Averting acute escalation in Russia's war against Ukraine

Abstract Russia's full-scale war against Ukraine and western military support in its defence have threatened to escalate to the use of nuclear weapons or a clash between Russia and NATO. Western fears regarding these risks have been stoked by Russia's nuclear threats and intimidation over its ‘red lines’. Yet during 2022–25 western powers gradually lifted restrictions on their military deliveries to Ukraine in this unprecedented large European war fought by a nuclear power. This article argues that the effort to avert and mitigate dangerous escalation during the first three years of great power confrontation around the war combined strategic threats and strategic restraint. The policies adopted are consistent with strategic studies theory on threats and the manipulation of risk in nuclear deterrence. However, the article argues that deterrence has coexisted with policies of restraint by western states, in the form of ad hoc and tacit ‘ground rules’ to mitigate the risk of escalation. Such informal rules are inferred from the diplomatic and discursive signalling between the western powers, Ukraine and Russia. Facing down Russian threats has been essential for deterrence. Yet overcautious restraints on western military support for Ukraine enabled Russia to further subvert the Ukrainian state and the European security order, which leaves a range of escalation risks in the medium term.