Introduction. The article deals with an important and eventful period of Russia-Mongolia relations, special attention be paid to the shaping of a new regional order in East Asia. The collapse of China's monarchy resulted in a political vacuum in Russia's border territories which required utmost consideration and involvement, and the Soviets did seize the opportunity. However, the Agreement on Friendly Relations concluded in November of 1921 can hardly be viewed as a starting point, the former having been rather supposed to actualize previous mutual commitments discussed in the paper. Goals. So, the work attempts an interdisciplinary insight into the mentioned documents (addresses, diplomatic notes, letters, etc.) to have preceded the Agreem...