Since November 5th, 2024, Donald Trump’s second US Presidential term has been at the forefront of the minds of politicians and policymakers, especially those in Europe. President Joe Biden and many European leaders, including Keir Starmer, held a broadly united position on foreign policy issues, such as support for the territorial integrity of Ukraine. The US and the UK had a particular unity of approach, sharing the same ideological appreciation for global democracy, free market politics and a rules-based international order. President-elect Trump, however, has indicated he would fundamentally change the US’ stance on international affairs, which could threaten these shared understandings.
During the presidential election campaign, Trump suggested that his administration would pursue an isolationist approach to foreign and defence policy, which would see the US military support domestic national security aims over global defence and deterrence projects. This pivot from Biden’s policies could see the US reduce its role in European security. As a consequence, states such as Ukraine could see Trump prioritise the quick conclusion of conflicts to avoid US involvement and cost, including in cases where peace would disregard the rights of affected states under international law.
Many in the UK see this shift as a serious threat to the UK/US special relationship, which has historically thrived on unity of foreign policy and complementary investment projects. The current UK defence architecture also relies heavily on US support, with the defence-trade relationship between the US and UK alone worth $3bn per year. Additionally, for the UK, having US backing in international humanitarian projects is a significant asset – both in terms of financial support and in its rhetorical weight.
In this context, the re-election of Donald Trump as President of the United States has become a prominent feature in UK Parliamentary debates, with Members debating how the UK should interact with the second Trump Administration. The Liberal Democrats have suggested a policy of ‘Trump-proofing’, particularly when it comes to the ensuring continued NATO support for Ukraine, regardless of US backing. The Conservative Party, meanwhile, have said that Trump should be pre-briefed on ongoing security agreements before he reaches office. What is more, the Lords International Relations and Defence Select Committee opened an inquiry into “The UK’s future relationship with the US”, specifically aiming to “explore the impact a second Trump Administration may have” on the special relationship, just two days after Trump’s election.
Meanwhile, the Labour Government have been clear that the election of Donald Trump should not change the relationship between the US and the UK – at least on Labour’s end. In a bid to maintain the historically close ties, Foreign Secretary David Lammy – who has previously criticised Trump – has made a clear gesture of conciliation to the incoming Trump Administration. Specifically, in his recent Locarno speech, Lammy agreed with Donald Trump and JD Vance that Europe needs to do more to secure its own defence.
While British politicians are evidently concerned about maintaining the special relationship, there has been little regard given so far to how the Biden Administration should act – or has acted in – preserving the UK/US special relationship.
Defence Investment and the Strategic Defence Review
In early December 2024, Biden’s Deputy Secretary of Defense, Kathleen Hicks, visited the UK to partake in the bi-annual US/UK Defence Dialogue. While there was plenty to discuss, Hicks said that the top item on her trip’s agenda was the UK’s forthcoming ‘Strategic Defence Review’.
She indicated that the US was keen to see strategic investment form a key part of the review and its recommendations. She also outlined a preference for the UK to prioritise increased munitions production and establish clear funding plans for sustaining maritime and nuclear assets. Hicks argued that although maintaining these assets could be costly, and therefore somewhat unpopular, the benefits of effective deterrence would outweigh the costs. Hicks emphasised that deterrence was a collective act, with the UK and the US defence sectors feeding into and complementing one another. Even more importantly, Hicks said the respective defence sectors must make up for any shortfalls in the other. For deterrence to be effective, the prospect of having war-winning technology must be credible – something that dated, crumbling ships and empty munitions stockpiles cannot not achieve.
Hicks’s preference for coordination and complementarity does not come as a surprise, as one of the hallmark defence agreements of the Biden Administration was the AUKUS agreement. The AUKUS (Australia, the United Kingdom and the United States) agreement seeks to equip Australia with a modern fleet of nuclear-powered submarines capable of supporting US/UK initiatives in the Indo-Pacific. Having the capacity to sail and repair ships in the Indo-Pacific is a clear asset to both the UK and the US, enabling them to deter China, defend Taiwan and support democracy in the region. It therefore appears consistent for Hicks to demonstrate a preference for commitments to fund areas of significant cooperation between the US and the UK that support their shared ideological approach.
Failure to cooperate on defence investment could also be expensive for the US. A UK Government which took a non-cooperative approach to defence investment – for example by abandoning historic investment trends – could lead to the re-calculation of capability assessments in the States. This could be a costly endeavour for the Americans, with the US having to invest further to make up for areas that it once felt were covered by UK capabilities.
From this, it can be seen how the US/UK special relationship is based on unity of practice and ideology – a shared approach to achieve shared goals. If either falls out of step, the special relationship falters. Through Hicks’ visit, the Biden Administration has sought to remind Britain of the importance and benefits of keeping in step with US defence investment trends.
Defence projects often outlive Presidencies, so securing British alignment with the US now could help the relationship endure potential disruption during Trump’s administration, and even beyond.
However, material cohesion and interoperability are only one piece of the puzzle.
Politicisation of the US Military
While the “changing of the guard” is an often-used phrase for the transition of power, key figures in the defence and military sphere are often the most enduring in the US and UK, serving across multiple premierships and presidencies. For decades now, the widespread understanding among democracies in the West has been that the military should be apolitical. General Omar Bradley, the first Chairman of the Joint Chief’s of staff served under both Harry Truman (Democrat) and Dwight Eisenhower (Republican). More recently, General Mark Milley served as the Chairman under both Donald Trump and Joe Biden. In the UK, Admiral Sir Tony Radakin was appointed Chief of the Defence Staff in November 2021 and still holds the post today despite having served under 4 different Prime Ministers to date.
In the US, continuity in the service of military personnel, defence investment and foreign policy has been the norm. There are rarely significant defence posture changes between administrations. Defence budgets also provide investment for projects with decades-long timelines and with the understanding that these capabilities will be used for even longer than that. This continuity underpins the concept of an apolitical military whose work is separate to party politics.
However, with the re-election of Donald Trump, the political position of the military may change. The current role of the Joint Chiefs and the Heads of Forces in the UK is to give their ‘best military advice’ to political leaders – something Trump has indicated could change during his administration. President-elect Trump has made it clear that he has a very specific view on how politics should be conducted and that those loyal to him are best placed to enact his policies.
For example, the Secretary to the Navy is set to be John Phelan, one of Trump’s biggest donors, who, crucially has no military experience. Likewise, Steven Witkoff has been named as the Special Envoy to the Middle East, a role of key importance due to the ongoing conflict in Gaza. Witkoff is also a significant donor to Donald Trump, as well as his golf partner, and has a background in real estate. While these positions are politically appointed, in past administrations it tended to be experience, not exclusively political loyalty, which typically factored into the candidate’s appointments. This is indicative of the potential shift towards overtly political appointments in the realm of defence and foreign affairs.
Furthermore, in his first Administration, Trump faced significant tension between himself and his military colleagues, with many key defence figures resigning ‘on principle’. Jim Mattis resigned as Secretary of Defense, Army Lt. Gen. H.R. McMaster left the role of national security adviser, and General John F. Kelly resigned as his Chief of Staff. Confidence in Trump’s ability to be an effective Commander-in-Chief has waned, with many former figures from his administration like General John Allen and former Head of the Joint Chiefs Mark Milley speaking publicly on how Trump does not respect the political-military divide.
This apparent politicisation of the US military threatens a core ideological aspect of the UK/US special relationship. If the United States decides to change its military doctrine and create a more political role for the military, functionally, the US and the UK will be unaligned and, therefore, not as interoperable as before. Military figures from each nation could have contrasting strategic objectives that make campaign planning difficult all the way from the grand strategic level to the tactics used on the ground. If each military is following a rule book that lays out clashing initial premises, even if the US and UK wanted to collaborate, they may find it difficult. This could affect everything from humanitarian missions to deterrence of transnational threats against democracy, where the US and UK are typically aligned.
The Royal United Services Institute Welcomes It’s New Director
It is no surprise, then, that when Hicks was on this side of the Atlantic, she spent time not only giving the Labour Government a very clear rundown of the Biden Administration’s expectations and rationale for best military practice, but also visited the UK’s preeminent defence think tank. The Royal United Services Institute (RUSI) is the world’s oldest defence and security think tank, founded by the Duke of Wellington in 1831. The Institute is rooted in British military tradition and always has a visiting fellow who is a career service person.
In 2015, RUSI appointed Dr Karin von Hippel as their Director. Dr von Hippel was the first woman elected to this position and was also the first American. At the time, this could be understood as a response to the increasing ‘Americanisation’ of the UK. The UK under Boris Johnson, Liz Truss and Rishi Sunak increasingly made space for American politicians and business figures to give advice to UK politicians and invest in UK industries. The appointment thus felt like a gift extended by the UK to keep itself in the US’ orbit.
This year, RUSI elected Rachel Ellehuus to the helm, its second woman and second American Director. Ellehuus took over from von Hippel on January 6th, 2025. In contrast to von Hippel’s appointment, the choice to maintain a US defence figure as Director could be interpreted as the Labour Government and the Biden Administration making it difficult for Trump to disengage from the UK.
Hicks’ December 2024 speech at RUSI also reflected this. The speech was both a call to action and a justification of the Biden Administration’s foreign and defence policies. She spent a considerable amount of time explaining that despite war breaking out in Europe and the Middle East, and the heightening of conflicts in Africa, the US pivot to the Indo-Pacific was the correct choice for global security. In justifying this choice, she described the lessons learned from Ukraine as a textbook, the rules from which could also be applied in the event of a conflict with the People’s Republic of China.
Her focus on AUKUS, the UK’s investment in maritime technologies, and the importance of collective defence and interoperability can be seen as a defence of the current position of the UK/US special relationship, as well as bid to ensure its longevity.
What remains to be seen is if the UK Strategic Defence Review 2024 takes on board Hicks’ insights, and if it will be enough to withstand the pressure of an isolationist, and potentially politicised defence architecture under President Donald Trump.
Only time will tell if Biden’s attempt to secure the UK’s commitment to long-term investment in support of shared objectives will outweigh Trump’s possible ideological shift in military doctrine and ensure the longevity of the US/UK special relationship.