 The Mongol Northern Yuan dynasty used to send ahead a force of up to a thousand men that carried pickaxes to break
down the wall whose core consisted mostly of rammed earth.In academia, opinions about the Wall's role in the Ming dynasty's downfall are mixed.Historians such as Arthur Waldron and Julia Lovell are critical of the whole wall-building exercise in light of its ultimate failure in protecting China; the former compared the Great Wall with the failed Maginot Line of the French in World War II.