The UK is facing a security crisis. Great power competition has returned, and the threat of hostility from Russia, China, Iran and North Korea is increasing. The west can no longer assume military superiority, and the UK can no longer depend unconditionally on the US. The character of war itself is changing as new technology is introduced.

This is the situation laid out in the latest strategic defence review. The implications for the UK are clear: the country must prepare for high-intensity, protracted war, not counter-insurgency operations like Iraq or Afghanistan.

In order to address these challenges, the review says, “the UK must pivot to a new way of war.” Nuclear weapons are important here, and will be renewed and expanded. But the recommendations in the review focus on conventional weaponry and, above all, new remote and autonomous technology.

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The ongoing Ukraine war underpins much of the thinking about the military changes the UK needs to make. That conflict has demonstrated a significant change in the character of 21st-century warfare. Most obviously, it has involved a proliferation of cheap, expendable remote systems, some of which have autonomous capabilities.

Remote first-person-view drones, and drones controlled by unjammable fibre-optic cables, have become ubiquitous on the frontline – reconnoitring, targeting and striking troops on both sides. They have made conventional strategic manoeuvres at the front almost impossible, while also striking civilian and military targets deep in Russia and Ukraine.

At sea, uncrewed naval drones have struck Russian shipping and infrastructure in Crimea. The Ukrainian armed forces have also developed a digital battle management system and live-data, AI-enabled targeting system, drawing together information from satellite, open-source, ground-sensor and signal intelligence. This has allowed Ukrainian commanders to see deeply across the battlespace, and target Russian forces with an unprecedented depth and precision.

As a result of remote systems enabled by digitised targeting, military forces have become exponentially more lethal in close battle – and also in the deep.

The strategic defence review aims for the UK to incorporate these two elements into its war-fighting capabilities, recommending massive investment in remotely controlled and autonomous systems.

It calls for the UK to create a “leading, tech-enabled defence power”. Part of this involves integrating UK forces and the construction of a unified “digital targeting web”. This would be fed by sensors from every domain (land, air and sea) so that all forces have access to the same intelligence and a common operating picture. The idea is that a target identified in one domain might be prosecuted by forces in another, to “enhance the Armed Forces’ precision and lethality at scale and reach”.

In order to achieve this, the review also calls for improved and more innovative relationships between British defence, tech and industry. Once again, a lot has been learnt from Ukraine, whose industrial and tech sectors have been integrated into the war from the start.

The missing link

The review’s authors – three external experts led by former defence secretary and Nato chief, Lord Robertson – are correct to highlight the increasing importance of remote (and sometimes autonomous) systems in warfare. They are clear that military forces should increasingly draw on live data, processed by artificial intelligence, to help them understand the battlespace, plan and target. The UK must remain competitive with peer enemies who are developing these capabilities.

However, even assuming that all of this is affordable at 2.5% of the UK’s GDP from 2027 (a 0.2% rise from where defence spending is now), there is a serious gap in the review’s proposals.

As a scholar who has studied war in the 21st century, and has just completed a book on AI and war, I believe the document vastly overexaggerates the capability of AI and autonomy. For example, it states:

In modern warfare, simple metrics such as the number of people and platforms deployed are outdated and inadequate. It is through dynamic networks of crewed, uncrewed, and autonomous assets and data flows that lethality and military effect are now created.

This analysis presumes that autonomy will be vital in the future, and implies it will displace the need for large numbers of human combatants. In fact, true autonomy is still rare in combat – and will remain so, according to my research.

Even if autonomous drone swarms appear, they will not eliminate the need for human programmers or operators behind the frontline. AI has limited military functions which require a huge amount of human input.

A soldier explains to john healey, who is holding a controller
Defence secretary John Healey being shown unmanned and autonomous units on a demonstration. UK MOD Crown Copyright 2025

The review prioritises preparedness for protracted inter-state war. But it ignores the blindingly obvious from Ukraine: the imperative of mass.

The Ukrainian frontline combat forces have expanded to about 300,000 – Ukraine claims its whole force, including allied fighters, is around 1 million. There are about 400,000 Russian combat troops in Ukraine. Casualties have been eye-watering: the Russians have suffered about 800,000 casualties, the Ukrainians nearly 500,000.

In my view, the strategic defence review has been mesmerised by the prospect of new technology – and, perhaps, by some wishful thinking.

In 21st-century war, troop mass matters. Fleets of drones and the most sophisticated digital targeting will be irrelevant without human forces willing to fight and to operate them.

What is the review’s answer to this? While acknowledging that in the cold war, the British fielded forces of 311,000, UK regular armed forces are to remain the same size: 136,000, of which the army will consist of only 73,000 troops and staff.

The review proposes that active reserves (volunteer, part-time forces) will be increased by 20%, and that the strategic reserve (ex-regulars) “is central to military mobilisation and must be reinvigorated”.

It is not surprising that the review’s authors have offered such thin solutions to the question of mass. There has been profound resistance from successive governments, Whitehall and civil society to any expansion in the size of British military forces in the UK. But it is doubtful that an expanded reserve and a reinvigorated strategic reserve will be remotely enough for the UK to fight and win a war of any kind in the coming decade.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Anthony King, University of Exeter

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Anthony King does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.