Complex sentence: The Bastille has been credited as the most extensive example of early 18th-century fortifications in all of France and then held an important strategic point on the Alpine frontier with the Kingdom of Savoy.
Split into simpler sentences: The Bastille has been credited as the most extensive example of early 18th-century fortifications in all of France. It then held an important strategic point on the French Alpine frontier with the Kingdom of Savoy.