Abstract: The goal of this research is the analysis of organization of the Cossack military formations of White Movement and structure of their officer corps in Transbaikal territory over the period from August 1918 to November 1920. The subject of this work is the history of involvement of Transbaikal, Orenburg, Yeniseian, Siberian and Ussuri Cossack troops in the Civil War overall and Transbaikal region in particular. The chronological framework cover the period since the moment of the collapse of Soviet regime in Chita in the August 1918 until withdrawal of the White Army from Transbaikal in November 1920. The scientific novelty consists in generalization of information from the various published and little-studied sources for the purpose of restoring the organizational and corps structure of the White Cossack armed forces. The article also examines their engagement in military actions against partisan units of the Red and People’s Revolutionary Army of the Far Eastern Republic, which allows restoring a full picture of the exceptionally dramatic pages in the history of Civil War and foreign military intervention in Transbaikal territory.