A large portion of the Vilnius area was part of the Second Polish Republic during the interwar period, particularly the area of the Republic of Central Lithuania, which had a significant Polish speaking population. For example, the Wilno Voivodeship (25% of it is a part of modern Lithuania and 75% - modern Belarus) in 1931 contained 59.7% Polish speakers and only 5.2% Lithuanian speakers; see Ethnic history of the region of Vilnius for details. From 1918 to 1921 there were several conflicts, such as the activity of the Polish Military Organization, Sejny uprising (that was met with massive outrage in Lithuania) and a foiled attempt at a Polish coup of the Lithuanian government. From the documents stolen from Polish Military Organization headquarters safe in Vilnius and given to Prime Minister of Lithuania Augustinas Voldemaras, it is clear that this plot was directed by Józef Piłsudski himself. The Polish-Lithuanian War and Żeligowski's Mutiny contributed to a worsening of Polish-Lithuanian relations; increasingly Polish-speaking people were viewed with suspicion in Lithuania. The loss of Vilnius was a painful blow to Lithuanian aspirations and identity. The irredentist demand for its recovery became one of the most important elements of socio-political life in interwar Lithuania and resulted in the emergence of hostility and resentment against the Poles.