The Great Wall of China

  The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China in part to protect the Chinese Empire or its prototypical states against intrusions by various nomadic groups or military incursions by various warlike peoples or forces. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall. Especially famous is the wall built between 220–206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty.

  Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.

  The main Great Wall line stretches from Shanhaiguan in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km (5,500 mi). This is made up of 6,259 km (3,889 mi) sections of actual wall, 359 km (223 mi) of trenches and 2,232 km (1,387 mi) of natural defensive barriers such as hills and rivers. Another archaeological survey found that the entire wall with all of its branches measure out to be 21,196 km (13,171 mi).

   The collection of walls known today as the Great Wall of China was referred by a number of different names. The current English name evolved from enthusiastic accounts of "the Chinese wall" from early European travelers; by the end of the 19th century "the Great Wall of China" became the name of the walls. In Chinese, they are most commonly known as changcheng (長城), meaning "long wall". The term can be found in the Records of the Grand Historian (1st century BC), where it referred to the walls built by the Warring States, and most particularly, the walls of Qin Shi Huang. The notion of it being "ten thousand li" long (figuratively meaning "endless"), as reflected in the full Chinese name of the Great Wall in modern times (萬里長城 Wanli Changcheng), also comes from the Records, though the words "Wanli Changcheng" were rarely used together in pre-modern times—a rare example being the Book of Song written in 493, where it quotes the frontier general Tan Daoji.

   Historically, the dynasties after Qin avoided using the term changcheng to refer to their own "Great Walls", as the term was said to evoke imagery of Qin's tyranny. Instead, historical records indicate the use of various terms such as "frontier" (塞 sai), "rampart" (垣 yuan), "barrier" (障 zhang), "outer fortresses" (外堡 waibao), and "border wall" (邊牆 bianqiang), in addition to poetic and folk names like "purple frontier" (紫塞 zisai) and "earth dragon" (土龍 tulong). Only in modern times did changcheng become the catch-all term to refer to the long border walls regardless of location or dynastic origin, equivalent to the Western term "Great Wall".

   The Chinese were already familiar with the techniques of wall-building by the time of the Spring and Autumn period between the 8th and 5th centuries BC. During this time and the subsequent Warring States period, the states of Qin, Wei, Zhao, Qi, Yan and Zhongshan all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were made mostly by stamping earth and gravel between board frames.

  

Qin Shi Huang conquered all opposing states and unified China in 221 BC, establishing the Qin Dynasty. Intending to impose centralized rule and prevent the resurgence of feudal lords, he ordered the destruction of the wall sections that divided his empire along the former state borders. To position the empire against the Xiongnu people from the north, he ordered the building of new walls to connect the remaining fortifications along the empire's northern frontier. Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources. Stones from the mountains were used over mountain ranges, while rammed earth was used for construction in the plains. There are no surviving historical records indicating the exact length and course of the Qin Dynasty walls. Most of the ancient walls have eroded away over the centuries, and very few sections remain today. The human cost of the construction is unknown, but it has been estimated by some authors that hundreds of thousands, if not up to a million, workers died building the Qin wall. Later, the Han, Sui, and the Northern dynasties all repaired, rebuilt, or expanded sections of the Great Wall at great cost to defend themselves against northern invaders. The Tang and Song Dynasties did not build any walls in the region substantially. The Liao, Jin, and Yuan dynasties, who ruled Northern China throughout most of the 10th–13th centuries, constructed defensive walls in the 12th century, but those were located much to the north of the Great Wall as we know it, within today's Inner and Outer Mongolia.