This week marks the fourth anniversary of the beginning of the Russia–Ukraine war. On Feb. 24, 2022, Russian President Vladimir Putin launched a “special military operation” against Ukraine. Four years later, the “military operation” continues as the largest conventional war in Europe since World War II. Even now, the war’s end remains uncertain. The latest trilateral talks in Geneva among the United States, Russia, and Ukraine ended without success, once again failing to reach consensus on key settlement issues such as territorial sovereignty and the postwar security framework. In Russia and Ukraine — and worldwide — widespread war fatigue is accompanied by anxiety over the war’s eventual outcome. The war has reaffirmed a number of familiar geopolitical lessons. It has also introduced new lessons for policymakers facing contemporary geopolitical challenges. Although “learn from history” is a cliche that is often unfulfilled or misapplied, commemorating past and present military conflicts should challenge us to better understand the origins, prevention and termina