The Possible Trump Effect on UK National Security and What to Do About It

Impossible to ignore: former US President Donald Trump leaves in his car after a visit to Downing Street in December 2019. Image: NurPhoto SRL / Alamy

The spectre of Donald Trump returning to the White House looms over European security and Ukraine. Instead of displaying indignation at Trump’s increasingly anti-NATO rhetoric, Europeans need to collectively act to strengthen their resolve and capabilities. For the UK, it is an opportunity to transform its approach to defence and security.

The prospect of ‘Trump 2.0’ is a strategic nightmare for most European policymakers. Trump’s anti-NATO posturing has escalated from arguably justified criticism of allies’ defence spending, to encouraging Russia to attack laggards. Simply complaining about such corrosive statements will not achieve anything. A second Trump presidency is a risk, and risks must be mitigated. In an increasingly dangerous world, no single country can provide suitable mitigations alone, or compensate for the leadership and military capability vacuum that US disengagement would create.

The next US president will occupy the Oval Office until 22 January 2029, and this period will likely experience overlapping global crises. First, NATO allies assess that Russia could attack, or pose a real conventional threat to, a member state within a decade and the most pessimistic assessments are between three to five years. Second, President Putin will not stop in his aim to subjugate Ukraine, and plans to achieve this by 2026. Third, some US assessments indicate that the Chinese People’s Liberation Army will be ready to move against Taiwan by 2027 and have a strategic window to complete annexation by 2030. Finally, the war in Gaza is not abating and is already escalating regionally, with the Red Sea becoming a flashpoint. Strong leadership has never been more indispensable.

The UK and Europe are in this Together

The latest comments from Trump should not come as a shock for Europe, although the approach is clearly deplorable. The uncomfortable truth is that Trump has a point – Europe has taken US protection for granted for over 30 years. Now, there are no wake-up calls left, and very limited options for defending Europe without American support.

The EU is clearly not the answer, as 80 % of NATO’s defence expenditure comes from non-EU NATO allies. However, it is not certain that NATO can be kept together without the US. In 2021, the rest of NATO were unable to find the 3,000 to 5,000 troops, plus enablers, that might have kept the Alliance’s Resolute Support Mission in Afghanistan going once the US decided to withdraw. Moreover, Europeans were only able to evacuate their nationals because the US secured Kabul airfield – one of the more basic military tasks. But NATO represents the best option and Europe must collectively do everything it can to strengthen the Alliance, otherwise European security will fragment – and Russia will win.

Therefore, Trump’s unpredictability is an imperative for Europe to do more on defence – it can make the funds available if politically it chooses to do so. Even if President Biden wins, the driver for action is still there as the US pivots away from Europe. In addition, US politics is now structurally polarised and Trumpism could have many cycles left to run. Relying on around 300,000 US voters in five swing states every four years is not a viable strategy.

The UK, as the only other NATO member that assigns its strategic deterrent to NATO, could play a vital leadership role to rapidly build NATO’s European capabilities and decisiveness to act. Leveraging other treaty-based relationships with traditional allies such as France, and new ones with emerging hard powers such as Poland, will be key. Moreover, there is strong potential for building a similar relationship with Germany and supporting the country to anchor its Zeitenwende in European security. This would provide a very strong ‘European Quad’ leadership grouping, or even a new ‘European Quint’ with Italy. In addition, the UK also has strong bilateral and collective relationships with the Joint Expeditionary Force members, and is a powerful force in the defence and deterrence of northern Europe. The collective agenda should include a nuclear posture review, in conjunction with France, to reassure allies; increasing support to Ukraine, which will become more demanding – and vital – if the US pulls the plug; and increasing European capabilities within NATO and getting their militaries ready to fight.

NATO, Five Eyes and AUKUS

Although NATO has thus far received most of his ire, Trump appears to dislike alliances in general, and has a transactional worldview. This is particularly worrying for the UK and its triad of current national security priorities – NATO, Five Eyes and AUKUS.

Without moderating and challenging voices within the Oval Office, Trumpian policy will be inherently unstable

A US withdrawal from NATO is by far the most dangerous outcome, but it is not the most likely. Policymakers in the US have pushed the legislative route as a bulwark against Trump, with Congress passing a special law in December 2023 to require the pro-NATO Senate’s consent to withdrawal from the Alliance. However, Trump does not play by these rules, and relying on legislative and legal routes to blunt his aspirations has thus far failed. Europe cannot put its faith in such weak mechanisms, as Trump can undermine NATO – and therefore the defence and deterrence of the Euro-Atlantic area – more easily from the presidential lectern.

Equally concerning will be how to manage the Five Eyes intelligence relationship. Intelligence relationships benefit greatly from trust and stability. The revelations in 2023 that hundreds of classified documents were found in a shower and elsewhere in Trump’s Mar-a-Lago resort, including details of allies’ defence capabilities and potential vulnerabilities, will send shivers through the UK intelligence community. Deeper cooperation may be problematic, but it is increasingly vital, with US and UK intelligence being invaluable to Ukraine’s defence.

Finally, the AUKUS partnership, which is a long-term infrastructure and technology transfer programme as much as a defence and security initiative, requires stability and predictability. Here, there is a risk that Trump withdraws if he is persuaded by his advisors that the US cannot afford to give up any Virginia-class submarines, or he could chose to reopen the deal to drive a harder bargain with Australia. Moreover, Trump has already proposed a 10 % universal tariff on imports, and such an ‘America First’ policy on International Traffic in Arms Regulations could make AUKUS non-viable for the UK and Australia, destroying the incentive to cooperate on Pillar 2’s advanced military capabilities.

Against this backdrop, there is a danger of a second Trump administration being more chaotic than the first. In 2016, Trump was able to convince established defence seniors to serve. None survived. It is therefore unlikely that similar ‘grown-ups’ will risk their reputations, so UK ministers must be prepared to work with the third or even fourth string. Without moderating and challenging voices within the Oval Office, Trumpian policy will be inherently unstable – a fear confirmed by his own former National Security Adviser, John Bolton. Therefore, the UK senior ministerial team will really matter. Many experienced Conservative ministers have already declared they are not standing at the next election, with others facing significant electoral challenges in their constituencies. For Labour, only two shadow national security briefs have Cabinet ministerial experience.

Within this context, the UK must prioritise deeper military-to-military and intelligence-to-intelligence relationships, at all levels, to insulate itself from the political weather. The choice of the next UK National Security Adviser will be a crucial appointment, and the next government should consider appointing a dedicated minister, or ambassador, to both AUKUS and Five Eyes to strengthen coherence.

What Should the Next Government Do?

The next prime minister will need to give serious personal consideration to the possibility of being the UK’s first total wartime leader since Churchill. The government should prepare by breaking the mould of recent UK defence reviews that deliver far too little of what is promised, and ultimately fail to make the UK safer. If the Conservatives are returned to government, there is likely to be continuity. Labour is well ahead in the polls and can be more radical.

Each post-Cold War UK defence and security review has been blown off course after only a few years by new geopolitical realities or economic constraints

Labour has committed to a Strategic Defence and Security Review in the first 12 months – its first in 27 years. There is a risk here of analysis paralysis, in which a future government takes comfort in the process, despite knowing what needs to be done, for fear of making hard choices. There will certainly be pressure to undertake a grand international relations-based analysis to position the UK away from Conservative policies such as Brexit and ‘Global Britain’. Yet each post-Cold War UK review has been blown off course after only a few years by new geopolitical realities or economic constraints. They have been successively more expansive and ambitious and not underpinned by adequate resources, leaving the current equipment programme £16.9 billion in the red to 2033 and key capabilities delayed.

Without first reforming the machinery – for which there is no time – it would be a case of doing the same thing but expecting a different outcome. Indeed, regardless of who wins power, the same people will draft the review who have already conducted two in the last four years, limiting the options for change. Instead, the review should be an unequivocal call to arms and to adopt a ‘fight first’ approach, focusing on fighting formations being ready as soon as practically possible. This can be best achieved through three major structural changes.

First, the UK must increase defence spending. Global defence spending has risen 9 % since the 2022 Russian invasion of Ukraine, and the trend is upward. In 2024, 18 of 31 NATO members will meet the 2 % GDP target for defence spending, representing an additional €600 billion for non-US allies – an 11 % increase – since Russia’s 2014 annexation of Crimea. Yet between 2014 and 2023, the UK had the lowest real increase – just 6.84 % – among all NATO members. For comparison, Lithuania and Hungary’s spending has increased 270 % in the same period. This is no longer a defensible position. Instead of more hollow commitments to a totemic 2.5 % or 3 %, the analysis should focus on firing up the UK industrial base, first to sustain Ukraine as an investment in Euro-Atlantic defence and deterrence by destroying the Russian military in the field, and second to prepare for a future war with Russia. In doing so it must be brutally honest with the public about the cost of protecting the UK’s citizens and those of its allies.

Second, the review must get back to basics and deliver capabilities, not concepts. You can have all the digital backbone you want, but if you only have a week’s worth of ammunition, you can only fight for a week. Instead of designing an exquisite idealised future force and doctrine target for 2035, the UK must prepare to fight with the force it has, not the force it wants, by focusing on readiness, with 3rd Division, as a major contribution to NATO, as the main effort – due to be ready for NATO by 2030, already delayed from a target of 2025. A capability-led approach should have confidence in the Western technological overmatch against Russia, and deliver capabilities quickly and at scale to stay ahead of Russian recapitalisation. The Global Combat Air Programme and AUKUS, with no delays, will only start delivering from the mid-2030s. Both are therefore largely irrelevant if a war with Russia and/or China begins this decade.

Finally, to demonstrate leadership and transparency, NATO planners should be invited into the core review team to understand where unique UK capabilities can add the most value and mitigate any US shortfall. If NATO is truly the cornerstone of UK defence, then the UK should integrate the NATO Defence Planning Process into its national planning from the start, thereby negating uncomfortable future Alliance conversations.

The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.

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Ed Arnold

Senior Research Fellow, European Security

International Security

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