Original sentence: Luninets became part of Poland in 1920 following the Polish-Soviet War, but nineteen years later was incorporated back into the Soviet Union in 1939, and -- with the exception of occupation by Nazi Germany from 1941 to 1944 -- remained part of the Soviet Union until 1991, at which time sovereignty ceded to the Republic of Belarus
Edited sentence: Luninets became part of Poland in 1920 following the Polish-Soviet War, but nineteen years later was incorporated back into the Soviet Union in 1939, and—with the exception of occupation by Nazi Germany from 1941 to 1944—remained part of the Soviet Union until 1991, at which time sovereignty ceded to the Republic of Belarus