The territorial expansion of the Western Han, notably under Emperor Wudi, placed considerable stress on the maintenance of the army. In the first place, military force was deployed to take new territory, particularly in the northwest, where huge tracts were occupied beyond the Jade Gates into the Tarim Basin. To the south, the Han Empire was extended as far as the rich Hong (Red) River Basin in Vietnam, and colonization also extended into the Korean Peninsula. Thereafter, it was necessary to provide for frontier defense, particularly along the extended Great Wall, where the Xiongnu were a constant threat. There was also a problem of security within the empire itself, newly founded after the long Warring States period, for provincial discontent and uprisings, such as those of the Red Eyebrows and the YELLOW TURBANS, were always possible.
To provide for the army, military conscription was compulsory except for top aristocrats and, on occasion, those who could afford to buy exemption. At the age of 23, men underwent a year of military training in their home commandery, in the infantry, cavalry, or navy. Then they were posted for another year to active service, which could involve guard duties at the capital or frontier defense. Thereafter, they could return home but remained in a state of readiness for recall. Under the Western Han, they were required to return regularly for further training until they reached the age of 56. There was also the socalled Northern Army, a force of regulars under five commanders who served as guards of the capital and of the passes leading into the heartland of the empire, the Wei Valley. This force numbered about 3,500 men. If war threatened, as, for example, with Xiongnu incursions in the north, the militia reserve could be called up and deployed. Militia units were also assembled in the event of internal threats to security. With the Yellow Turban uprising of 184 C. E., there was a major mobilization appointment of a military commander with the title general of chariots and cavalry.
The growing administrative machine and maintenance of a standing army, not to mention the need to conscript young men into military training, placed major demands on agricultural production. An efficient rural sector and the ability to gather taxes were essential for the survival of the state.
The Han administrative system also incorporated wang guo, “kingdom.” Initially, these were ruled by the sons of the emperor and were granted a considerable measure of independence aside from the maintenance of an army. However, their very presence contained the seeds of possible dissension, and this became a reality with the rebellion of the seven kingdoms in 154 B. C. E. Thereafter, the independence of the kings was severely curtailed. No longer able to raise their own revenue, the kings received a state salary, and the appointment of their staffs was also taken over by the court. In this way, the title became increasingly honorific, and kingdoms began to resemble commanderies in all but name. Specified lands were also provided to the nephews or grandsons of the emperor, who were given the title lie hou, “marquis.” These aristocrats were awarded prefectures but had no effective power in their lands and received both retainers and an income from the court. The wealth of some marquises can be judged from their opulent burials.
The establishment of an empire, territorial expansion under Wudi, and the growth of long-distance trade relationships opened China to a new and wide range of contacts with foreigners. This even extended to Rome, whose empire was growing at the same time far to the west. It is recorded, for example, that a group of Romans claiming to be from the court of An-tun reached Luoyang in 166 C. E. This may well have been the Chinese transcription of the name of the Roman emperor Marcus Aurelius.
The most immediate and persistent issue in Han foreign relations, however, centered on the Xiongnu, the confederation of tribes who occupied the steppes to the northwest of the Great Wall. The name Xiongnu is Chinese and means “fierce slave.” The actual name used by the Xiongnu themselves is not known.
No sooner had he established himself on the throne as emperor than Gaodi faced a major challenge from the Xiongnu, for in 209 B. C. E., a new and dynamic leader, or shanyu, had emerged, named MAODUN (r. 209-174 B. C. E.). He won over rival tribal groups and expanded his territory to include the strategic Gansu Corridor that leads to the heart of China. His presence and his establishment of a capital at Lung Cheng in Outer Mongolia had the effect of attracting Chinese dissidents, particularly those who had suffered under the establishment of the Qin and Han empires. The list even included the king of the former state of Han. This Gaodi chose not to ignore, and in 200 B. C. E. he mounted a massive punitive expedition, which he led in person. At Pingcheng, his army was surrounded for a week by the Xiongnu cavalry, and only by good fortune did the emperor extricate himself. Clearly, the Xiongnu were not going to be easily defeated, and a diplomatic solution was sought. This involved a treaty, in which it was agreed to send a Chinese royal princess as a wife to the Xiongnu leader, provide gifts of silk and food, recognize the equality of the Han and the Xiongnu states, and agree on the frontier line of the Great Wall.
This treaty was renewed with each new emperor, at which point a further princess would be sent to the Xiongnu, with increasingly expensive gifts that included pieces of gold. The increasing quantity of gifts is a measure of the regard of the Han for the disruptive power of the Xiongnu. Indeed, before his death in 174 B. C. E., Maodun’s demands steadily increased. He was succeeded by his son, Ji-zhu (r. 174-160 B. C. E.), who is named in the official histories as Lao-shang and then Jun-chen. Until 134 C. E., there was an uneasy relationship in which the Chinese adopted a policy of bribery and appeasement, while the Xiongnu mounted incursions beyond the frontier at will, even reaching close to the Han court. Under the emperor Wudi, however, there was a major change in policy. In 127 B. C. E., his general Wei Qing led a successful campaign against the Xiongnu, who were forced to retreat from the frontier. Six years later, the Han forces again defeated them. Despite almost insurmountable problems of food supply in these remote regions, a further campaign in 119 B. C. E. again scattered the Xiongnu, and the Han were able to establish themselves in new commanderies across the western regions.
The Han dominance thereafter had much to do with the fragmentation of the Xiongnu confederacy into factional kingdoms, whose rulers ceased to acknowledge the supremacy of the shanyu. There was also the problem so often faced by the Han themselves, that the Xiongnu succession was formally passed from father to son. This opened the possibility of succession of a very young ruler; the shanyu Hu Hanye (r. 58-31 B. C. E.) decree that the leader should be succeeded by his younger brother protected the succession. However, between the victories under Wudi and the end of the Western Han dynasty, repeated efforts by the fragmented Xiongnu to negotiate a renewal of the treaty on the basis of equality foundered, because the Han insisted on the formalization of a client relation in which the Xiongnu acknowledged a vassal status.