Russia’s war on Ukraine has generated a new chain of insecurities in Europe: energy and food crises, new migration flows from Ukraine, Belarus and Russia, military threats sharpened by Russia’s invasion are triggering a spatial and territorial reshuffling of Europe’s Eastern flank. In this context, regional dynamics within and across the Eastern frontiers of Europe have undergone a succession of path-breaking transformations ranging from overt support to the Ukrainian war effort to decoupling from the Russian economy and an unprecedented boost to expanding the European Union’s security architecture. However, one of the most important effects of the war is the growing gap between two regional models which might be dubbed normative (Europeanization within the EU- and NATO-led European normative space) and post-colonial (exemplified by different Russia-centric projects within the post-Soviet space). The original contribution of this special issue is to address the conceptual connections between security, borders and national identity to discuss the evolving European landscape. While we do not explore the military side of the war, we focus on the nexus of (in)security and bordering practices to capture how a combination of geopolitical changes, economic dynamics and human dimensions of war has created new borders and reshaped existing ones.