With the death of Qin Shi Huang, and the fall of the Qin Dynasty, the majority of the Wall fell into disrepair. After the fall of the han dynasty, a number of the border tribes, took control of northern China. The most powerful of these was the Northern Wei Dynasty, that had been built on and expanded the existing walls in order to protect themselves from the attacks of other tribes.
Bai Qi kingdom (550-577), or repaired more than 900 km of the great wall, and the short-lived but effective Sui Dynasty (581-618), repaired, and extended the Great Wall of China-on several times.
With the fall of the Sui Dynasty and the rise of the Tang Dynasty, the Great Wall has lost its significance as a fortress, which it defeated the Tujue tribe, in the north, and has expanded outside of its original borders, with a defensive wall.
During the Song Dynasty, the Chinese withdrew and was forced under the threat of the Liao, the Jin, the peoples of the north, and the capture of many of the areas on both sides of the Wall. The strengths of the Yuan dynasty (Mongols) (1206-1368), which was founded by Genghis Khan, he eventually controlled all of China, as a part of Asia, and other parts of Europe.
Even though the Wall was not of great value to the Mongols, the military fortifications, soldiers, and was entrusted with the defense of the walls in order to protect the merchants and caravans traveling along the lucrative Silk Road trade routes established during this period.