Complex sentence: At the end of the World War II, there were more than five million "displaced persons" from the Soviet Union in the Western Europe, of whom circa three million had been forced laborers (OST-Arbeiters).
Split into simpler sentences: At the end of the World War II, there were more than 5 million "displaced persons" from the Soviet Union in the Western Europe. About 3 million had been forced laborers (OST-Arbeiters).