The UK Strategic Defence Review draws the right lessons from Ukraine – but still relies on continued US commitment 

Proposals to improve armed forces integration, harness new technology and boost societal resilience are the right lessons to draw from Ukraine. But much depends on spending, implementation, and a reliable US partner. 

Expert comment Published 4 June 2025 4 minute READ

Olivia O’Sullivan

Director, UK in the World Programme

Dr Marion Messmer

Senior Research Fellow, International Security Programme

The UK government’s Strategic Defence Review (SDR), published this week, clearly prioritizes the UK’s contribution to NATO and European security, setting out plans to orient the armed forces around deterring a full-scale war in Europe and protecting civilian infrastructure at home. 

The Review is threaded through with lessons from Russia’s full-scale invasion of Ukraine. That is right and inevitable: the war has dramatically reordered European security and provided hard-won battlefield lessons: About the use of technology in warfare; the industrial production needed to sustain a fight against a peer adversary; and the whole-of-society effort required to fend off unconventional warfare including cyberattacks, and attacks on infrastructure. 

The Review also reflects a wider, and longer-running shift away from the assumptions of the US-led ‘war on terror’ to those needed in an era defined by threats from hostile states – specifically Russia – and authoritarian competitors including China. The Review makes new commitments to support those aims, including the use of autonomous and uncrewed systems, ramping up submarine and munitions production, and greater use of digital targeting. 

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Olivia O’Sullivan and Marion Messmer discuss key points from the UK’s SDR.

Yet the SDR also echoes some conclusions from previous reviews. Its immediate predecessors, the 2021 Integrated Review and its 2023 update, and the 2024 ‘Defending Britain’ paper, also emphasized the shift to deterring hostile states, harnessing cutting-edge technology, and prioritizing resilience over efficiency. 

The question for this Review is whether its recommendations can be fully implemented. Having the Review led by external experts has its benefits. But the UK Ministry of Defence (MOD) and armed forces must ‘own’ the implementation and make some difficult investment choices. This is especially true as the UK government has set an ambition to spend 3 per cent of GDP on defence only at some point in the next parliament. Meeting all the SDR’s commitments in that budget will be tight. 

Hanging over the document is the knowledge that the Review has not quite delivered what some hoped for: that is, hints that UK defence may be planning for a future in which it is less reliant on US partnership. 

The positives

The SDR has a promising emphasis on innovation, industry relations and procurement reform. It also acknowledges that increasingly the UK will not choose the conflicts in which it is involved and therefore needs to maintain a level of ‘warfighting readiness’. 

A central commitment is the development of ‘always on’ munitions capacity – creating an industry that is capable of rapidly increasing production in the event of high-intensity conflict. That is a key lesson from Ukraine, which exposed European allies’ inability to produce munitions at a sufficient pace to support sustained warfare with a peer adversary like Russia.  

The SDR also emphasizes the use of common digital systems to drive truly integrated working and more effective armed forces…This is a massive undertaking and a big step away from previous practice.

The SDR also recommends tapping into a broader range of defence suppliers and integrating commercial and emerging technologies into plans and procurement. Again, this reflects a welcome lesson from Ukraine – which has rapidly developed new defence tech capabilities under pressure in war – and thus avoids the pitfalls of relying on untested industry claims. 

There is detail here, including plans to ringfence funding for new technologies and to approach procurement with a focus on export potential and international collaboration. UK procurement has been plagued by the pursuit of overly-specified or bespoke capabilities. Timelines are also being tightened, with targets of five years to field major platforms and even shorter cycles for digital and un-crewed systems. 

But many of these problems with procurement, innovation and industry relations have been well-described before. What is needed is a focus on implementation. The recent appointment of a new National Armaments Director is a good step towards that.  

The Review also emphasizes the use of common digital systems to drive truly integrated working and more effective armed forces. This would enable UK armed forces to better collaborate, and prevent service branches developing poorly integrated parallel digital architectures. This is a massive undertaking and a big step away from previous practice. Some legacy projects will continue siloed development unless there is the willingness to pull the plug or integrate them. 

For example, the SDR recommends a Defence-wide Secret Cloud – how will this work with the Royal Navy’s Project Stormcloud? Could Project Stormcloud become the ‘Secret Cloud’ or are the requirements of the two projects incompatible? These are the kinds of tricky questions that will need to be worked out in the implementation phase.  

The Review also has an important focus on resilience at home, recommending that the government identifies the highest-priority elements of UK national infrastructure for protection from cyber and other grey zone attacks and potentially explore a new reserves-style force to protect them. 

But this idea is not fleshed-out. There are questions about how any new force would integrate with existing reserves and other forces, who would join it, and how it would be trained – especially given the existing military recruitment crisis.  

What’s missing

The post-9/11 ‘war on terror’ period saw the military oriented to confront non-state adversaries, focusing on expeditionary warfare, counterinsurgency, and prevention of terrorism. Alongside this came the effects of austerity policies: cuts to the size of the armed forces, and a tendency to seek to maintain a full-spectrum of military capabilities on a shoestring budget. 

The UK’s 2021 Integrated Review, while often remembered for its focus on the Indo-Pacific, already signalled a broader shift towards threats from other states and the need to build up the defence forces, technological edge and resilience to deal with them. This SDR builds on that diagnosis, tightening the focus on European and homeland security. The question now is how it will be implemented and paid for. 

The challenge now will be for the MOD to make the necessary spending choices – likely set out in the forthcoming Defence Investment Plan. 

The Review’s plans are predicated on an ‘ambition’ for defence spending to reach 3 per cent of GDP at some point in the next parliament. But even within that budget they will be hard to achieve: the Review retains most of the UK’s existing commitments. 

Existing spending goals may also be overtaken by events: NATO is already signalling a desire for higher spending targets from member states more quickly – especially as Russia is determined to reconstitute its own forces at a rapid pace. That will increase pressure on the government to allocate more money in this parliament. The challenge now will be for the MOD to make the necessary spending choices – likely set out in the forthcoming Defence Investment Plan. 

There is another potential gap here: the Review acknowledges the United States’ security priorities have changed, and the resulting need for the UK to spend more and focus on European and homeland security. But it does little to address recent challenges created by President Donald Trump’s transactional and unpredictable approach to NATO. 

Instead, the Review continues to position the US as the UK’s key military partner, making reference to stronger transatlantic defence industrial cooperation. That is understandable, given the desire to maintain the US commitment to NATO in the long term, and the US’s critical role providing and maintaining UK defence capabilities. Much depends on the Trump administration’s trajectory – it may become distracted by domestic problems, or more traditional US foreign policy voices may prevail. If not, fundamental assumptions in the Review may need revisiting.