Russia’s war in Ukraine is violating the rules-based international order and poses a significant threat to European security. The EU and NATO have responded by taking coordinated action. The measures taken have varied from unprecedented sanctions on Russia to assisting Ukraine with the delivery of arms and ammunition. The war in Ukraine has led to an even stronger focus on collective defence, which was already put in motion after Russia’s annexation of Crimea in 2014. Furthermore, the European security architecture has witnessed a significant change with Finland (and later this year Sweden) joining the North Atlantic Alliance. At the Vilnius Summit (11-12 July 2023), NATO has taken new decisions to strengthen its deterrence and defence posture.