The book is devoted to the activities of Japanese military intelligence against the Russian Empire and Soviet Russia in 1874-1922. The work assesses the effectiveness of the activities of Japanese military intelligence and domestic counterintelligence, traces the influence of information from special bodies of the two countries on the adoption of the most important decisions in the field of foreign policy and defense. The events of the Russo-Japanese (1904-1905) and Civil (1918-1922) wars in the context of intelligence activities are examined in detail. The book was written on the basis of a comparative analysis of documents from Russian and Japanese archives with the involvement of research from Russia, Japan, the USA and Poland. All documents are introduced into scientific circulation for the first time.