Complex sentence: Anjou's political origin is traced to the ancient Gallic state of the "Andes", on the lines of which was organized, after the conquest by Julius Caesar, the Roman "civitas" of the "Andecavi".
Split into simpler sentences: Anjou's political origin is traced to the ancient Gallic state of the "Andes". After the conquest by Julius Caesar, the area was organized around the Roman "civitas" of the "Andecavi".