In 206 B.C., the Qin Dynasty was overthrown due to its tyrannical rule mostly for the large expenses required for building the Wall. In 202 B.C., after several years' civil war, it was finally replaced by a new feudal dynasty – the Han Dynasty. Historians call the period from 202 B.C. to A.D. 8. Earlier Han, and Later Han from A.D. 25 to A.D. 220. Between the two periods was a transient ruling time of Wang Mang and Liu Xuan. Han Dynasty lasted over 400 years and is regarded as the first golden time in Chinese history.
When the Han Dynasty was established, for the long-time war against the Qin Dynasty, the agriculture had almost ruined. The economy recessed and the national treasury was virtually empty. To bring through this severe crisis, Emperor Liu Bang, also know as Han Gaozu, softened some crucial policies related to the peasants, such as taxation, and made it the chief task to recover the agriculture and stabilize the social order. Gradually, the agriculture, handicraft industry and commerce restored and began to develop.
Accompanying the renewal, Hun in the north was stronger than ever and ambitious. To appease Hun, Han Gaozu married daughters of his family to Hun, wishing through this alliance to relent the two-county relation. The marriage treaty with Hun handed down to later emperors of Han Wendi and Han Jingdi. It existed for over 100 years.
When Junchen became ruler of Hun, he often dispatched troopers to Shangjun and Yunzhong Counties on the north border of Han. Hun killed people and looted properties and put the border in turbulence. On the other hand, due to the softened policies continuously adopted during the rule of Han Wendi and Han Jingdi, the economy of the Han Dynasty recovered, and the military strength was becoming powerful too. After Han Wudi had succeeded, he saw the fit to fight back against Hun. A war that lasted more than 30 years finally broke out.
In 127 B.C., General Wei Qing led an army and marched west from Yunzhong County and recaptured the Great Bend area of the Yellow River. To consolidate the frontier, he set up Shuofangzhen County and repaired a part of the wall left by the Qin Dynasty.
Later, Han built walls mainly for three times.
In 121 B.C., Huo Qubing, titled by Han Wudi General of the Flying Cavalry, led an army of 10,000 troopers from present Longxi and defeated Hun utterly. Hu Xiewang, Hu official governing the west area to the Yellow River, i.e. the Hexi Region, was captured and submitted to the Han Dynasty. The area he ruled was also incorporated within the territory of Han. To secure the Gansu Corridor, thoroughfare on the Silk Road, in 121 B.C., Han set up the two counties of Wuwei and Jiuquan, and the next year Zhangye and Dunhuang Counties. To protect and maintain the Silk Road leading to the West Regions, King Han Wudi built the wall that ran west from now Yongdeng to Jiuquan.
Han's control of the Hexi Region paved way to Zhan Qian's second diplomatic mission to countries in the West Regions, which marked the formal opening of the celebrated Silk Road. But the Road was since harassed. In 108 B.C., Han Wudi dispatched troops and broke up the two states of Cheshi and Liulan, puppets under Hun in this area. Moreover, he built a wall that ran towards the west from Jiuquan to Yu'me.
In 102 B.C., General Lu Bode was appointed for stationing troops in present Luobupo. He presided over building the wall running west from Yu'men to Yanze, i.e. present Luobupo.
In 101 B.C., to perpetuate the safety of the Gansu Corridor, Han Wudi set up fortresses along the line 500 kilometers north parallel to the middle portion of the Hexi-Region Wall.
The three walls combined as one, celebrated as the Hexi-Region Wall of Han Dynasty, which linked up to a fair part of the Qin-Dynasty Wall, forming a new wall that ran up to 10,000 kilometers, the longest wall in Chinese history that traversed present six provinces, i.e. Liaoning, Inner Mongolia, Hebei, Ningxia, Gansu and Xinjiang. The east end of the Wall extended to as far as the north part of Korea. Containing a large part of the Wall of the Qin Dynasty, the 10,000-kilometer Wall is also referred to as the Qin-Han Great Wall.
Lying in the border area, the wall of Earlier Han was also mentioned as "border wall". It was usually three to four meters high and about two meters wide. Though stacked or stamped with earth and stone, it was considerably solid; in present Min'qin, Dunhuang and Yumen of Gansu Province, relics of the Wall and beacons can still be found. Along the wall were set up garrisons equipped with beacons.
In the Han Dynasty, firing the beacon when enemies pushed in abided by a rigid formula. At an exigent event, if in the daytime, hay and dried reed were burned, giving off heavy smoke signifying an alarm; while at night, blazing fire lighted the dark sky. It is recorded in one literature that "small beacons were apart every five li and larger ones every ten li; a fortress was built every 30 li and a city every 100 li".
In 8 B.C., Wang Mang, whose family gained ascendance then, managed to usurp the throne and changed the dynasty to "Xin". Proceeding to it was a 17-year turbulence. Wang Mang reformed the social system, but some new diplomatic policies caused the resentment of Hun, which was then recovering from the utter defeat in the Earlier Han. Hun finally won the war against Wang Mang. To maintain his regime, Wang Mang also exerted coercion on his government. All these eventually led a wave of uprisings. In A.D. 25, Liu Xiu, of loyal birth of the Earlier Han Dynasty, supported by the Lulin Army, one uprising power, finished Wang Mang's short-lived Xin dynasty. Liu Xiu returned the dynasty of Han. For distinction, historians call it Later Han and the period before Wang Mang's rule Earlier Han. Liu Xiu became Later Han's first emperor, i.e. King Guang Wudi.
In the first years of Later Han, Hun was developing fast and began raiding the north border again, while Liu Xiu was involved in the civil war with his opponent forces and had hardly taken any measures.
On winning the war, Liu Xiu added more soldiers to the border and built more than one lower and thinner border walls to the south of the Earlier-Han Wall, and near their lines set up beacons and fortresses. These border walls thickened the defense area in the frontier. It is mentioned in the Book of Later Han, a complied historical literature, that "in the year Jianwu 12 (A.D. 36), General Du Mao ordered garrisons build beacons and fortresses" and that "in the 14th year of Guangwu (A.D. 39), General Ma Cheng took over Du Mao, continuing to build the four border walls separately from the Hexi Region to Weiji, from Heshang to Anyi, from Taiyuan to Jingxing and from Zhongshan to Ye. Besides, "he furnished the walls with beacons and deposited command posts along the walls every five li". The four barriers well guarded Later Han's capital – Luoyang. The present positions of the walls are as follows:
* The wall from Hexi Region to Weiji: from Lishi County of Shanxi Province to southeast Xianyang of Shannxi Province* The Wall from Heshang to Anyi: from east Gaoling County of Shannxi Province to Anyi County of Shanxi Province* The wall from Taiyuan to Jingxing: from Taiyuan of Shanxi Province to Jingxing County of Hebei Province * The wall from Zhongshan to Ye: from south Dingxian County of Hebei Province to Linzhang County of He'nan Province
Later, Hun occurred certain inner cleavage and was eventually divided into two groups: the south and the north. The Southern Hun merged into Han people and contributed to the peace of the north border. The Northern Hun was afterwards driven out of the Mongolia Plateau and Xinjiang in the time of King Han Hedi (88 ~ 105). The Han Dynasty expanded its territory to the further north and West Regions that were far beyond the Wall. Han Dynasty since didn't build any walls.
In recent years, along the middle part of the Wall of Han Dynasty, i.e. Wuyuan and Yunzhong County of that time, mainly present Wulateqianqi, Baotou, Dongsheng, Tumoteqi, Hohehot of Inner Mongolia, archeologists have discovered more than 20 walls and fortresses of the Later Han. These medium-sized fortresses monopolize strategic positions, each consisting of two circles. One fortress site, stamped with earth, lying at the foot of Yanshan Mountain in the Butu Village of Huhehot, of its outer circle is about 900 meters wide from north to south and 850 meters from east to west. Its layout indicates that the offices were planted in the inner city, and in outer city were mainly deployed barracks, croplands and training grounds.