While the debate surrounding the promise and limits of alternative European nuclear umbrellas has recurred for decades whenever transatlantic tensions arise, the urgency has grown against the backdrop of Russia’s war in Ukraine and uncertainty about U.S. political commitment. This is less about replacing the U.S. nuclear umbrella than about exploring complementary models, ranging from strengthening the UK-French deterrent partnership under the new Northwood Declaration to more speculative ideas like building a European nuclear submarine or creating collective control mechanisms. However, proliferation in Europe is unrealistic unless the NPT and NATO’s Washington Treaty collapse, which remains an unlikely scenario. The Northwood Declaration marked a turning point because, for the first time, France indicated readiness to coordinate nuclear deterrence with another state, and the UK signalled willingness to do so beyond its U.S. relationship. Together, this creates the potential foundation of a European pivot in deterrence without directly mimicking U.S. force posture.
On plausibility, opinions are more divided. One school argues that the UK and French nuclear arsenals, if better coordinated and perhaps modestly expanded, could provide reassurance and deterrence tailored to Europe’s needs. In this model, burden-sharing might take the form of financial contributions, intelligence cooperation, or hosting arrangements from non-nuclear allies. Another school argues that European deterrence remains hampered by a “numbers problem”: neither the UK nor France possess sufficient warheads, tactical systems, or escalation management tools to replicate the credibility of U.S. extended deterrence. Whereas the U.S. offers a wide ladder of escalation (from tactical to strategic options), Europe has a more constrained set of responses, raising doubts about its ability to deter Russia effectively. Credibility is both a deterrence issue, where Russia decides if it is deterred by NATO, and a reassurance issue, where European allies such as Poland or the Baltics judge whether they feel protected. This dual perspective complicates any purely European model.
There are also interesting questions that arise regarding the conception deterrence. On one hand, deterrence requires damage equivalent to the stakes at risk, implying that UK and French forces would need to grow significantly to be credible against Russia. On another, deterrence hinges on inflicting intrinsically unacceptable damage, regardless of numbers, and that adversary perceptions matter more than strict parity. Cold War-era U.S. frameworks, which stressed counterforce and damage limitation, should not dictate European strategies indefinitely. Instead, deterrence credibility today requires adaptable plans, flexible response options, and political resolve rather than mirroring U.S. nuclear doctrines.
New capabilities fall into three principal areas:
- Europe requires more flexible and scalable conventional forces to strengthen escalation management and raise costs for Russia before reaching nuclear thresholds.
- Modest increases in tactical nuclear capabilities and delivery systems could enhance credibility, though such steps would take time and face political hurdles.
- Non-nuclear contributions (such as intelligence sharing, hosting arrangements, and permanent protection of nuclear assets) are critical areas where non-nuclear allies could bolster deterrence. Declaratory policy was another gap identified: unlike the U.S. Nuclear Posture Review, neither the UK nor France have comprehensive public doctrines, limiting transparency and reassurance.
The Northwood Declaration provides a meaningful step toward Franco-British coordination and demonstrates that complementary models are possible, but Europe still faces structural challenges: insufficient numbers, limited escalation management tools, and political uncertainties about future leadership. For now, the priority should be strengthening transatlantic deterrence, modernising conventional capabilities, and deepening UK-French cooperation, while leaving space for contingency planning should U.S. commitments weaken.