Volhynia
In 1939, at the start of World War II, the Soviet Union conquered and annexed western Volhynia. It used to belong to Poland before that point in time. When Nazi Germany invaded the Soviet Union in Operation Barbarossa in 1941, Volhynia came under Nazi German rule for several years. Almost all of the Jews who were not evacuated by the Soviet Union ahead of time were murdered by the Nazis in the Holocaust.