The book examines the most important aspects of the daily work of military counterintelligence officers - special departments of the NKVD of the USSR and the Main Counterintelligence Directorate of SMERSH of the USSR NPO during the Great Patriotic War and in the post-war period. The activities of honest, decent, courageous military counterintelligence operatives in their struggle on an invisible front are shown. In a secret war with the enemy, both the front-line and internal army Chekists were assisted by all citizens of the multinational Soviet Union. They understood that criminal peoples do not exist, there are only criminals in their mass. Military counterintelligence officers fought with them. The book is intended for a wide range of readers.