The UK Strategic Defence Review Explained: 12 Submarines, 7,000 Missiles and a “10x More Lethal” Army

In June 2025 the UK published its Strategic Defence Review (SDR), the most important rethink of British defence in a generation. Led by former NATO Secretary General Lord Robertson, General Sir Richard Barrons and Dr Fiona Hill, it concluded that Britain must move to “warfighting readiness” to deter Russia and other threats. The government accepted all 62 recommendations. Here is what it means in practice.

NATO first

The review puts the defence of Europe and the North Atlantic at the centre of British strategy. The UK will lead in NATO, especially in the High North and on the eastern flank, while keeping a presence in the Indo-Pacific through AUKUS and carrier deployments. Defence spending was set to rise to 2.5 percent of GDP by 2027, with a longer path toward NATO’s new 3.5 percent core target by 2035.

Submarines and nuclear deterrence

The Royal Navy will build up to 12 SSN-AUKUS nuclear-powered attack submarines, replacing the Astute class and greatly expanding the fleet. The review also confirmed around £15 billion for the sovereign nuclear warhead programme. Separately, the UK announced the purchase of 12 F-35A fighters able to carry American nuclear bombs, rejoining NATO’s airborne nuclear mission for the first time since the Cold War.

Missiles and munitions

Lessons from Ukraine run through the SDR. Britain plans to buy up to 7,000 UK-built long-range weapons and to build at least six new munitions and energetics factories so that production can surge in a crisis. That is meant to fix one of the UK’s biggest weaknesses: very small stockpiles.

A “ten times more lethal” Army

The Army is to become ten times more lethal by combining crewed vehicles, drones and long-range fires. The review describes a future force where only a fraction of combat power comes from traditional platforms, with the rest from reusable and expendable uncrewed systems. A new Digital Targeting Web is meant to connect sensors and shooters across all services by 2027.

Cyber, space and the home front

A new Cyber and Electromagnetic Command will lead in digital and electronic warfare. The review also calls for a “whole-of-society” approach: better protection of critical infrastructure, more reservists and closer ties between the armed forces and industry.

Will it be delivered?

Critics say the SDR’s ambitions outstrip its budget, and that recruitment problems, an overstretched shipbuilding sector and slow procurement could delay key projects. The real test is the detailed investment plan and whether money follows the strategy year after year.

Verdict

The SDR marks a clear shift from expeditionary operations to deterrence and high-intensity war in Europe. If funded, it will give Britain a larger submarine force, deep missile stocks and a drone-heavy Army, but the gap between strategy and spending remains the biggest risk.

Featured image: U.S. Navy photo by Mass Communication Specialist 2nd Class Cameron Stoner / Public domain, via Wikimedia Commons