In the 1930s, the Soviet Union found itself on the brink of war with Japan, whose imperial ambitions extended from Lake Baikal and Primorye to China and the European colonies in the South Seas. Fierce military battles on Khasan and Khalkhin Gol were a test of strength and a desire to determine the power of the northern neighbor. The crushing defeat in these battles and the military superiority of the USSR in the Far East forced the military leadership of the empire to turn to the South. Under these conditions, intelligence activities were crucial for making optimal and correct decisions. Thanks to the professionalism of intelligence officers, the USSR was able to timely transfer military formations to the Far East, and this kept Japan from attacking, which was bogged down at that time in a protracted war with China. The book of military historian E. A. Gorbunov, based on a huge array of documents, tells about the secret war in the Far East East in the 20-30s of the XX century.