Russia's invasion of Ukraine, initiated on February 24, 2022, is among the most—if not the most—significant shocks to the global order since World War II. This piece assesses the stakes of the invasion for the core principles that lie at the heart of contemporary international law and the world order that it has helped to create. We argue, relying in part on the other contributions to the October 2022 agora on Ukraine in the American Journal of International Law, that however this war ends, it will reshape, in ways large and small, the world we all inhabit.