In c. 220 B.C., under Qin Shi Huang, sections of earlier fortifications were joined together to form a united defence system against invasions from the north. Construction continued up to the Ming dynasty (1368–1644), when the Great Wall became the world's largest military structure. Its historic and strategic importance is matched only by its architectural significance.
Known to the Chinese as the 'Long Wall of Ten Thousand Li', the formidable defensive structures built to ward off invasion of the Celestial Empire by barbarians is called the Great Wall or the Wall of China by Europeans. The principle of these extraordinary fortifications goes back to the Chunqiu period (722-481 BC) and to the Warring States period (453-221 BC).
The construction of certain walls can be explained by feudal conflicts, such as that built by the Wei in 408 BC to defend their kingdom against the Qin. Its vestiges, conserved in the centre of China, antedate by many years the walls built by the Kingdoms of Qin, Zhao and Yan against the northern barbarians around 300 BC. Beginning in 220 BC, Qin Shi Huang, the founder of the Empire of the Ten Thousand Generations, undertook to restore and link up the separate sections of the Great Wall which had been built in the 3rd century BC, or perhaps even earlier, and which stretched from the region of the Ordos to Manchuria.
Towards the west, he had extended the fortifications, the first cohesive defence system of which significant vestiges still remain in the valley of the Huanghe all the way to Lanzhou shortly before the accession of the Han dynasty (206 BC). During their reign the Great Wall was extended even further, and under the emperor Wudi (140-87 BC) it spanned approximately 6,000 km between Dunhuang in the west and the Bohai Sea in the east. The danger of incursion along the northern Chinese border by the federated Mongols, Turks and Tunguz of the Empire of the Xiongnu, the first empire of the steppes, made a defence policy more necessary than ever. After the downfall of the Han dynasty (AD 220), the Great Wall entered its medieval phase. Construction and maintenance works were halted; China at that time enjoyed such great military power that the need for a defence policy was no longer felt.
It was the Ming Emperors (1368-1644) who, after the long period of conflict that ended with the expulsion of the Mongols, revived the tradition begun by Qin Shi Huang. During the Ming dynasty, 5,650 km of wall were built. To defend the northern frontier, the Wall was divided into nine Zhen, military districts rather than garrisons. At strategic points, fortresses were built to defend the towns, passes, or fords. The passageways running along the top of the wall made it possible to move troops rapidly and for imperial couriers to travel. Two symbolic monuments still proudly stand at either end of the wall - the First Door under Heaven at Shanhaiguan, located at the wall's eastern end, and the Last Door under Heaven at Jiayuguan, which, as part of the fortress entirely restored after 1949, marks its north-western end.
This complex and diachronic cultural property is an outstanding and unique example of a military architectural ensemble which served a single strategic purpose for 2,000 years, but whose construction history illustrates successive advances in defence techniques and adaptation to changing political contexts. The purpose of The Great Wall was to protect China from outside aggression, but also to preserve its culture from the customs of foreign barbarians. Because its construction implied suffering, it is one of the essential references in Chinese literature.
The Great Wall of the Ming is, not only because of the ambitious character of the undertaking but also the perfection of its construction, a masterpiece. The wall constitutes, on the vast scale of a continent, a perfect example of architecture integrated into the landscape. During the Chunqiu period, the Chinese imposed their models of construction and organization of space in building the defence works along the northern frontier. The spread of Sinicism was accentuated by the population transfers necessitated by the Great Wall.
That the great walls bear exceptional testimony to the civilizations of ancient China is illustrated as much by the tamped-earth sections of fortifications dating from the Western Han that are conserved in Gansu Province as by the admirable and universally acclaimed masonry of the Ming period.