After the establishment of the Qin Dynasty, the first unified, centralized state in Chinese history, Emperor Qin Shi Huang's foremost task was to reform the national system. During the Warring States period, each state had its own policies, leading to significant differences in the daily lives of the people, including their clothing, food, housing, and transportation. For example, the wheel spacing of carriages varied among the feudal states, and roads differed in width. Qin Shi Huang decreed that all carriage wheels must have a spacing of six chi (a Qin chi equaled about 0.23 meters), and every road should be fifty bu wide (one bu in the Qin Dynasty equaled six chi). He also standardized the written script, mandating the use of the small seal script throughout the empire. This was known as "carriages on the same track, writing with the same characters." Additionally, the Qin Dynasty unified weights and measures and established the square-holed copper coin as the national currency. Through these reforms, the daily lives of the people became standardized, and trade was no longer difficult.
Just as the First Emperor of Qin was busy with state affairs, unwelcome news arrived: the northern territories had been invaded by the Xiongnu. The Xiongnu were a nomadic people active in northern China, known for their fierce fighting skills and exceptional horsemanship. As early as the Warring States period, the states of Zhao, Yan, and Qin had built sections of the Great Wall along their borders to defend against Xiongnu raids, but these walls were fragmented and short, not yet connected into a single line. When the power of Zhao and Yan gradually declined, the Xiongnu grew restless and systematically seized much of their northern lands, including a large portion of the Hetao region along the Yellow River. Yet they were not satisfied and repeatedly launched attacks southward.
In 214 BCE, shortly after the Qin Dynasty was established, foreign invaders threatened the borders, greatly angering Emperor Qin Shi Huang. He appointed General Meng Tian to pacify the Xiongnu nomads. Living up to expectations, Meng Tian led 300,000 troops and successfully recaptured the Hetao region. To prevent further Xiongnu incursions from the south and to secure the Qin Empire's territory, the emperor ordered the demolition of defensive walls built by various feudal states within the country. He then used the natural mountain contours to establish barrier fortresses, connecting the northern Great Walls of the Zhao, Yan, and Qin states. After linking them, he extended the combined wall to create an impregnable, formidable barrier against invasion.
The construction of the Great Wall was an immensely massive project that drained both resources and manpower. Not to mention the vast sums of money the state spent, the soldiers and laborers conscripted for the task numbered in the hundreds of thousands. The 600,000 troops sent to attack the state of Chu nearly accounted for all of Qin's military forces at the time, possibly including some young laborers hastily rounded up to fill the ranks. The soldiers dispatched to build the Great Wall alone numbered in the hundreds of thousands, and if commoners were added to the count, the figure would be an astronomical sum. It could be said that Qin conscripted nearly every able-bodied man available for the wall's construction. The resulting loss of social labor caused widespread resentment among the people, who were already barely clothed and fed, making their lives even more difficult.
In an era when transportation, productivity, and technology were extremely underdeveloped, such a vast and arduous project involved hardships that we modern people cannot imagine. Countless common people fell at the foot of the Great Wall, which is precisely why later poets often used their poems to express mourning and sympathy for the laborers who built the Wall.
The construction of the Qin Great Wall took five years and was not completed until 210 BC. The wall stretched from Lintao (near the Tao River in present-day southern Gansu Province) in the west to Liaodong in the east, spanning over ten thousand li. The building method used by Qin Shi Huang for the Great Wall was very ancient: first, a layer of raw soil was laid, then a layer of loess was compacted on top, which had to be pressed extremely tightly and firmly to support the weight of the wall. The wall was then built using yellow clay mixed with small crushed stones. In an era when technology was underdeveloped, the emergence of such a great engineering project can only be described as a miracle in the history of human architecture.