Complex sentence: The town of Radom fell to the Germans during the invasion of Poland on September 8,1939; at that time the population of Radom was 81,000, out of which 25,000 were Jews.
Split into simpler sentences: The town of Radom was overrun by the Germans on September 8,1939 during the Invasion of Poland. At that time the population of Radom was 81,000, out of which 25,000 were Jews.