Complex sentence: Under its terms the north and west of France were occupied by the German Army, the remaining one third of the country was ruled by a French government located at Vichy and headed by the aging Marechal Philippe Pétain.
Split into simpler sentences: Under its terms the north and west of France were occupied by the German Army. The remaining third of the country was directly controlled by a French government located at Vichy headed by the aging Marechal Philippe Pétain.