The article discusses the political mood of the population of Western Transbaikalia during the existence of the Far Eastern Republic. We present a general description of the political situation in the region, especially the national and social structure of the population. The emphasis is made on the reasons of dissatisfaction of the population with the Government of the Far Eastern Republic, heavy duties, and mobilization to the People’s Revolutionary Army. We consider the difference between the mood of the population in Western and Eastern Transbaikal, the characteristic of the anti-government armed units on the territory of Western Transbaikalia. Consideration is given to the reasons for the replenishment of military detachments with peasants and the reasons for their support by the local population. The authors show the role of the Whites and the remnants of the Semenov’s troops in the formation of anti-government armed groups. The article reveals the role of the invasion of Baron Ungern’s troops to Transbaikalia to change the sociopolitical situation, the political mood of the population in Western Transbaikalia and attitude of different layers of the population to Baron Ungern. General conclusions are made on the development of political mood in Western Transbaikalia during the existence of the Far Eastern Republic.