A Hollow Force? Choices for the UK Armed Forces


Challenges ahead: a Warrior armoured vehicle moves across Salisbury Plain Training Area in Wiltshire. Image: Defence Imagery / OGL v3.0


As the new UK government grapples with the current state of the Armed Forces, hard thinking and prioritisation are needed to ensure they can provide capable and coherent forces to NATO and deal with modern threats.

We have been told we live in a ‘pre-war’ era, characterised by a darkening global mood, conflict and competition and the erosion of the so-called global order, and with a requirement to defend UK interests, by force if necessary. This is the context in which the previous UK government announced its intent to increase defence spending to 2.5% of GDP, and regardless of how much this produces in terms of ‘new’ funding (it certainly isn’t £75 billion), the UK’s Armed Forces face a series of major decisions, especially given the forthcoming review of Defence.

(Re)learning the Lessons of Major War

Governments and commentators alike have identified a rogues’ gallery of state threats, with Russia and China in the vanguard, Iran and North Korea following close behind, and non-state groups like Yemen’s Houthis filling in the gaps. While the headline is one of state-based competition and ‘peer conflict’, no cosy assumptions can be made about the end of significant threats from terrorism, nor insecurity caused by threats which don’t reach the threshold of open war, but which affect trade or business. To reinforce the point, NATO’s most recent Strategic Concept sets out the same range of threats, highlighting Russia along the way. With a core task of deterrence and defence, there is no doubt that industrial warfare is one of the key factors shaping NATO militaries.

Russia’s full-scale invasion of Ukraine follows on from the war between Armenia and Azerbaijan as a testbed for the clash of arms on a scale unseen in Europe since the end of the Second World War. The Middle East is also highlighting the role of long-range missiles, air defence, urban warfare, and irregular or non-state forces with an ability to pose a threat to forces on land, in the air or at sea, as well as to target critical infrastructure. And the continued growth of the Chinese military is a modern case study in the development of armed forces with an assumed focus on challenging a superpower in a war that will be fought in all environments over a vast area.

Learning lessons is not as straightforward as it might be, given the human tendency to fall prey to biases such as anchoring around pre-conceived ideas and recency, as well as the difficulty in identifying long-term trends based on snapshots of incomplete information. But it seems plausible to advance several arguments.

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The UK can do some things well, but not at a particularly impressive scale when the adversary is a state with significant military power of its own which is prepared to suffer losses

First, numbers matter. Firepower and destructive force are the overarching measures of a force’s combat output, and military power is about threatening to use or actually using force to destroy things and kill or coerce people. The war in Ukraine has seen casualties and losses of equipment on a scale consistent with previous major wars, but which boggle the mind in a modern context. The Russian invasion force in Ukraine now numbers over half a million after an estimated 460,000 killed or wounded. It has lost thousands of tanks and armoured vehicles. The artillery duel has seen requirements for shells reach as high as 7,000 a day for the Ukrainians on the offensive. Looking across to the Middle East, Iran used nearly 200 cruise missiles and drones in its attack on Israel, and in firing 110 ballistic missiles, it assembled the largest single salvo of such weapons seen in the past 40 years, other than in the first 48 hours of the Russian attack on Ukraine in 2022.

These numbers not only matter for combat output, but also for the resilience of countries in war, their industrial capacity and their ability to sustain a campaign. The Russian ‘special operation’ was supposed to be short, lasting days not years, but Sir Lawrence Freedman has written compellingly about the (seductive) myth of the ‘knockout blow’, and Ukraine provides an ample modern reminder. It is obvious but bears re-stating: industrial war is protracted and costly, more so when national survival is on the line.

Once in such a conflict, militaries are stressed across the full range of their capabilities and not just the combat arms. The oft-quoted line about amateurs, professionals and logistics is well-worn, but warranted. Militaries that can’t resupply and sustain themselves have no endurance, and precision or one-shot firepower is of little use if it can’t achieve repeated success, especially in major war. RUSI has written recently about the challenges of land logistics on the front-line, but the same is true of being able to resupply navies at sea, and to ferry weapons to air forces who have to conduct strikes repeatedly. Logistics supply chains and capabilities need to be either very rapid or integrated into the combat force (ideally both) and capable of surviving in modern combat environments, with pervasive surveillance and long-range weapons able to strike in shortening timelines. The force that cannot be sustained can’t fight for long.

You and Whose Army?

Can the UK’s Armed Forces put together such a force for modern warfare? The answer, at least in the eyes of the UK Parliament’s Defence Committee, as well as some recently responsible for testing Defence planning, would appear to be no. The trend of the past 35 years has been to trade numbers for sophistication, but this has overall led to a diminution of total firepower. The UK can do some things well, but not at a particularly impressive scale when the adversary is a state with significant military power of its own which is prepared to suffer losses. Even a recent defence secretary admitted that the forces had been ‘hollowed out’ over a period of years.

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Consider the carrier strike group; this represents a sovereign UK capability, with a full range of aircraft and vessels deployed. But in the case of the Royal Navy, a ‘full fat’ carrier group comprises almost the totality of the deployable Royal Navy. Two Type 23 frigates and two Type 45 destroyers would – on most days – be all that the current Navy could sustain for major operations beyond an additional frigate as the Fleet Ready Escort for home waters. Protecting it with a hunter-killer submarine would also be taxing, given the UK generally only has one or two deployed at any given time. Meanwhile, the slow buildup of the F-35B force means there are enough pilots currently qualified for carrier operations for a single squadron (hopefully soon to be two). Each jet represents a potent stealth aircraft, able to evade enemy air defences. But a closer look at the programme gives us pause to consider the combat output of each jet. If it is operating within range of hostile air defences, it will only be using its internal weapons bay; it is currently only able to carry Paveway IV guided bombs and air-to-air missiles, so no stand-off weapons are available to strike ground targets. The missiles being developed under SPEAR Capability 3 won’t be integrated with F-35 until ‘the end of the decade’. Additionally, it only has room for two such bombs, and as it would be risky to allocate one bomb to any given target, the best each jet can be expected to strike is a single target of modest size given the 500 lb payload of each Paveway. In other words, the current entire output of the carrier wing in a single set of sorties is 8–12 targets, assuming 100% aircraft availability and success rate. For a demonstration of intent, as part of a coalition operation, this might suffice, but in a genuine state war of attrition, this is limited.

Similarly, when RUSI analysts last looked at the Army, and the combat division the UK claims to have, it measured the number of main battle tanks and self-propelled artillery in the UK’s inventory and found the numbers wanting when set against a ‘credible’ armoured division of anywhere from 170 to over 300 tanks and around 110 to 220 artillery pieces. The numbers have not improved in the subsequent four years: under the Challenger 3 programme the UK will have a total of 148 main battle tanks (in 2030). Meanwhile, the UK has essentially removed the AS90 artillery from service by donating 32 to Ukraine, replacing them with 14 Archer guns until such time as the ‘Mobile Fires Platform’ is procured (some time ‘this decade’). The Challenger 3 may be the ‘most lethal tank’ ever fielded by the British Army, but it is going to be available in such limited numbers that it will have to perform heroically in the face of a notional foe in the form of Russian ground forces, such as a Combined Arms Army.

Tooth to Tail: Sustaining the Combat Force

Beyond the industrial capacity modern states need to go to war, and the volume of ammunition or fuel consumed, forces in combat require the ability to move supplies around, to conduct surveillance to target the enemy, and to use other systems such as electronic warfare to ensure that their weapons can reach their targets and their forces can communicate. For the UK, the picture here is no less problematic in terms of the gap between aspiration and reality. RUSI experts assess that for the Army to deploy a single armoured brigade would require the commitment of around 70 to 80% of its total combat engineering capabilities in order to cross gaps and rivers or to breach minefields. The notion that the UK has enough to properly deploy a full division is fanciful. Meanwhile, manoeuvring this force successfully will require effective coordination via secure modern communications. Unfortunately, the Army will have to once again extend its obsolete Bowman system because of delays to MORPHEUS, already late and now possibly another decade from proper service. It may also come as a surprise to a generation weaned on popular culture’s pervasive use of spy satellites to learn that the UK is wholly dependent on others for space-based imagery; the ISTARI network is in development, but won’t start launching until 2026.

Once deployed, ground forces need protecting, especially from air attack. But the UK has a tiny number of Sky Sabre systems currently available; while public debate has focused on the (wholly unnecessary) idea of an ‘Iron Dome’ across the UK, the more pertinent question would be who is defending UK land forces if they face an enemy air threat: at the moment this would have to be done by partners or the RAF (which lacks the ability to suppress sophisticated enemy air defences).

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It will take novel thinking and the development of doctrine and tactics to achieve increased combat output and effect with forces that appear unlikely to increase in terms of personnel

Use of air power requires also effective coordination. The RAF has replaced its ageing E-3D Sentry airborne early warning aircraft with the E-7 Wedgetail. However, these won’t start being in service until 2025, and the UK is only buying three; this doesn’t even guarantee 24-hour availability (a ‘task line’) of a single aircraft, once again putting the emphasis on partners and ensuring that each aircraft is irreplaceable. Meanwhile, the RAF has also retired its C-130 Hercules transport fleet, to be replaced by the A-400M Atlas aircraft. This is more capable in terms of the payload it can carry individually, but with smaller numbers in the replacement force compared to the original C-130 force, just sustaining the same number of task lines will require much improved aircraft availability.

Returning to the carrier strike group, the UK ability to sustain it over long distances relies on a single Fleet Solid Support Ship, RFA Fort Victoria. When that is in maintenance (or if it were destroyed in a war), the UK has no backup and must rely on others. It is at least being replaced by three new ships, but they are not due to arrive in service until 2031 (and one of the industrial partners involved in their construction is now in financial difficulties).

Less than the Sum of its Parts?

These are but a selection of the issues facing the modern UK Armed Forces in terms of combat power, before we even consider recruitment, retention, training and other personnel issues. The conclusion should not be one of despair, or that the UK does not have capable people and equipment. But it has tried to pursue a classic ‘full spectrum’ of capabilities, and found itself stretched thin beyond the point where it can deploy fully integrated and credible forces that could fight in a modern war for any length of time. The choices available to the government have therefore been constrained, such that the UK can make a decent contribution to a coalition force in terms of specific capabilities, but it can’t provide a sizeable fully coherent force commensurate with its status as the (now) third-largest spender in NATO without the support of others.

Solutions are available, but they will require hard thinking and prioritisation. In some cases, increased firepower will be desirable. But it may be that the UK should be investing in sustainment and enablers like bridging equipment before purchasing a single additional tank or jet that it can’t, in any case, deploy and support. Technology should play a key role – for example, learning the lessons about where drones can complement artillery and provide effective local surveillance. But it will take novel thinking and the development of doctrine and tactics, allied to new training, to achieve increased combat output – and effect – with forces that appear unlikely to increase in terms of personnel. More radical choices about improving output – for example, through the use of uncrewed systems, or AI to make sense of information and take decisions – should also be considered. In addition, the UK will need to decide where it provides a sovereign advantage that acts as a force multiplier for the rest of NATO, and where it will create tough, capable, fully integrated forces that do not create obligations for other NATO Allies. Otherwise, the UK’s claim to be a leading country in NATO will be undermined by a military providing less than the sum of its parts.

The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.

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WRITTEN BY

Matthew Savill

Director of Military Sciences

Military Sciences

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