Lithuania, after declaring independence from the Russian Empire, claimed the Vilnius Region based on this historical legacy.
Direct military conflicts (Polish–Lithuanian War and Żeligowski's Mutiny) were followed up by fruitless negotiations in the League of Nations.
Later, the western limit of the region became a de facto administration line between Poland and Lithuania following Polish military action in autumn 1920.
Lithuanians used geographical and historical arguments and underlined the role Vilnius played as the capital of the Grand Duchy of Lithuania.
The Lithuanian government, however, failed to recruit soldiers among the Vilnius area inhabitants and was unable to organize the defence of the region against the Bolsheviks.
The Lithuanian Taryba left Vilnius together with the German garrison at the start of January 1919, when the first Polish-Soviet military clashes occurred east of the city.
The advancing Polish Army managed to retake much of the disputed area before the Lithuanians arrived, while the most important part of it with the city of Vilnius was secured by Lithuania.
The negotiations and international mediation led to nowhere and until 1920 the disputed territory remained divided into a Lithuanian and a Polish part.
The Polish government never acknowledged the Russo-Lithuanian convention of July 12, 1920, that granted the latter state territory seized from Poland by the Red Army during the Polish–Soviet War, then promised to Lithuania as the Soviet forces were retreating under the Polish advance; particularly as the Soviets had previously renounced claims to that region in the Treaty of Brest-Litovsk.
Some historians speculated, that the loss of Vilnius might have nonetheless safeguarded the very existence of the Lithuanian state in the interwar period.
Vilnius Region was under Lithuanian administration unitl June 1940, when the entire Lithuania was annexed by the Soviet Union.
The Soviet Union was awarded the Vilnius region during the Yalta Conference, and it subsequently became part of the Lithuanian SSR.
It was subjected to East Slavic and Polish cultural influences and settlement, which led to its gradual Ruthenization and Polonization.
[22] Jerzy Ochmański [pl] writes that by the 18th and 19th centuries, the city's environs were predominantly Slavic, while the Vilnius region became more and more ethnically diverse Belarusian-Polish-Lithuanian territory.
Belarusians migrated into the south-eastern Lithuanian areas that were destroyed by conflicts of the 17th and 18th century (particularly the counties of Vilnius, Trakai, Švenčionys and northern Ašmena).
[11][26] Vilnius at that point was divided nearly evenly between Poles and Jews, with Lithuanians constituting a mere fraction (about 2–2.6%) of the total population,[26][27][28] but these figures were questioned by the Lithuanian side already after the censuses were performed, pointing to the fact, that even German censuses in 1915-1916 were actually carried out predominantly by the Poles on site.
[citation needed] These censuses and their organisation were heavily criticized by contemporary Lithuanians of the region as biased.
According to E. Bojtar, who cites P. Gaučas, the surrounding villages were mainly inhabited by Belarusian speakers who considered themselves Poles.
However, during this census the Vilnius region was expanded greatly and ended near Brest-Litovsk, and included the city of Białystok.
[34][35][36] The population, including those of "the locals" (Tutejshy) who live in the other part of Vilnius region that was occupied by the Soviet Union and passed on to Belarus, still has a strong presence of Polish identity.
[35][38] The population, including those of "the locals" (Tutejszy) who live in the other part of Vilnius region that was occupied by the Soviet Union and passed on to Belarus, still has a strong presence of Polish identity.