One of the key transformations of Chinese society during the Han was the abolition of universal military service, an institution that had underpinned the Warring States and the Qin.22 With the Han’s defeat of the feudatory kingdoms in 154 B.C., the possibility of large-scale warfare in the interior of China vanished, leaving only the threat of the Xiongnu on the northern border. The inability of peasants serving one-year terms to master horsemanship and the crossbow left them ill-equipped for expeditionary forces. Their relatively short terms also made them unsuitable for long-term garrison duty. Emperor Wu allowed some peasants to pay a tax in lieu of military service and used this money to recruit professionals. Nomadic enemies of the Xiongnu and dissident elements of the Xiongnu themselves were also recruited to provide skilled cavalry. In some cases convicts were sent to the frontiers to man garrisons. Thus, during the last century B.C. the Chinese army began to shift away from peasant levies to an army based on professionals, nomads, and criminals.
The rebellion against Wang Mang turned this gradual and informal process into official policy. The rebellion had demonstrated that peasant conscripts could be turned against the state, especially during the autumn training session, when adult males of a commandery gathered for inspection. It also showed that peasants would follow locally powerful families to whom they were bound rather than officials. Training peasants to fight thus simply provided potential rebels with a superior quality of soldier. Furthermore, in the course of the rebellions, much of the population had been displaced, and loss of registered population meant a drastic decrease in tax income for the court. Motivated by the need to decrease expenditures and reduce internal threats, and by the uselessness of conscripts on the frontier, the newly established Eastern Han regime abolished both the annual training sessions and the local military officials. This did away with a formal peasant army, and left only a small, professional army stationed around the capital.
Following the split of the Xiongnu into southern and northern confederacies in 48 A.D., nomads were internally resettled on a large scale. To supervise these new inhabitants, the Eastern Han government set up standing army commands in camps at the frontier, one command for each major nomadic group resettled in China. These standing armies were manned by professional Han soldiers. The total number of troops in the camps is not recorded, but scattered citations indicate that they were in the tens of thousands. These camps remained a permanent feature of the Han army, and their troops took part in most of the major campaigns of the second century A.D.
Expeditionary armies were distinct from the standing armies, and drew their forces primarily from resettled barbarians. Most of the cavalry in the campaigns of the first century A.D. that destroyed the Xiongnu confederacy consisted of nomad soldiers. The Han founder had already employed tribal soldiers during the civil war. After the reign of Emperor Wu, these tribes were usually classified as “dependent states” and allowed to keep their own leaders and customs, under the supervision of a commandant. But the Eastern Han went beyond the policy of “using barbarians to control barbarians.” Non-Han soldiers also quelled internal rebellions, much as foreign mercenaries did for monarchs in early modern Europe. The histories record more than fifty cases of the participation of non-Han soldiers in Chinese armies. Twenty-seven of these list no Han troops in the forces involved, and six were under the command of tribal chieftains.
From this evidence it is clear that after the middle of the first century A.D. the primary source of mounted warriors was non-Han soldiers. State-controlled grasslands and stables for rearing military horses, which the Western Han had maintained since the reign of Emperor Jing in the second century B.C., were largely abandoned. The warlords of the Three Kingdoms period (220-280 A.D.) continued to rely on non-Han peoples to provide their cavalry.
In addition to using non-Han troops in their army, the Han also paid bounties for the heads of slain enemies. Xianbei chieftains, before submitting to the Han, received payments for the heads of Xiongnu. In 58 A.D. they again received payments for crushing a force of invading Wuhuan, and at that time they formally submitted. They received annual payments of 270,000,000 cash, and in return they controlled the Wuhuan and killed Xiongnu. Thus the most common military man in the Eastern Han was the nomad warrior serving the empire under the command of his tribal chieftain.
In contrast with the Warring States period, when regional cultures constituted the primary divisions in the Chinese sphere, the imagining of a world divided between nomads and Chinese marked a major step. It posited the fundamental unity of a single Chinese civilization defined by what was not nomadic, and it reduced regional divisions to secondary status. China first emerged as a unity through the invention of a Chinese/ nomad dichotomy, and this bipolar concept remained central to Chinese civilization in later periods.
It is ironic, then, that the political partition of the world into two spheres lasted only a few decades. In spite of increasing payments, Xiongnu incursions did not cease. Each agreement lasted a few years, only to be broken by a new invasion, which was followed in turn by demands for a resumption of peaceful relations based on an increase in payments. The Chinese attributed this to barbarian perfidy, but it reflected the nature of the Xiongnu state. While the Chinese emperor was unchallenged as chief lawgiver, judge, and administrator, power within the Xiongnu state was constrained and divided by kin bonds, customary practice, and horizontal segmentation between clans or tribes. The chanyu maintained control over his subordinate chiefs only by constant negotiations in which he was first among equals rather than an absolute authority. Consensus on his power hinged on his success in battle and distribution of booty.
In such a system, the chanyu could not refrain from military action indefinitely. Nor could he stop his subordinates from attacking on their own, for the power and prestige of chiefs likewise depended on their success in battle and distribution of booty. Sometimes they invaded because of tensions with local Chinese officials, sometimes because of resentment of the chanyu. The he qin policy failed because it relied on a structure of authority that did not exist among the Xiongnu.19
As treaty after treaty was violated, debates at the Chinese court were increasingly dominated by calls for war. Decades of peace had given the Chinese time to develop a new style of army based on cavalry and crossbows that could successfully engage the Xiongnu in the field. In 134 B.C. Emperor Wu finally undertook to destroy the Xiongnu through military action. Although his attempted ambush of the chanyu failed, in the decades that followed, Chinese armies pushed deep into Central Asia and inflicted substantial losses of both men and flocks on the Xiongnu.
However, Han losses were also considerable, and repeated campaigns drained the treasury without achieving any decisive result. Difficulties in transporting supplies and harsh weather meant that no army could spend even as much as one hundred days in the field, so victories could not be translated into an enduring occupation. Emperor Wu’s successors consequently abandoned his policy of launching expeditions and instead retired behind a defensive line, while refusing to pay tribute. This policy was successful, for it deprived the chanyu of Han tribute and also reduced his role as defender against Han invasions. The position of the chanyu deteriorated, and in 120 B.C. a dissident Xiongnu king surrendered to the Han with 40,000 men. In subsequent decades other chiefs refused to attend the chanyu’s court.20 Between 115 and 60 B.C. the Han also secured control of the former Xiongnu sphere of influence in eastern Central Asia (modern Xinjiang).
A battle over succession split the Xiongnu empire in 57 B.C., with no fewer than five kings claiming the title of chanyu. After several years one king acknowledged Han suzerainty, visited the Han court, and resettled inside China. This proved to be highly advantageous, for in exchange for obeisance he received generous gifts from the Han. He repeated his visit to the court in 49 and 33 B.C. and sent a son there as a hostage, whose well-being depended on his father’s good conduct and who learned Han culture. The wealth that the vassal chieftain gained allowed him to build up his following and defeat his rivals. Eventually, he grew powerful enough to return to the north and resume the old pattern of demanding tribute, until a second succession struggle renewed the civil war in 48 A.D. This led to a permanent split between the southern Xiongnu, who dwelt in China and submitted to the emperor, and the northern Xiongnu, who resided beyond the boundaries of the Han empire.
The southern Xiongnu became dependent on Han assistance, as indicated in 88 A.D. in a memorial from the southern chanyu: “Your servant humbly thinks back on how since his ancestor submitted to the Han we have been blessed with your support, keeping a sharp watch on the passes and providing strong armies for more than forty years. Your subjects have been born and reared in Han territory and have depended entirely on the Han for food. Each year we received gifts counted in the hundreds of millions [of cash].”21 This policy of resettling nomads still grouped in their tribes inside the Chinese empire would have disastrous long-term consequences, as we will see, leading to a breakdown in civil order in the northwest and the southward flight of large numbers of Han Chinese.
Although the northern Xiongnu continued to defy the Han, they were defeated on several occasions by allied armies of the Han and the southern Xiongnu. Moreover, other tribal peoples such as the Wuhuan and Xianbei broke away from the Xiongnu and received large bounties from the Han for killing Xiongnu. In 87 A.D. a Xianbei army defeated the Xiongnu, killed the northern chanyu, and flayed his body. More than 200,000 Xiongnu tribesmen surrendered after this defeat, and a great Han victory in 89 A.D. completed the destruction of the Xiongnu state.