Historians not without reason call the Second World War "The Great Battle of Intelligence." The role of special services during the war can hardly be overestimated, because the number of participants in hostilities on the "invisible front" was in the hundreds of thousands. In the USSR, its activities were headed by two departments. Foreign policy intelligence PSU NKVD and military intelligence GRU. They influenced each other, and often competed with each other with unprecedented success, providing the Soviet leadership with an overwhelming intelligence advantage over their opponents.