Ukraine. Beware the semantic minefield

Barbara Tuchman in her epic The Guns of August recounts that in 1910 Major-General (later Field Marshal Sir) Henry Wilson discussed with French General Ferdinand Foch the possible size of any British force which might be committed in the event of a continental war.

‘What is the smallest British military force that would be of any practical assistance to you?’ Wilson asked.

Foch’s replied, ‘A single British soldier – and we will see to it that he is killed.’

In April 1982 the British politician Enoch Powell berated the Royal Marines on South Georgia and the Falklands for surrendering without suffering any fatalities following the Argentine invasion. He even suggested that a court martial should be convened.

These two stories explain the importance of the badly-named tripwire concept. The whole point is that the invader should be deterred by the risk of killing troops belonging to a powerful nation which would then retaliate. The second and implicit strand to the tripwire idea is that, to act as a deterrent, the offended nation must have credible military or economic resources to deliver a coherent retaliation.

In recent weeks Prime Minister Keir Starmer and French President Emmanuel Macron have been valiantly trying to create a credible European response in the event of Russia breaking any putative Ukraine peace deal reached between the United States and Russia (with or without the participation of Ukraine and other key European countries).

It is not entirely clear whether these efforts have been intended just to show robust intent to President Trump in order to bind him into NATO and persuade him to provide a backstop or whether there is a real intention to deploy such a force. The strong probability is the former. Why?

Firstly the UK and France know full well that Putin will never agree to having forces belonging to NATO countries inside Ukraine. And judging by comments of Steve Witkoff the US administration is unlikely to contest the point.

Secondly there are no European troops, other than the Ukrainians themselves, equipped and trained to fight the Russians. The new forms of warfare, from drones to glide bombs, are completely alien to armies which last fought (and lost to) Afghan tribesmen with their inventive use of roadside bombs, mobile phones and Honda 125cc scooters.

Thirdly, given the likelihood that Russia will attempt to conquer more of Ukraine (if it only wanted the east, it would not have launched its February 2022 attack from Belarus against Kyiv) the European force will face either military defeat or political humiliation.

Fourthly Europe is split between the northerners (particularly Poland, Finland, Sweden and the Baltic States) which feel the Russian threat intensely and the south (Spain, Portugal, Greece and Italy) which have gone along with wider Western policy but without much enthusiasm. There are also the pro-Russian countries, notably Hungary, Slovakia and possibly Austria. Finally there are the UK, France and Germany which have sounded tough but still regard the issue as one of foreign policy rather than national survival.

A Coalition of Declining Willpower

Each meeting of ‘the coalition of the willing’ has sent a message to Moscow (and Washington) that Europe still cannot get its act together. The idea of 100,000 troops forward deployed (and so acting as a tripwire) has gradually morphed into 20,000 providing ‘reassurance’ well back from the frontline. Most fatuous of all was Macron’s recent suggestion that it would be a ‘pacifist force’. Italy (Europe’s fourth most powerful country) has already opted out, adding to the impression that Georgia Meloni is more politically sympathetic to Trump than to Macron.

As well as becoming smaller with each meeting, the proposed European force is to be placed further and further from the front line. With no danger of its soldiers dying from a Russian incursion it is therefore no longer a tripwire. This raises the question of whether a force of European (or any other) soldiers based in Lviv or even Dnipro provides any assurance at all.

For President Zelensky watching events from Kyiv the important thing is to focus less on the spaghetti soup of words than on the intentions. Guarantees, backstops, tripwires, peacekeeping and reassurance are becoming hopelessly confused. Zelensky will not need reminding that the Budapest Memorandum of 1994 spoke of ‘security assurances’ (all broken) and not of guarantees.

Poland (and Romania) should also advise him about the word ‘guarantee’. Under pressure from France, Neville Chamberlain issued a guarantee to Poland and Romania following Hitler’s invasion of Czechoslovakia in March 1938, which was a clear breach of the Munich agreement only six months before. But the guarantee was useless to Poland. Britain honoured the guarantee but only to declare war on Germany, but without any hope of saving Poland itself.

So if the words are unreliable, what can Zelensky cling on to? In normal times Article 5 of the NATO Treaty would be the gold standard guarantee because it comes with United States military power and ultimately nuclear capability. But with President Trump in the White House even Article 5 can no longer be trusted. President Macron’s alleged thoughts about whether to make the French Force de Frappe available to NATO should be taken with a pinch of salt. Equally there is no chance that Britain would use its nuclear deterrent to prevent a Russian conquest of Ukraine.

Credible Defences of a Peace in Ukraine

The International Institute of Strategic Studies has produced a paper A European Reassurance Force for Ukraine: Options and Challenges on potential European force deployments with three options labelled small, medium and large. However its focus too is on capability rather than intention. What really matters is the political will in major European capitals which needs to be enshrined in the Rules of Engagement.

This brings us back to the only credible option. Any immediate opposition to future Russian aggression will have to be provided by the Ukrainians themselves stationed close to the front line. The backstop will have to be provided by Britain, France and possibly Poland, Sweden and Finland. If the US is willing to join then that would be a major bonus, but cannot be relied upon. The key prior agreement must be that any Russian aggression across the ceasefire line would prompt a forceful kinetic response by Western air power.

Of course, the likelihood is that Putin would game the system. He would engineer a scenario whereby a shallow Russian incursion might appear justified due to specific conditions on the ground or in response to a perceived or fabricated Ukrainian breach of the ceasefire terms. There would be hesitation and uncertainty in one or more of London, Paris, Warsaw, Stockholm and Helsinki. Furthermore any European retaliation would be limited to the Russian incursion itself without attacks deep into Russian territory both out of concern about unsuppressed anti-aircraft defences and at provoking a wider war – or even a demand by Washington to cease and desist.

Meanwhile Europe must beware of Russian suggestions that a peacekeeping force should be supplied by the Global South. This may sound unthreatening but any such force would severely limit the ability of European air forces to deliver backstop airstrikes against Russian breaches of any ceasefire. There would be inevitable claims from Brasilia or Islamabad or Pretoria that these were endangering peacekeeping forces. This is, of course, exactly what the Russians intend.

And yet the bigger danger is that there is no peace agreement and that the war continues with Ukraine continuing to lose ground.

© Tim Willasey-Wilsey, 2025, published by RUSI with permission of the authors.

The views expressed in this Commentary are the authors', and do not represent those of RUSI or any other institution.

For terms of use, see Website Terms and Conditions of Use.

Have an idea for a Commentary you'd like to write for us? Send a short pitch to commentaries@rusi.org and we'll get back to you if it fits into our research interests. View full guidelines for contributors.