A recent report by the Royal United Services Institute (Rusi) argues that within the next decade, Russian missile defences may be able to stop a British and French nuclear strike.
Russia’s strategic missile defences remain extremely limited in number and are concentrated largely around Moscow
Britain is right to be concerned about this. After all, nuclear weapons are the ultimate guarantor of a country’s safety and territorial integrity. It is right, therefore, that we remain vigilant to any attempts to neutralise them. That said, the current state of Russia’s ballistic missile defences, and its likely future advancements, show little sign that a major shift in the nuclear balance of power in Europe is underway.
Stopping any type of ballistic missile is a difficult task. Ballistic missiles fly towards their targets from high altitude and at high speed. A defender has to find, track, and successfully hit them with expensive and highly-optimised interceptors. This has sometimes been compared to shooting a bullet with another bullet – only more difficult.
These challenges are demonstrated almost daily in Ukraine, which struggles to cope with the large number of Russian short- and medium-range ballistic missiles launched against the country every day.
Compared to intercepting shorter-range ballistic missiles, however, defending against intercontinental ballistic missiles (ICBMs) – such as those used by Britain’s Trident nuclear programme – are a different and far more severe challenge. Incoming ICBM warheads approach their targets from outside the atmosphere and at much higher speeds. This means you need significantly better sensor, tracking and guidance systems to stop them.
In principle, Russia has access to two types of ballistic missile defence systems that could feasibly intercept British nuclear warheads: its stationary A-135 missile defence system deployed around Moscow and the road-mobile S-500.
The A-135 is believed to field around 60 to 70 nuclear-armed interceptors intended to destroy incoming nuclear warheads with a nuclear blast before they can reach Moscow. The system is currently being transitioned to the A-235, which is expected to replace nuclear interceptors with ‘hit-to-kill’ interceptors that collide directly with the incoming target.
In 2021, Russia also signed a contract for ten S-500 units. Deliveries were originally expected to begin in 2022, though the programme has faced significant delays, likely due to the war in Ukraine, which forced Russia to reprioritise resources toward other, higher-priority missile defence capabilities. As of 2026, only one S-500 unit is believed to be operational.
As such, Russia’s strategic missile defences remain extremely limited in number and are concentrated largely around Moscow, leaving other population centres, notably St Petersburg, uncovered.
Russian strategic missile defences also face severe technical limitations. Compared to American missile defence systems, Russian interceptor technology appears to suffer from reduced performance and accuracy. This constrains the ability of Russian interceptors to stop incoming nuclear warheads outside the atmosphere, which is necessary for effective defence against an ICBM threat.
The Americans have traditionally assumed that even for their better strategic missile defence systems (such as those deployed in California and Alaska) at least three interceptors are needed for each inoming nuclear warhead. Given that the performance of Russia’s defence systems is likely significantly lower, substantially more interceptors per target would be required to achieve a comparable outcome.
The United Kingdom is commonly estimated to retain a nuclear arsenal of roughly 225 warheads, of which about 120 are assumed to be operationally available at any given time. Today and in the near term, Russia could likely intercept only a small fraction of these and could not comprehensively defend against a large-scale British retaliatory strike.
This does not imply that British decision makers can afford to be complacent. Technological shocks – developments that alter the balance of power over a relatively short period – remain possible. For the United Kingdom, however, the more immediate nuclear challenge is less about Russian strategic missile defence and more about the British nuclear submarine fleet.
This challenge comes from ageing Vanguard-class submarine hulls, prolonged refit cycles, and limited dockyard capacity, which reduce the number of deployable submarines at any given time. Extended maintenance delays also lead to submarines embarking on unusually long deterrent patrols. This accelerates the material wear of the submarines and places immense strain on their crews. Manpower shortages and industrial bottlenecks further undermine Trident’s readiness.
Overall, this has contributed to an increasingly fragile at-sea deterrent that, together with other external factors, raises difficult questions about the future credibility of the British nuclear deterrent.
Investments to maintain a credible nuclear deterrent are therefore necessary – not only for the United Kingdom but for Europe, which will increasingly rely on British nuclear weapons for its security.
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