Complex sentence: As soon as the Allied forces broke through at Normandy and fought their way to free Paris, the Gestapo killed prisoners at Fresnes such as Suzanne Spaak, who was executed there on August 12,1944, little more than a week before the city was liberated.
Split into simpler sentences: As soon as the Allied forces broke through at Normandy and fought their way to liberate Paris, the Gestapo peremptorily killed prisoners at Fresnes. An example was Suzanne Spaak, who was executed there on 12 August 1944, less than two weeks before the city was liberated.