The use of terror has been a characteristic of Russia from the days of the Tsars. The Okhrana was the oppressive police force of the Romanovs. Then came the Cheka, the OGPU, SMERSH and the NKVD - organisations that used terror to control every aspect of military and civilian life. So, during the Great Patriotic War , Soviet soldiers and citizens feared not only the Germans but the tentacles of the secret police. To maintain iron discipline in the face of the German onslaught, to root out dissent and defeatism and to counter the threat of treachery and collaboration, the agents of the NKVD waged a merciless campaign against their own people. The full extent of this extraordinary wartime operation is told in Rupert Butler's compelling study.