The Defence Investment Plan: The view from Washington

The Memorandum | No. 31.2026

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On 30th June 2026, Sir Keir Starmer, outgoing Prime Minister, finally released the much-delayed Defence Investment Plan (DIP) , which sets out how His Majesty’s (HM) Government will resource the prior year’s Strategic Defence Review (SDR). The process of arriving at the DIP was nothing if not painful, resulting in the resignation of John Healey, Secretary of State for Defence, and Al Carns, Minister of State for the Armed Forces. Putting the political machinations behind and pain of delivery aside, there is some good news buried within the DIP for the United States (US).

First, the United Kingdom (UK) is consciously making choices in its defence policy and strategy. While the SDR identified and enumerated priorities, it singularly failed to make definitive choices. This meant that Britain was pursuing a multi-domain ‘Integrated Force’ without prioritisation or the resource base to support or sustain such an order of battle. It had consequently – the quality of its men and women in uniform notwithstanding – suffered a crisis of credibility as of late within the political circles of defence in Washington ( the British Armed Forces remain highly regarded within American military circles). At least now there is a clearer direction that the UK’s military is taking.

Emblematic of these choices is the DIP’s emphasis on uncrewed and autonomous systems across multiple domains, which reflects lessons learned from Ukraine and the changing character of war. It also establishes a course for the UK to develop key enabling capabilities that would complement those of the US in-theatre, allowing the British to offset these capabilities should a crisis – such as one over Taiwan, or as Operation EPIC FURY vividly demonstrated – require American attention elsewhere.

There are, however, risks in doing so. It is too early to tell what the right balance is between crewed and uncrewed systems. Clearly the British Armed Forces are leaning more into autonomous systems than some of their partner militaries. The UK’s experience in developing this hybrid force will be informative. How will the ‘New Hybrid Navy’ execute traditional sea control operations in the North Atlantic and in support of Atlantic Bastion? How will it manage operating crewed assets in traditional missions along with autonomous subsurface and undersea operations?

Here, the DIP, while retiring the Type 45 class destroyer in favour of six Common Combat Vessels (CCVs), retains a commitment to crewed systems – including the reinvestment in the Defence Nuclear Enterprise, partnership with Norway for the Type 26 class frigate, and the SSN-AUKUS class nuclear submarine. Notably, if the Defence Nuclear Enterprise is removed from Royal Navy’s budgeting, the Royal Navy receives less than the British Army and Royal Air Force (RAF), despite the UK being an island nation.

Washington will look to London’s experiences in this area, as the question of what that future force looks like is as yet unanswered in the Pentagon. The Department of War is pushing to achieve its own version of drone dominance and recently announced a drone ‘tsar’ to oversee most uncrewed programmes, but what the high-low mixture looks like is still in development. If HM Government sticks with the 20-40-40 model of crewed, uncrewed, and attritable effectors as outlined in the SDR, it could well end up with a more balanced force. Seeing drones as, however, a cheaper and cost-saving alternative to crewed systems is ill-advised – much of the present conversation focuses on what drones can do, not what they cannot.

Second, the DIP recognises the changing strategic landscape of European defence and adapts accordingly. In response to both the threat posed by Russia and the demands by Donald Trump, President of the US, that North Atlantic Treaty Organisation (NATO) member states shoulder more of the defence burden, the European pillar of the alliance is stepping up in a big way. Germany’s ‘Responsibility for Europe’ envisions a force of 460,000 by 2039. Poland aims to double its military to 500,000 by the same year.

Beyond raw personnel numbers, Berlin is investing heavily in space and enabling capabilities to shift some of the burden away from America as it seeks to pivot to the Pacific. This, in turn, means that Britain can reconceptualise its own defence strategy and position within NATO. Here again there are risks. If the plans Berlin and Warsaw have set out fail to materialise, or national politics charts a different course while the US is rebalancing its attention away from NATO, gaps could emerge.

More broadly, the UK is stepping up its partnership with and support of NATO’s defence and deterrence mission. Through bilateral cooperation with Norway on the aforementioned Type 26s, co-development of long-range precision strike with Germany, and commitment to the Global Combat Air Programme (GCAP) with (thus far) Italy and Japan, Britain is working to embed itself deeper into NATO’s European defence architecture while expanding its defence industrial base and reach. These are, in aggregate, welcome developments from Washington’s point of view, demonstrating practical burden shifting through planning and acquisition.

Third, and least appreciated, the DIP is indicative of at least an upward trajectory in defence spending for the UK. The £15 billion uplift is well short of the £28 billion service chiefs said was necessary, and it means that HM Government will not hit the 3.5% of Gross Domestic Product (GDP) core defence spending target in the near term. That Washington had any belief that London would be able to do so was, however, misguided from the start.

HM Government stated that defence would be its top priority in the next spending review, but it has thus far been unwilling to cut anything other than international development spending in order to make that happen (beyond what is already outlined in the DIP). Put simply, the increase is welcome, but not nearly enough for Britain to act independently, or to lead within NATO.

Trump is overwhelmingly a president who focuses on outcomes, not processes. That the DIP is finally published counts, but only just. The President will almost certainly lambast the UK for failing to reach NATO’s 3.5% of GDP core defence spending target agreed to at The Hague last year, even if reaching it within one year was never likely.

There is certainly a risk that at the forthcoming Ankara Summit Trump singles out Britain for its underperformance in the spending league tables. His previous, curiously cordial, relationship with Sir Keir has all but evaporated, and the delay in issuing the DIP will not have improved 10 Downing Street’s standing. He is less interested in the details (and the devil of creative accounting is very much in the DIP details), but London’s counterparts, both political and military, in the Pentagon will be watching closely to see how these precious pounds are spent.

The pressing challenge is whether and how HM Government executes on the funding plan, and if the plan survives first contact with Andy Burnham, Mayor of Manchester and expected successor to Sir Keir. As the second largest economy in Europe, what the UK does matters, certainly more than the smaller NATO partners (whose respective contributions are absolutely to be welcomed and applauded). HM Government needs to find more resources to meet the 3.5% defence spending target and the additional 1.5% of non-military defence-related expenditures.

Given Britain’s current political challenges, the question is whether the DIP survives the transition between prime ministers. Assuming Burnham enters No. 10, will he demand a refresh of the SDR? Will he support the decisions his predecessor made, given his priorities and the challenge of balancing an eclectic Labour Party? Will he in fact make defence the top priority in any future spending reviews?

The savings found in departmental budgets, halted road improvement works, and Net Zero targets (sacrifices which are fundamentally necessary), will almost assuredly cause the incoming prime minister political headaches from within their own Labour Party. They will also undoubtedly be less than pleased with the fact that there is at least £4.7 billion in unfunded mandates over the duration of the four-year plan itself.

There are, of course, issues within the DIP, and at times creative accounting undertaken to facilitate the increased budget. They should not be dismissed, and HM Government should be held to account by its allies in Washington and indeed across NATO. Nonetheless, Britain is taking steps in the right direction and on the journey to increased defence spending. Along the way, it is recognising both the changing character of war and the shifting strategic landscape on the continent of Europe and responding accordingly.

These are all messages that will be welcomed by Washington. The challenge is turning commitments into action.

Joshua Huminski is Senior Vice President for National Security and Intelligence at the Centre for the Study of the Presidency and Congress, and an International Fellow at the Council on Geostrategy.

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