After Germany and the Soviet Union had partitioned Poland in 1939, most of the ethnically Polish territory ended up under the control of Germany control while the areas annexed by the Soviet Union contained ethnically diverse peoples, with the territory being divided into several areas, some of which had a significant non-Polish majority (Ukrainians in the south and Belarusians in the north) many of whom felt alienated in the nationalist interwar Poland and welcomed the Soviets. Nonetheless Poles comprised the largest single ethnic group on the territories annexed by the Soviets, too.
