Original sentence: Polish September Campaign and Soviet invasion of Poland (1939)) in accordance with the Molotov-Ribbentrop non-aggression pact between Nazi Germany and the Stalinist Soviet Union.The Bielski family served as low-level administrators in the new government set up by the Soviets which strained their relations with the local Poles, to whom the Soviet Union was an occupier.The Bielski family were millers and grocers in Stankiewicze (Stankievichy) near Nowogródek, an area that at the beginning of the Second World War belonged to the Second Polish Republic and was occupied by the Soviet Union in September 1939 (cf
Edited sentence: Following the Soviet invasion of Poland, the region was administered by the Soviet Union, and annexed to the Byelorussian SSR.The Bielski family served as low-level administrators in the new government set up by the Soviets.The Bielski family were millers and grocers in Stankiewicze (Stankievichy) near Nowogródek, an ethnically diverse region (Belarusians, Jews, Poles, and others) that prior to the war was part of the Second Polish Republic