They were mostly composed of Poles in Lithuania and Belarus loyal to the nascent Second Polish Republic formed after over a century of the Partitions of Poland.
[1] The Self-Defence of Lithuania and Belarus was created by a group of officers of the former Polish I Corps in Russia, which initially formed the Union of Military Poles in Vilnius.
"[3]On December 8, 1918, General Władysław Wejtko, formerly of the Imperial Russian Army and one of the Self-Defence's organisers, arrived in Warsaw, Poland's capital.
[1] Wejtko received 375,000 marks from the Kresy Defence Committee for Self-Defence's needs, including provisions, pay, firearms, and horses.
When Minsk fell to Soviet troops on December 10, 1918, this greatly affected the morale of Self-Defence activists, and even their commander did not expect to successfully defend Vilnius against the invading Bolsheviks.
[5] Polish commands were established in Adamavichy [be], Sapotskin, Zhytomlia [be], Indura, Vyalikaya Byerastavitsa, Kapciouka [be], Porechcha [be], Novy Dvor [be], Hozha [be], and later in Kuźnica, Aziory [be], Talochki [be], and Skolabava [be].
[5] Although there was no confidence to defend Vilnius after the fall of Minsk, but enthusiasm in the ranks was increased due to speeches about relief from Poland by Capt.
[6] Meanwhile, the command of the Self-Defence of Lithuania and Belarus, taking into account the possible relief from Poland, intended to act against the approaching Russian troops, whose arrival was expected around January 5, 1919, because the Germans announced they would end their occupation of Vilnius that day.
In a four-day battle for Vilnius lasting till 5 January, Polish forces were pushed back near Naujoji Vilnia.