The history of ethnic Polish settlement in what is now Ukraine and Belarus dates to 1030–31. More Poles migrated to this area after the
Union of Lublin in 1569, when most of the territory became part of the newly established
Polish–Lithuanian Commonwealth. From 1657 to 1793, some 80 Roman Catholic churches and monasteries were built in
Volhynia alone. The expansion of Catholicism in
Lemkivshchyna,
Chełm Land,
Podlaskie,
Brześć land,
Galicia, Volhynia and
Right bank Ukraine was accompanied by the process of gradual
Polonization of the eastern lands. Social and ethnic conflicts arose regarding the differences in religious practices between the
Roman Catholic and the
Eastern Orthodox adherents during the
Union of Brest in 1595-96, when the Metropolitan of Kyiv-Halych broke relations with the Eastern Orthodox Church and accepted the authority of the Roman Catholic Pope and Vatican. The
partitions of Poland, toward the end of the 18th century, resulted in the expulsions of ethnic Poles from their homes in the east for the first time in the history of the nation. Some 80,000 Poles were escorted to
Siberia by the Russian imperial army in 1864 in the single largest deportation action undertaken within the
Russian Partition. "Books were burned; churches destroyed; priests murdered;" wrote
Norman Davies. Meanwhile, Ukrainians were officially considered "part of the
Russian people". The
Russian Revolution of 1917 and the
Russian Civil War of 1917-1922 brought an end to the Russian Empire. According to Ukrainian sources from the
Cold War period, during the
Bolshevik revolution of 1917 the Polish population of
Kyiv was 42,800. In July 1917, when relations between the
Ukrainian People's Republic (UNR) and
Russia became strained, the Polish Democratic Council of Kyiv supported the Ukrainian side in its conflict with
Petrograd. Throughout the existence of UNR (1917–21), there was a separate ministry for Polish affairs, headed by
Mieczysław Mickiewicz; it was set up by the Ukrainian side in November 1917. In that entire period, some 1,300 Polish-language schools were operating in Galicia, with 1,800 teachers and 84,000 students. In the region of
Podolia in 1917, there were 290 Polish schools. Beginning in 1920, the Bolshevik and nationalist terror campaigns of the new war triggered the flight of Poles and Jews from Soviet Russia to newly sovereign Poland. In 1922 Bolshevik Russian
Red Army, with their Bolshevik allies in Ukraine overwhelmed the government of the
Ukrainian People's Republic, including the annexed Ukrainian territories into the
Soviet Union. In that year, 120,000 Poles stranded in the east were expelled to the west and the
Second Polish Republic. The Soviet census of 1926 recorded ethnic Poles as being of Russian or Ukrainian ethnicity, reducing their apparent numbers in Ukraine. In the autumn of 1935, Stalin ordered a new wave of mass deportations of Poles from the western republics of the Soviet Union. This was also the time of his purges of different classes of people, many of whom were killed. Poles were expelled from the border regions to resettle the area with ethnic Russians and Ukrainians, but Stalin had them deported to the far reaches of Siberia and Central Asia. In 1935 alone 1,500 families were deported to Siberia from Soviet Ukraine. In 1936, 5,000 Polish families were deported to
Kazakhstan. The deportations were accompanied by the gradual elimination of Polish cultural institutions. Polish-language newspapers were closed, as were Polish-language classes throughout Ukraine. Soon after the wave of deportations, the Soviet NKVD orchestrated the
Polish Operation. The Polish population in the USSR had officially dropped by 165,000 in that period according to the official Soviet census of 1937–38; Polish population in the Ukrainian SSR decreased by about 30%. ==Second Polish Republic==