Delivering 'Mass' for the British Army: Defence Reviews and Second Echelon Choices

With near-peer threats and stiff economic challenges, 2025's Strategic Defence Review has hard balance to find if it is going to provide a credible Land force, but such a balance has been struck before.

The British Army needs depth to be sustainable in war: both a second echelon to follow close behind the first, and structures to generate a third and subsequent ones. The Strategic Defence Review (SDR) and the Treasury, despite the recent increased announcement in spending, are unlikely to both fund more regular troops for a second echelon and maintain the equipment programme and extra munitions required for modernisation. Army Reserve units and formations can provide the cost-effective additional mass to expand the army in war and deliver that second echelon.

The Strategic Reserve can provide individual reinforcements but cannot grow the army with additional units. The current Future Soldier warfighting structure inhibits the ability of the Army Reserve to expand the British Army in war. This commentary looks to the last time a Defence Review had to balance ‘NATO First’ with modernising the army in fiscally challenging times, set against a peer-level threat in Europe. It illustrates how the British Army embraced their reserve forces to reorganise and modernise into an army that was sustainable, affordable and played a key role in successfully delivering deterrence.

The Current Demand for ‘Mass’

There has been much mention of ‘mass’ and the British Army, aligned to the SDR’s considerations. To be credible for high intensity warfighting experience from Ukraine suggests that the British Army will require access to more mass. Mass in these reports usually implies access to more numbers of people, more equipment and more munitions. However, the continuing financial pressures on UK Defence will likely prevent any significant increase to the numerical mass of full-time forces if it is to also provide the better firepower, enablement, readiness and resilience required. As a result, there has been more of an emphasis on the current force structure’s ability to successfully mass the effect of combat power through enhanced lethality delivered by modernisation, improved command and control, robotics and faster exploitation of information.

These enhancements are indeed important to win the first battle, especially for the UK’s medium sized army, but wars are rarely won by the first battle and peer-level opponents will return for a second round. It is important for an Army to retain enough people, equipment and munitions to deal with a wartime level of attrition and to continue to provide the range of capabilities to ensure it can at least take part in the second battle, and beyond. The Chief of Defence Staff Admiral Tony Radakin is correct that war in Europe is a remote chance but NATO’s land force sustainability is also important for keeping the odds low through deterrence. What balance of investments will deliver the optimum and sustainable British Army for its near-term readiness for warfighting?

In simple force development terms sustainable depth is attained through the provision of additional capability, such as follow-on echelons. The structural basis of capability in the British Army, as in most other armies, is the unit and the formation. Most nations cannot afford to have standing armies made up of the required number of trained and equipped units ready to fight large wars. Peacetime armies are limited in size by national budgets and as Andrew Sharpe points out must be ready to expand rapidly to cope with the heavier demands of war. Threats and tasks increase greatly in war, formations suffer attrition, units need to be replaced, areas of operation grow larger. The medium-sized British Army must be ready at the outset to have a structure, a second echelon, which can generate more formations and more units for war, or it risks becoming very small, very quickly.

The British Army has traditionally relied on part-time Army Reserve units, who train collectively in peacetime, to generate the second echelon additional units for the expansion of the British Army in war. As has been pointed out many times before this remains the most cost effective and most successful way to expand the British Army for war. Additional units cannot simply be conjured up at the start of a war from pools of individual reinforcements, let alone untrained wartime volunteers.

The necessity for a funded, equipped and trained Army Reserve in peacetime has been a key lesson from Ukraine and from our own history. The peacetime formed reserve units of the Ukrainian Army were vastly more effective than those units pulled together from scratch with little cohesion and very poor combat effectiveness. While Army Reserve units are not equivalent in capability to Regular units, history, and our allies performance, show they can provide a “good enough” contingent capability within a few weeks from mobilisation, for the focussed wartime missions they should be allocated. This provides mass and sustainability, to allow time for subsequent echelons to be generated.

Peacetime armies also need many individual reinforcements on wartime mobilisation. They are needed to fill inevitable peacetime gaps in both regular and reserve units and to bring all units up to a wartime strength, not needed in peace, to ensure units can cope with the rigours of war. Individual reinforcements are also needed to provide formations with a battle casualty replacement pool. The British Army has traditionally called back ex-Regulars (the Regular Reserve and those with liability for recall, now termed the Strategic Reserve) to provide most of these individual reinforcements.

Individual reinforcements by themselves do not expand the Army, since they do not provide additional units, but are vital for making units and formations more resilient. Under current legislation you cannot “grow” the Strategic Reserve. They are fixed by virtue of being ex-regular so as a regular force shrinks so will the Strategic Reserve since their numbers are determined by regular leavers. Historically the Army have also developed plans to scour their peacetime-only structures to deliver more regulars in war for the deployable forces.

This simple-to-understand system, where the Army Reserve expanded the British Army in war with additional units on mobilisation and where the Regular Reserves were called back to provide resilience through individual gap filling, lasted for over 100 years. It was far from perfect, had its bumps, but was reasonably affordable in times of financial difficulty and was relatively successful when it came to fighting actual large-scale war and deterring a cold one. Unfortunately, this system has been slowly abandoned by the British Army over the last 30 years and the British Army will struggle to expand and deliver the mass it seems to have on paper.

The Un-Expandable 'Future Soldier' British Army

It has been acknowledged that some part of the “Future Soldier” programme have not been ideal for the British Army. This is especially true for the Army Reserve. The Chief of Staff of Field Army wrote in 2023 that “Without the Army Reserve, any notion of maintaining the Army’s combat endurance beyond the first ‘thunderclap’ is fanciful”. Yet, the bulk of the fighting power of the Army Reserve is structurally tied up with that first ‘thunderclap’. Under Future Soldier, on mobilisation for war, the majority of Army Reserve units will provide up to 70% of the Army Reserve unit workforce to backfill the gaps in Regular Army units.

This Future Soldier backfill demand on the Army Reserve effectively removes the capacity of the British Army to rapidly expand on mobilisation and fundamentally undercuts the role of the Army Reserve to provide additional units for wartime. It also risks undermining the first echelon readiness, as Army Reserve personnel are at lower levels of readiness, and many could not deploy immediately with their combat formations without some additional training.

The traditional second echelon of the British Army, with up to 70 Army Reserve units on paper, is currently planned to be spent against the first echelon. The British Army has no depth. Meanwhile, the pool of individual Regular Reservists that traditionally provided a backfill function have been allowed to assume they will never be needed and despite repeated attempts, going back decades now, they have not yet been brought out of abeyance. I have previously written on why this has been culturally difficult for the British Army to achieve.

Future Soldier, building on the slow withering of Army Reserve unit training since the end of the Cold War, has created a British Army for war that is primarily based on its full-time Regular Army structure in peace. The privileging of the units of the first echelon to the detriment of second echelon Army Reserve unit capability is explainable given financial pressures, is culturally understandable, has been influenced by political aversion to honest discussions about the Army, and has happened before. It makes the British Army in war a potentially “first battle” winning organisation, if the logistic problems of deploying can be overcome, but at the risk of being small and fragile for actual war winning. It has stripped out the capacity of the army to expand rapidly and to be more sustainable in war. Future Soldier has created the best possible single echelon force.

Any first rate second echelon will be a very long time arriving under Future Soldier. Yet the British Army has enough Army Reserve units now to create a second echelon; it has chosen to disinvest in their collective capability. The current Future Soldier structure also makes the British Army relatively more expensive for the units and resultant capability it can deliver in war in comparison to our NATO allies armies. Our NATO allies, including those who are also expeditionary, such as the Americans, still rely on cost effective expansion from reserve units and those like the French are investing heavily in building more reserve units. The fundamental withering of British Army Reserve capability has happened at a period when UK Defence is under pressure to deliver more wartime Land Forces for NATO and now also for UK Home Defence.

Thankfully, there is now growing recognition that in order to sustain itself in a large-scale war the British Army’s “Reserve force will form our second echelon.” To do this it will need to use units from the Army Reserve and call upon individual reinforcements from its Regular Reserves. The SDR call for evidence indicated that Reserve capability is going to be an important factor in their thinking. They appear to have a desire to make more of the Army Reserve and the Regular Reserves. Without additional money this will involve tough choices and indications are that the Treasury will be hard pressed to provide much more for defence.

For the Army, various Defence Reviews have been in this space before – with regard to the poor and misunderstood state of reserves – and perhaps lessons can be drawn. The 2010 Strategic Defence and Security Review and resultant Future Reserves 2020 programme show parallels, but were focused on developing operational reserve forces for lower intensity warfare. The review with some striking similarity to today’s British Army is perhaps the radical 1981 UK Defence Review.

The 1981 Defence Review - NATO First, High Threat but Little Extra Money

The early 1980’s saw a heightened peer-level threat from Eastern Europe leading to demands to improve the UK Land contribution to NATO. There was also an increased threat to the UK Homeland. This was set against severe financial constraints on growing UK Defence spending, but with Conservative party election pledges to increase the offer to Defence and make up for a decade of retrenchment and shrinkage.

On attaining power in 1979, a generous pay offer from the new government had been given to Defence to try to improve retention in 1980 while still having to deal with severe in-year pressures to reduce costs and cancel expenditure from an over extended budget. A Defence review was called for to match ambition to the resources available. The review was to be focussed on a ‘NATO First’ strategy.

Like today, the British Army was not in the best state. Some claimed the Army had the most outdated equipment in NATO. The Army had begun a process of modernisation of its key equipment, but with poor morale personnel recruitment was poor and outflow high. A previous review saw the warfighting corps adopt a structure that was not optimal.

The Army also needed to become more sustainable for a more flexible NATO warfighting response. This would require increased stocks and increased mass. The British Army of 1981 did not have enough units on mobilisation to cover the requirements of a deployed and sustainable Corps for war in Europe. As the CGS of the time later remarked “There was not too bad a front line, but there was literally nothing to sustain it.” The Army needed more units in war, but an expansion of the regular forces was unlikely given the costs involved and that any extra funds would be needed for modernisation.

The 1981 Defence Review team made it clear they wished to prioritise commitments to Trident, NATO Land Forces and Home Defence. While there was actually an overall increase in the defence budget, the proportion for each of the services changed, reflecting a deliberate focus on the NATO alliance for UK security and the resulting political imperative to reinforce SACEUR’s needs. The Royal Navy aspect of the review has been covered in much detail over the years and the measures in light of the 1982 Falkland’s conflict, were effectively shelved a year later. The RAF budget was increased with their politically aligned focus on improving the Air Defence of the UK. The Army did uncharacteristically well and saw their overall budget estimates grow with some increased investment to continue to modernise the Army’s equipment and improve levels of stocks.

To deliver a more sustainable Army it had accepted the more radical change in the 1981 Defence Review that is often overlooked. The review was “determined to make more use of reserve forces” as an affordable way of delivering more capability for its NATO First policy. Improvements to Reserve Forces had been identified by the review team from early in the process.

To meet NATO demands for more sustainable forces and in order to preserve funds for their modernisation programme the Army invested in its reserve forces. The Territorial Army in 1980 (the TA, whose name changed to the Army Reserve in 2014) was suffering somewhat from a recruitment and retention crisis and the Regular Reserve was known to be needed but somewhat languishing. They would need some investment.

The investment in additional reserve capacitywas controversial at the time in some quarters but it was seen to offer the best route to the political imperative of NATO First and delivering affordable sustainability. The 1981 Defence Review therefore saw a planned increase in the TA of 25% over ten years. This would grow it in personnel numbers from 45% of the size of the Regular Army to nearly 60% and so bring it more in line with NATO allies. Additional investment was also confirmed for the Regular Reserves with the introduction of the 1981 Individual Reinforcement Plan.

To balance the books the Army reduced its full-time operating costs. It did this primarily through re-organisation and reducing associated personnel costs. The army had, as now, the largest proportion of its budget allocated to personnel costs across the single services, primarily to its full-time personnel and families. The Army cut its high-level administrative HQ in British Army of the Rhine by 20% and removed one of the four divisional HQs in the 1st British Corps assigned to NATO. They absorbed the workforce from the disbanded division, and this allowed for three fully resourced and more powerful divisions of three brigades rather than the four, weak and under-staffed, divisions. This improved the readiness of first echelon by removing the immediate need for reserve reinforcements to backfill across the four divisions.

The TA Second Echelon – Sustainable Mass for Expansion

There was a very clear doctrine for the use of the TA in war that helped to achieve its growth over the decade. The TA would provide the additional reinforcement of units and formations needed to expand the Army in war. The TA provided the bulk of a complete second echelon Division for rear area security and mobility plus additional Corps Troops and Lines of Communication support. TA units would be given enough equipment to allow unit training with an increase in training days to 44 to ensure they could train to a reasonable level of collective capability and there were plans in place to receive an additional wartime increment of equipment on mobilisation.

The TA expansion was greatly helped by the Army accepting most of the 1979 Shapland Report recommendations to improve TA recruitment and retention by assigning specific wartime missions, better training, more modern equipment and some improved benefits. Between 1980 and 1990 the trained strength of the TA increased by 15% and since UK Reserve Forces recruitment is based on local patches there were funded improvements to existing TA accommodation. The modest investment transformed the TA over the decade. The system was certainly far from perfect, as some have argued, and the short timelines to reinforce Germany were extremely optimistic, but the strategic depth potential, at least, from the Army’s Reserves did contribute to deterrence and pacified NATO demands.

The Regular Reserves – Affordable Reinforcement

The 1981 Defence Review endorsed the Army’s Individual Reinforcement Plan to deliver more assured Regular Reserves. Their primary role was to provide individual reinforcements in wartime as Regular and TA units were rarely at 100% of their peacetime liability and each unit also had to receive a top up to their Warfighting Establishment. The Regular Reserves also provided the Battle Casualty Replacement (BCR) pools for the Army in this period.

They retained a basic uniform scaling with their mobilisation instructions for reporting in war and were required to attend an annual briefing at a local TA Centre. With a bonus payment for attendance, 92% attended annual briefings by 1983. There was an optional one-week training refresher for those who left regular service three years previously and many could volunteer to join major exercises.

Delivering Deterrence by Planning for Mobilisation

The 1981 improvements to the army’s reserves also succeeded because the British Army was oriented to planning for NATO warfighting. Transition to war would potentially impose so many concurrent demands on the army that an ad hoc approach to force generation would impose delay and risk. This would subvert the future sustainment of any deployed forces, especially mobilisation of the second echelon TA. This risk was well recognised in the Cold War and there was a deliberate force-generation plan pre-written, and exercised, to mobilise the entirety of the TA and Regular Reserve.

While this plan foresaw a short war it did include detail on how the UK could put in place structures to regenerate and reconstitute for a longer attritional conflict. To be clear, this was not a plan for how to fight a war but how to deliver an army ready and expanded for war. The 1981 Defence Review recognised the importance of having such a plan for deterrence – crucially this included exercising the mobilisation of the Reserve components.

Since the demise of the Cold War the British Army has had little need for a plan to expand and fight against a peer-level adversary. The army has been able to respond to recent operational demands with a bespoke force-generation process often drawing together varied units and personnel from across the army and mobilising small groups or individual personnel from among the reservists. There was no requirement to mobilise and expand the army with additional units. Challenging this “just in time” Lego bricks model that has lasted for over 30 years across expeditionary armies like the British Army and developing a plan for mobilisation that naturally includes reserves will be difficult for the army. Our allies have been quicker to realise this necessity but the 1980’s demonstrates we have done this before.

Conclusions

The 1981 Defence Review is chiefly remembered for the negative impact on the Royal Navy, but it was also radical for the focus on improving reserve forces for NATO warfighting. The Army made a rare comparative success of the review by embracing and investing in the reserve forces to deliver affordable sustainability for the mass required, while preserving vital funds for modernisation. Then, as now, it was not affordable to expand the number of Regular units to meet the NATO First demand.

The investment in training and equipping TA units and formations provided a “good enough” second wartime echelon for NATO. Regular Reservist reinforcements were made an offer to attend refresher training and allocated war roles. This effort was underpinned by thorough mobilisation planning and steady funding. It worked. The TA grew in numbers and capability with its expanded role through the decade helping to deliver a NATO Corps that was more capable than before 1980.

The current Army Reserve could be used to deliver unit capability to the army’s second echelon but to do so they will need to embed the new stable funding model and be trained, and equipped. A consequence of the 1981 decision to use the TA to provide the second echelon to the NATO Corps was the creation of a Long-Term Costing equipment and training programme to support it. To be effective, the Army’s need to modernise training has to include Army Reserve units for large-scale exercises and prioritised use of simulation. The Ukraine war has shown that affordable, older equipment is better than no equipment at all for Reserve Forces. The recent MOD response to changing its policy on disposals for this purpose is hardly encouraging.

Today, Labour has outlined a similar NATO First focus to 1981. The Cold War of the 1980’s has long gone but parallels regarding military workforce balance and affordability remain today in an era of increased threat and fiscal difficulty. The increased funds for Defence today are welcome but will be limited. For the Army it is difficult to see how increasing lethality through modernisation while concurrently improving sustainability for warfighting will be achievable with the limited additional funding available. The Army Reserve can deliver the affordable sustainability needed for today’s NATO First focus and provide that vital peacetime trained-and-equipped second echelon mass available for war – but investment will be required. Tough choices indeed.

© Vincent Connolly, 2025, published by RUSI with permission of the author.

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