The great wall of china
Large parts of the fortification system date from the 7th through the 4th century BCE. In the 3rd century BCE Shihuangdi (Qin Shihuang), the first emperor of a united China (under the Qin dynasty), connected a number of existing defensive walls into a single system. Traditionally, the eastern terminus of the wall was considered to be Shanhai Pass (Shanhaiguan) in eastern Hebei province along the coast of the Bo Hai (Gulf of Chihli), and the wall’s length—without its branches and other secondary sections—was thought to extend for some 4,160 miles (6,700 km). However, government-sponsored investigations that began in the 1990s revealed sections of wall in Liaoning, and aerial and satellite surveillance eventually proved that this wall stretched continuously through much of the province. The greater total length of the Ming wall was announced in 2009
History of construction
The Great Wall developed from the disparate border fortifications and castles of individual Chinese kingdoms. For several centuries these kingdoms probably were as concerned with protection from their near neighbours as they were with the threat of barbarian invasions or raids
About the 7th century BCE the state of Chu started to construct a permanent defensive system. Known as the “Square Wall,” this fortification was situated in the northern part of the kingdom’s capital province. From the 6th to the 4th century other states followed Chu’s example. In the southern part of the Qi state an extensive perimeter wall was gradually created using existing river dikes, newly constructed bulwarks, and areas of impassable mountain terrain. The Qi wall was made mainly of earth and stone and terminated at the shores of the Yellow Sea. In the Zhongshan state a wall system was built to thwart invasion from the states of Zhao and Qin in the southwest. There were two defensive lines in the Wei state: the Hexi (“West of the [Yellow] River”) and Henan (“South of the River”) walls. The Hexi Wall was a fortification against the Qin state and western nomads. Built during the reign of King Hui (370–335 BCE), it was expanded from the dikes on the Luo River on the western border. It started in the south near Xiangyuan Cave, east of Mount Hua, and ended at Guyang in what is now the Inner Mongolia Autonomous Region. Henan Wall, built to protect Daliang (the capital, now Kaifeng), was repaired and extended in King Hui’s later years. The Zheng state also built a wall system, which was rebuilt by the Han state after it conquered Zheng. The state of Zhao completed a southern wall and a northern wall; the southern wall was built mainly as a defense against the Wei state..
In the Yan state two separate defensive lines were prepared—the Northern Wall and the Yishui Wall—in an effort to defend the kingdom from attacks by northern groups such as the Donghu, Linhu, and Loufan, as well as by the Qi state in the south. The Yishui Wall was expanded from the dike of the Yi River as a defense line against Qi and Zhao, its two main rival states. It began southwest of Yi City, the capital, and ended south of Wen’an. In 290 BCE the Yan state built the Northern Wall along the Yan Mountains, starting from the northeast in the area of Zhangjiakou in Hebei, passing over the Liao River, and extending to the ancient city of Xiangping (modern Liaoyang). This was the last segment of the Great Wall to be erected during the Zhanguo (Warring States) period.
