Abstract: The main mission of the Imperial government in the early XX century consisted in ensuring foreign policy security of the eastern trans-border region. The construction of Trans-Siberian Railway, defeat in the Russo-Japanese War, and the beginning of the World War I in 1914 severely affected the geopolitical situation in Trans-Baikal Region. Thus, in the conditions of the outbreak of the World War I, the question of uninterrupted supply of weapons, food, etc. along the railway line from the east to the center of the country was critical. All this turned Trans-Baikal Region into a special zone for the foreign intelligence agents. Leaning on the materials of the State Archive of Irkutsk Region, description is given to the system of obtaining information from various sources on the attempts of creating secret network, alleged military espionage, and sabotage attempts in the territory of Trans-Baikal Railway. The article also reveals the interaction of command levels in the region and their activity in the event of manifestation of the persuasive threat to foreign policy security. No actual sabotage attempts are detected according to the archival sources. This may be due to absence of such data in the civil archive. However, the archive stores an array of information on the alleged attempts of creating secrent network in the territory of Trans-Baikal Region.