These horrors were not accidents. At the Yalta summit in February 1945, British Prime Minister Winston Churchill and Foreign Secretary Anthony Eden had accepted Stalin’s demand that every Soviet citizen in Allied hands be repatriated, willing or not. The Americans, after initial resistance, fell in line. As part of Operation Keelhaul and related handovers, nearly 3 million men, women, and children were forced across the lines. To Stalin, they were all traitors. Many were executed on the spot; countless others vanished into the gulag. In Murmansk, witnesses described repatriated Soviet prisoners being herded into warehouses, followed by the rattle of...