History of China's Greatwall

Qin Dynasty: the "First" Great Wall: Qin Shi Huang unified China into a centralized feudal state. To protect his newly established state, Qin decided a large defense barricade was needed. He sent one million soldiers and laborers to work on the project that would last nine years.

Ming Dynasty: The Wall's Importance Reaches a New Height:
During the Ming Dynasty, the Great Wall became an important line of defense again. Emperor Zhu Yuanzhang began renovations at the outset of his reign. He assigned his son Zhu Di and one of his generals to repair the existing wall and build forts and watchtowers. The Great Wall for the Ming was ultimately a way to keep raiding Mongols from the north from invading and ransacking Beijing. For the next 200 years the wall was fortified ultimately covering 7,300 kilometers