In early March 2025 Prime Minister Donald Tusk of Poland called for his country to have access to nuclear weapons and vowed to increase massively the size of its army. Within a fortnight Poland and the Baltic states announced their intention to withdraw from the Ottawa Convention banning anti-personnel land mines, sending another clear message to their friends and likely adversaries. The world is a dangerous place, they don’t trust their near neighbour to the east, and they are no longer convinced that their principal post-Cold War ally, the United States, will provide a reliable security backstop for the sovereign states along NATO’s European front line. By withdrawing from the Convention they are joining Russia, the US, China and other non-signatories and effectively declaring their willingness to lay defensive minefields in their own territory.
Just a day later the European Commission published a White Paper on rearming the continent by 2030.
Why are these things happening? The answer seems clear and is all the more pressing given President Donald Trump’s emerging grand strategy: they are an attempt to deter Russia from further military adventurism in Europe as it recovers, reconstitutes and pushes its luck after the long, hard slog in Ukraine.
But are such moves really a contribution to deterrence or could they be seen as alarming escalation fuelling an unnecessary arms race at a time of great geopolitical uncertainty? To us, deterrence and escalation are not mutually exclusive concepts. We argue that carefully considered and realistic escalation management can be an effective tool in any deterrence strategy. This is not the false promise of the mythical ‘escalate to de-escalate’ approach too often assumed to be part of Russian doctrine. Rather, it is about being able to offer choice to political leaders and military planners whilst simultaneously putting pressure on an adversary’s decision-making abilities.
The idea of an ‘escalation ladder’ was first mooted by Herman Kahn in the 1960s, addressing the reality of the Cold War at that time. In its simplest form the ladder is a metaphor for a spectrum of possible actions of ever-increasing seriousness with each step taken. Country A does x, and country B responds with x+1 and so on until nuclear annihilation is reached. However, the more simplistic the metaphor, the more misleading it can be, as Sir Lawrence Freedman has pointed out in connection with the Russo-Ukraine war. A more nuanced understanding of the ladder can introduce concepts of vertical (the simplistic), horizontal (responses in other domains or sectors), precise (through targeting or sequencing) or imprecise escalation, each giving the ability to move closer to mutually assured destruction or back to business-as-usual co-existence.
We wonder if a better metaphor for the escalation ladder is the Penrose Staircase. Often seen in artworks and optical puzzles, the staircase is seemingly impossible but somehow works in the mind. A two-dimensional image, the steps appear to be constantly rising as they turn, only to be descending and returning the climber to their original position.
Creative, dynamic movement on the ladder is more useful in deterrence than predictable, fixed steps.
That dynamism can only happen, however, if the staircase or ladder has a sufficient number of steps or rungs. Steps and rungs can be made and added through new capabilities or policies, or they can be broken and removed by disinvesting or retiring a capability or disengaging from an alliance or partnership. During the Cold War the blunt instrument of massive retaliation doctrine gave way to the idea of flexible response as new technology, greater precision and a clearer, if still dangerous, era of geopolitical alignment made it possible. But after the Cold War the so-called peace dividend allowed some countries, including the UK, the space to disinvest and, in effect, remove rungs from the ladder. Of course, this was sustainable for a quarter of a century, especially when the United States acted as Europe’s guarantor, but it also left a ‘dangerous gap’ in European NATO’s strategic posture. Countries such as the UK no longer have the option of flexible response and rely instead on massive retaliation for their deterrence. There is nothing in the cupboard politically or militarily between limited but destructive conventional war and the use of strategic nuclear weapons such as Trident.
This was not always the case as the UK maintained a sub-strategic nuclear capability until 1998, by which time all nuclear depth charges and free-fall bombs (various types of the WE 177 bomb) were decommissioned. Sub-strategic – or tactical – nuclear weapons are generally described as short-range or theatre level. NATO’s 1991 Strategic Concept had confirmed a requirement for sub-strategic nuclear weapons, though at a much-reduced level. In that context, the UK decommissioned 80% of its WE177 gravity bombs by 1996 and the 1998 Strategic Defence Review withdrew the rest from service. It did, however, argue that a sub-strategic capability was still required and designated Trident to take on this role.
While Trident was initially deployed as both a strategic and sub-strategic weapon system, that duality is no longer part of defence rhetoric and reference to the term ‘sub-strategic’ ceased altogether after 2006. As Professor Sir Lawrence Freedman pointed out: ‘for the UK to use a Trident missile in response poses awkward operational issues, especially with regard to assuring that an SSBN will still have missiles available for “strategic” use.’ In any case, use of Trident in this role risks inadvertent escalation. How would an adversary know whether a missile launched from a submarine is intended for short-range, tactical use on the battlefield or is part of a huge existential attack?
Some commentators are starting to suggest that reinvesting in some form of sub-strategic or tactical nuclear weapons systems is once again becoming necessary for the UK. Others are suggesting that a reinvigorated partnership with France, a country which retained its tactical nuclear weapons, could be the way ahead. If the UK did develop a sub-strategic capability, it could share this with countries like Poland, in the same way that the US currently shares its tactical nuclear weapons with Belgium, Germany, Italy, the Netherlands and Turkey.
And we should remember that this is nothing new. Mechanisms existed in the past to facilitate Anglo-French nuclear cooperation, such as a Joint Nuclear Commission in the early 1990s, a body which went into abeyance but was never formally disestablished. The Sunak government made reference to it in talks with France in 2023, and the ongoing Strategic Defence and National Security Reviews afford an opportunity to revisit the ideas in 2025.
Creating a new step on the ladder could assist in de-escalation. We are not arguing that the only option is sub-strategic nuclear strike, but we do believe that the time for that conversation has arrived.
