UNDO was founded at a party congress in 1925 through the merger of three western Ukrainian political parties, under the leadership of Dmytro Levytsky. It was the direct descendant of the prewar Ukrainian National Democratic Party, which had been the leading western Ukrainian political party during Austrian rule through western Ukraine's failed war of independence against Poland. The vast majority of western Ukraine's intelligentsia and clergy were members of UNDO. Prominent figures in the party included Kost Levytsky, former head of the government of the West Ukrainian National Republic, Dmytro Levytsky, who led the party for ten years, and Vasyl Mudry, who would become the speaker of Poland's parliament (the Sejm). UNDO's members controlled many of the region's Ukrainian financial, cooperative, and cultural institutions, including the principal western Ukrainian newspaper . During the elections, it obtained approximately 600,000 votes and a large majority of the Ukrainian seats in the Polish parliament. Its main competitor within the Ukrainian community, the socialist Ukrainian Radical Party, received 280,000 votes.