Britain’s defence policy has been dysfunctional for decades. The slow implementation of the 2025 Strategic Defence Review and delays in the release of the Defence Investment Plan (DIP) – originally scheduled for autumn 2025 – are the continuation of a litany of failures. As Britain’s capabilities have withered, allies have become increasingly sceptical of Britain’s ability to function as a military actor and frustrated at the slow pace of reform.
A core problem of UK defence strategy, revealed in new research I have published with Dr Maeve Ryan and Dr William Reynolds of King’s College, London, is that dishonesty is endemic. It operates across a spectrum, from self-deception via optimism bias, to engaging in ‘alchemy’ over budgets, to lying for self-interest. It affects every aspect of defence planning.
The issue is: will the DIP continue this trend or break it – by confronting the choices and costs involved in providing for UK defence? When the plan finally appears, a series of key questions will determine whether it is a valuable step forward, or another badly flawed exercise.
Strategic ambition
UK policymakers see Britain as a leading military actor, despite the sharp decline in its capabilities. In recent years, they have explored various ambitious projects, including: leading a coalition to stay in Afghanistan after the US withdrew; providing a peacekeeping force to Ukraine; leading a freedom of navigation mission in the Strait of Hormuz; and providing a Corps-sized contribution to NATO.
The disconnect between these ambitions and the UK’s resources suggests a high level of self-deception about what the UK can do militarily. Each mission would stretch the armed forces to or beyond their limit.
The Strategic Defence Review (2025) is ambitious enough, calling for the UK to play a leading role within NATO and take on more responsibility for European security. This would require a rapid and significant increase in UK capabilities.
Yet the record so far is clear: rhetoric about heightened insecurity and urgency, followed by a lack of money and action in response.
The first question must therefore be: does the DIP set out a plan for defence that aligns actual resources with realistic and achievable strategic goals?
Trade offs
For decades, policymakers have argued that Britain could do ‘more with less’, using technology to make up for declining mass. The result is the UK now has a shadow force of the full spectrum of capabilities – but so little of any one capability that it has few military options on the table when a crisis breaks out.
This was starkly illustrated at the outbreak of the US/Israel/Iran war in 2026, when the UK had no maritime presence in the Gulf or the eastern Mediterranean and took weeks to deploy one ship to reassure allies. (The ship then had to be diverted for maintenance).
At the same time, the core assumption of all British defence planning for decades – that the US will always take the lead and the UK will be a niche provider in support of the mission – is no longer true. Yet it continues to underpin procurement decisions.
The Defence Investment Plan therefore must make some big calls about how to de-risk the UK’s defence relationships, and the costs involved. Sourcing military equipment domestically, to bespoke designs, is slower and more expensive than buying on the open market. And the evidence for the economic benefits of defence industry spending is weak.
Furthermore, the UK simply doesn’t have the military resources to do what it used to, whether that be global force projection, or continental land deterrence, at scale.
If it’s honest, the DIP will finally have to make a choice between focusing on capabilities to defend the mainland UK and the Arctic and ‘High North’ or opt for a massive effort to reconstitute its ability to project force around the world – with all the associated costs.
The next questions should therefore be: does the DIP explain how it will decide between sovereign capabilities or ‘off the shelf’ procurement options? Does it acknowledge the costs and trade-offs involved? And does it commit to investing in a force posture directed to address specific threats?
The money
UK defence once again finds itself facing a financial black hole, this time estimated at £28 billion. In the past, these have been met with two tactics, both of which have failed.
Firstly, officials and service chiefs promised efficiency savings which never materialized. The 2025 SDR and NSS were undermined at the outset by the promise of £6 billion in savings. In our research, senior military officers talked about the ‘alchemy’ involved in pretending cuts would not affect frontline capabilities and budgets would be balanced by savings; privately acknowledging these were either wildly optimistic or put forward disingenuously for political reasons.