By Joshua C. Huminski*
The UK’s Strategic Defence Review is not about the United States (US), but Washington’s policy priorities and changing geostrategic orientation loom in the background. The ‘America First’ agenda of Donald Trump, President of the US, and the prioritisation of the country’s southern border and the Indo-Pacific region, are accompanied by a downgrading of the Euro-Atlantic in the administration’s calculus. (From Britain’s World.)
As part of this strategic downgrading, the President (and the broader Washington ecosystem) expects North Atlantic Treaty Organisation (NATO) allies to take greater financial and practical responsibility for continental defence. It is through this strategic lens that Washington will view the Review and the UK’s policy priorities.
The authors sensibly avoid commentary on the president’s agenda, but observe that the Trump administration’s rhetorical and practical shift results in ‘major questions about the future of European security that inevitably follow the United States’ change in security priorities, as its focus turns to the Indo-Pacific and the protection of its homeland.’ Nevertheless, the authors do lean into the special relationship, writing that Britain should look to ‘maximise the relationship’s potential as a force multiplier in renewing deterrence’ and adding that there is ‘enormous potential for expanding industrial and technological collaboration with the US’.
From a military perspective, the language which the SDR uses to characterise the shift in the British Armed Forces’ orientation will find a warm reception in the Pentagon. The shift to ‘warfighting readiness’ parallels the focus of Pete Hegseth, US Secretary of Defence, for the Department of Defence (DOD), who stated: ‘Our job is lethality and readiness and warfighting. [The United States] will be no better friend to our allies and no stronger adversary to those who want to test us and try us’.
Beyond merely a rhetorical flourish, the emphasis on lethality among the British Army, the integration of technology and the services (going beyond simply ‘joint’) and the 20-40-40 force balance – wherein 20% of crewed assets will control 40% of reusable platforms and guide 40% of attributable assets on the battlefield – will find a receptive (and likely intrigued) audience among America’s military planners. The Review’s emphasis on what amounts to a post-industrial defence industrial base will also find favour, particularly as the DOD under Hegseth is embarking on its own sweeping review of acquisition reform.
Though less appreciated in Washington (outside of the Pentagon), the ongoing defence reform efforts may well have a longer-lasting effect on the reformation of the Ministry of Defence (MOD) and the British Armed Forces than the SDR itself. In October 2024, HM Government established a new Military Strategic Headquarters, created a new National Armaments Director to coordinate and execute defence industrial strategy, and provided new powers to the Chief of the Defence Staff, enabling the office to command the individual service chiefs. While structural in nature, it will better improve the operations of the MOD and the British Armed Forces, as well as joint activities with the US.
The White House will welcome the Review’s ‘NATO First’ prioritisation. While a reflection of the UK’s assessment of its own capabilities and interests, it fits well within what Trump – and indeed his predecessor Joe Biden, President of the US between 2021 and 2025 – wishes to see: NATO allies taking on greater responsibility for continental defence. Here, there are smaller, but no less notable, indications that Britain will assume greater defence and deterrent capability. Reports that HM Government is exploring the acquisition of F-35A Lightning II Joint Combat Aircraft, capable of delivering lower yield air-dropped nuclear weapons, and the Review’s commitment to expanding munitions production, are investments in the long-term defence capability of the UK.
The commitment to the AUKUS programme and the production of ‘up to’ 12 nuclear-powered attack submarines will also find purchase in Washington – increased collective shipbuilding capacity will, over time, see the partner nations able to generate and project greater force into the Indo-Pacific while offsetting any risks of Washington prioritising its own submarine deployments in the region.
The rub lies, however, in the nuance between the policy and the politics; something which is not lost on Washington. The MOD’s review teams – both internal and external, whether the civil service-produced Defence Command Papers of 2021 and 2023 or the troika of Lord George Robertson, Gen. Sir Richard Barrons and Dr Fiona Hill on this Strategic Defence Review – prepare excellent policy frameworks, but it is the politics between 10 and 11 Downing Street, and the accompanying competing priorities, which constrain (and will continue to constrain) the SDR’s ambitions.
Above all else, the Trump administration is focused on the defence expenditure line – how much are allies spending, and how quickly? In February 2025, just ahead of his meeting with Trump, Sir Keir Starmer, Prime Minister, brought forward the commitment to spend 2.5% of Gross Domestic Product (GDP) on defence to 2027. In doing so, the Prime Minister made a difficult trade-off, cutting official development assistance to fund the proposed increase – the least bad option available at the time (without increasing taxes or adjusting social welfare programmes).
This commitment carries through to the Review, but Sir Keir stopped short of officially committing Britain to spending the 3% of GDP which the authors find is necessary to support the SDR’s ambitious agenda. It is notable that John Healey, Secretary of State for Defence, indicated that HM Government would ‘without a doubt’ spend 3% in an interview ahead of the Review’s publication, but subsequently walked that commitment back. In the introduction to the SDR, the Prime Minister, hedging, wrote: ‘we have set the ambition to reach 3% in the next Parliament, subject to economic and fiscal conditions.’ The authors conducted the Review in a budgetary context of investing 2.5% of GDP into defence, although noted that ‘as we live in such turbulent times it may be necessary to go faster.’
In failing to commit publicly to the 3% spending target, Sir Keir has, in the first instance, sent the signal that HM Government is only somewhat serious about its defence programming – the SDR is long on ambition, but short on resourcing (a criticism also levelled at previous British defence reviews). In the second instance, the failure to commit to an elevated floor looks doubly weak to the US when it is expected that NATO countries will commit to a new defence investment pledge of 3.5% of GDP on core defence spending and 1.5% on military-related spending such as support to Ukraine, resilience, etc. Even if the new aggregate 5% of GDP target carries with it a ten-year timescale, the Prime Minister’s hesitancy will not send the right signals to Washington, which expects the UK to act as a leader in the provision of European security.
The tension between policy and politics sits at the heart of the Review and its execution. It does not make any fundamental trade-offs which are necessary to reconcile its ambitions with fiscal realities.
The fiscal challenge is further compounded when the bonnet is lifted on British defence spending. The 2.5% of GDP commitment is not all that it seems, and Washington knows this. The increased spending covers already committed capital expenditures, and does not represent wholly new spending. With the removal of the nuclear enterprise from the equation, defence spending falls to ~1.9% of GDP. Taking out the intelligence component (which will no longer be classified as defence spending under new NATO rules), it falls further still to ~1.7%.
The tension between policy and politics sits at the heart of the Review and its execution. It does not make any fundamental trade-offs which are necessary to reconcile its ambitions with fiscal realities. Instead, decisions on capabilities and investment are pushed back to autumn, when the Defence Investment Plan is due to be published. Nevertheless, the statements and priorities of the SDR will find a receptive audience in the White House and the Pentagon. Warfighting, a prioritisation for NATO and Europe, as well as greater independence, are all in line with the signal of Trump’s demands for America’s allies in the rhetorical noise. Delivering on these commitments, even if over the next ten years, is where Washington will want to see actual progress and activity. The real art of the deal is in the execution, not the process.
*Joshua C. Huminski is the Senior Vice President for National Security and Intelligence Programmes, and the Director of the Mike Rogers Centre for Intelligence and Global Affairs at the Centre for the Study of the Presidency and Congress.
