ENThe article examines the role of Lithuania in the struggle for the Eastern European region during the Soviet-Polish War of 1919–1920. Thee author shows that from the very beginning, from the first days of January 1919 and later until the autumn of 1920, the military conflict in the space between Warsaw, Kaunas and Minsk was trilateral, as Lithuania actively participated in it (not counting the participation of other forces north and south of the specified region). In 1919, Lithuanian troops acted against the Reds in a de facto alliance with the Poles. Soviet Russia pretended that it was not waging war with Poland and Lithuania, hiding behind formally independent Soviet Lithuania and Belarus, which in February 1919 were united into a single republic, abbreviated as Litbel; it was supposed to play the role of a “buffer” between Russia and Poland. e existence of Litbel excluded the recognition of a separate Lithuania by Soviet Russia. The Soviet-Polish-Lithuanian conflict developed in a territory where the formation of modern nations was far from complete, the borders were still plastic and ethnic interstices prevailed. There was a struggle of incompatible projects on this territory. The Soviet Federation opposed the federation project centered on Warsaw. But even in Poland, the desire to create a state with a Polish majority and non-Polish minorities without any federation or national autonomies was influential. The Lithuanian leadership in Kaunas sought to implement a similar project. At the same time, there was an irreconcilable contradiction between the national Polish and Lithuanian projects – the question of Vilna (Vilnius). The disappearance of the Soviet-Lithuanian front in January 1920 opened the possibility for the conclusion of the Soviet-Lithuanian peace. But its specific parameters depended on the course of the Soviet-Polish war.Under the conditions of the Red Army’s offensive on Vilna (Vilnius), the Lithuanian side agreed to sign peace on July 12, 1920, which was advantageous from a territorial point of view and actually turned Lithuania into a military ally of Soviet Russia. As a result of the defeat of the Red Army near Warsaw, Lithuania could not hold Vilnius, which, due to the position of the Entente, required a complex solution with the formation of a “Central Lithuania” joining Poland. But the Soviet side continued to support Lithuania’s claims to Vilnius, which determined the relatively warm Soviet-Lithuanian relations in the interwar period. Keywords: Soviet-Polish War of 1919–1920, Soviet-Lithuanian conflict of 1919–1920, Soviet-Lithuanian peace of 1920, Litbel, “Central Lithuania,” Lenin, Ioffe, Voldemaras, Narushevicius, Pilsudski. [From the publication]