The Great Wall, also known as the Great Wall of Wan Li, was an ancient military fortress in China. It is a tall, solid and continuous long wall, which is used to limit the enemy's actions.
The history of building the Great Wall can be traced back to the Western Zhou Dynasty. In order to resist the attack of nomadic people in the north, the Zhou Dynasty built a series of castles "Fierce Cities" for defense. The total length of the Great Wall in the Ming Dynasty was 885 1.8km, which was more than 1.000km in the Qin and Han Dynasties and its total length was more than 21.000km.. During the Spring and Autumn Period and the Warring States Period, in order to compete for hegemony and defend each other, countries built the Great Wall on their borders according to their respective defense needs. The earliest building was the "Chu Fangcheng" in the 7th century BC. Later, the vassal states of Qi, Han, Wei, Zhao, Yan, Qin and Zhongshan all built the "Great Wall of Mutual Defense" for self-defense.