Traditionally, the crises affecting the EU have been characterized either as “failures,” where vulnerabilities in capacity and institutional design come to light, or, more recently, as “attacks,” indicating a direct assault on the Union’s foundational values and interests. However, we claim that the Russo-Ukrainian War transcends this conventional dichotomy by combining both characteristics simultaneously. On one hand, Russia’s aggression intensifies demands for moral solidarity and existential defense, reflecting collective values. On the other hand, the war highlights important capacity gaps within the EU’s energy infrastructure, defense capabilities, and enforcement of sanctions—a set of capacity shortfalls that underscore failure-type crisis characteristics. By adopting an inductive, theory-building approach, we develop a dual-path framework to explain how moral mobilization and capacity-building efforts interact in shaping the EU’s functional boundaries. While moral urgency accelerates consensus around far-reaching measures—including costly sanctions and military aid—capacity-building reforms are necessary to sustain this alignment by remedying underlying vulnerabilities. Through a detailed case study of the EU’s policy and institutional realignments in response to the war, our process tracing challenges the assumption that crises can exclusively be either failure- or attack-driven. We argue instead that some crises can simultaneously stimulate community-building while requiring tangible capacity-building. Ultimately, this article refines crisis-driven integration theories and offers insights into how external attacks can decisively affect European integration through complementary causal pathways, taking seriously the possibility of equifinality.