Andrew M Dorman examines three key nuclear dilemmas that the UK must face, especially in light of the US’ declining role in European security.

Although the 2025 Strategic Defence Review released at the beginning of June alluded to the UK acquiring some of the F-35A variant of the Joint Strike Fighter, confirmation was only made just before the NATO summit.

Yet, the Downing Street press release outlining plans to acquire 12 new F-35A fighter jets and to join NATO’s dual capable aircraft nuclear mission received remarkably little attention. More importantly, it did not address the nuclear dilemmas that currently lie before the United Kingdom and, by implication, its European allies. Instead, the government has continued to keep its head in the sand.

In practice the UK’s F-35A decision has three immediate implications. First, it reaffirms NATO as a nuclear alliance. Currently, two of three nuclear states in NATO – the UK and US – commit nuclear forces to NATO’s deterrent posture each based on a small force of nuclear-powered submarines equipped with the Trident nuclear armed ballistic missile. In addition, the US maintains other nuclear capabilities which it can declare to NATO. France has chosen not to commit any of its nuclear forces to NATO.

To supplement this, five NATO members – Italy, Germany, Turkey, Belgium, and the Netherlands – maintain a small number of aircraft that are equipped for and trained to carry US supplied freefall nuclear bombs (B-61) under a dual-key arrangement.  This force which the UK is proposing to join, provides NATO with a nuclear option that is significantly smaller than that provided by the US and UK Trident ballistic missiles and thus provides an earlier step or rung in a ladder of escalation.

However, critics point out that this NATO force remains entirely dependent on the US releasing the B-61 nuclear bombs in a crisis. This cannot be guaranteed, especially with Donald Trump as president.

Second, proponents argue that Britain’s involvement makes the force more militarily credible. The assumption is that Britain would be more likely to accede to a NATO request to use nuclear armed F-35As because it possesses its own nuclear deterrent and would, therefore, be less likely to suffer a nuclear response.

Critics argue that as a freefall nuclear bomb the requirement to fly close to the target makes the F-35A unduly vulnerable to enemy action thus undermining its credibility. Here they point out that the French national equivalent involves a medium range air delivered cruise missile that allows the carrying aircraft to fire the missile some way short of the target.

Third, in acquiring F-35As and training for the nuclear role it will allow the Royal Air Force (RAF) to re-learn a role that it gave up in 1998. Thus, it potentially provides a stepping stone toward the re-establishment of a second independent nuclear capability similar to France.

However, critics have pointed to the extra costs associated with acquiring a different variant of the F-35, the inability of the RAF to refuel the F-35A at present, the modest number of aircraft being acquired and the slow timeframe for their delivery.

What the F-35A announcement does not do is address the three nuclear quandaries currently confronting the British government and non-US NATO allies more generally.

First, there remains a significant question mark over the commitment of the US to Article V and particularly the US nuclear guarantee. This raises the question of whether the UK as NATO’s only other nuclear guarantor needs to enlarge its capabilities to fill the US vacuum?

If so, then the UK will need to consider acquiring more than 4 Dreadnought-class ballistic missile submarines to replace both the UK’s current Trident boats and their US counterparts that are committed to NATO. Such a change will take a considerable amount of time given how long it takes to build such submarines and a significant expansion in the UK’s production capacity. Moreover, it also has implications for the next generation of conventionally armed nuclear-powered submarines that the UK is acquiring in partnership with Australia. Building two or more additional Dreadnought-class ballistic missile submarines would mean either delaying the start of construction of the UK-Australian conventional submarines or constructing additional build capacity at significant additional cost.

Second, in light of Vladimir Putin’s threat to use ‘tactical’ nuclear weapons and doubts surrounding the US, the UK might have to consider the development of further nuclear options to provide an additional rung in the NATO ladder of escalation and add to deterrence. This would require the resurrection of a capability that was relinquished in 1998. In whatever form this raises challenging questions in terms of time frame, capacity, cost and form of capability for the British government.

Third, is the question of China. Previous defence reviews have spoken of deterring China in the conventional area but were noticeably silent on the nuclear domain. The Strategic Defence Review sought to identify China as both as a threat and an opportunity. All have spoken of the conventional deterrence of China and have been noticeably silent on the nuclear side.

Russia is being deterred by the current form of the ‘Moscow Criterion’ – the ability to threaten the destruction of a number of Russian cities including Moscow and St Petersburg. What has not been debated, at least in the public domain, is whether there is or needs to be an equivalent ‘Beijing Criterion’.

These three unanswered quandaries have been left hanging in the latest defence review. If the answer to any, or all of them, is that the UK must respond, then this will have a profound impact on where defence spending is focused.

What this will mean for investment on the UK’s conventional capabilities, increasing UK resilience and the potential overall size of the defence budget remain unclear. All make the case for a very rapid move towards NATO’s new 3.5 / 5% GDP target which is not good news for the Treasury, especially after the compromises on welfare reforms that had to be made recently.

Perhaps even more importantly, these three dilemmas are not really being considered in the public space, probably because they are simply too difficult.

By Andrew Dorman, Professor of International Security, King’s College London.