In the closing weeks of World War II, advancing Allied armies uncovered the horror of the Nazi concentration camps. The first camp to be liberated in western Germany was Buchenwald, on 11th April 1945. Within days, a team of German-speaking intelligence officers from the US Army was dispatched to Buchenwald to interview the prisoners there. In the short time available to them before the inmates' final release, the team prepared a report to be used against the Nazis in future war-crimes trials. Nowhere else was such a systematic effort made to talk with prisoners and record their first-hand...