Following the German and Soviet invasion of Poland in September 1939, Polish territory was divided between Germany and the USSR. Both regimes were hostile to Polish culture and Polish society and aimed at their destruction.
Seventeen days after the German invasion of Poland in 1939, which marked the beginning of the Second World War, the Soviet Union entered the eastern regions of Poland (known as the Kresy) and annexed territories totalling 201,015 square kilometres (77,612 sq mi) with a population of 13,299,000.
Firstly, the Soviet authorities conducted the de-Polonization process of the occupied territory. They exterminated the leading groups of Polish society – the landed gentry and the intelligentsia.
Hundreds of thousands of families of the intelligentsia, military, police and wealthier farmers suffered from mass deportations into the depths of the USSR.
In this way, during the 21 months of occupation, social, cultural, economic and national changes were initiated and often carried out. A huge part of the deportees (about one-third) did not return to the country.