How the 21st Century Corps Fights

This RUSI Commentary was submitted by Commander of Allied Rapid Reaction Corps ahead of the RUSI ARRC Corps Level Study Day.

It is safe to say this is a challenging time for the NATO Alliance and Euro-Atlantic Security. In this changing world, when the UK is taking a leading role in Europe’s adaptation to the new security paradigm, there is a requirement for demonstrable action and leadership today. The delivery of a fully-enabled corps is one of the British Army’s essential contributions to UK Defence. How the corps will fight is the subject of this RUSI study day.

What is a Corps?

Within the tactical, operational and strategic framework the modern corps sits on the seam between the higher tactical and operational levels of NATO’s warfighting architecture. While still very much focussed on the battle, the corps looks much wider than the division and has a very different role. Divisions focus on enabling the close battle, allowing their subordinate brigades to fight and win against our adversaries. The corps fights the deep battle, striking key enemy command and control, long range fires, electronic warfare, air defence and logistics capabilities, thereby shaping the environment and setting the conditions for the divisions and brigades in their close fights to come. The advent of new technologies, driven in part by the war in Ukraine, are offering new capabilities that increase the range of the corps deep battle to 300km and beyond. The corps also protects the force, an increasingly difficult proposition in modern times, ensuring forward echelons can survive to fight, supply lines remain intact and that troops can rest and rehabilitate before being redeployed. In the close battle the corps synchronises the divisions providing protection and support from corps level capabilities.

Our recent focus on counter insurgency operations means the corps level of warfighting is not well understood. I believe it has three key characteristics: scale, complexity and endurance. In terms of scale, a corps commander can expect to command at a minimum, two divisions and a range of key capabilities, between 50,000–150,000 people and their equipment, with a requirement to synchronise effects across all of the domains in support of the divisional fight. In terms of geographic scale, planning distances mean that the corps area of operations is approximately 100km wide by 200km deep, with the corps deep extending another 300km beyond that. Or to put it another way, an area roughly the size of Wales. Complexity exists everywhere: from protecting the force against increasingly sophisticated threats; the logistics designed to keep a large force supplied with food, ammunition, fuel and medical support; and managing the thousands of data points produced every minute, all while contending with whatever the enemy decides to throw at it. The corps also endures in a way that no other formation can. A division can rotate in and out of the fight, but a corps remains throughout; managing complex logistical trails, supporting the host nation and providing a consistent command and point of presence until the task at hand is complete.

How the 21st Century Corps fights

To quote a former French Prime Minister “Generals always prepare to fight the last war, especially if they had won it”. Our insights from Ukraine provide an indication of what the next war may look like. To ensure we are ready to fight and win there are a number of key areas where we are focusing, to improve how the corps fights in the future.

I start where we normally finish. For most of my career, logistics has been the last thing that is covered in any planning meeting or orders session. It is now my first point of call and for good reason. We all must understand the scale of logistics required for the UK’s corps to be credible in delivering deterrence. For the ARRC to arrive in the right place, at the right combat effectiveness, ready to fight and win – the challenge is vast. But that is the tip of the sustainment iceberg; we then must sustain the force over protracted and contested lines of communication. The complexities involved in deploying a multinational force across oceans and multiple international borders are significant; while we are working closely with NATO and national formations, it would likely be a national undertaking of a scale not seen since the Gulf War. Our ability to sustain the fight would require a whole-of-society and industry approach, one now capably being led by the National Armaments Director to give us the magazine depth and production capacity to match that of our adversaries.

Our adversaries have a sophisticated and effective system of layered defence, both in the physical and electromagnetic spectrums on the Land and in the Air. We must learn from this and change our view of how we deliver protection and how we manage risk. Protection cannot be something we consider for defending our critical assets. Instead, it must become integral to everything we do – it is a building block of modern corps warfighting. At the most simplistic level the bubble of protection creates freedom of manoeuvre in the corps’ rear and close which enables timely effects to be delivered in the corps’ deep. In future battles the corps with the most extensive and lethal bubble will wrestle a significant advantage, and those corps that are able to move and synchronise their bubbles with multi-domain effects will be able to dominate the battlefield. To prosecute the corps battle we have traditionally fired to manoeuvre – suppressed the enemy then moved. But without the protection from layered defences both physically and in the electro-magnetic spectrum any attempts to fire into the enemy’s deep are likely to attract the wrath of the enemy’s recce-strike complex.

With logistics and layered protection in place, my next priority is to strike the enemy at distance, creating the unfair fight for the divisions. The proliferation of uncrewed systems has changed the character of conflict and how we fight in the deep. There is still a vital role in modern warfare for our survivable systems, the tank, the attack helicopter and the artillery piece. But as Ukraine has showed, we can be smarter with how we develop and integrate these with less-expensive attritable and consumable systems. CGS has set the target that in the future 40% of the Army’s lethality will come from the attritable, 40% from consumable and 20% from the survivable. With this in mind we are ideally positioned to ensure that we are preparing to fight the next war, not the last.

In a period of our history where demonstrable action and leadership is required today our reinvestment in the UK’s corps has started. . There is much work still to do and I hope the focused study day at RUSI will provide much of the impetus we require.

© Ralph Wooddisse, 2025, published by RUSI with permission of the author.

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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