UK considers reintroducing air-launched tactical nuclear weapons

The United Kingdom’s Strategic Defence Review, published on June 2, announced a substantial investment of more than £15 billion (about $20 billion) in its nuclear forces. The review also opened the door to the deployment of air-launched tactical nuclear weapons by saying that the UK Ministry of Defence “should commence discussions with the United States and NATO on the potential benefits and feasibility of enhanced UK participation in NATO’s nuclear mission.” The need for the United Kingdom to deploy lower-yield, so-called tactical (non-strategic) nuclear weapons will doubtless be hotly debated. Already, the move has raised concerns about a nuclear arms race and the undermining of nonproliferation commitments.

Before making any investment, the United Kingdom should carefully evaluate whether air-launched nuclear weapons are at all required, and whether there is a practical capability to meet this requirement.

Most headlines on the issue zeroed in on the possible purchase of F-35As equipped for US B-61 bombs. By contrast, the review team told Parliament this week that the option still needs a detailed study. In practice, the option would add little to the United Kingdom’s deterrent capabilities. Instead, if an air-launched nuclear weapons capability is deemed necessary for European security, the United Kingdom would likely need to invest in a new tactical nuclear warhead delivered from an air-launched cruise missile—something that would have a considerable cost and could likely not be available until perhaps the 2040s. Presented with these two options, it is unclear whether either offers a meaningful short-term capability to bolster European security.

The early role of tactical nuclear weapons. Nuclear strategists have long argued that there is no such thing as a so-called tactical nuclear weapon: A nuclear weapon used in anger is likely to trigger a nuclear response. It doesn’t matter its size or how it is delivered.

While management of escalation dynamics is certainly a complex and open question, the United Kingdom historically recognized a need to maintain tactical nuclear weapons in addition to its strategic submarine-launched Trident missile system. This provided the United Kingdom with a quick-to-deploy, limited nuclear strike option. Historically, such weapons provided a capability to target fixed and mobile-but-stationary targets in Eastern Europe in a way that was clearly distinguishable from the United Kingdom’s strategic sea-based nuclear deterrent. In the later years of the Cold War, this capability was based on the UK-designed WE-177 free-fall (gravity) bomb, which included variants with a wide range of explosive yields.

The WE-177 bomb was as important for its military effect as for its contribution to European security through NATO. The United Kingdom committed its nuclear forces to NATO in recognition that any warfighting on continental Europe would require a Europe-wide response, which also drew on US support. The United Kingdom’s contribution to the tactical nuclear mission of NATO was therefore seen as essential to allay its allies’ worries, address proliferation risks, and offset US burden-sharing concerns.

In the late 1980s, it was recognized that free-fall bombs delivered via available aircraft did not meet military planning needs: Free-fall bombs require the delivery aircraft to penetrate hostile airspace, and at least in the late 1980s and 1990s, aircraft survivability had become unlikely. Therefore, the credibility and effectiveness of a free-fall bomb option had been undermined. When the Supreme Allied Commander Europe, or SACEUR, identified a requirement for an air-launched tactical nuclear weapon capability with a range of at least 400 kilometers to support NATO’s warfighting plans, the United Kingdom moved to develop a replacement for the WE-177 free-fall bomb: a nuclear air-launched cruise missile capable of propelling itself hundreds of kilometers into enemy airspace. The United Kingdom examined a host of other delivery modalities but recognized that no one system could meet all requirements. An air-launched cruise missile, however, could meet many of the requirements since it could be stealthy and could be launched from within allied airspace.

The United Kingdom had already entered into discussions with France and the United States about the provision of a suitable air-launched cruise missile when the government decided to eliminate its air-launched nuclear capability altogether and instead rely on a so-called sub-strategic warhead for the sea-based Trident missile system. (Most analysts consider this capability conceptually challenged because an adversary would have difficulty distinguishing between an incoming strategic and a tactical missile, given they are launched using the same delivery system. The latest Bulletin’s Nuclear Notebook for the United Kingdom suggests this capability may have since been eliminated.)

Reconstituting capability and the importance of stealth. The United Kingdom’s nuclear posture review opens the door to the United Kingdom reintroducing air-launched tactical nuclear weapons. The design of such a capability cannot be separated from the missions it would be deployed for.

Today, Eastern Europe’s borders look very different from those during the Cold War. While by then an air-launched weapon may have been released over Germany targeting Soviet facilities, today the primary targets would be inside Russia or Belarus. This is especially the case as novel conventional forces such as drones are now able to target maneuvering forces. To be sure, the introduction of stealth aircraft opens possibilities that were not available to the United Kingdom in the 1990s. Still, the idea of sending UK F-35As deep inside Russian territory to deliver free-fall bombs seems fraught with risk, which will only grow as Russia improves its radar systems. (China reportedly is developing radars that can track latest-generation stealth aircraft, including the F-35.)

Should an air-launched tactical nuclear weapon capability be considered necessary, a more realistic option would be to revisit a 1990s concept: an air-launched cruise missile to be mounted on an existing Royal Air Force airframe. For instance, the United Kingdom could select France’s latest ASMPA air-launched cruise missile, an option the United Kingdom already explored in the 1990s with an earlier version of the missile. Such a system would help offset the United Kingdom’s reliance on the United States for the entirety of its nuclear weapon delivery platforms. In addition, the nuclear missile would most probably be launched from a fighter jet located inside allied airspace rather than from inside Russia, thereby partly resolving the issues of stealth. In addition, the high speed, reduced radar cross-section, and complex flight characteristics of an air-launched cruise missile could also allow it to evade air defenses, making it an effective air-launched delivery system.

However, such a solution is fraught with challenges.

Because of the decisions taken in the 1990s, the United Kingdom probably does not have the capacity to produce a new tactical nuclear weapon for at least a decade. The Atomic Weapons Establishment—the United Kingdom’s research agency responsible for the design and manufacture of nuclear warheads—will be focused on producing the new A21/Mk7 warhead for the Trident missile throughout the 2030s. Therefore, it could be into the 2040s before the United Kingdom could produce a warhead for an air-launched cruise missile.

More than 15 years is an extremely long time for the United Kingdom to remain without a tactical nuclear weapon capability—if indeed it is deemed that such a capability is required. Reintroducing an air-launched nuclear weapon system will also come with a substantial financial cost. Based on 1990s estimates, the costs of a new warhead and delivery system would be upwards of £10 billion (about $13.5 billion) today.

This is where the F-35A option—carrying US gravity bombs—enters the discussion. That would allow the Royal Air Force to resume tactical nuclear missions while saving the United Kingdom the cost of developing its own dedicated nuclear warhead and acquiring an air-launched cruise missile for its delivery. The United Kingdom already has slots in the F-35 aircraft production line, which can presumably be repurposed for F-35As for delivery in the early 2030s. Still, while less costly in financial terms, this option does little to bolster European security, not least because it does not lessen the reliance on the US weapon systems.

Broader considerations. The United Kingdom’s nuclear program is at a crossroads. It is politically notable that a Labour government is the one considering reconstituting the United Kingdom’s nuclear force by proposing billions of pounds in new investment and opening the door to introducing an air-launched tactical nuclear weapon. Although the measures announced in the review have been under development for several years—and therefore span multiple administrations—Labour governments have historically leaned toward nuclear disarmament or at least a lower profile for nuclear weapons and nuclear strategy.

While the security environment in Europe calls for more defense investment and a reevaluation of deterrence requirements, the United Kingdom should work carefully through what nuclear options are essential in close consultation with the United States and European allies. It may seem inexpensive and tempting to swap out the F-35B orderbook for the nuclear-capable F-35A to carry US nuclear weapons. But the United Kingdom should carefully evaluate whether this system would provide a meaningful additional capability over that already provided by its NATO allies.

Similarly, while the present geopolitical environment may favor the idea of using a French-provided air-launched cruise missile, careful thought should be given to whether the extra billions of investment are warranted, particularly given that such a capability would likely not be fielded until at least the 2040s. Any investment in new nuclear weapons capabilities is certain to come with significant financial, political, and diplomatic costs and risks.

As a shorter-term—and presumably much cheaper—option, the United Kingdom could reintroduce the sub-strategic capability for Trident, or clarify its status if it continues to be operational. The United Kingdom would then need to work through how to message and use the capability, given the risk of it being mistaken for a strategic system.

The British government will also have to manage the domestic and diplomatic fallout of giving nuclear forces greater prominence in the United Kingdom’s defense strategy. The decision contrasts sharply with the growing number of states that back the Treaty on the Prohibition of Nuclear Weapons, and it will almost certainly surface at the next Review Conference of the Nuclear Non-Proliferation Treaty (NPT), during which many non-nuclear-weapon states already accuse the treaty’s five recognized nuclear-weapon states of hypocrisy.

Meeting the NPT obligation to negotiate in good faith toward disarmament depends on the willingness of counterparties—something in short supply as Russia continues to wage war in Ukraine. The United Kingdom should keep pursuing risk-reduction and arms-control opportunities while it addresses the near-term deterrence requirements that Europe’s current security environment mandates.

Editor’s note: This article draws on recently declassified UK national archive materials relating to the United Kingdom’s decision to retire its air-launched tactical nuclear weapon in the 1990s, including AIR 8/3882, OPD ( N ): UK Nuclear Warhead Capability and the prospects for cooperation with France and the United States; DEFE 25/1016: UK Nuclear Warhead Capabilities; DEFE 25/678: National nuclear policy on UK sub strategic weapons TNWPSG; and DEFE 13/2247: Nuclear Weapons Policy: Polaris Improvement. A complete list of archive file references is available from the author.