The solution of urgent tasks to develop modern approaches to the organization of military libraries functioning is impossible without using the existing achievements in the field of military librarianship. Retrospective analysis of the work of the Information Historical and Scientific Center — Military Historical Library of the General Staff of the Armed Forces of the Russian Federation (IHSC — MHL GS AF RF) in the Soviet period can be used to improve the work of Russian military libraries at the present stage.Due to the lack of comprehensive studies on the history of the IHSC — MHL GS AF RF in the first years of Soviet power, this article attempts to fill this gap, in particular, to establish the sources of formation of the collection of the library, which changed its name. The aim of the study is to reconstruct the history of creation and formation of one of such sources — the library of the Auditorium of Military Affairs (later — the Department of Universal Military Training at the headquarters of the Petrograd District Commissariat for Military Affairs) in the context of the construction of the Workers’ and Peasants’ Red Army (WPRA) in 1918—1921, as well as to analyze the dynamics of the library holding.The relevance of the issue under study is conditioned, on the one hand, by its insufficient research, and on the other hand, by the demand for the historical experience of military libraries to develop principled approaches to their reform. The source base of the research is represented by the materials of Russian archives (the Russian State Military Archive, the Central State Archive of Literature and Art of St. Petersburg, the Current Archive of the IHSC — MHL GS AF RF), documents of the main and central bodies of military administration of the RSFSR, publications in the periodical press.The research has broadened the understanding of the fate of military book collections of the Russian Empire after its collapse and the initial stage of formation of military librarianship in Soviet Russia. The fate of some nationalized book collections before they were added to the holding of the library of the Auditorium of Military Affairs has been established. The documents revealing the main directions of the library’s activity have been introduced into scientific turnover; its organizational and staff structure has been analyzed; the interrelation of the library’s history with the history of the Red Army in the first years of Soviet power has been traced. The results obtained show that the impressive book collection accumulated by the library of the Auditorium of Military Affairs is now a part of the holding of the IHSC — MHL GS AF RF.