The writer is deputy director-general of the Royal United Services Institute think-tank
Avril Haines, US director of national intelligence, said last week she assessed the likelihood of nuclear conflict to be low, indicating that Vladimir Putin would probably only authorize the use of nuclear weapons if he perceived an existential threat to the Russian state.
But what would qualify as an “existential threat”? Most obvious would be a direct clash of arms with the US. The past seven decades have seen multiple military interventions by both powers – from the Korean war through to the current war in Ukraine – often offset by large-scale weapons deliveries to the other’s opponents. But none of these wars have involved any direct fire between US and Soviet (now Russian) armed forces. This mutual restraint is one of the main reasons why no nuclear weapon has been used since 1945.
Some commentators are now urging NATO to call Russia’s bluff and use military force for defined humanitarian purposes, for example to break the Odesa blockade and allow Ukrainian grain to reach global markets. Yet, once NATO and Russia have crossed the threshold into military conflict, it would be hard to avoid escalation. Moscow’s strength has been eroded by combat losses. In a conflict with NATO, many of its key military assets, including command centers and bases, could come under threat within days. Russia’s strategic nightmare – a US pre-emptive attack on its nuclear retaliatory potential – would look uncomfortably realistic.
Some say Putin’s threats of nuclear action are evidence he has lost touch with reality. Yet if the US believes a nuclear threat is credible, it would have to take such a risk seriously. Given the US is at lower risk than Russia from conventional military invasion, the Kremlin might think it holds the advantage in a game of nuclear chicken. A shared fear of this scenario explains why mutual restraint has held up until now.
Another possible trigger would be Ukrainian military advances on the battlefield which threaten Russian territory. Already, successful Ukrainian counteroffensives are bringing new opportunities to launch limited cross-border attacks – for example with artillery or special force teams – to destroy bridges, railheads, storage sites and air bases within the areas around Belgorod. Fortunately, since Ukraine has no desire to occupy this area, it is hard to see this as an existential threat.
If there is an escalatory risk, it is more likely to come in territories which Ukraine lost in 2014, and which Kyiv is now committed to liberating. Here it is important to draw a clear distinction between the Donbas and Crimea.
In the Donbas, Moscow had (until February) recognized the two breakaway republics as nominally belonging to Ukraine. Crimea is in a different position. Until its transfer to the Ukrainian Soviet Socialist Republic in 1954, it had been part of the Russian Empire for nearly two centuries. As the home of Putin’s Black Sea fleet, the prospect of losing the peninsula in battle would be seen as a fundamental challenge to Russia’s own territorial integrity.
In the absence of a ceasefire, however, Ukrainian forces will be keen to prevent Crimea becoming a sanctuary from which the Kremlin can resupply its forces in the rest of Ukraine. Supplies of longer-range weapon systems from western states are opening up new targeting possibilities. The Kerch bridge could be a tempting prize, as could Russia’s naval base in Sevastopol.
If attacks on these targets were perceived as precursors to a full-scale Crimean invasion, they could increase the risk of nuclear escalation. This is one of the most concerning scenarios. Putin was at pains to emphasize this risk in the months before the invasion.
Putin’s spurious nuclear threats of recent months have begun to lose their potency. In order to be credible, Russia would have to make explicit that an invasion of Crimea constituted a red line. Faced with losing Crimea, Putin might consider this a worthwhile gamble, believing Ukraine (with western encouragement) would blink first. This would be a moment of extreme peril.
A nuclear crisis would make it easier for leaders to make difficult compromises. Provided the war ended and the Black Sea blockade was lifted, Ukraine might leave Crimea to the Russians for now. Putin meanwhile could mitigate the humiliation of a failed invasion by arguing Russia’s strategic arsenal had successfully deterred NATO. This could be enough for both sides to avoid the worst outcome of all.
In doing so, they would have reinforced the conclusion, reiterated by all five recognized nuclear-weapon states in a joint statement in January, that “a nuclear war can never be won and must never be fought”.