Self-Defence of Lithuania and Belarus (Polish: Samoobrona Litwy i Białorusi) was a voluntary military formation (militia) composed primarily of Poles that was created in the aftermath of First World War during the formation of Second Polish Republic in the Kresy Polish-Russian borderlands.
The areas of operation of this militia formation were centered on Wilno (now, Vilnius), Mińsk and Grodno. The units, former around autumn 1918 were primarily involved in protection the local residents from deserters and bandits, quelled unrest among the peasant and faced the increasing incursions by the Bolshevik forces which were following the retreating German Ober-Ost forces.
On 8 December 1918 general Władysław Wejtko who was involved in the creation of militia arrived in the Polish capital of Warsaw, where Chief of State Józef Piłsudski confirmed him as the 'leader of all Polish forces in Lithuania and Belarus'.
However the militia was soon faced with numerically superior Bolshevik forces. In December 1918 in Minsk, a group of roughly 1500 Poles and Belarusians under the 'Samoobrona' banner rose to arms to defend the city against the advancing forces of Soviet Russia. However, due to Russian numerical superiority and lack of support from the side of the short-lived Belarusian National Republic, the group withdrew towards central Poland. Shortly thereafter, a roughly 2,500 men strong 'Samoobrona' force was created in Wilno (modern Vilnius) to defend it against the Reds in January 1919. In the effect of four day long fights for the city, the Polish forces were pushed back and the city had to be abandoned. In the coming months the cities would change hands several times during the struggle of various factions (for example, during Vilna offensive and Operation Minsk).