underpowered EU scheme
Yet, even with SAFE and the new declarations of cooperation and grandiose press conferences in Brussels and London, the defense pact between Britain and the European Union remains more a foundation than a fortress. History teaches us to be skeptical of Europe’s security announcements. From the 1998 Saint-Malo declaration, which promised to build a European defense identity, to the launch of the Permanent Structured Cooperation (PESCO) in 2017, the continent has repeatedly unveiled initiatives heralded as breakthroughs.
Unlike NATO, which is held together by treaty obligations, the EU-UK pact is a political agreement, vulnerable to the volatility of domestic politics. A future British government, swayed by populist pressures or economic austerity, could choose to distance itself again from European commitments and current polls make this all but inconceivable. The challenge now is to ensure that symbolism evolves into substance. That means money on the table, factories producing at scale, armies capable of deploying rapidly, and politicians willing to explain to their citizens why all of this is essential.
But if formal EU membership is difficult, informal coalitions are Britain’s natural habitat. The Joint Expeditionary Force (JEF), led by the UK and including Nordic and Baltic countries, has emerged as one of Europe’s most dynamic defense groupings. It conducts regular exercises, deploys rapidly, and operates with a flexibility that Brussels often lacks.
Another coalition, the so-called E5 (UK, France, Germany, Italy, Poland), functions as a directorate within NATO — an inner circle capable of coordinating strategy when the alliance’s full machinery is too slow. These groups illustrate Britain’s enduring advantage: the ability to convene, to lead, to act outside rigid institutional structures.
Beyond multilateral frameworks, Britain has advanced its European foothold through reinvigorated bilateral security pacts. Notably, the October 2024 Trinity House agreement with Germany strengthens joint defense capability and interoperability — a relationship further cemented in mid-2025 through a precision-weapons development pact under the Kensington Treaty. Moreover, at the July 2025 Franco-British summit, the Lancaster House Treaties were modernized to enhance nuclear coordination, revive the Combined Joint Force (CJF), and expand collaboration in cyber, space, and industrial domains.
For Europe, such coalitions are not a substitute for NATO or the EU but a complement, allowing rapid response while broader institutions deliberate. For Britain, they are lifelines — a way to demonstrate relevance without rejoining the EU and a way to anchor itself in Europe while maintaining autonomy. And there is another element Britain provides to Europe: deterrence. Alongside France, it remains one of only two European nuclear powers.
In normal times, this fact is background noise. In an era of American doubt and Putin’s imperialist fantasies, it takes on new significance. If Washington’s guarantee weakens, Britain’s nuclear arsenal could become Europe’s last credible shield. And while politically, any suggestion that Britain might become Europe’s nuclear guarantor would ignite fierce debate at home, the very possibility underscores how much the continent’s security order is shifting.
But with all the conversations about Britain becoming more integrated with Europe, one must not forget that the “special relationship” with Washington has long been more than rhetoric. It is the organizing principle of British defense. From the Second World War through Iraq and Afghanistan, London has defined its global role through the prism of American alignment. The intelligence-sharing “Five Eyes” network, the continuous integration of British officers into US commands, and the co-development of weapon systems have entrenched this dependence to a degree unmatched by any other European ally.
This alignment remains, but it now carries new risks. Trump’s return has injected radical unpredictability into the White House. However, even beyond Trump, US politics is shifting toward strategic prioritization of China, meaning Europe may face long-term American disengagement regardless of who is in the White House. And if the previous election has taught us anything, it is that internationalism is no longer a winning ticket. The British government must therefore engage in a delicate balancing act: offering Washington constant reassurances, while simultaneously preparing Europe for the possibility that those reassurances may mean little.
The British government must therefore engage in a delicate balancing act: offering Washington constant reassurances, while simultaneously preparing Europe for the possibility that those reassurances may mean little
Starmer has tried to tread this line. He reassures American interlocutors that EU initiatives are meant to complement NATO, not undermine it. He avoids public clashes with Trump — even soft-pedalling on Ukrainian NATO accession — to preserve working ties. But this restraint comes at a cost. Britain risks looking reactive, rather than proactive, in shaping the Western response to Russia. European partners notice the hesitation, and some might question whether London will prioritize American moods over European necessity.
Right now, Britain is neither the unquestioned deputy of Washington nor a fully estranged former European. Instead, it is a power in demand, courted simultaneously by NATO allies and by Brussels, envied for its military heft, yet haunted by the limits of its politics and finances. Amid this, three potential futures present themselves.
Britain doubles down on its Atlantic vocation, aligning itself closely with Washington even in the face of Trump’s transactional worldview. London becomes the pivotal mediator between the US and Europe, the go-between who can interpret Trump to Brussels and Brussels to Trump. This strategy preserves NATO’s cohesion but carries the danger of dependence: if Washington truly withdraws, Britain’s bridge collapses into the sea.
Britain throws its weight behind Europe’s nascent security structures, not as a supplicant but as a co-architect. It invests in Franco-German initiatives, expands defense industrial integration, and shapes the European Security Council into a real institution. In this role, Britain supplements NATO, anchors itself in Europe’s strategic core, and ensures its nuclear deterrent remains central to the continent’s defense. Yet this path requires political courage and a willingness to accept compromises with Brussels that Brexit once made taboo. Success here would elevate Britain from transactional partner to key architect of Europe’s security.
Paralyzed by domestic populism, fiscal constraints, or strategic indecision, Britain opts for neither bridge nor builder. It clings to nostalgic illusions of “Global Britain,” offers rhetoric without resources, and allows others like Paris, Berlin or even Warsaw to set the pace. This outcome would leave Britain diminished: too small to shape Washington’s strategy, too aloof to influence Europe’s trajectory, and increasingly peripheral in the very continent whose defense it once helped shape.
Of these scenarios, a Builder-Bridge hybrid now appears the most plausible. The UK is set neither to retreat into isolation nor subsume under transatlantic whim alone. Instead, it is leveraging industrial ties — through SAFE, EU-UK procurement pathways, and the UK-EU security pact signed in May 2025 — to anchor itself as a European architect, even as it maintains its transatlantic lane. Purely serving as mediator is untenable; France and Germany push hard on autonomy, making a unilateral bridge role insufficient for influence. And a Bystander posture would squander the UK’s moment to contribute to European defense revival.
The Builder-Bridge hybrid is Britain’s likely lodestar: construct European capability while still talking with Washington — a balance that for now best preserves relevance, influence, and security for all actors involved.
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