Today, the Wall has become a must-see for every visitor to China. Few can help saying 'Wow!' when they stand on top of a beacon tower and look at this giant dragon. For centuries, the wall served succeeding dynasties as an efficient military defence. However, it was only when a dynasty had weakened from within that invaders from the north were able to advance and conquer. Both the Mongols (Yuan Dynasty, 1271-1368) and the Manchurians (Qing Dynasty, 1644-1911) were able take power because of weakness of the government and poverty of the people but never due to any possibility of weakness of the Wall.…