Andrew Fox is a senior associate fellow at the Henry Jackson Society. He served for 16 years in the British Army.
The last thing Britain needs is another defence governing document that flatters ministers, reassures Parliament, and leaves the Armed Forces to manage the gap between ambition and resources. The delayed Defence Investment Plan should be held to a tougher test: does it tell the country what we must be able to do, what we can actually do, what we cannot yet do, and what it will cost to close the gap?
The familiar government habit is to announce strategic ambition before the force structure, stockpiles, industrial base and personnel model are in place. That habit is no longer tolerable. Russia’s war against Ukraine has exposed the scale of attrition in modern warfare. Missiles, shells, drones, interceptors, spares, engineers, logistics, medical capacity and electronic warfare are consumed at rates that peacetime procurement systems are not designed to replace. A state that cannot replenish cannot deter for long.
The Defence Investment Plan should therefore begin with tasks instead of the usual slogans. It should set out a finite number of planning cases: a sustained NATO Article 5 crisis or war in Europe; attacks on the UK homeland and critical national infrastructure; Russian grey-zone coercion below the threshold of open war; prolonged support for Ukraine or another European partner; and the long-term AUKUS and Indo-Pacific technology task. For each case, ministers should identify the assigned force elements, readiness deadlines, stockpile assumptions, allied dependencies, and funded risks.
That would make the plan a threat-task-resource contract. It would also end the evasive practice of describing unfunded risk as transformation. Every major capability should be recorded in a published risk ledger, showing what Britain can do now, what it can do only with allied support, and what it cannot do until the specified investment has been delivered. Efficiency savings should count only once they have been delivered and banked.
The first investment priority must be Euro-Atlantic deterrence and homeland defence. Britain’s diffuse global posture must be subordinate to the capacity to deter and, if necessary, fight a high-intensity European war alongside NATO. That means readiness, survivability, munitions, air and missile defence, anti-submarine warfare, seabed security, port and airbase protection, long-range fires, electronic warfare, logistics, engineering, medical support and protected command networks.
For the Army, the test is whether Britain can make a credible division-level contribution in Europe, not simply attend exercises with impressive labels. That requires artillery depth, counter-battery systems, short-range air defence, electronic warfare, protected mobility, maintenance and battlefield logistics. For the Royal Navy and Royal Air Force, persistence and survivability are the key priorities: escort availability, mine countermeasures, maritime patrol, undersea surveillance, hardened airbases, resilient tanker and lift capacity, and layered defence against missiles and drones.
The second requirement is to shift from procurement to mobilisation. Industrial depth is a critical warfighting capability. The plan should distinguish between sovereign capacity that must remain in the UK, allied-assured capacity delivered through binding NATO, European and AUKUS arrangements, and global commercial capacity for lower-risk items. Sensitive nuclear, cryptographic, undersea, munitions, secure communications, cyber and repair capacities belong in the sovereign category.
Ministers should publish multi-year demand signals for missiles, shells, interceptors, torpedoes, drones, spares, engines, batteries, secure electronics and repair capacity. Contracts should include surge clauses, warm production lines and supply-chain war games for energetics, propellants, microelectronics and machine tools. In a long war, repair and replenishment rates are as decisive as the initial order of battle.
The third requirement is scale across autonomy, counter-autonomy and electronic warfare. Ukraine has shown that cheap, expendable systems do not replace high-end platforms, but they alter sensing, targeting and attrition. Britain should not buy a small boutique collection of exquisite uncrewed systems. It needs families of low-cost, mid-tier and high-end uncrewed air, land, surface and subsurface systems, with open architectures and rapid payload replacement. Units should have routine budgets to buy, test and lose systems during training.
Counter-autonomy deserves equal status. Forces need counter-drone sensors, jammers, decoys, guns, low-cost interceptors and proven directed-energy systems. They also need deception, concealment, hardened communications and defensive electronic warfare down to unit level. Multi-domain integration must be a funded technical and training architecture, not a Whitehall phrase.
The fourth requirement is people. Ships, squadrons, cyber teams and logistics units cannot be fielded without trained personnel. The plan should fund retention, housing, healthcare access, family support, technical pay, lateral entry and specialist career tracks in cyber, AI, engineering, nuclear, medicine, logistics and space. Reserve reform should define clear roles in homeland protection, airbase and port security, medical surge, engineering repair, logistics, cyber, space support and industrial backfill.
The fifth requirement is resilience below the threshold of war. Britain must expect cyberattacks, sabotage, coercion, pressure on undersea cables, and attempts to degrade space-enabled command and intelligence. The MoD should maintain standing contributions to the protection of critical national infrastructure, exercised with private operators in energy, ports, telecoms, finance, data centres, and transport.
The fiscal conclusion is unavoidable. A serious plan will require roughly £120-170 billion in additional funding over ten years, with £150 billion as a working figure. If ministers will not provide that funding, they should cut tasks rather than pretend all missions remain affordable. Readiness and stockpiles should take priority over new discretionary commitments. NATO and homeland defence should not be cannibalised by prestige programmes.
The central test is simple. Britain needs a force capable of mobilising, replenishing, absorbing losses, protecting the homeland, operating with NATO in Europe, and sustaining advanced cyber, space and undersea operations. Anything less is another declaratory review.
Andrew Fox is a senior associate fellow at the Henry Jackson Society. He served for 16 years in the British Army.
The last thing Britain needs is another defence governing document that flatters ministers, reassures Parliament, and leaves the Armed Forces to manage the gap between ambition and resources. The delayed Defence Investment Plan should be held to a tougher test: does it tell the country what we must be able to do, what we can actually do, what we cannot yet do, and what it will cost to close the gap?
The familiar government habit is to announce strategic ambition before the force structure, stockpiles, industrial base and personnel model are in place. That habit is no longer tolerable. Russia’s war against Ukraine has exposed the scale of attrition in modern warfare. Missiles, shells, drones, interceptors, spares, engineers, logistics, medical capacity and electronic warfare are consumed at rates that peacetime procurement systems are not designed to replace. A state that cannot replenish cannot deter for long.
The Defence Investment Plan should therefore begin with tasks instead of the usual slogans. It should set out a finite number of planning cases: a sustained NATO Article 5 crisis or war in Europe; attacks on the UK homeland and critical national infrastructure; Russian grey-zone coercion below the threshold of open war; prolonged support for Ukraine or another European partner; and the long-term AUKUS and Indo-Pacific technology task. For each case, ministers should identify the assigned force elements, readiness deadlines, stockpile assumptions, allied dependencies, and funded risks.
That would make the plan a threat-task-resource contract. It would also end the evasive practice of describing unfunded risk as transformation. Every major capability should be recorded in a published risk ledger, showing what Britain can do now, what it can do only with allied support, and what it cannot do until the specified investment has been delivered. Efficiency savings should count only once they have been delivered and banked.
The first investment priority must be Euro-Atlantic deterrence and homeland defence. Britain’s diffuse global posture must be subordinate to the capacity to deter and, if necessary, fight a high-intensity European war alongside NATO. That means readiness, survivability, munitions, air and missile defence, anti-submarine warfare, seabed security, port and airbase protection, long-range fires, electronic warfare, logistics, engineering, medical support and protected command networks.
For the Army, the test is whether Britain can make a credible division-level contribution in Europe, not simply attend exercises with impressive labels. That requires artillery depth, counter-battery systems, short-range air defence, electronic warfare, protected mobility, maintenance and battlefield logistics. For the Royal Navy and Royal Air Force, persistence and survivability are the key priorities: escort availability, mine countermeasures, maritime patrol, undersea surveillance, hardened airbases, resilient tanker and lift capacity, and layered defence against missiles and drones.
The second requirement is to shift from procurement to mobilisation. Industrial depth is a critical warfighting capability. The plan should distinguish between sovereign capacity that must remain in the UK, allied-assured capacity delivered through binding NATO, European and AUKUS arrangements, and global commercial capacity for lower-risk items. Sensitive nuclear, cryptographic, undersea, munitions, secure communications, cyber and repair capacities belong in the sovereign category.
Ministers should publish multi-year demand signals for missiles, shells, interceptors, torpedoes, drones, spares, engines, batteries, secure electronics and repair capacity. Contracts should include surge clauses, warm production lines and supply-chain war games for energetics, propellants, microelectronics and machine tools. In a long war, repair and replenishment rates are as decisive as the initial order of battle.
The third requirement is scale across autonomy, counter-autonomy and electronic warfare. Ukraine has shown that cheap, expendable systems do not replace high-end platforms, but they alter sensing, targeting and attrition. Britain should not buy a small boutique collection of exquisite uncrewed systems. It needs families of low-cost, mid-tier and high-end uncrewed air, land, surface and subsurface systems, with open architectures and rapid payload replacement. Units should have routine budgets to buy, test and lose systems during training.
Counter-autonomy deserves equal status. Forces need counter-drone sensors, jammers, decoys, guns, low-cost interceptors and proven directed-energy systems. They also need deception, concealment, hardened communications and defensive electronic warfare down to unit level. Multi-domain integration must be a funded technical and training architecture, not a Whitehall phrase.
The fourth requirement is people. Ships, squadrons, cyber teams and logistics units cannot be fielded without trained personnel. The plan should fund retention, housing, healthcare access, family support, technical pay, lateral entry and specialist career tracks in cyber, AI, engineering, nuclear, medicine, logistics and space. Reserve reform should define clear roles in homeland protection, airbase and port security, medical surge, engineering repair, logistics, cyber, space support and industrial backfill.
The fifth requirement is resilience below the threshold of war. Britain must expect cyberattacks, sabotage, coercion, pressure on undersea cables, and attempts to degrade space-enabled command and intelligence. The MoD should maintain standing contributions to the protection of critical national infrastructure, exercised with private operators in energy, ports, telecoms, finance, data centres, and transport.
The fiscal conclusion is unavoidable. A serious plan will require roughly £120-170 billion in additional funding over ten years, with £150 billion as a working figure. If ministers will not provide that funding, they should cut tasks rather than pretend all missions remain affordable. Readiness and stockpiles should take priority over new discretionary commitments. NATO and homeland defence should not be cannibalised by prestige programmes.
The central test is simple. Britain needs a force capable of mobilising, replenishing, absorbing losses, protecting the homeland, operating with NATO in Europe, and sustaining advanced cyber, space and undersea operations. Anything less is another declaratory review.