A National Endeavor

The United Kingdom’s approach to maintaining and enhancing its nuclear deterrent capabilities is a multifaceted national endeavor, encompassing extensive investments in infrastructure, technology and human resources. This initiative is critical to the nation’s security, economic prosperity and its role in international stability.

“Our nuclear deterrent has been the cornerstone of our national security, safeguarding our values and way of life, for more than 70 years,” Rishi Sunak, then British prime minister, said in the foreword of a March 2024 report by the U.K.’s Defence Nuclear Enterprise (DNE) titled “Delivering the U.K.’s Nuclear Deterrent as a National Endeavour.” “It has protected the U.K. and our NATO Allies from the most extreme acts of aggression and nuclear blackmail from our adversaries. Our deterrent is more relevant now than ever before. We face new and diverse challenges from nuclear-armed states that make deterrence as critical today as it was in the last century.”

The history of the British nuclear deterrent is grounded in decades of strategic development and international cooperation. The U.K.’s nuclear deterrent policy was shaped significantly during the Cold War, a period marked by intense geopolitical tensions. The Royal Navy’s continuous-at-sea deterrent (CASD) patrols,  initiated in 1969, became a critical component of this strategy. These patrols, carried out by Vanguard-class submarines equipped with the Trident II D5 missile system, ensured a constant state of readiness and deterrence.

The credibility of the U.K.’s deterrence is enhanced by ensuring it remains operationally independent. Only the prime minister can authorize the use of nuclear weapons, even if deployed as part of a NATO response, according to the DNE. The U.K. is also “deliberately ambiguous” about precisely when, how and at what scale it would use its weapons. “Alongside our decision to no longer publicize figures for our operational stockpile or deployed warheads, this posture enhances our deterrent effect by complicating the calculations of potential aggressors, thereby reducing the risk of deliberate nuclear use by those seeking a first-strike advantage,” the DNE report said.

In the contemporary context, the U.K. has embarked on an ambitious modernization program to sustain and enhance its nuclear deterrent capabilities. The DNE is at the forefront of this effort, integrating advanced technologies and fostering partnerships across government, industry and academia.

“We are now in a period of heightened risk and volatility that is likely to last beyond the 2030s,” the DNE report said. “We are therefore reaffirming our commitment to a credible nuclear deterrent and investing to sustain and renew our capabilities for as long as required. We will keep our nuclear posture under
review in light of the international security environment and the actions of potential adversaries.”

Submarine Programs and Infrastructure Investments

A cornerstone of the U.K.’s modernization efforts is the development of the Dreadnought-class submarines, set to replace the Vanguard class in the early 2030s. These submarines will be “the largest, most technically advanced” ship, submersible, ballistic, nuclear (SSBN) vessels ever operated by the Royal Navy and will feature new nuclear reactors designed and manufactured by Rolls-Royce Submarines Ltd. The construction and maintenance of these submarines is concentrated in Barrow-in-Furness, a location of  “critical national importance” due to its shipbuilding infrastructure.

“This investment in our future security will ensure that the U.K. has a minimum, credible, independent nuclear deterrent for as long as the global security situation makes it necessary,” according to a U.K. Ministry of Defence guidance statement on its nuclear deterrent. “We will continue to keep our nuclear posture under constant review in light of the international security environment and the actions of potential adversaries. We will maintain the minimum capability required to impose costs on an adversary that would far outweigh the benefits they could hope to achieve should they threaten our security, or that of our Allies.”

At least one nuclear-armed, nuclear-powered submarine has covertly patrolled the world’s oceans for more than 50 years, carrying the U.K.’s sovereign warheads. The Royal Navy’s Operation Relentless is the longest sustained military operation ever undertaken by the U.K. It receives support by maritime patrol aircraft providing a seamless and world-leading antisubmarine warfare
capability, while the fleet-ready escort is held at readiness to monitor, track and intercept adversary vessels approaching and transiting British waters, deterring attempts to intercept and disrupt submarine operations.

Playing a critical role in the U.K.’s nuclear deterrent strategy is the Atomic Weapons Establishment (AWE), responsible for the design, manufacture and maintenance of nuclear warheads. The organization employs 3,500 scientists and engineers who work with industrial, government and academic partners to ensure the safety, security and effectiveness of the U.K.’s warhead stockpile.

Commitment to Nonproliferation and Disarmament

Despite its emphasis on maintaining a credible nuclear deterrent, the U.K. remains committed to a world without nuclear weapons.

“We remain committed to the ultimate goal of a world without nuclear weapons and support full implementation of the Treaty on the Non‑Proliferation of Nuclear Weapons (NPT),” according to the DNE. “There is no credible alternative route to disarmament. The U.K. continues to support the entry into force of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and will continue to press for key steps towards multilateral disarmament through the NPT.”

The British government believes, however, that a world where potential adversaries have nuclear weapons and NATO and the U.K. do not, “is not a safer world.”

“Our security is enhanced by our partnerships with our Allies. We have a strong relationship and engagement with the U.S. Our standing as a responsible nuclear power remains an important part of our long history of defense cooperation, enhancing Euro-Atlantic security,” the DNE report said.

The U.K. works closely with the U.S. on all nuclear matters,
including nuclear policy, operations and technology. It also has a close relationship with France, the U.K.’s European nuclear Ally, with cooperation on nuclear deterrence issues increasing. “The U.K. is also committed to building understanding and expertise on nuclear issues in NATO,” the DNE said. “This includes ensuring coherence between the Alliance’s nuclear and conventional policies and
developing the capabilities needed for the future.”

The U.K.’s nuclear policies closely align with those of its international Allies, particularly France and the U.S. The Mutual Defense Agreement and the Polaris Sales Agreement with the U.S. provide a framework for cooperation on nuclear materials, technology and information. The U.K.’s collaboration with France through the Lancaster House Treaties and the Teutates Treaty further strengthens its nuclear capabilities and expertise.

“Our engagement with our international partners underpins our ability to guarantee nuclear security. Our responsibilities extend to joint programs with the U.S., France and Australia, and our nuclear deterrence commitments with NATO sit alongside our international commitments on nuclear security and non-proliferation,” the DNE report said. “These agreements and obligations are essential to ensuring our national security while guaranteeing the security and cooperation of our Allies.”

Security and Innovation

The U.K.’s Replacement Warhead Program, announced in 2021, further underscores its commitment to an effective nuclear deterrent. The program aims to develop a new warhead using modern and innovative developments in science, engineering, manufacturing and production at the AWE. It’s being developed in parallel with the U.S. W93/Mk7 warhead, and each nation is developing a sovereign design.

“This will be the first U.K. warhead developed in an era where we no longer test our weapons underground, upholding our voluntary moratorium on nuclear weapon test explosions,” according to the DNE. “This is possible because of the long history of technical expertise and extensive investment in U.K. modelling and simulation, supercomputing, materials science, shock and laser physics at AWE.”

The British government says that thousands of people work across the military, public sector and industry to achieve a shared mission: to deliver capabilities, deter the threat and protect the nation. To ensure this deterrent is sustained for as long as needed, the U.K. has made the following commitments:

• Invest more than $39 billion in the new Dreadnought-class SSBNs with the first boat due to patrol in the early 2030s.
• Develop a replacement U.K. sovereign warhead while maintaining existing stockpiles.
• Recapitalize critical elements of infrastructure to modernize naval bases and manufacturing processes, supporting growth with anticipation of future fleet needs and weapons requirements.
• Finalize completion of the U.K.’s fleet of conventionally armed, nuclear-powered Astute-class submarines and continue designing the next generation of attack submarines.
• Enhance nuclear power generation over the long term by investing in nuclear technology, with many parallels to the investments needed to support the U.K.’s energy security plan.
• Work with industry partners to safeguard supply chains for the future.
• Invest in Barrow-in-Furness as the home of nuclear submarine building in the U.K., recognizing its criticality to the nation’s security.

“These are some of the largest and most complex programs ever seen. They require unique cutting‑edge technology and world‑leading expertise in science, engineering and manufacturing,” the DNE said.

A Critical Role

The U.K. is the only power besides the U.S. that has pledged its nuclear deterrent to NATO, underscoring its “indispensable role” in the Alliance and its unique position in global nuclear deterrence, according to Ryan Tully, a senior fellow focusing on nuclear deterrence, missile defense, space policy and European security at the Hudson Institute, a Washington, D.C.-based think tank. The U.K. also plays a crucial role in helping the U.S. confront the two near-peer competitors, China and Russia.

“A strong UK nuclear posture would help maintain strategic stability in an era of renewed great power competition. As Russia continues its aggressive behaviour and China rapidly expands its nuclear capabilities, the deterrent value of Western nuclear forces has only grown. The UK’s nuclear arsenal, though smaller than that of the U.S. or Russia, plays a vital role in this broader deterrence landscape,” Tully wrote in a September 2024 commentary for the Royal United Services Institute for Defence and Security Studies, a U.K.-based research institution focused on defense, security and international affairs. “The stakes are high, and the world will be watching closely. Translating the new prime minister’s rhetoric on nuclear modernisation into action and resources will help ensure the continued effectiveness of the Western deterrent and the stability of the transatlantic Alliance for decades to come.”