Introduction: the 2022 Russian invasion of Ukraine and the re-making of the European security order

Russia’s increasing aggression, the return of great power rivalry, and eventually the 2022 invasion of Ukraine have brought back questions about Europe's security order. In response to Russia’s war against Ukraine, both states and security organisations–the EU and NATO–have implemented new policies to address Europe’s vulnerabilities and to support Ukraine politically and militarily. This introduction to this special issue serves two purposes. First, it explores the war, examining debates on the origins of the war and tracing the evolution of the war to summer 2025. Second, it places the war in the context of longer-term debates on European security order, arguing that a largely liberal European security order was consolidated after the Cold War, but that relations between Russia and the West remained partly characterised by more traditional realist dynamics. The articles in this special issue explore how far and in what ways Russia’s full-scale war against Ukraine since 2022 can be viewed as a critical juncture for Europe’s security order, resulting in major and lasting changes to that order. Taken together, the articles highlight that while February 2022 may have been a turning point, the impacts of the war vary in important ways across states and institutions.