Strategic Defence Review: Does it Pass its Tests?

In December 2020, RUSI published our occasional paper entitled Five Tests for the Integrated Review. The Integrated Review was then published in March 2021, and since then we have applied the same tests – to the extent that it is possible – to the Integrated Review Refresh and the Defence Command Paper Refresh in 2023, and offered them as advance ‘tests for success’ for the Strategic Defence Review (SDR) following its launch in mid-July 2024. Now, a month after its eventual publication and with the new National Security Strategy (NSS) and the NATO Summit behind us, it is timely to apply the same method to assessing the SDR’s conclusions.

To recap briefly, our tests – which we developed from our analysis of the main themes (and subsequent fates) of successive post-Cold War defence and national security reviews – were:

• Is the assessment of the risks/threats right?
• Are the proposed defence planning responses right?
• Are the proposed changes to capabilities and force structure right?
• Is there a sustainable balance between policy, commitments, the forward programme and the budget?
• Do the proposed changes to organisation/management enhance effectiveness/efficiency?

Applying these tests to the SDR is not straightforward – mainly because, meaty though it is in many respects, the SDR published on 2nd June was but a first instalment, in part a consequence of being ‘externally-led’. A range of other reviews are now catching up. The NSS, published on 24th June, reflects the conclusions of the SDR. The ‘Modern Industrial Strategy’ published the previous day aims to boost investment in a range of high-growth sectors including Defence. But we have not yet seen the new Defence Industrial Strategy, which should explain the part the Government will expect industry to play in delivering the outcome of the SDR.

More significantly from a Defence perspective, the SDR – unlike previous reviews – contains no recommended future force structure and no specific capability decisions (although a few emerged in separate announcements by the Government, such as ‘up to 12 SSN-AUKUS submarines’ and 12 F-35/A dual capable aircraft to form a contribution to NATO’s sub-strategic nuclear mission).

These major elements, which have always been regarded as the centrepieces of Defence reviews, will be produced as a Defence Investment Plan ‘in the autumn’. A Defence Reform & Efficiency Plan will be produced in the same timeframe, which will presumably explain how the newly reformed MOD plans to implement the conclusions of the review and the contribution efficiencies will make to its affordability.

So, ‘What do you think of the show so far?’ to quote the late Eric Morecombe.

Assessment of Risks and Threats

On the assessment of risks and threats, the review is brutally frank – and is clear that the main danger is Russia, in terms of (conventional and nuclear) military and ‘hybrid’ activities. It also, intriguingly, highlights potential future risks from ‘middle’ powers. In terms of US intentions, the review is diplomatically guarded – but its message is clear.

Previous reviews were soon overtaken by events thereafter. This review was overtaken by events in real time. The review was understandably circumspect about how to describe political developments, in particular the rapid roll-out of Donald Trump’s ‘America First’ agenda after 20th January. Ukraine’s audacious Operation Spider’s Web took place the day before its publication, and we have since seen the ‘12-Day War’ between Israel and Iran and the US exercising hard military power in a way that not all anticipated. The review claims that its recommendations are adjustable in terms of speed and scale – which takes us to the next test.

Defence Planning Responses

Reconfiguring the UK’s defence planning responses is the centre of gravity of this review. It delineates a defence posture which, while broad brush, contains a number of key elements. As we predicted, it advocates an acceleration of technology-led modernisation. It also begins to explain the concept – used in the ‘Propositions’ circulated at the outset of the SDR – of an ‘Integrated Force’, with a top-down force design set by the Chief of Defence Staff through the new ‘full-functioning’ Military Strategic Headquarters (MSHQ). But what this really means in practice is still difficult to divine, not least because the subsequent sections on the environmental domains are set out in traditional Single Service terms.

It champions a ‘new partnership with industry’ and streamlined acquisition processes. Given the evolving strategic context, greater agility in that area is clearly right. Defence industrial capacity would need to be grown and performance significantly improved to deliver the ambitions of the SDR. Great expectations are being placed on the appointment of a new National Armaments Director to plan and deliver these changes.

The review embraces the Government’s ‘NATO-first’ mantra and advocates closer cooperation with allies and partners, although it shies away from concepts such as ‘International by design’ or ‘Allied by design’ advanced in previous reviews – and it misses the opportunity to call for a decisive break from the rather transactional approach taken by previous governments. It also makes no effort to reconcile the impetus to favour UK defence industry with the need to rationalise capability planning and procurement across the European NATO Allies.

The final element is a ‘whole-of-society’ approach to building national resilience. Overall, the review offers a tighter and more coherent package than, say, the Integrated Review or the Defence Command Paper Refresh. The big question with this review – as with its predecessors – is how much of it will actually be implemented.

Changes to Capabilities and Force Structures

As we remarked above, the review proposes few specific changes to capabilities and force structures. Like previous reviews, it sets itself a 10-year head mark (2035) but, unlike them, does not outline a future force structure, arguing that there is no end state for the Integrated Force as its design and capabilities must continue to evolve. We will have to wait to see how the Defence Investment Plan squares this circle.

Notably, it does not recommend any reduction in regular Service personnel – but suggests that, despite the greater investment in novel technologies, there is a ‘strong case’ for an increase in Army regular numbers ‘when funding allows’. (The reality for the last ten years has been that demography and wider social factors are more salient than any manpower targets concocted by HMG).

In essence, the review largely goes with the grain – as we noted in previous commentaries, the scope for adjusting the forward defence programme is limited. Given the current pace of military innovation, this seems too cautious. And the sections on the various domains do little more than endorse the single Services’ existing aspirations, including the implausibly bold claim that the Army can deliver a ten-fold increase in lethality. Given its earlier analysis of the threats to the UK, the box on Integrated Air and Missile Defence is underwhelming. And, while the section on cyber contains some new thinking, that on space is thin: while correctly noting the fragmented nature of the UK space enterprise, the review has few ideas on solutions.

Balancing Policy, Commitments, the Forward Programme and the Budget

With respect to balancing policy, commitments, the forward programme and the budget, the SDR benefitted – like the Integrated Review – from a change in the budgetary envelope at the eleventh hour (in fact, in February) with the shift to 2.5% GDP by 2027 and an ‘ambition’ to reach 3% in the next Parliament. The reviewers insisted that their vision was affordable within this revised envelope.

Given Defence’s difficulties in funding the current programme, there were reasonable grounds for scepticism about whether the enhanced defence posture which the review advocates to meet the geo-political challenges that it so eloquently outlines could be achieved within the budget parameters that the review was based upon.

That scepticism was effectively vindicated by the Prime Minister’s announcement at the NATO Summit that the UK would commit to spending 5% of GDP on national security by 2035, with 3.5% to be spent or core Defence capabilities. The Government has not been prepared to explain how the further significant increase will be funded. If this funding can be found, then the claim that the ambitions of the SDR are affordable would be more credible – but this is a very big ‘if’.

Organisation and Management

On changes to organisation and management, the review has relatively little to say – a pattern followed by every review since the 1998 SDR. It ‘strongly’ endorses the new Defence Reform model (about which very little information has been made publicly available). It also endorses a target of an additional £6 billion in efficiency savings (helping to balance the costs of new investments).

As we have discussed in previous commentaries, Defence’s track record in both areas is distinctly spotty – with reorganisations often achieving sub-optimal results and mooted efficiency savings significantly evaporating. Given that, it might have been wiser for the review to have taken a more detached stance on these matters.

We expect that the new Defence Reform model will face stiff challenges in implementing the 62 recommendations made by the review. Thoughtful prioritisation will be required to progress the most important of these recommendations at the pace necessary to deliver the transformation the review promises.

There is much more that could be – and indeed already has been – said about the SDR. This commentary has deliberately focused on our ‘Five Tests’ as experience with previous reviews suggests that they are good indicators as to whether a defence (and/or security) review will stand the overarching test of time.

With respect to those specific tests, we can be cautiously positive about the first two – the SDR’s assessment of risks/threats and its proposed defence planning responses. The former seems realistic if sobering, and the latter set the right direction. But we are more sceptical about the remaining three: capabilities; balancing policy and budget; and organisation. We will need to see the next steps – and particularly the Defence Investment Plan as well as the Defence Reform & Efficiency Plan – before offering an overall assessment of the SDR

Finally, a word on process. The Government made a major issue of the fact that this review would be externally-led, with a ‘first-of-its-kind’ approach for UK strategic defence planning. The three of us (and some 150 others) contributed during the early stages of the review, as part of a process of external challenge. Following the reviews we led during our time in the MOD, we conducted lessons-learned exercises to assess what went well and less so during the conduct of the reviews. We would expect such a process to be underway now. It remains to be seen whether the Government will repeat the approach of bringing in external reviewers to lead the next SDR, whenever it takes place.

© RUSI, 2025.

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