Beginning in 324 b.c.e. three northern Chinese states with nomadic neighbors—Qin (Ch’in), Zhao (Chao), and Yan (Yen)—began to build defensive walls. After Qin unified China in 221 b.c.e. the first emperor ordered his most able general, Meng Tian, to connect these existing walls and extend them to form a unified system of defense. The result is the Great Wall of China.
For 10 years beginning in 221 b.c.e. Meng Tian commanded a force of 300,000 men (soldiers, convicts, and corvee laborers), who simultaneously campaigned against the Xiongnu (Hsiung-nu) and other nomads and built the wall. There is no detailed information about the project.
The great historian Sima Qian wrote this account in The Historical Records: "He [Meng Tian] ... built a Great Wall, constructing its defiles and passes in accordance with the configurations of the terrain. It started at Lin-t'ao and extended to Liao-tung, reaching a distance of more than a myriad li. After crossing the [Yellow] River, it wound northward, touching the Yang mountains".
Controversy remains over the length of the Qin wall. Sima Qian used the word wan, which translates as "ten thousand" or "myriad" in English; myriad was often used to designate a large but not precise number.
Regardless of its precise length, the logistics for its building was daunting, far more so than building a pyramid, because the wall advances and so the supply line is always changing.
Moreover, it extends over mountains and semideserts where the local population was sparse and the weather inclement. A vast army of support personnel was also involved, and death among the workers must have been high.
Legends that the bodies of the dead were used as wall fillers have proved untrue from excavations; however, they reflect the resentment the relentless demand for labor for the project created. Unlike the Ming wall built almost 2,000 years later of rocks and large fired bricks, the Qin wall was made of tamped earth from local materials.
The completed wall stretched from Gansu (Kansu) in the west to north of Pyongyang in present-day North Korea. The building of the wall and earlier Qin defeat of the Xiongnu also had the unintended result of solidifying and unifying the various Xiongnu tribes under their leader Maotun in 209 b.c.e.
The fall of Qin in 206 b.c.e. resulted in neglect in China’s northern defenses and Xiongnu incursions, which the first Han emperor Gaozu (Liu Bang) was unable to check. After defeat by Maotun in a major battle in 200 b.c.e., Han and Xiongnu made peace under the Heqin (Ho-chin) Treaty, which made the Great Wall their boundary.
Appeasement of the Xiongnu ended in 133 b.c.e. with major Han campaigns that ultimately broke up the Xiongnu confederacy and led to Han expansion to the northwest. The Great Wall was extended across the Gansu Corridor to Yumenguan (Yu-men Kuan), with forts and frontier posts along the way.
Military colonists guarded these posts, growing food, supplying provisions for government missions, and safeguarding horse stud farms for the cavalry. Many of the ruined Han forts and outposts remain to show the cost of the Pax Sinica that the Han created and that the Great Wall safeguarded.