The Great Wall of China

Great Wall of China, an ancient gigantic defensive project, is one of the greatest wonders of the world. It winds its way westward over the vast territory of China from the bank of the Yalu River and ends at the foot of snow-covered Qilianshan and Tianshan mountains, up and down across deserts, grasslands, mountains and plateaus stretching approximately 6,700 kilometers (4,163 miles ).
It is seldom that we can see any other gigantic in the world like Great Wall of China. As the Great Wall was reconstructed --in Qin, Han and Ming Dynasties -- its length exceeded 5,000 km (10,000 li). Hence the name "Wan Li Chang Cheng" or "the long wall of 10,000 li". Its size is better seen on a map or from an aerial photograph. According to astronauts who looked back from the moon, of all projects built by man, the Great Wall of China is the most conspicuous visible from space.
History of Great Wall
Construction of the Great Wall started in the 7th century B.C. Excitement abounds in the origin, vicissitude and nature of the great wall of the Qin, Han, and Ming dynasties. According to records put down in Chinese literature, as many as 20 principalities and dynasties took part in reconstructing the Great Wall.
The Great Wall was originally built in the Spring, Autumn, and Warring States Periods as a defensive fortification by the three states: Yan, Zhao and Qin. For self-protection, rival kingdoms built walls around their territories, laying foundations for the present Great Wall. The Great Wall went through constant extensions and repairs in later dynasties. In fact, it began as independent walls for different states when it was first built, and did not become the "Great" wall until the Qin Dynasty.
When Qin Shihuang (First Emperor of the Qin) unified China in 221 B.C., the walls was joined together to hold off the invaders from the Xiongnu tribes in the north and was extended to more than 10,000 li or 5,000 kilometers. The undertaking of such a huge project over difficult terrain at that time without any machinery was an extraordinary feat. A workforce of nearly a million, representing one fifth of the whole labor force of the country, was used to build it. Hardship and cruel treatment brought death to many of the laborers, and tragic stories were told, from which folk-tales and legends came into being. The Great Wall was renovated from time to time after the Qin Dynasty.
The Great Wall of China was continuously built during the Han Dynasty (206BC-220AD). It was extended towards the west to Lop Nur Lake in today's Xinjiang Uygur Autonomous Region. And an outer Great wall was added to the north of the Qin Great Wall. With its system of fortifications and beacon towers, the Han Great Wall reached a total length of about 10,000 kilometers.
With the expansion of the Tang Empire (618-907AD), the frontier was pushed further north, and the Great Wall ceased its function for almost 300 years. Once the Han, various dynasties, including Northern Wei,Eastern Wei, Northern Qi, Northern Zhou, Sui, Liao, Jin and Ming, rebuilt the Great Wall on extensive scale. The engineering projects undertaken in the Ming dynasties were the largest.
A major renovation started with the founding of the Ming Dynasty in 1368, and took 200 years to complete. The wall we see today is almost exactly the result of this effort. With a total length of over 6,000 kilometers, it extends to the jiayu Pass in Gansu Province in the west and to the mouth of the Yalu River in Liaoning Province in the east. What lies north of Beijing is but a small section of it.
Military value of Great Wall
The Great Wall can not be said to be a defense network of any great military value in modern society. However, when man's chief military weapons were the sword, arrows, bows, ge (hook weapon) adn mao (spear), the situation was quite different.
The Great Wall offers excellent defense since it had been built in strategic places. It played an vital role then. There were many instances in ancient times that it took a very long time to take a city or mountain pass. And even cases that those who launched the attack had to retreat without a fight, for they saw the strong defense work of the city. In the Central Plain of China such firm and high defense work proved to be very useful to foil the attacks of mobile cavalry, which roamed from one place to another.
As a result of Ming Dynasty's continuous construction and improvement, the Great Wall became a perfect defense network, whereby the central Chinese authority could, by means of various administrative and military levels of organization, reach the basic or grass root military unit, down to each soldier guarding the Great Wall. The Ming Dynasty overthrew the Yuan, obtaining ruling power throughout the nation. The original rulers, however, only retreated to their former positions. They were not destroyed. This made it possible for them to make a come-back. Under these circumstances, the Great Wall became a major security issue for the Ming Dynasty.