Major General Vitaly Nikolsky in his book for the first time spoke in detail about the activities of operational human intelligence, to which he devoted most of his work in the GRU. At first, Nikolsky worked as an operational agent in the central apparatus of the intelligence department of the General Staff of the Red Army, where he served from 1938 to 1941, carried out tasks at the front in the first months of the Great Patriotic War, creating reconnaissance groups in cities that could be captured by the enemy, and worked as an agent in the intelligence departments of the 10th army, western and Stalingrad fronts (1941–1943), then again in the central apparatus of the GRU (1943–1947). In 1944–1945 trained scouts to work behind enemy lines in the Moscow Silver Forest. Vitaly Alexandrovich in his “notes” names and describes the activities of many heroes of the “invisible front”, most of whom he knew personally.