Soviet foreign policy in the interwar (1918–1939) period was carried out on the basis of the strategy and tactics of the "world revolution", which, in turn, provided for the rallying of all "anti-imperialist forces", including the so-called oppressed peoples. While supporting the struggle of the Hindus against the British colonialists or the Chinese Kuomintang against imperial Japan, the Kremlin manipulators did not let the European continent out of their sight. One of the powerful knots of contradictions at that time became the Polish-Lithuanian relations, caused by the forceful annexation of the Vilnius region by the Poles, even contrary to the decision of the Versailles Conference. From the very beginning of the conflict, the Union of the SSR sided with Kaunas under the Pharisaic slogan of the right of nations to self-determination. Explanations for this lay on the surface. First, the interwar Second Commonwealth in its then borders was a project of the Council of Ambassadors of the Versailles Conference (primarily of France), concerned about the Soviet threat. Secondly, Moscow did not have a territorial conflict with Lithuania, but it did with Poland. Thirdly, actual (non)intervention in the conflict, its intensification or, on the contrary, its weakening could be used as a bargaining chip in relations with third states (such as Germany). Kaunas also had its interest, which lay on the surface (Vilnius region). The Soviet invasion of Poland, carried out under the pretext of taking under the protection of the population, which the "unreasonable policy of the Polish authorities" allegedly put in an extremely dangerous situation, was accompanied by a "generous" act of restoration of historical justice for the Lithuanians offended by the Polish invaders. However, in less than a year, the Soviet Janus showed his true face to the until recently friendly Lithuania.
Volodymyr Makarchuk (Sat,) studied this question.