Soviet–Lithuanian Peace Treaty in the context of "Byelorussian SSR"

The Byelorussian Soviet Socialist Republic (BSSR, Byelorussian SSR or Byelorussia; Belarusian: Беларуская Савецкая Сацыялістычная Рэспубліка; Russian: Белорусская Советская Социалистическая Республика), also known as Soviet Belarus or simply Belarus, was a republic of the Soviet Union (USSR). It existed between 1920 and 1922 as an independent state, and afterwards as one of fifteen constituent republics of the USSR from 1922 to 1991, with its own legislation from 1990 to 1991. The republic was ruled by the Communist Party of Byelorussia. It was also known as the White Russian Soviet Socialist Republic. Minsk was the capital and largest city of the republic.

Following the Treaty of Brest-Litovsk in March 1918, which ended Russia's involvement in World War I, the Belarusian Democratic Republic (BDR) was proclaimed under German occupation; however, as German troops left, the Socialist Soviet Republic of Byelorussia was established in its place by the Bolsheviks in December, and it was later merged with the Lithuanian Soviet Socialist Republic in 1919 to form the Socialist Soviet Republic of Lithuania and Belorussia, which ceased to exist as a result of the Polish occupation during the Polish–Soviet War. Following a peace treaty with Lithuania, the Socialist Soviet Republic of Byelorussia was re-founded on 31 July 1920 and later became known as the Byelorussian Soviet Socialist Republic.

Vilnius Region is the territory in present-day Lithuania and Belarus that was originally inhabited by ethnic Baltic tribes and was a part of Lithuania proper, but came under East Slavic and Polish cultural influences over time.

The territory included Vilnius, the historical capital of the Grand Duchy of Lithuania. Lithuania, after declaring independence from the Russian Empire, claimed the Vilnius Region based on this historical legacy. Poland argued for the right of self-determination of the local Polish-speaking population. As a result, throughout the interwar period the control over the area was disputed between Poland and Lithuania. The Soviet Union recognized it as part of Lithuania in the Soviet–Lithuanian Peace Treaty, but in 1920 it was seized by Poland and became part of the short-lived puppet state of Central Lithuania, and was subsequently incorporated into the Second Polish Republic.