Chinese Empire

The Great Wall as a Military Structure

The Great Wall is the most famous military structure in the world, and the most misunderstood. It is often described as a single continuous wall, built all at once to keep out the barbarians. None of these things is true. The Great Wall was built and rebuilt by many dynasties over more than two thousand years, in different materials, to different designs, and for different purposes. The first version was put together in the late Warring States period by the states of Qin, Zhao, and Yan to keep out the nomadic horsemen of the northern steppe; these early walls were of pounded earth and have largely eroded. The Qin emperor connected and extended these walls after 221 BCE, again in pounded earth. The Han rebuilt and extended the wall deep into the Gansu corridor, also in pounded earth, and pushed it into the Tarim Basin as a chain of garrison outposts that controlled the Silk Road. The Ming Great Wall, the one that survives today in its iconic form, was rebuilt in brick and dressed stone from the late fourteenth century onward, with watchtowers, garrison forts, beacon platforms, and elaborate gate complexes. The wall as a military structure, a logistical system, and a symbolic statement of imperial authority is the subject of this piece, and complements the section on the imperial Chinese army and the broader narrative in the Chinese military section.

Three things should be said at the outset. First, the Great Wall was rarely a single wall. Most of the time it was a system of walls, forts, beacon towers, garrison towns, and natural barriers (rivers, mountain passes, deserts) that worked together. Second, the wall was often outflanked: the Xiongnu simply rode around it, the Xianbei and Khitan penetrated the line in many places, the Jurchen Jin and the Mongols simply marched through it, and the Manchus were invited in through the Shanhai Pass by the Ming general Wu Sangui in 1644. Third, the wall was always a defensive structure, and the dynasty that built it was always on the defensive. The wall is best understood as a system of fixed defence that allowed a smaller force to hold a longer line, and the story of the wall is the story of how the Chinese empire managed the challenge of the steppe. The longer story of the Chinese engagement with the steppe is told in the Chinese dynasties survey, the Chinese emperors section, and the Chinese government section.

Defensive Philosophy

The Great Wall was the visible expression of a particular philosophy of defence. The Chinese tradition, going back to the Warring States strategists, distinguished between zheng (正, “orthodox”) warfare and qi (奇, “extraordinary”) warfare. The orthodox approach was to occupy fixed positions, build fortifications, and force the enemy to attack at a disadvantage. The extraordinary approach was to use manoeuvre, surprise, and deception to overcome a numerically superior enemy. The Great Wall was the supreme example of the orthodox approach: a fixed defensive line that the enemy could not easily bypass, supported by a logistical network that allowed the defenders to concentrate force at the point of attack.

The defensive philosophy was not static. The early Ming attempted to combine the wall with offensive operations. The Hongwu Emperor (r. 1368–1398) drove the Mongols out of north China. The Yongle Emperor (r. 1403–1424) personally led five major northern expeditions between 1410 and 1424, dying at the start of the fifth. After the Tumu Crisis of 1449, in which the Zhengtong Emperor was captured by the Oirat Mongol leader Esen Taiji, the Ming abandoned the offensive and turned the Great Wall into the primary line of defence.

Garrison Life

The wall was not a barrier in isolation. It was a framework for a permanent military presence along the frontier. The weisuo (衛所, “guard and battalion”) garrisons of the Ming, examined in our in-depth piece on army organisation, were the basic units of the system. A typical Ming frontier garrison was a fortified town of several hundred to several thousand soldiers and their families, surrounded by farmland, with a wall and moat. In practice, garrison life was harsh: the climate of the north China frontier was extreme and the soldiers were often unpaid for months. By the sixteenth century the Ming had to hire mercenaries (募兵, mùbīng) to fill the ranks.

The garrison soldiers’ duties included more than just manning the wall. They patrolled the frontier, escorted caravans on the Silk Road, built and repaired the wall, and manned the beacon towers. The garrison was, in effect, a self-contained military colony, with its own economy and social structure. The garrison populations along the wall developed their own dialect (Junhua, 軍話, “army speech”).

Signal Beacons and the Communication Network

The beacon fire (烽火) was the most distinctive feature of the Great Wall’s communication system. Beacons were built at intervals of roughly 5 to 10 kilometres along the length of the wall, on high points with good sight lines. A single beacon fire might mean “enemies in sight”; two or three might mean “raiding party”; a large number, with smoke added in daytime and extra fires at night, might mean “major invasion.” The beacon system was capable of transmitting a major alert from the western end of the wall to Beijing in a single day, a remarkable speed for the pre-modern world.

The beacon system was supplemented by a courier network of horses and riders, with post stations (驿站, yìzhàn) at intervals of 25 to 50 kilometres. The system’s decay, as a result of the fiscal crisis of the late Ming, was one of the factors that left the empire unprepared for the Manchu invasion of 1644.

The Wall as Logistical System

The Great Wall was, finally, a logistical system. Behind it was a network of roads, supply depots, arsenals, and granaries that allowed the defenders to maintain the wall and the garrisons. The Ming maintained a system of military colonies (屯田, túntián) along the frontier, in which soldiers were given land to cultivate in peacetime. The colonies produced much of the food for the garrisons, and freed the central government from the cost of transporting grain over long distances.

The wall was also a barrier against smuggling and unauthorised movement. The Ming required travellers to use designated passes (關, guān) and to obtain permits from the local military authority. The most famous pass was Juyongguan (居庸關), northwest of Beijing, with the Shanhai Pass (山海關) at the eastern terminus of the wall where the wall meets the Bohai Sea. The passes were heavily fortified and guarded, and were also major commercial centres.

The Wall as Symbol

The Great Wall was, finally, a symbolic structure. It was a permanent declaration of the empire’s claim to a frontier, and an architectural statement of the legitimacy of the dynasty that built it. The wall has appeared in Chinese poetry, painting, and literature as a symbol of imperial grandeur and the melancholy of the frontier. The most famous such poem is Wang Changling’s “At Liangzhou” (涼州詞), which evokes the loneliness of garrison life. By the Qing, the wall had become one of the wonders of the world. The wall’s symbolic role in the cultural life of imperial China is treated in the Chinese culture section and the Chinese architecture section.

The wall’s symbolic role was not, however, always positive. The fall of the Ming in 1644, when the Manchus were invited in through the Shanhai Pass by the defector Wu Sangui, was a humiliation that Chinese historians have never quite forgiven. As a system, the wall worked for centuries. As a symbol, it carries the weight of two thousand years of imperial ambition and anxiety.