On 27 February 1919 the Lithuanian SSR and Belarusian SSR were merged and the Lithuanian–Belorussian Soviet Socialist Republic (Litbel) was formed. Mickevičius served as the Chairman and Minister of Foreign Affairs of the Litbel government. Polish military offensive of 1919 against the Red Army was pushing into the territory of Litbel, while newly established Lithuanian Army was taking control of central and western Lithuania. The support for Mickevičius' government mostly came from the city proletariat and farm laborers. Lithuanian farmers mostly supported the Council of Lithuania, who promised land to those who cultivate it. In an agrarian country, as Lithuania was at that time, farmers' support was essential. Understanding his limited support base, Mickevičius resisted Lenin's demands to recruit more Lithuanians to the Red Army and reported to Lenin that such an effort would be counter-productive and would reduce Lithuanian support for his government. By August 1919 almost entire Litbel territory was under occupation. In July 1920, the Soviet–Lithuanian Peace Treaty was concluded, and the Lithuanian Soviet Socialist Republic ceased to exist.