Americans call the Second World War “the Good War.” But before it even began, America’s ally Stalin had killed millions of his own citizens—and kept killing them during and after the war. Before Hitler was defeated, he had murdered six million Jews and nearly as many other Europeans. At war’s end, German and Soviet killing sites fell behind the Iron Curtain, leaving the history of mass killing in darkness. Assiduously researched, deeply humane, and utterly definitive, Bloodlands is a new kind of European history, presenting the mass murders committed by the Nazi and Stalinist regimes as two aspects of a single story.