In June 1941 Hitler launched Operation Barbarossa, sending roughly three million soldiers across the Soviet border in the largest invasion force assembled in history. This episode traces how the plan took shape inside German high command, the speed of the early advances toward Leningrad, Moscow, and Kiev, and the miscalculations about Soviet resistance and Russian winter that turned a campaign meant to end in weeks into a war of attrition. Archival footage of tank columns, burning villages, and Red Army retreats sits alongside expert commentary explaining the ideological dimension of the invasion, framed by the Nazi leadership as a war of extermination rather than conventional conquest. The film sets Barbarossa within the wider collision of eastern and western wars that fused into the Second World War, showing how one campaign reshaped alliances, casualty counts, and the postwar map of Europe. It is part of Timeline's Price of Empire strand, using period film and historian interviews rather than dramatization to reconstruct the decision-making and the consequences.