This book is dedicated to the operation of the Soviet-Mongolian troops against the Japanese aggressors who encroached on the territory of the Mongolian People's Republic. The battles, which lasted from May 11 to September 16, 1939, ended in the complete defeat of the Japanese troops, which convincingly demonstrated the superiority of the Red Army in tactical terms and in the technical equipment of the armed forces. The work shows Soviet and Japanese views on various military events, and summarizes the experience of using rifle troops, tanks and aviation of the warring parties. The book contains 108 photographs, 6 diagrams. 12 color illustrations.