1 Introduction

The term ‘Special Relationship’ was popularized by Winston Churchill on 5 March 1946 when, at the invitation of President Truman, he delivered his ‘Iron Curtain’ speech in Fulton, Missouri. Since then, leaders of the UK and the US have consistently employed the term ‘Special Relationship’ to denote the unique and unparalleled relationship between the two nations. For more than 75 years, the rhetorical significance of ‘Special Relationship’ has been constantly highlighted in official discourses by both sides. This tradition was upheld when British Prime Minister Rishi Sunak visited Washington in June 2023, where he and President Joe Biden reaffirmed their commitment to the Special Relationship. In the words of President Biden, ‘Earlier this week, we marked the 79th anniversary of D-Day, and … a timely reminder of the proud history … our nations share and the … values that we have long stood together to defend. That’s the unshakable foundation of this special relationship. And it is a special relationship. There’s no country closer to us than Great Britain’ (The White House 2023).

Like any bilateral relationship between states, the US’s relationship with the UK is one between two sovereign states pursuing their national interests within an anarchic international system. Along a continuum between enmity and amity, the UK and the US represent what might be termed ‘super allies’, given the unprecedented depth and breadth of their long-term cooperation in intelligence, nuclear, and military affairs. This cooperation surpasses that found in any other bilateral state-to-state relationship. As a result of their unparalleled closeness in the realm of security—a domain in which sovereign states typically find it most challenging to cultivate enduring cooperation—it remains fitting to employ the term ‘Special Relationship’. Despite the inherent deficiencies and the controversies it may spark, the UK–US relationship has achieved the highest level of security cooperation.

Scholarly debate has ebbed back and forth about the nature of the postwar Anglo-American relationship. There has been broad agreement that the Special Relationship has been primarily a security and defense-driven pattern of cooperation. But assessing the degree to which the relationship deserves the epithet ‘special’, and the extent to which it has survived the ups and downs of postwar events, has been the subject of considerable debate. There are primarily three schools, or groups of scholars, concerning the study of the Special Relationship. They consist of the evangelical school (or the school of sentiments), the functional school (or the school of interests) and the terminal school (Danchev 1996; Dobson and Marsh 2013).

The evangelical school upholds the specialness of Anglo-American relations, underscoring the profound bond forged by shared values and a collective identity deeply entrenched in Anglo-Saxon heritage (Reiss 2009). Evangelists emphasize the intrinsic cultural and historical ties that bind the US and the UK. They argue that these connections elevate the relationship beyond mere diplomatic interactions to a unique status, separating it from other relationships among Western nations. They believe that the commonalities in language, legal systems, and democratic ideals not only foster a natural affinity between the two nations but also serve as a foundation for their enduring partnership.

In contrast, the terminal school refutes the notion of any inherent specialness in Anglo-American relations. Proponents of terminalism contend that the description ‘Special Relationship’ is merely a linguistic fabrication, serving to perpetuate a sense of self-delusion on the part of the UK (Danchev 1996; Baylis 1997). They argue that such a linguistic construct is not only misleading but also cultivates a detrimental national myth, ultimately hampering the UK’s perception of its actual standing on the world stage and masking its decline in power.

Positioned at the nexus between the evangelical and terminal schools, the functional school adopts a measured stance on the specialness of Anglo-American relations, contingent upon the prevailing circumstances. This school is characterized by its pragmatic approach, acknowledging a conditional endorsement to the continuity of the Special Relationship through a utilitarian lens (Reynolds 1982). For proponents of functionalism, the endurance of the Special Relationship hinges on the mutual recognition by the US and the UK of each other’s strategic prowess as indispensable allies. The relationship allows each side to pursue their own security interests, while also contributing to the realization of its allies’ goals. They underscore the importance of tangible benefits and mutual interests in maintaining the relationship rather than relying solely on historical ties or ideological similarities.

This article aligns with the functional school on the Special Relationship, underscoring the importance of common interests. It sees the two countries as having built a network of institutional linkages that provide depth and durability to cooperation. These institutional strands facilitate adaptable and evolving cooperation strategies in response to current and future challenges. The specialness of Anglo-American relations needs to be constantly nurtured in both peacetime and wartime. For these states, the way to sustain their relationship has lain in collaborative efforts to address shared threats.

This article examines the waxing and waning of the Special Relationship in three distinct epochs: the Cold War, the post-Cold War era, and the emerging new security environment since 2021. The post-Cold War era commenced on 25 December 1991, with the break-up of the Soviet Union, and extended until 22 February 2022 when the Russia–Ukraine war erupted. The Russia–Ukraine war signaled the end of the post-Cold War era (Ashford 2022; Ward et al. 2022). As the Biden administration asserts in its 2022 National Security Strategy, ‘..the post-Cold War era is definitively over and a competition is underway between the major powers to shape what comes next’ (The White House 2022, 6). The Special Relationship flourished in the face of two common strategic threats, the Soviet Union during the Cold War and Islamist terrorism during the ‘War on Terror’. Across two different periods of time and against very different types of threats, these external dangers drew the US and UK into a tight embrace. By contrast, due to a lack of common strategic threats or disagreements over how to deal with certain threats, the Anglo-American relationship experienced drift in the greater part of the post-Cold War era. The identification of Russia, following its assault on Ukraine, and the rise of a more assertive China, present renewed challenges that have served to galvanize the Special Relationship.

2 Common threats and the vitality of the Special Relationship

Common threats are a result of the US and the UK sharing their perspectives and agreeing that their mutual interests are being put at risk. These perspectives are not just determined at the highest political levels but throughout the institutional structures of their governments and security and defense services. This has resulted in patterns of collaboration ranging from agreement on threat perceptions to the coordination of military planning and to the procurement of weapon systems. Institutional networks between their security agencies and armed forces have exhibited durability in working together and help to account for their capacity to adapt existing patterns of collaboration to the needs of contemporary and future challenges (Rees 2024, 11–26).

As a result of highly institutionalized habits of cooperation and a ‘common cast of mind’ (Marsh 2023) among governmental officials, intelligence officers and military personnel from both countries, common threat perceptions have emerged within the Special Relationship. Among all American allies, the UK has been the one that most closely aligns with their threat perceptions. This alignment in threat perception is not coincidental but reflects the regular dialog across the Atlantic and the channels of communication that have been cultivated over time. This synergy enables the two countries to recognize and jointly respond to challenges, thereby reinforcing their security and defense cooperation.

This ‘togetherness in adversity’ (Marsh 2023) has fortified the Special Relationship, ensuring that it is responsive and resilient amid the ever-changing international security environment. Former Prime Minister John Major contended, ‘There is a tendency for Britain and America to see international problems in the same way. Occasionally there are different points of emphasis … but overwhelmingly we tend to see the same sort of problems and see the same solutions for them’ (Major 1994). In particular, America has valued having an ally like Britain with a global perspective on contemporary challenges.

The relationship has been most intense when the US and the UK have shared a common adversary that poses a strategic threat to not only their national security, but also their shared values of freedom, democracy and human rights. ‘Strategic threats’ are defined as grave challenges that impose profound and enduring adverse effects on a state’s physical or ontological security. In other words, a strategic threat poses immediate risks to a state’s territorial integrity and the wellbeing of its populace and undermines its sense of national identity. Addressing strategic threats necessitates a comprehensive whole-of-government approach, encompassing the full spectrum of tools of statecraft, such as diplomacy, technology, military power, intelligence, foreign aid, cultural influence, trade and investment (Niblett 2024). By leveraging these diverse instruments in a coordinated manner, the state can effectively counteract and mitigate the impact of such threats.

The UK and the US have jointly confronted numerous threats since the inception of the Special Relationship in World War Two. However, only a few of these threats rise to the level of common strategic threats. These are distinguished by their profound and pervasive impact on both states, threatening not only their immediate security interests but also their long-term strategic objectives. Instances of common strategic threats include Nazi Germany in World War Two, the Soviet Union during the Cold War and the contemporary challenge of Russia and China. Although Islamist terrorism did not present the same level of existential threat, its devastating impact on the U.S through the 9/11 attacks led both countries to mobilize their military resources during the War on Terror.

This experience of dealing with common strategic threats leads the US and the UK to work alongside each other in a manner that has not been replicated with other allies. In addition to bilateral cooperation, it has brought them together as leaders of a multinational community of western countries. World War Two provided a template for their collaboration that was pursued thereafter (Dobson and Marsh 2013, 10). Conversely, the Anglo-American relationship languishes during periods when they lack a shared external threat. During such times, the vitality of their bilateral cooperation diminishes as the distinct and separate interests of the two powers assert themselves. In the absence of unifying factors, the US and the UK have been predisposed to criticize the policy directions of each other and to lament their allocation of defense resources. Similarly, multilateral cooperation deteriorates during low threat periods as other nations seek to detach the US or UK from the intimacy of their bilateral relationship. For example, in the Trump era, the UK drew closer to its European allies, and particularly to France, in dealing with global challenges, when the intimacy of its relationship with the US diminished.

3 The robust nature of the Special Relationship in the Cold War

The Cold War threat of the Soviet Union was treated by the US and the UK as multi-dimensional. The Soviet Union was an existential military threat: its strategic nuclear weapons could have inflicted irreparable harm on western countries, while a conventional attack on Western Europe might have been the prelude to a global war. It also presented a danger across a broader spectrum. Soviet support for anti-western forces was seen as a subversive risk that could erode internal strength and lead to the collapse of western unity. The US and UK shared the view that the Soviet Union and its allies had to be opposed throughout the world.

The UK believed that it was vital to secure US support to defend Europe due to the need for a powerful military force to counterbalance Soviet power. Both the conventional and nuclear capabilities of the US were essential to western defense strategy and the UK sought the maximum degree of influence over the US decision to employ nuclear weapons (Kandiah and Staerck 2005). As early as 1952, in the Global Strategy Paper written by the British Chiefs of Staff, it was accepted that nuclear weapons would play an essential role in the defense of the west (Baylis and Macmillan 1993). To this end, the UK was willing to host US forces on its own soil. In 1958, America received approval to base its Thor Intermediate Range Ballistic Missiles (IRBMs) on UK soil under a dual key arrangement with the Royal Air Force (Clark 1994). The UK also made a major military contribution to NATO’s defense of Europe, pledging four divisions and a tactical air force. This contribution was designed to justify and complement a US commitment of conventional and nuclear forces.

Outside of Europe, the UK stationed military forces in bases that were designed both to support friendly countries and oppose Soviet influence. As its empire contracted, the UK struggled to find the manpower and the resources needed to sustain its overseas presence. It regarded its relationship with the US as a means to underpin its status as a global power. In the words of Richardson, aligning with the US offered the UK, ‘..a means of exercising more influence internationally than would be warranted by an objective assessment of its power’ (1996, 215). Postwar, the US took a critical stance toward British imperial possessions, as it perceived itself to be a champion of self-determination and human rights. This was illustrated in the Suez crisis of 1956 when the US opposed the Anglo-French military operation. Nevertheless, the shared interest of opposing the Soviet Union helped to heal the breach at Suez and the US grew to welcome the contribution of another country with a world-wide perspective to the defense of western interests (Dockrill 2002). As the UK’s global footprint shrank, the US grew increasingly concerned that it was shouldering the burden of policing and maintaining global stability alone.

In 1967, Britain withdrew its forces from East of the Suez Canal to concentrate on the defense of NATO (Darby 1973). This was driven above all by economic constraints and the pressure defense spending had put on its balance of payments. The US lamented this contraction of British commitments and argued that its world-wide presence was as important, if not more important, than its contribution to NATO. This reflected an important change in American attitudes toward Britain’s global posture.

British nuclear weapons were regarded as a way of perpetuating the country’s great power status and compensating for smaller conventional forces. The UK came to recognize that although an independent nuclear force was a priority, sustaining it by a purely national nuclear program risked placing too great a strain on its defense budget. It sought access to US nuclear systems as a means of avoiding research and development costs as well as duplication of effort. The UK believed it was necessary to demonstrate a level of nuclear proficiency in order for the US to take them seriously as a nuclear partner. There was a fear that discontinuing the deterrent would be perceived as a signal of British decline in the eyes of adversaries, and more importantly, in the eyes of the US.

The 1962 Nassau Agreement ensured that Polaris ballistic missiles were sold to the UK, while being fitted with warheads and carried by nuclear powered submarines that were built in Britain (Baylis and Stoddart 2014, 75). This marked the beginning of a strategic nuclear pattern of cooperation that continues to this day. The successor system to Polaris, the Trident missile system, continued the nuclear relationship. It was testament to the intimacy of the Anglo-American relationship that these weapons of last resort were shared by the two countries. Simpson describes it as the ‘jewel in the crown’ of Anglo-American defense cooperation (Simpson 2013, 241).

The conventional armed forces of the two countries established enduring patterns of cooperation during the Cold War years. An especially close bond was created between the Royal Navy and the US Navy, both in surface vessels and submarines (Wells 2017). A key dimension of NATO strategy envisaged the wartime reinforcement of US forces across the Atlantic and as a result, the two navies worked closely to control the seas. The Royal Navy specialized in Anti-Submarine Warfare (ASW) operations so as to prevent Soviet submarines from disrupting trans-Atlantic convoys. The Royal Air Force and the US Air Force also trained together and collaborated to dominate the skies over Europe.

Close intelligence cooperation was a facet of the Anglo-American relationship that was motivated by the Cold War. The UK had provided some of the inspiration for the development of the US intelligence community during World War Two and in its aftermath. As the US intelligence effort grew in size and sophistication, close cooperation with the UK remained a key feature (Aldrich 2004). The two sides worked together in signals intelligence and the UK later benefitted from the provision of American photo-reconnaissance images. Collaboration between the two sides extended to civilian and military intelligence agencies. In military intelligence, the Royal Navy contributed to information gathering by hunter-killer submarines (Ring 2001), while the Royal Air Force came to work with the US Air Force on Unmanned Aerial Vehicles and the Rivet Joint program.

4 The post-Cold War drift in the Special Relationship

The Special Relationship waned in the 1990s following the collapse of the Warsaw Pact and the subsequent dissolution of the Soviet Union. Between 2001 and 2007, it was re-energized by the 9/11 attack on the US and the ensuing ‘War on Terror’. This period was characterized by the close cooperation between the administrations of President George W. Bush and Prime Minister Tony Blair. The Anglo-American relationship then diminished in strength in the later period of the War on Terror, 2008–2021, when the strategic threat of Islamist terrorism dwindled.

4.1 The Special Relationship in the 1990s: the absence of a common strategic threat

During periods in which there is no over-arching strategic threat to draw the US and the UK together, the relationship is susceptible to drift. Consistent with its determination to preserve cooperation, the UK has worked diligently to sustain contact with the US through joint exercises and personnel exchanges. The relationship has been underpinned by the risk or actuality of external conflict: its absence has required additional effort to keep the relationship vibrant.

The 1990s was ‘a decade of greater uncertainty in terms of threats—sandwiched between the dominance of the Cold War and the so-called war on terror’ (Aldrich et al. 2014, 381–382). The break-up of the Soviet Union removed much of the raison d’etre for the Special Relationship (Dickie 1994). The strategic priorities of the US were both more extensive and less overlapping with those of the UK than during the Cold War (Marsh 2023). The complexity of post-Cold War conflicts bore out the difficulty of preserving trans-Atlantic cooperation in the absence of a unifying threat (Xu 2017, 188). The UK was determined to ensure the continuity of America’s commitment to the defense of Europe and insisted on the primacy of NATO as this guaranteed the trans-Atlantic link. However, the UK faced pressure from other European allies, led by France, for a more robust role for the European Union as a security and defense actor (Howorth 2007).

The conflicts that occurred in territories like Bosnia and Kosovo presented new issues for Anglo-American relations. First, they were ‘wars of choice’ in which it was difficult to discern a clear justification for US involvement. Second, they were civil wars and among the warring factions it was not obvious with whom to align. Lastly, they were low intensity conflicts fought amidst civilian populations that required force to be used in a highly controlled and precise manner.

In spite of the tradition of planning and consulting together, these conflicts tested the Anglo-American relationship. Britain urged US engagement because it would provide access to America’s enormous military strength and its technological sophistication. Nevertheless, the US military was reluctant to be distracted from what it perceived as its core mission: the application of decisive force against state actors (Kagan 2006, 252). It feared that other types of missions would blunt its warrior ethos. In the words of Egnell, the ‘..uncompromising focus on conventional warfighting has left the US military ill-prepared for complex peace operations and post-conflict type settings’ (2009, 67). This resulted in tensions when contrasting British and American military cultures were involved. For example, the British and American governments fell out during the Kosovo conflict over the need for a ground force invasion to complement the air campaign.

Similarly, US administrations were averse to becoming bogged down in ‘Phase IV operations’: namely, post-conflict stabilization and reconstruction. The US was opposed to using its forces for the purpose of nation-building, fearing that they could be drawn into protracted commitments. It envisaged the rapid withdrawal of its forces after a conflict and the transfer of the situation to international peacekeeping forces or the United Nations. America’s National Security Strategy during the Clinton administration envisaged that the US would conduct overseas interventions but would extricate itself rapidly once a conflict was over (The White House 1994). The interventions carried out by the US and UK in the 1990s resulted in numerous frictions between the two countries. These frictions included the political objectives they were pursuing, the size of the forces they were committing and the level of casualties that they were willing to tolerate.

4.2 The Special Relationship 2001–2007: aligned during the War on Terror

The robust institutional cooperation between the US and UK during the Cold War years experienced a renewed lease of life during the War on Terror. The institutional memory of collaboration and the reflex within their armed forces to work together experienced a revival. This time the threat was no longer Soviet power, but the more nebulous danger of sub-state, Islamist violence. The tragedy that occurred on 9/11 was ‘not an ordinary event but a world-changing one’ (Blair 2010, 345). It was regarded as an attack ‘..against western civilization, especially the Anglosphere ideals of life, liberty and property’ (Colucci 2009, 197). The Bush administration reacted by declaring a war on terrorism wherever it manifested itself in the world.

The War on Terror provided a cause for which the US mobilized its great strength and resulted in the invasions of Afghanistan and Iraq. The US looked for allies to share its burdens and to help to provide legitimacy for its actions. It found this in the UK, who shared America’s fears regarding the threat of jihadist violence. The UK also shared the US’s intelligence assessment that Iraq was trying to obtain Weapons of Mass Destruction. The UK was a willing partner in US operations, eager to demonstrate its alignment with Washington. Elliott argues that, ‘..the UK’s pre-eminent policy objective for the decade was to support its “special relationship”’ (2015, 150). Its armed forces were capable of interfacing with the US military, albeit at a less technologically advanced level (Weisner 2013). The British refrained from imposing limitations on where its armed forces could be employed and were prepared to undertake leadership roles in coalition operations.

In the wars against Afghanistan and Iraq, the Special Relationship was thrown into sharp relief. The war was an opportunity to test American ideas of military ‘transformation’ in which small, agile forces employed precision weaponry to rapidly overcome their adversary (Rumsfeld 2002). While the Bush administration declined offers of force contributions against Afghanistan from European allies, on the grounds that a coalition operation would only add complexity, it accepted UK participation. The US accepted the British contribution of special forces, aerial refueling assets, Tomahawk cruise missiles (Finlan 2014, 100) and links to the Pakistani government. In 2003, during the invasion of Iraq, the British contributed a whole armored division (Foreign Affairs Select Committee 2010). They believed that providing such a substantial force would help them secure the role of deputy commander and give them influence over US decision-making.

Both of these conflicts resulted in Anglo-American tensions. This was unsurprising considering the protracted nature of the conflicts—the so-called ‘Forever Wars’—and the attendant casualties. The US blamed the UK for being insufficiently robust in counteracting Iraqi Shia militias, like the Jaish al-Mahdi, in Basra and Maysan. By 2004, the UK had drawn down its forces to less than 9000 personnel and consequently was incapable of carrying out large-scale counter-insurgency operations (Egnell 2009, 14). The US accused the UK of pursuing an exit strategy from Iraq while America was providing extra forces to counteract the violence. In turn, the UK was critical of the inadequate US planning for the aftermath of the invasion as well as the decisions, in May 2003 by Paul Bremer, Head of the Coalition Provisional Authority (CPA), to de-Baathify the Iraqi government and disband the Army (Greenstock 2016, 243–44). The UK also criticized the intense levels of force, including air strikes and heavy artillery, that were employed by the US against cities, such as Fallujah, in the center and north of Iraq (McColl 2013, 116).

In Afghanistan, the US and UK sought to combat insurgents, train security forces and conduct reconstruction within a country without a functioning national government. The UK unwisely offered to lead the expansion of the Karzai government’s control into Helmand province, assuming that it could be achieved at minimal cost. The naivety of this undertaking was exemplified by the fact that only a half strength brigade of 3150 soldiers were dispatched to Helmand (Farrell 2009, 574). Instead, the British Army found itself in an intense fire-fight, suffering casualties as they attempted to counter the production of opium. The UK made the mistake of committing insufficient resources to operate simultaneously in Helmand and southern Iraq. In the words of one senior British officer, the Army ‘..thought Afghanistan was merely a way out of Basra’ (Maciejewski 2013, 162). The US criticized the UK’s lack of commitment and reliability. The campaign had a final sting in the tail in August 2021 when the US decided to conduct a speedy withdrawal from Kabul that left the UK feeling inadequately consulted.

Since the Anglo-American disputes over Afghanistan and Iraq were mostly operational and tactical rather than strategic in nature, they did not cause lasting and irreparable damage to the Special Relationship. As Eznack points out, ‘..contrary to the implications of much existing literature, crises among close allies—such as some of the founding members of the Atlantic alliance—are more signals of strength than weakness…because they reflect the affective attachment that characterizes the relationships between these countries’ (2012, 239).

4.3 The Special Relationship in 2008–2021: the absence of a unifying threat

The period from 2008 to 2021 witnessed another be-calming in Anglo-American relations. This phase saw the withdrawal of US combat forces from Iraq in 2010 and the switch from warfighting in Afghanistan to the ‘overwatch’ of indigenously trained units. The end of major combat operations not only reduced opportunities for Anglo-American interaction, but left behind a legacy in which both countries were reluctant to be involved in new conflicts. When subsequent crises arose, both governments hesitated to intervene. In the 2011 NATO intervention in Libya, the Obama administration encouraged Britain and France to assume command of the operation and chose to ‘lead from behind’. In the Syrian Civil War, both the US and the UK refrained from committing their own ground forces and relied solely on airpower.

This period experienced a lack of direction in Anglo-American relations. As before, a lack of momentum within the relationship led to criticisms between the two governments. The British Conservative government was locked into a period of austerity following the global financial crisis. This resulted in two defense reviews, of 2010 and 2015 (Brooke-Holland, Mills and Walker 2023, 32–37), that exacted heavy cuts on the country’s armed forces (Chalmers 2015; Rogers 2017). These reductions not only impacted the UK’s ability to project military power internationally but also raised questions about its commitment to maintaining its prominent role on the world stage (Zakaria 2015; Rothkopf 2015). Given that the US had long judged the Special Relationship through a utilitarian lens, the UK found itself castigated by its closest ally for cutting its defense expenditure (Coughlin 2015; Stacey 2014). Throughout the second term of the Obama presidency, the debate over whether the Special Relationship had come to an end became increasingly heated among scholars and commentators (Dobson and Marsh 2014).

Worries about the terminal decline of the Special Relationship were exacerbated in 2017 by the arrival of the Trump administration, which brought with it a hostility toward many of America’s traditional allies. According to Dobson, ‘While Britain’s capabilities have relatively declined, asymmetry in its relations with the US grown, the importance of the Special Relationship declined…that sense of we-ness between the US and Britain seems to have endured…at least one could say that with a considerable degree of confidence until the arrival of Donald Trump in the White House in 2017’ (2023, 101–102).

In the first two years of the Trump presidency, when Theresa May was the British prime minister, the Special Relationship was devalued (Wemer 2018). By intentionally disparaging and undermining the liberal international order, the Trump administration’s transactionalist foreign policy damaged the foundations of the relationship with the UK. President Trump deviated from established practices of policy consultation and coordination with the UK and engaged in critiques of senior British government officials (Marsh 2023). His actions, including forcing out the British ambassador to Washington, Sir Kim Darroch, underscored a significant departure from traditional diplomatic conduct. This shift in approach not only strained the fabric of Anglo-American relations but also raised questions about the future dynamics of bilateral engagement between the two countries. Britain’s departure from the European Union further diminished its value to the US.

After Boris Johnson became the UK prime minister in July 2019, the Special Relationship saw a slight improvement, largely due to the Johnson government’s increasing alignment with the Trump administration’s China policy and their concerted efforts to negotiate a bilateral free trade agreement. Johnson and Trump had sharp disagreements in foreign policy, especially over whether and how to prop up the liberal international order. Nevertheless, Anglo-American functional cooperation in intelligence, nuclear and conventional military areas continued despite the political squalls of the Trump era. These routine institutional linkages persisted regardless of the tensions at the leadership level.

5 The revitalization of the Special Relationship in the face of new threats

The US and the UK appear to have embarked upon a new phase of close cooperation since 2022. The driver behind this renewed period of intimacy is once again new strategic threats, at a time when US power appears diminished within the international system. These threats take the form of a dual challenge from Russia and China, whose coalescence puts forward an alternative to the US-led world order. China in particular is a peer competitor with the US in the military, cyber, technological, and economic domains.

Although the Trump administration was the first to designate China as the foremost threat to US interests, the succeeding Biden administration has not deviated from this assessment. The economic rise of China has put it on a trajectory to rival, or even surpass, that of the US. China has been developing a military commensurate with its strength, the size of its naval fleet now exceeds that of the US and it is reputed to be tripling the size of its nuclear arsenal. In 2024, President Xi Jingping announced a further 7.2% increase in his country’s defense expenditure, meaning that it will have doubled in the last decade (Yoon 2024). America sees China as a major strategic challenge and the island of Taiwan as a potential flashpoint for war between them.

The eruption of the Russia–Ukraine war and China’s speedy alignment with Russia have sharpened the threat environment. The so-called ‘China–Russia Axis’, which is imbued with the phraseology of a ‘no-limits friendship’, has ‘knitted America and its European and Pacific allies together in opposition’ (Lin 2023; Ellison et al. 2023; Niblett 2024). If there were any doubts about the durability of the China–Russia relationship, they were dispelled by the meeting of their foreign ministers in Beijing in April 2024 that declared their joint opposition to the west. This has rejuvenated a sense of western cohesion that was in danger of disappearing after the Cold War (Kausikan 2022). Britain has contributed to US efforts in the Indo-Pacific theater by its participation in the Australia–UK–US (AUKUS) submarine arrangement (The Economist 2023, 45–46) and its efforts to develop closer cooperation with Japan. The Biden administration has cast Sino-American relations in starkly ideological terms—democracy versus authoritarianism, leaving little room for flexibility or compromise when dealing with China (Lampton 2024).

Despite Russia’s invasion of Ukraine, the US still prioritizes the contemporary challenge from China, asserting that China seeks to change the character of the liberal international order. For its part, Beijing seems to have hardened its belief that US policy represents a Cold War-style containment. According to Lampton (2024), ‘The ascribed goal of each country is unacceptable to the other…Each side is transforming the other into its existential threat, which will accelerate a stair-step action-reaction cycle’. As frictions and conflicts between the two countries continue to gain momentum, Sino-American rivalry increasingly resembles a new Cold War in which ‘these two countries are on the opposite sides of a profound and open-ended global competition between two political systems that are incompatible and mutually hostile’ (Niblett 2024). The Russia–Ukraine war has placed America in a strategic dilemma because it faces the risk of conflict in both the Euro-Atlantic and Indo-Pacific theaters simultaneously. The UK can make a contribution here by focusing its efforts on balancing the Russian threat and motivating its European allies to do the same. This would provide America with more room to maneuver and focus its defensive preparations on China.

The UK finds itself compelled to increasingly align with the US, amidst the contemporary threat environment, to preserve the integrity of the Special Relationship. As global geopolitical rivalry among great powers unfolds in this age of uncertainty, the UK’s approach continues to side with the US, underscoring America’s significance in UK foreign policy. From the US perspective, the UK remains one of its most capable and reliable allies. As Marsh (2023) contends, ‘When the United States casts around for allies in protecting the rules-based international order and energizing democracy in its defense, few rival Britain in terms of vested interest and established patterns of cooperation’.

6 Conclusion

The Anglo-American relationship remains the UK’s most important security partnership due to the benefits it derives from aligning with a superpower. The UK armed forces have always appreciated that they have to cultivate the relationship with their American counterparts by continually investing in cooperation. In comparison, for the US, the UK is an important but much less significant ally. British participation in coalition operations helps to confer legitimacy on US actions, but America has the strength to act alone.

Since the Second World War, the Anglo-American relationship has operated within a fluctuating threat environment. High levels of threat brought the two countries together as they acknowledged their need for each other. Operating together in various sorts of operations has led to tensions between the two countries, as conflicts exposed differences in priorities as well as differences in strategic culture. Paradoxically, a relatively low threat environment has also resulted in divergence between the two countries as their interests drifted in different directions. Nevertheless, even during these periods of reduced threat, the UK armed services worked assiduously to ensure links and patterns of cooperation with American forces. This has enabled the two sides to work together whenever the need arose.

Britain’s armed forces have cultivated cooperation with their sister services in the US military. They have embedded their personnel in US structures, maintained a constant dialog and striven to understand American doctrine and planning. Preserving the UK’s ability to operate alongside the US in all circumstances has become progressively harder. As the size of British armed forces has contracted, it has been necessary to make choices about which capabilities can be upheld.

In giving evidence to Parliament, a senior British Army officer contended that, ‘It will continue to be in the UK’s national interest to remain strategically relevant to the US’ (Defence Select Committee 2011). The contemporary environment, characterized by the threat from Russia and China, provides motivation for the two countries to work together once again. A second Trump administration is likely to devote more attention to the Indo-Pacific region. In a recent book by the America First Policy Institute, entitled ‘An America First Approach to U.S. National Security’, it was argued that China should outweigh the Russia–Ukraine war as a second Trump administration’s priority issue (Moriyasu 2024). Trump would be expected to scorn the value of a Western liberal order by denigrating the value of multilateral relationships such as NATO (Ikenberry 2019, 10–11). All of this will increase the sources of friction with a future British government and make the Anglo-American relationship less comfortable. Nevertheless, it is worth stressing that the Anglo-American special relationship has outlived over seven decades of leadership changes.

The durability of the Special Relationship is a testament to the highly institutionalized functional cooperation in the most sensitive security matters that transcends individual leaders. These strong institutional ties are crucial to facilitate a seamless continuation of security cooperation in dealing with the shared strategic threats of Russia and China, regardless of the political fluctuations or ideological shifts that might occur with the potential return of Trump to the White House.