Complex sentence: Flanders is a term that now refers specifically to distinct parts of Belgium, but during the 15th to mid 16th centuries, the modern national borders of France, Germany, Belgium and the Netherlands did not exist.
Split into simpler sentences: Flanders is a term that now refers specifically to distinct parts of Belgium. During the 15th to mid 16th centuries, the modern national borders of France, Germany, Belgium and the Netherlands did not exist.