Between the summer of 1937 and November 1938, the Stalinist regime arrested over 1.5 million people for "counterrevolutionary" and "anti-Soviet" activity and either summarily executed or exiled them to the Gulag. While we now know a great deal about the experience of victims of the Great Terror, we know almost nothing about the lower- and middle-level Narodnyi Komissariat Vnutrennikh Del (NKVD), or secret police, cadres who carried out Stalin's murderous...