The special relationship between the United States and the United Kingdom has experienced a decline in significance over the past decade. This decline is evident in the waning relevance of bilateral ties for policymakers, particularly in Washington.
Several factors contribute to this shift, including the diminishing joint military engagements in Iraq and Afghanistan. However, these military considerations are only part of the picture.
In recent years, the UK has faced numerous challenges, including the complexities surrounding Brexit, detachment from Europe, sluggish economic growth, and cuts to its military forces. This has resulted in a diminishment of the UK’s role as a prominent actor in Europe, a global economic player, and a military presence on the world stage.
Even in light of the ongoing conflict in Ukraine, Washington’s strategic focus has shifted towards the Indo-Pacific, particularly addressing the challenges posed by China. Furthermore, the U.S. has placed an increased emphasis on economic security and competition with China, necessitating more coordination with the European Union due to its vast single market. The UK’s estrangement from the EU has thus rendered it more peripheral in these discussions.
With new administrations taking office in both London and Washington, policymakers are presented with a vital opportunity to rejuvenate and enhance the special relationship, ensuring it meets contemporary needs. UK Prime Minister Keir Starmer and U.S. President Donald Trump have initiated this process, displaying a strong personal rapport akin to historical partnerships between leaders from opposing sides of the political spectrum.
For the UK, reviving the special relationship necessitates rebuilding ties with Europe, as previous successes in global cooperation were rooted in strong European relationships. To regain its position as a transatlantic bridge, the UK should focus on reestablishing connections with the EU, enhancing NATO commitments, and taking a proactive role in supporting Ukraine.
Additionally, the UK must streamline its defense strategies due to resource constraints. Historically, the special relationship led to close cooperation across various global issues, sometimes resulting in overstretch and an inability to deliver on ambitious commitments. Recognizing its limitations, the UK is encouraged to concentrate its efforts on a select number of areas where it excels.
The Strategic Defence Review (SDR) is pivotal for reviving the special relationship. Following Starmer’s appointment in 2024, he commissioned a comprehensive review of the British military, culminating in a report released in June 2025. This report presents a forward-looking framework assessing the UK’s strategic interests and necessary military capabilities, reinforcing cooperative value for both nations.
However, the path forward remains fraught with challenges. The increasingly tense relationship between the Trump administration and Europe poses a growing diplomatic gulf, emphasizing the UK’s crucial role as a bridge between the two.
This article delineates the current defense and security relationship between the U.S. and UK while evaluating the SDR’s objectives and their implications for American foreign policy in Europe and beyond. It also explores the difficult decisions facing UK defense policymakers amid economic constraints, evolving U.S. foreign policy priorities, and growing geopolitical competition.
**Mapping the Special Relationship on Defense**
The ties between the U.S. and the UK are bolstered by a shared strategic culture and outlook on global issues. Both countries have historically viewed threats similarly and displayed a broader understanding of national interests, leading to a willingness to engage militarily when necessary.
For instance, after Russia invaded Ukraine in February 2022, both nations quickly mobilized military assistance and coordinated efforts to rally European allies against potential aggression through comprehensive sanctions.
Maintaining and reinforcing the special relationship is central to British foreign policy, similar to the priorities of every U.S. president starting from Franklin D. Roosevelt. It is not merely a rhetorical concept; the special relationship possesses substantial depth, especially in matters of defense and security.
**Intelligence Cooperation**
The United States and the United Kingdom have established the most extensive intelligence alliance within the Western world. This collaboration has evolved through years of countering fascism, communism, and terrorism.
In the wake of World War II, the two nations agreed to exchange sensitive signals intelligence under the 1946 UKUSA Agreement, with the U.S. relying on British intelligence capabilities to monitor Soviet activities from its vast overseas territories and Commonwealth.
This partnership laid the groundwork for the Five Eyes intelligence-sharing alliance—comprising the UK, U.S., Canada, Australia, and New Zealand—formally established in 1956. The Five Eyes alliance has since become the gold standard for intelligence cooperation, facilitating extensive coordination and sharing of intelligence across various domains and regions.
This arrangement has seen its global significance grow, particularly during the Cold War, when the U.S. relied heavily on British intelligence to monitor Soviet activities across the globe. Today, collaboration continues across diverse areas, including maritime traffic monitoring, nuclear missile surveillance, and joint offensive operations in cyberspace.
**Nuclear Technology Collaboration**
Cooperation on nuclear technology represents another integral aspect of the special relationship that dates back to the early Cold War. The 1958 Mutual Defense Agreement solidified ties and allowed for advancements in the UK’s nuclear arsenal through U.S. technology integration.
Since 1962, the UK has benefitted from U.S. nuclear weapons delivery technology alongside the production of its submarines and warheads. The UK’s Trident system, consisting of nuclear-armed submarines, is closely tied to U.S. systems, though they operate independently.
In 2024, the Mutual Defense Agreement was indefinitely extended, reinforcing U.S.-UK cooperation and providing essential budget stability during the modernization of the UK’s nuclear capabilities. This extension assures continued collaborative efforts, regardless of domestic political flux.
**Defense Industrial Base**
The 2021 Defence and Security Industrial Strategy (DSIS) signified a shift in UK strategy regarding its defense industrial base. This strategy emphasizes developing a resilient defense industry that decreases reliance on foreign suppliers, contrasting previous trends of outsourcing to optimize costs.
As a key response to crises such as Russia’s invasion of Ukraine and the Covid-19 pandemic, the focus has shifted to prioritizing the sustainability of the UK defense industrial base. The SDR acknowledges the UK defense industry as crucial for both security and economic growth, reflecting this evolving mindset.
In FY 2023, nearly $40 billion was allocated to the UK defense industry, sustaining 440,000 jobs, with significant defense exports contributing to the overall economy. The U.S. remains the UK’s closest defense partner, with robust engagements such as the $18.6 billion Foreign Military Sales portfolio primarily centered around joint projects, including the F-35 program. The UK’s role as a tier-one partner in the F-35 program exemplifies its vital contribution to integrated defense operations with the U.S.
The establishment of the AUKUS agreement in 2021 reinforces the bond between the three allies—Australia, the UK, and the U.S.—aiming to enhance joint capabilities in the Indo-Pacific. This agreement not only focuses on delivering advanced nuclear-powered submarine technology but also prioritizes collaboration in numerous domains, including cyber capabilities, artificial intelligence, and electronic warfare.
The successful implementation of AUKUS and its various objectives will require substantial investment from both the U.S. and UK defense sectors and underline the importance of joint innovation in the context of growing competition with China.
**Military Presence and Bases**
The United States has maintained military bases in the UK since 1942, currently housing around 10,000 military personnel, further strengthened through numerous contractor partnerships. In return, approximately 750 UK military personnel train at U.S. military bases across various states.
Both countries benefit from each other’s global military infrastructures. The U.S. has utilized bases in remote UK territories for strategic operations, such as the shared U.S.-UK military base on Diego Garcia, emphasizing mutual interests in power projection and operational synergy.
A recent agreement concerning Diego Garcia emphasizes the strategic importance of preserving military capabilities in the region. This continued cooperation highlights the intertwined defense postures of the U.S. and the UK amid global geopolitical shifts.
**Special Operations Forces**
The historical relationship between U.S. and UK military representatives has predominantly existed through specialized communities, primarily seen in their special operations forces collaboration. Despite the absence of formal frameworks, this area of partnership remains significant, compensating for quantity with quality and interoperability.
Notably, joint deployments of special operations units during the Iraq War and collaborative training efforts underscore the importance of these relationships, showcasing the depth of military coordination between the two nations.
**Current Challenges for the UK**
Following the Brexit referendum in 2016, the UK’s political landscape has shifted, altering its economic and strategic outlook. Instead of enhancing global engagement, Brexit has introduced structural barriers and economic stagnation.
The desire to pursue a ‘Global Britain’ strategy has not yielded the anticipated economic benefits, as businesses now face cumbersome trade dynamics with the EU. The situation has only worsened since the onset of the Covid-19 pandemic and subsequent geopolitical challenges, evident in the UK’s status as the only G7 country struggling to return to pre-pandemic economic levels by 2023.
Concurrent austerity measures implemented post-Global Financial Crisis have further aggravated the economic situation, leaving the UK in a technical recession as of late 2023. Resource constraints hinder the UK’s capability to maintain its role as a global defense partner for the U.S., compounded by a decrease in defense spending during the last decade.
**Strategic Defence Review (SDR)**
Starmer’s government has recognized the necessity for a comprehensive reassessment of the UK’s defense capabilities, leading to the commissioning of the Strategic Defence Review (SDR). Announced in 2024, the SDR aims to address the threats facing the UK and propose requisite capabilities and resources.
This third iteration of the UK defense strategy in five years seeks to significantly overhaul existing frameworks. The SDR, directed by a panel of independent experts, is designed to closely analyze military readiness, capability gaps, and resource requirements in light of recent geopolitical developments.
In contrast to previous reviews, which offered minimal defense investment changes, the SDR proposes a more ambitious posture in response to the current security environment. This strategy seeks to lay a robust foundation for addressing critical defense challenges while augmenting operational readiness.
**The Imperatives of the SDR**
The SDR aims to tackle the UK’s armed forces predicament, particularly in sizes. While there is an acknowledgment that increased personnel strength is needed, the SDR firmly establishes a focus on technological advancements to improve overall military efficacy.
By advocating for a resilient defense production capacity and fostering rapid munitions manufacturing capabilities, the SDR seeks to adapt and modernize the UK’s military infrastructure. Utilizing lessons learned from ongoing conflicts, such as Ukraine, is integral to this revised strategy, which emphasizes critical rapid production of munitions and adaptable strategies to enhance national defense.
A ‘NATO-first’ approach is central to the SDR, while still maintaining aspirations for a global British role. This strategy underscores the need for readiness to modernize UK force structures by embracing integrated operations across various domains and ensuring coherent procurement strategies.
The SDR also highlights the importance of coordinated procurement efforts with European NATO partners, facilitating economies of scale in defense production—vital to the overall effectiveness of the UK defense strategy.
**Confronting Difficult Choices**
The UK faces a significant strategic dilemma: pursuing an ambitious defense agenda while navigating limited resources. This conflict demands a re-evaluation of the UK’s strategic footprint in Europe and Asia, as well as a recalibrated relationship with the EU.
To realize reforms, key areas must be prioritized, including the integration of emerging technologies into defense frameworks, enhancing domestic resilience, streamlining procurement, and balancing military capabilities across land and sea forces.
As preparation for the upcoming NATO Summit in 2025, the UK government aims for a significant increase in defense spending commitments from the current 2.3 percent of GDP to potentially 3.5 percent, with an additional 1.5 percent directed to defense-associated areas. Achieving these targets will necessitate an additional $41 billion annually, with little clarity on the sources of this funding.
Additionally, London must also address high-profile defense initiatives that occupy significant budget allocations, including maintaining a nuclear deterrent, the AUKUS agreement, and collaborative defense programs. While the emphasis on army size growth is acknowledged, the resources to realize this objective remain lacking, diminishing flexibility in filling capability voids.
**Strategic Focus: Global Britain vs. NATO First**
U.S. administrations have been inconsistent in guiding how the UK should balance its resources between Europe and the Indo-Pacific. Increased U.S. demands for UK military participation in the Indo-Pacific have clashed with contemporary European security needs, especially in light of renewed Russian threats.
As pressures mount for more robust UK contributions to NATO, particularly in response to growing tensions with Russia, a focus on European security will underpin UK-U.S. relations. Enhanced collaborations with key European powers present opportunities for the UK to restore its relevance and demonstrate leadership within NATO.
**Joint Expeditionary Force (JEF)**
Strengthening the UK’s leadership in the Joint Expeditionary Force (JEF) offers an avenue to bolster European defense initiatives. Comprising ten nations, including those in the Nordic and Baltic regions, the JEF aims to enhance rapid response capabilities.
Given anticipated reductions in U.S. military presence in Europe, reinforcing the JEF may serve to fill defensive gaps within the current security architecture. While it cannot replace the full scope of U.S. military contributions, it can significantly enhance regional deterrence measures.
**AUKUS Agreement**
The AUKUS agreement, emphasizing cooperation in nuclear submarine technology, also applies strategically to U.S.-UK military cooperation beyond the Indo-Pacific. The lines of effort associated with this partnership aim to strengthen the critical capability of the UK within both European and Pacific realms.
The success of AUKUS hinges not only on resource investments but also requires the UK to develop the infrastructural capacity necessary to produce advanced military technology at scale. This collaboration will enhance the UK’s position in relation to its nuclear deterrent while reinforcing its global standing as a military power.
**UK-EU Relations**
If the UK aspires to take a leadership role in European defense, it must deepen cooperation with the European Union. Recent summits have initiated discussions on defense agreements, but a more intricate future framework will be necessary for UK involvement in EU defense initiatives.
Strengthening collaboration may also capitalize on the European Union’s emerging defense financing structures, such as the new €150 billion Security Action for Europe fund. Preceding the EU’s development into an active defense procurer could benefit UK defense industries,
Moreover, UK integration into these initiatives will require financial contributions, akin to non-EU NATO countries like Norway, to establish a more solid footing in upcoming defense endeavors.
As the UK navigates its post-Brexit landscape, prioritizing economic growth alongside defense commitments remains critical for long-term stability. Achieving economic prosperity will enable enhanced investments in defense, reinforcing the special relationship with the U.S. while positioning the UK as a reliable partner in European security.
**Conclusion and Recommendations**
The current UK government under Prime Minister Starmer is positioned to revive the economic landscape while navigating a highly volatile international environment. However, economic constraints limit its capacity to implement a bold reform agenda.
To ensure the vitality of the special relationship, the UK should continue leading efforts to support Ukraine militarily, portraying itself as a cornerstone of stability in the region and enabling broader allied engagement.
Fostering proactive defense cooperation with the European Union will also stabilize UK-EU relations, enhancing the country’s influence within the European security context.
Assuming a leadership role in defense planning, intelligence coordination, and strategy formulation will further establish the UK as a key player in European security matters.
Sustaining economic growth is paramount, urging both the UK and EU to lower trade barriers. As economic interdependence fosters stability, the UK can gradually improve defense spending in alignment with its strategic objectives.
Finally, the U.S. must recalibrate its expectations concerning the special relationship, recognizing the pragmatic limitations of the UK’s circumstances. An understanding of the prevailing financial and military realities will lead to more effective collaboration and clearer prioritization.
By focusing on established priorities, sharing the innovative aspects of the SDR with NATO allies, and promoting lessons learned throughout implementation, the UK can fortify its defense capabilities while enhancing its global standing as a leading partner for the United States in today’s intricate geopolitical landscape.
image source from：csis
