The concept of the Great Wall as it exists today originated with the Ming Dynasty walls built from 1368 to 1644. The sections that remain today are almost certainly from the 16th century. The Ming wall stretched from the Yalu River in the east to Jiayuguan Pass in the west and was divided into nine administrative sections. The defences of Beijing and the Ming tombs added a further two, making a total of 11. The three most important forts along the wall were Jiayuguan in Gansu province, Zhuyongguan near Beijing, and Shanhaiguan on the Gulf of Bohai. In the second half of the 16th century when war with Korea broke out and the threat from the Manchus increased, these fortifications became vital.
The walls were built in three stages: the first from 1368-1449, the second until the end of the 15th century, and the third from about 1540 on. At some vulnerable points, the Ming built between five and nine successive walls. A total of 4,526 miles were built and patrolled by almost 100,000 men. Wall building escalated in the first half of the 16th century with the weakening of Ming leadership. Increasing political incompetence met the Mongol threat, and walls were built with vigor. By the middle of the 16th century, building walls -as opposed to the negotiations with border tribes- remained the Ming's only viable option for border defence.
