Prompted by a rapidly changing and more dangerous geopolitical environment, particularly due to growing multipolarity and technological advances, the review proposes a "new era for UK Defence" centered on a "NATO First" approach. Key areas for transformation include achieving an Integrated Force that is tech-enabled and innovation-led, increasing defense spending to 2.5% of GDP by 2027, and undertaking radical reforms in areas like defense procurement, workforce management (the "One Defence" concept), and the sustainment of the nuclear deterrent. The review, which was externally led and involved extensive consultation, provides specific recommendations for modernizing the maritime, land, air, space, and CyberEM domains to ensure warfighting readiness against peer adversaries by 2035.

1.0 The Strategic Imperative: The Case for Transformation

1.1 A New Era of Threat

The 2025 Strategic Defence Review (SDR) is a direct response to a global security environment more volatile and uncertain than at any time since the Cold War, making a clear and urgent case that a fundamental shift in the United Kingdom's defence posture is no longer a choice but a necessity. The return of state-on-state conflict to Europe, evidenced by Russia's full-scale invasion of Ukraine, marks a definitive strategic inflection point. This new reality is compounded by the steady erosion of the West's long-held military advantage and the rise of adversaries who intentionally blur the lines between conventional, sub-threshold, and nuclear threats. The UK and its allies find themselves under daily attack in a "grey zone" of intensifying international competition, making the imperative for transformation both immediate and profound.

1.2 Analysis of the Strategic Context

The review's strategic analysis pivots on two dominant and accelerating trends that will shape the security environment through 2040, each with profound implications for UK defence policy and force structure.

• Growing Multipolarity and Intensifying Strategic Competition: The post-Cold War international order is fracturing, giving way to a more complex and competitive multipolar world. For the UK, this trend complicates deterrence, particularly as states like Russia, China, Iran, and the Democratic People's Republic of Korea (DPRK) deepen their strategic and opportunistic alignment. Russia is identified as an immediate and pressing threat, one that uses "nuclear rhetoric in an attempt to constrain decision-making." China poses a sophisticated and persistent challenge through its rapid, large-scale military modernisation, which includes an unprecedented diversification of its conventional and nuclear missile forces, with missiles that "can reach the UK and Europe." The source projects that China's arsenal is "expected to double to 1,000 nuclear warheads by 2030," adding a dangerous new dimension to the global strategic balance.

• Rapid and Unpredictable Technological Progress: Technology is changing the character of warfare more profoundly than at any point in history. Advances in Artificial Intelligence (AI), robotics, autonomy, and hypersonic missiles are reshaping the battlefield. The widespread availability of commercial, off-the-shelf technologies, such as drones, enables a broader range of actors to possess advanced capabilities, altering the economics of defence and challenging the UK's freedom of manoeuvre across all domains. This technological race means that armed forces that fail to adapt at pace risk becoming rapidly obsolete.

1.3 Evaluating the State of UK Defence

While the UK's Armed Forces are respected worldwide for their professionalism, the SDR presents a candid assessment of their current state. The review concludes that Defence remains largely shaped by the operational demands of the post-Cold War era, optimized for counter-insurgency rather than high-intensity state-on-state warfare. This has led to a "hollowing out" of warfighting capability, with inadequate stockpiles, a lack of resilience in the strategic base, and a procurement system ill-suited to the pace of technological change. Compounding these material shortfalls is a persistent workforce crisis marked by poor recruitment and retention. The document underscores the gravity of the situation with a stark conclusion: "business as usual is not an option."

The review's unsparing diagnosis of a force hollowed out and optimised for a bygone era thus frames its new strategic vision not as an incremental adjustment, but as a radical and necessary response to existential challenges.

2.0 A New Strategic Vision and 'NATO First' Posture

2.1 Defining the New Vision

In response to the formidable challenges of the new era, the Strategic Defence Review articulates a clear and ambitious vision for UK Defence to be realised by 2035:

A leading tech-enabled defence power, with an Integrated Force that deters, fights, and wins through constant innovation at wartime pace.

This vision is not confined to the military alone; it is explicitly underpinned by a "whole-of-society" approach, integrating the strengths of government, industry, and the wider public to build national resilience. At its core, the vision is anchored by a landmark shift in strategic focus, codifying a "NATO First" policy to guide all aspects of defence planning, development, and action.

2.2 Deconstructing the 'NATO First' Policy

The "NATO First" policy represents a significant change, moving beyond mere membership to a deep, systemic integration with the Alliance. It requires that NATO considerations become the default starting point for UK Defence. The practical implications of this policy are detailed below.

2.3 Defining the Core Defence Roles

To structure its efforts, the review defines three core and two enabling roles for UK Defence, which are enduring, mutually reinforcing, and aligned with the "NATO First" approach.

1. Defend, protect, and enhance the resilience of the UK, its Overseas Territories, and Crown Dependencies.

2. Deter and defend in the Euro-Atlantic.

3. Shape the global security environment.

• Develop a thriving, resilient defence innovation and industrial base.

• Contribute to national cohesion and preparedness.

Achieving this new strategic vision requires more than a shift in policy; it demands a transformation in the fundamental mechanics of how UK Defence operates, innovates, and equips itself for a new era of conflict.

3.0 The Three Pillars of Warfighting Transformation

3.1 The Mechanics of Modernisation

The SDR's vision is operationalized through three interconnected pillars of reform designed to drive the UK's transformation into a leading tech-enabled power. These fundamental changes in approach—being integrated by design, innovation-led, and industry-backed—provide the blueprint for modernizing UK warfighting capability and ensuring the Armed Forces can deter and win in the 21st century.

3.2 Pillar 1: Integrated by Design

The review mandates a decisive shift from a "joint" force, where single services cooperate, to a fully "integrated" one, designed and directed from the top as a single coherent entity. This transformation is enabled by the newly established authority of the Chief of the Defence Staff (CDS), who now commands the Service Chiefs and directs the single force design. The Integrated Force is underpinned by a common digital foundation and a single digital mission to deliver a "digital targeting web" in 2027, connecting sensors, deciders, and effectors to enhance lethality and speed. Crucially, this technological integration is matched by a human capability component: the creation of an expert "Digital Warfighters group" designed to deploy digital expertise directly alongside front-line personnel, ensuring rapid adaptation and exploitation of technology on the battlefield.

3.3 Pillar 2: Innovation-Led

The SDR recognizes that Defence must embrace its role in seeding innovation by transforming its ability to find, buy, and use new technology at a wartime pace. To achieve this, existing structures will be reorganised into two distinct new bodies:

• Defence Research and Evaluation (DRE): This organisation will focus on enabling external early-stage scientific research and will serve as the primary gateway to academia and research institutions, ensuring Defence can leverage world-class UK science and technology.

• UK Defence Innovation (UKDI): This new body will be focused on harnessing commercial innovation, including dual-use technologies. It will connect external innovators with Defence procurement teams and will be empowered with a ringfenced annual budget of at least £400m to drive the rapid adoption of new capabilities.

3.4 Pillar 3: Industry-Backed

A revitalized partnership with industry is deemed essential to overhauling the UK's "broken" acquisition processes. This pillar introduces a segmented approach to procurement, tailored to accelerate delivery and engage a wider range of suppliers.

• Major modular platforms: Contracting timelines are mandated to be within two years.

• Pace-setting spiral and modular upgrades: Contracting will be completed within one year.

• Rapid commercial exploitation: Contracting for novel technologies will occur within three months, with a requirement that at least 10% of the equipment procurement budget is spent in this category each year.

This ambitious transformation of technology and industry is critically dependent on the military personnel, civil servants, and industrial partners who must ultimately deliver it

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4.0 The 'One Defence' Approach: Reforming People, Culture, and Training

4.1 The Human Component of Transformation

The SDR firmly establishes that the success of its strategic vision is fundamentally dependent on its people. The review directly confronts a long-standing workforce crisis, aiming to empower military and civilian personnel by reforming culture, training, and workforce planning under a unified "One Defence" mindset. This approach seeks to reverse years of declining recruitment and retention and build a workforce that is agile, skilled, and motivated to deliver on the review's ambitions.

4.2 Whole Force Workforce Planning

The review outlines a "whole force" approach to workforce planning, blending Regulars, Reserves, and civil servants to create a more dynamic organisation. Specific targets include:

• Regulars: No further reduction in the number of highly trained Regulars, with an envisioned increase in the total number of personnel when funding allows. This includes a small uplift in Army Regulars as a priority.

• Active Reserves: An increase in the number of Active Reserves by 20% when funding allows, most likely in the 2030s, to restore mass and strategic depth.

• Civil Service: A reshaping of the civilian workforce with an emphasis on performance and skills, aiming to reduce costs by at least 10% by 2030.

4.3 Reforming Recruitment, Retention, and Culture

To fix the recruitment and retention crisis, the SDR proposes targeted reforms aimed at modernizing the offer to service personnel. The primary focus is on speed and flexibility, learning from international models such as Australia's military "gap years" to drastically shorten the time between application and entry. For retention, a planned "flexible working" initiative will enable military personnel to dial their commitment up and down throughout their careers. Critically, the review also mandates a cultural shift to empower personnel by cutting bureaucracy and eradicating unacceptable behaviour.

4.4 An Adaptive Training System

The Defence training and education system will be redesigned to deliver innovation at speed and ensure personnel train how they will fight. The guiding principles for this transformation are:

• Whole Force by Default: Where possible, training will be delivered for the entire "One Defence" workforce—Regulars, Reserves, and civilians—to foster a shared culture.

• NATO First: The Alliance's exercise programmes, doctrine, and planning processes will form the basis for UK training and education.

• Adapting at Pace: The system will be re-engineered to rapidly apply innovations and lessons from operations to doctrine and concepts, reversing a trend of risk aversion in training.

The internal transformation of the force is inextricably linked to its external role in strengthening national resilience and its reliance on a global network of allies.

5.0 Foundational Strength: Home Defence and Allied Integration

5.1 Building National Resilience

The SDR asserts that modern deterrence is no longer the exclusive domain of the armed forces but requires a "whole-of-society" approach to be credible. Consequently, the review places a renewed and urgent emphasis on home defence, national resilience, and the critical role of alliances in creating the strategic depth necessary to withstand and deter aggression in a more dangerous world.

5.2 A Whole-of-Society Approach

To reconnect Defence with the society it serves, the review recommends several tangible initiatives designed to raise public awareness and foster a shared sense of responsibility for national security. Key actions include:

• Expanding the Cadet Forces by 30% by 2030, with an ambition to reach 250,000 members in the longer term.

• Working directly with the Department for Education to develop a better understanding of the Armed Forces among young people in schools.

5.3 Protecting Critical National Infrastructure (CNI)

The SDR proposes a "new deal" for the protection of the UK's Critical National Infrastructure, which is increasingly vulnerable to state-backed attack and sabotage. To support this effort, the Royal Navy will assume a new leading and coordinating role in securing the UK's vital undersea pipelines, data cables, and maritime traffic.

5.4 Strengthening Alliances and Partnerships

Bolstering collective security through a prioritized network of alliances is central to the SDR's strategy. The relationship with the United States remains the UK's closest and most critical defence partnership. In Europe, bilateral agreements with key NATO Allies—notably France, Germany, and Poland—are prioritized as powerful tools for strengthening Euro-Atlantic stability. The review also highlights the strategic importance of capability partnerships like AUKUS (with the US and Australia) and the Global Combat Air Programme (GCAP) (with Italy and Japan) as exemplars of industrial and technological collaboration.

This strategic framework, which re-establishes the foundations of national and collective security, provides the necessary context for examining the specific military capabilities the future Integrated Force will wield.

6.0 The Integrated Force in Detail: A Domain-by-Domain Capability Overview

6.1 A Force Fit for the 21st Century

This section details the specific capabilities required to field a transformed Integrated Force fit for the challenges of the modern era. The review's recommendations are guided by a focus on a "high-low" mix of equipment, a decisive pivot towards autonomy and Artificial Intelligence, and the urgent need to restore warfighting readiness across all five operational domains. This conventional transformation is underwritten by the UK's steadfast commitment to maintaining a credible, independent nuclear deterrent.

6.2 The Nuclear Deterrent

The UK's independent nuclear deterrent is reaffirmed as the "bedrock" of national defence and a "National Endeavour" providing the ultimate guarantee of UK and Allied security. Key investment priorities to ensure its long-term credibility include the new fleet of Dreadnought class submarines, the replacement sovereign warhead (program ASTRAEA), and the next-generation nuclear-powered attack submarines developed through the SSN-AUKUS partnership.

6.3 Maritime Domain

The Royal Navy will be transformed into a "New Hybrid Navy," blending traditional crewed platforms with a growing proportion of autonomous systems. This includes the development of hybrid carrier airwings, which will combine crewed F-35 fighter jets with autonomous collaborative platforms. To secure vital sea lanes, the Navy will implement its "Atlantic Bastion" plan, a multi-domain approach to secure the North Atlantic for the UK and NATO.

6.4 Land Domain

The British Army will be modernized through a new "Recce-Strike" model that combines armoured capability with AI, long-range weapons, and land drone swarms. This model aims to deliver a ten-fold increase in lethality, measured against a conventional armoured brigade model, to find and strike enemy forces with unprecedented speed and precision. The Army is committed to providing a fully modernized Strategic Reserve Corps to NATO.

6.5 Air Domain

A "next-generation RAF" will be created, centered on a mix of advanced crewed and uncrewed aircraft. Key components of this future force include F-35 fifth-generation fighters, upgraded Typhoon jets, the Future Combat Air System being developed through the Global Combat Air Programme (GCAP), and the integration of autonomous collaborative platforms to generate mass.

6.6 Space and Cyber & Electromagnetic (CyberEM) Domains

The review recognizes the heightened importance of space and cyberspace as critical warfighting domains. Investment will be directed toward creating resilient military space systems to ensure assured access to satellite capabilities. To bring greater coherence to the digital battlefield, a new CyberEM Command will be established by the end of 2025, responsible for integrating military action across cyberspace and the electromagnetic spectrum.

Ultimately, the 2025 SDR presents a comprehensive and technologically ambitious blueprint for transformation; its success, however, will be defined not by the vision itself, but by the political will and fiscal discipline required to reverse decades of strategic drift and deliver this generational response at the 'wartime pace' it demands.