6

The Xiongnu and Chinese Emperors at War

After nearly ten years of captivity among the barbarian Xiongnu, Zhang Qian, envoy of the Han emperor Wudi, at last reached his destination, the distant western land of the Yuezhi (today Tajikistan). In 138 BC, the emperor Wudi had commissioned Zhang Qian to conclude an alliance with the Yuezhi, Tocharian speakers whom the Xiongnu had expelled from their homeland fifty years earlier.1 Zhang Qian and his party, however, were captured by Xiongnu soon after they had passed through the Jade Gate. Zhang Qian, a gentleman and officer, won the favor of the Xiongnu ruler Jurchen, grandson of Modu Chanyu, and was treated as an honored guest until he managed his escape with his barbarian wife, their son, and the guide Ganfu. Zhang Qian was the first Chinese to penetrate so far west. He was impressed by what he saw. He was also disappointed because he failed in his mission. The emperor Wudi had ordered Zhang Qian on a daring mission to convince the Yuezhi to attack the Xiongnu from the west. The Yuezhi had close contact with Chinese civilization before their exodus to their new home in Ferghana. Zhang Qian had marveled at the magnificent beasts, which, at the gallop, sometimes sweat streams of blood because they were infected by a parasite. There alfalfa fields nourished the heavenly horses then prized as the finest cavalry horses in Eurasia.2 But the Yuezhi showed no interest in taking on the Xiongnu again. In 128 BC, Zhang Qian set out for home, but he and his family were again captured by the Xiongnu. They were again treated honorably until they escaped soon after the death of Jurchen Chanyu. Three years later, Zhang Qian reached the Han court and reported his findings to an astonished Emperor Wudi, who had long ago given up his envoy for dead. From Zhang Qian, the Han court obtained its first accurate information about the Xiongnu, the Western Regions, the great kingdoms beyond, and the profits to be gained from the Silk Road.3

By the time Zhang Qian returned, the emperor Wudi had already declared war on the Xiongnu. The emperor had not taken the decision lightly. The historian Sima Qian reports a debate between a frontier official and general Wang Hui and the minister and Confucian scholar Kong Anguo. Wang Hui pressed for war, frustrated by the frequent violations of the treaty by the Xiongnu, whereas Kong Anguo urged caution, warning that war was unpredictable save for emptying the treasury.4 The emperor Wudi, a nervous autocrat, feared that gifts to the barbarians could be viewed as a sign of weakness and spur on plots against him. The emperor Wudi had good cause for his suspicions. By all accounts, he lacked the commanding presence expected of an emperor. Disfigured from smallpox when a child, he was ugly and unassuming. Yet this retiring and taciturn ruler possessed a powerful intellect, thinking in farsighted strategic terms. In my opinion, today Wudi could outthink the best Russian chess masters by six moves in advance. He was the first Chinese ruler to pursue a long-term strategy that has characterized Chinese regimes ever since.

The emperor Wudi ordered his ministers to draft memoranda on how to defeat the nomads. They based their recommendations on a memorandum written a generation earlier by Chao Cuo, the minister of his grandfather, the emperor Wen, who had briefly considered, and then rejected, war against the Xiongnu. Wudi implemented many of these recommendations.5 He rearmed his infantry with pikes and crossbows with improved triggers and fitted for shooting multiple bolts.6 He replaced bronze weapons and armor with iron ones. Even more ambitious, he ordered the mounting of cavalry in place of chariots. Few Chinese at the time knew anything about horsemanship. The Chinese craftsmen would have to learn how to produce saddles, stirrups, and harnesses on short notice. The emperor would also have to overcome the prejudices of Chinese who long disparaged the leather trousers, boots, and kaftans of nomadic horsemen as barbarous garb. Furthermore, Chinese horses were too small and fragile to serve as cavalry mounts.7 Wudi needed to acquire and breed the best horses of Eurasia, the heavenly horses from Ferghana. Among his priorities, Zhang Qian was to negotiate a trade deal with the Yuezhi to supply thousands of Ferghana horses to the imperial army. In preparing for war, Wudi had to put the empire’s economy on a permanent war footing.

During a reign of fifty-four years, Wudi relentlessly waged a war against the Xiongnu on two fronts.8 On the northern front, Wudi sought to reoccupy and colonize the upper valley and great bend of the Yellow River and the Sixteen Prefectures, which had been lost to Modu Chanyu a generation earlier. The Great Wall, once repaired and extended, provided bases where Han generals concentrated men, horses, and matériel for an invasion of the Xiongnu heartland. Wudi aimed to break the power of the Xiongnu forever by forcing them to decisive battle. In the second theater to the west, Wudi ordered the conquest and annexation of the Western Regions beyond the Jade Gate. Here, the Han army first garrisoned the narrow Gansu (or Hexi) corridor between the steppes to the north and Tibetan highlands to the south. Then followed the occupation and colonization of the caravan cities of the Tarim Basin.

The war on the northern front opened in 133 BC, while Zhang Qian was languishing as an honored guest of Jurchen Chanyu. The emperor Wudi prudently decided not to lead the army himself, and he entrusted operations to his veteran general Wang Hui.9 Wang Hui planned an ambush outside of the city of Mayi (today Shaanxi) to annihilate the Xiongnu at a single stroke.10 Outside the city, the peasants and their livestock were left unawares that they were the tempting bait for the approaching Xiongnu. But Jurchen Chanyu sensed the deception, refused to take the bait, and withdrew. For the next seven years, the Xiongnu raided the northern Chinese frontiers in retaliation.11 Han frontier armies failed to check Xiongnu raiders, who easily escaped north across the Gobi.

In 127 BC, the Han general Wei Qing occupied the Ordos bend and upper valley of the Yellow River and repaired the Great Wall. The Xiongnu were again ruthlessly expelled, and one hundred thousand Chinese colonists were settled.12 Three times over the next eight years, Han generals mounted major invasions across the Gobi Desert, scattering the Xiongnu, and driving off livestock and captives. Zhang Qian, returned to imperial service, was attached to the imperial army, and he provided invaluable information on the sources of water and routes across the Gobi Desert. In 119 BC, the Han generals Wei Qing and Huo Qubing coordinated their strategy to defeat and compel the new Xiongnu ruler Ichise Chanyu, the brother of Jurchen and known as Yizhixie to the Chinese, to submit unconditionally.13 Each general led a separate column of large numbers of light cavalry into the Khangari Mountains.14 They then perfectly timed their attacks to converge on Ichise Chanyu’s tent city of Mobei, probably in the Orkhon valley (and close to Genghis Khan’s capital, Karakorum). The stunned Xiongnu fled across the Gobi, and Ichise Chanyu escaped to rally his people. For all its strategic brilliance, the battle failed to end the war. Chinese losses ran into the tens of thousands, while one hundred thousand horses died from exhaustion and dehydration.15 The generals Huo Qubing and Wei Qing pressed operations and acquitted themselves well in two lesser engagements. Huo Qubing encircled and destroyed a Xiongnu army led by the Wise King of the Left. Meanwhile, Wei Qing showed tactical finesse in defeating, for a second time, Ichise Chanyu, in open battle. Wei Qing drew up in a tight formation his chariots and heavy infantry armed with pikes and crossbows. They presented an unbroken front against Xiongnu horse archers who repeatedly charged, fired their arrows, and retired. The Chinese infantry held their ground in perfect discipline. Toward dusk, and under cover of a sandstorm, Wei Qing ordered his heavy cavalry to flank and encircle the charging Xiongnu, and so won the day. But Ichise Chanyu and many of the Xiongnu again escaped. These Han victories, while costly, ended major Xiongnu raids for a decade.

In 121 BC, the emperor Wudi directed his army west for the first time, to secure the Gansu corridor, and then to drive out the Xiongnu from the Western Regions (Xiyu). Once again, Zhang Qian provided vital information. General Huo Qing waged a campaign of maneuver, driving the Xiongnu out of the Gansu (Hexi) corridor. The next spring, he marched from Longzi, defeating another Xiongnu detachment, and then advanced as far as Lop Nur, seizing captives and livestock. Han armies methodically pacified district after district of the Western Regions over the next thirteen years. The eastern districts of the Tarim Basin just west of the Jade Gate were organized into Chinese military provinces. The Great Wall was extended to Dunhuang, the caravan city that yielded to Sir Aurel Stein so many commercial and religious texts. In 115 BC, Zhang Qian was again engaged as an envoy, this time to the Wu-sun, Iranian speakers who were perhaps ancestors of the Alans.16 The Wu-sun, disaffected vassals of the Xiongnu, were courted into an alliance against their overlords. In return for tribute payments of silk, the Wu-sun patrolled the steppes just north of the Gansu corridor. Between 108 and 101 BC, every oasis city of the Tarim Basin submitted to Chinese rule; the principal caravan centers such as Loulan and Turfan accepted Chinese garrisons.17 With the revenues of the caravan cities lost, the Xiongnu chanyu was hard-pressed to keep the loyalty of his western vassals, many of whom defected from the confederacy.

The emperor Wudi and his generals learned the value of cavalry from three decades of experience in waging brutal frontier warfare against an elusive mounted foe. Wudi was determined to assure the supremacy of the imperial army by obtaining breeding stock of Ferghana horses so that the imperial government would no longer depend on horses obtained in tribute from nomadic allies. In 104 BC, he entrusted an army to Li Guangli, brother of the emperor’s favorite concubine, to march over one thousand miles from the Dunhuang against the recalcitrant Sogdians, who were called the Dayuan by the Chinese.18 The Sogdians had refused to provide Ferghana horses to the imperial army. Li Guangli, while protesting his undying loyalty, was not up to the task. He botched the expedition and lost most of his army in the Taklamakan Desert before he ever reached his objective. In 102 BC, Li Guangli, thanks to the pleadings of his sister before a skeptical emperor, obtained an even larger army, one hundred eighty thousand strong. Only a fraction of this expedition reached the Sogdian city Khodjend (today Khujand in Tajikistan), the first major stop on the Jaxartes River for caravans descending from the Pamirs and heading west. Li Guangli cut off the city’s water supply, and compelled the Sogdians to provide Ferghana horses. Out of the one hundred eighty thousand who set out on the march, only one thousand cavalry and ten thousand infantry managed to return to base the next year. The war euphemistically called the War of the Heavenly Horses epitomizes the determination of Wudi to win at any cost. For the emperor, the loss of over two hundred thousand soldiers was acceptable in return for five thousand horses, which, in time, might breed fifty thousand horses for the imperial army. Yet the experiment in breeding never worked. The fodder fed to horses in China lacked the selenium necessary for strong bones and muscles, so Chinese-bred horses did not match those nurtured on the grasslands of the Eurasian steppes. In the end, Wudi could never free the imperial army from its dependence on horses provided by the steppe nomads.

Yet the war against the Xiongnu did not end with the Han conquest of the Western Regions. In his final years, Wudi witnessed several embarrassing setbacks, including the defeat and capture of the court favorite Li Guangli.19 Li Guangli, ever the opportunist, switched sides and married the daughter of Hulugu Chanyu, although he later ran afoul of his new master and was condemned to commit suicide on the grounds of treason.20 The later Han generals failed to achieve the same success of earlier invasions of the Xiongnu heartland, because the later chanyu Qiedi and Hulugu adopted a scorched-earth strategy and evaded decisive battle. At no point did Wudi consider negotiation and renewal of the tribute system. He thus committed his successors the emperors Zhao and Xuan to another thirty years of prosecuting this ruinous frontier war. Wudi also committed his successors to subjecting the resentful Tocharian and Sogdian inhabitants of the Western Regions, who shared far more in mores and outlook with the Xiongnu than the Chinese. They chafed under the heavy taxation of the Han administration that impaired their commerce. Chinese losses in men and horses over the course of forty-five years were staggering. The expeditions against Mobei in 119 BC or Sogdiana in 102 BC alone totaled losses of over three hundred thousand men and tens of thousands of horses.21 The Han treasury repeatedly faced crises; over half of the annual revenue (ten billion cash) was consumed in the campaign of 119 BC alone.22

Wudi waged his war against seven successive chanyu. Denied tribute from the Han emperor, and without the revenues from the caravan trade, each chanyu faced not just defeat but extermination. They would have preferred to return to the terms of the treaty of 198 BC, but they were denied this choice. So they could only fight on tenaciously. Three of them, Ichise, Qiedi, and Hulugu, displayed exceptional resilience and determination, and they inspired the Xiongnu to amazing defiance in the face of overwhelming odds. Chinese historians recording these events never comment on the courage and sufferings of the hated barbarians.23 They report that in the campaigns of 124 to 119 BC, over three hundred thousand Xiongnu were slain or captured. If these figures are at all accurate, between one-quarter and one-third of the confederacy’s population was lost due to direct Chinese military actions. Famine and disease carried off many more, because the same chroniclers report in glowing terms the millions of captured cattle, goats, sheep, and horses. The losses suffered by the Xiongnu, in modern terms, reached the level of genocidal.

War also revealed the political weakness of the confederacy despite the central administration forged by Modu Chanyu. The Xiongnu, like most nomadic peoples, practiced lateral succession.24 Upon the death of a chanyu, succession did not pass automatically to the eldest son, but rather to the eldest, and most charismatic, of the adult relatives of the chanyu’s generation. Kingship thus often passed from brother to brother, uncle to nephew, or cousin to cousin. Any transfer of power risked civil war. Under the hammer of repeated attacks by Han armies, rival candidates disputed, and even fought over, the right to succeed as chanyu. In 54 BC, civil war erupted among the Xiongnu, pitting Zhizhi Chanyu, who ruled over the northern tribes of the confederacy, against his brother Huhanye, who was recognized by the southern tribes dwelling north of the Chinese frontier.25 The Han emperor Xuan backed Huhanye, and awarded him a treaty and tribute. Huhanye eventually emerged the victor, and so at minimal cost, the emperor Xuan gained peace for the next sixty years. But later Han emperors failed to convert the benefits of peace into effective governing. In 9 AD, Wang Mang, an impoverished scion of the imperial house, ended his regency over a boy emperor and proclaimed himself emperor of a new Xin dynasty.26 He vowed to restore the legendary prosperity of the Zhou dynasty, and so his officials feverishly searched texts for precedents for a program of radical reform. Wang Mang himself had cut an impressive figure during his three decades of imperial service. Confident, inventive, and affable, he charmed many at court, but he also aroused jealousy in many others competing with him for imperial favor.

Wang Mang immediately set to work reforming the fiscal and military institutions undermined by decades of corruption and frontier wars. In the boldness of his vision, Wang Mang has been aptly compared with the Roman emperor Diocletian (284–305), another brilliant, conservative reformer who rescued his empire from crisis.27 Both rulers shared an understanding of the urgency for currency reform.28 But Wang Mang went much further, overturning the established social order and seizing and redistributing so much private property that he has ever since been condemned or praised as the first proponent of state socialism. Wang Mang, unlike Diocletian (who retired after a successful reign of twenty years to cultivate his cabbage garden), was not favored by fortune. Wang Mang could never overcome the hostility of imperial officers and officials for his audacious seizure of power. His ablest general, Wang Chang, an astrologer turned soldier, failed to win the decisive Battle of Kunyang, and then died mysteriously while hunting. His other generals failed to win the decisive battle against the rebels led by Liu Xiu (and the future Han emperor Guangwu). Even Zhi Chanyu was not impressed.29 As soon as the emperor’s envoys appeared bearing the customary gifts, the chanyu objected to the new seal on the treaty in the name of the Xin rather than the Han Son of Heaven. Zhi Chanyu could read Chinese ideograms, and he doubted the legitimacy of the new regime in Chang’an. The Chinese envoys refused to use the original seal to authenticate the treaty, and then destroyed it in front of Zhi Chanyu. Zhi Chanyu was enraged and declared the treaty broken. He immediately ordered attacks along the Chinese frontier. Wang Mang, just as infuriated, declared war, but failed to take military action. Instead, Wang Mang resorted to duplicity, encouraging Xiongnu pretenders. Twice, Wang Mang even violated safe conduct pledges and seized high-ranking Xiongnu as hostages. Meanwhile, Wang Mang was battling pretenders of the Han dynasty and peasant rebels outraged over his sweeping reforms. He was compelled to withdraw the garrisons of the Western Regions to counter the threats within the empire. The Xiongnu promptly imposed their rule over the cities of the Tarim Basin for the next sixty years.30 His dismal failure in checking the Xiongnu proved the final blow. Wang Mang died fighting in his palace against the forces of Liu Xuan. His body was mutilated and its head severed to be nailed to the city walls of Wancheng and later kept as a trophy in the imperial vaults. Liu Xuan, under the throne name of Gengshi, restored the Han dynasty.31

The new Han emperors and their historians condemned Wang Mang as an impious usurper who never enjoyed the Mandate of Heaven, but they quietly adopted his policy of dealing with the Xiongnu. Henceforth, the Han emperor showered titles and gifts upon any nomadic prince who would do his bidding. In contrast, early Han emperors had supported a single chanyu so that he could keep the tribes in line and assure trade. The emperors of this Latter or Western Han dynasty aimed to restore the northern frontier and control over the Western Regions. In 46 AD, the opportunity came with the outbreak of another civil war, this time between two first cousins.32 Prince Bi of the southern tribes challenged the right to rule by his cousin Punu, son of Huduershidaogao Chanyu. The emperor Guangwu backed Prince Bi and the southern Xiongnu, and so committed the Han dynasty to yet another Xiongnu war of nearly sixty years. The Xiongnu confederacy thereafter permanently split into a northern and southern one under rival branches of the house of Modu Chanyu.33 Chinese emperors henceforth distinguished between Inner Barbarians dwelling north of the Great Wall who were accorded a treaty and tribute from the remote Outer Barbarians on the Mongolian steppes, who were perceived as the prime threat.34 In effect, Han emperors drafted tribal regiments of the Inner Barbarians into the imperial army so that they were the equivalent of federate barbarian regiments of late imperial Rome.35 This modified tributary system exalted the Han emperor over barbarian rulers, maintained the conceit of the primacy of the Middle Kingdom, and gained invaluable nomadic cavalry. Yet the chanyu of the Southern Xiongnu profited even more because he held the decisive military power along the Chinese northern and western frontiers. In time, any Xiongnu prince could turn himself into an emperor in North China should the power of the Han dynasty ever weaken.

The later Han emperors entrusted to their generals in the field far more independence of action in conducting campaigns and imposing settlements on the defeated. In part, these Han emperors were far more concerned about frontiers in Korea and the far southern regions. None of them enjoyed the long reign and indomitable will of Wudi, who kept an iron grip over strategy and his armies. Furthermore, Han generals needed the freedom of action if they were to impress and inspire the Xiongnu allies to follow. Victory in this second war, in many ways, was as much the victory of the Southern Xiongnu tribes as it was of the Han army. Promoting disunity among the Xiongnu complicated both diplomacy and strategy as each Xiongnu prince shifted his allegiance between the Han emperor and the chanyu of the Northern Xiongnu. At the end of this second war, Chinese chroniclers were bewildered by the number and diversity of tribes on the Eurasian steppes, counting at least one hundred twenty tribes.36

Two of the ablest Han generals delivered final victory against the Northern Xiongnu on the eastern steppes. Dou Xian directed a series of campaigns between 89 and 92 that finally broke the power of the Northern Xiongnu. He owed his position to his sister, the empress Xiaowen, who was married to the emperor Wen. Dou Xian brilliantly served three successive emperors, but he was recalled in disgrace just after winning the final victory because he was implicated in a plot masterminded by his sister, then dowager empress, against her young stepson, the emperor He, and his powerful eunuch minister, Zheng Zhong. Dou Xian was spared due to his loyal service, but other members of his family were executed.37 Even so, Dou Gu won immortality among Chinese generals by his victory over the Northern Xiongnu at Yanran Mountain in 89 AD. He ordered a memorial inscription cut into the sandstone cliffs exalting his achievements in the traditional courtly poetry of the Chu Ci. Thereafter, the proverbial phase of praise of carving on a stone of Yanran was granted to a successful general. The location of the inscription was lost until it was rediscovered by a Mongolian travel writer in 2001.38 Sixteen years later, a team of Mongolian and Chinese scholars returned to the site on the southeastern edge of the Gobi. They photographed, transcribed, and translated the inscription. They were astonished to discover that the brother-sister team of historians, Ban Gu and Ban Zhao, had faithfully recorded the text soon afterward. Their record, in turn, was incorporated and preserved in the Hou Hanshu (Book of the Latter Han) of the fifth century AD.

In the Western Regions, the equally brilliant general Ban Chao expelled the Northern Xiongnu and reimposed imperial rule between 75 and 102 AD.39 Ban Chao, a Confucian mandarin from a family of historians, was assured that his deeds would be remembered in the most favorable light.40 Even so, he proved to be an able general and adroit diplomat. Even more important, he never ran afoul of the two emperors he served or the scheming factions at the court of Luoyang. Ban Chao, appointed Protector General of the Western Regions in 91, wielded regal power. He signed treaties of alliance with nomadic allies, elevated and deposed dynasts who ruled the caravan cities, and directed expeditions into the Central Eurasian steppes. In the course of twenty-seven years, he acquired eight native wives to cement political alliances. Six of them survived to accompany Ban Chao to a comfortable, well-deserved, and all too brief retirement at Luoyang in 102. Today, Ban Chao is honored with a heroic statue in the city of Kashgar, at the eastern end of the Xinjiang Uyghur Autonomous Region of the Chinese People’s Republic. He is rightly hailed as the founder of Chinese rule in the Western Regions, to the acclaim of Chinese residents and to the chagrin of Uyghur nationalists.

In 86, Ban Chao reached the banks of the Upper Jaxartes, and brought into submission Iranian-speaking nomads as far as the Aral Sea. He thus extended the Han Empire to its farthest limit. He now learned firsthand how the political geography of the lands beyond the Western Regions had changed since the visit of Zhang Qian over two centuries earlier. The Kushan emperor Vima Taktu, hailed as the great savior by his Greek subjects of Bactria, reigned as the Son of Heaven over a great empire stretching from the Jaxartes to the Ganges.41 Ban Chao must have been awestruck by how the descendants of the Yuezhi, despised by Chinese and Xiongnu alike, had risen to imperial status. The Kushan emperor could correspond on terms of equality with the other Son of Heaven at Luoyang. He could also challenge Han authority in the Western Regions. To the west of the Kushan Empire ruled the Arsacid king of Parthia, known to the Chinese as Anxi. They were yet another steppe nomadic people who had turned themselves into masters of a powerful empire. They were also possible allies against the Kushans. Beyond Parthia lay an even greater imperial power, Daqin, the Roman Empire. In 97, out of curiosity and fear, Ban Chao acted as the proxy of his emperor He and dispatched as an imperial envoy Gan Ying to learn about these distant powers and, if possible, to secure commercial and military alliances.

The travels of Gan Ying excited the imagination of later Chinese historians who faithfully recorded his extraordinary tour of the Kushan and Parthian Empires.42 Gan Ying, once he crossed the Jaxartes River, left the area of Chinese control.43 He followed the caravan route to Bactra (Balkh), crossed the Hindu Kush, and visited Gandhara in the heart of the Kushan Empire. He descended to the middle Indus, and then traveled west to Areia (Herat) via the Bolan Pass into the Parthian Empire. After a journey of three months, he finally reached Tiaozhi (Characene) and Sibin (Susiana) in southeastern Iran today. As far as can be determined, he never saw the Tigris River or the Parthian capital of Ctesiphon. At Susa, Gan Ying likely spoke with members of the Arsacid court about Daqin. His Parthian informants discouraged him by exaggerating the dangers and the length of the journey to Daqin, which, they alleged, could only be reached by an ocean voyage of three months. They were referring to the trade route from Charax, on the Persian Gulf, around the Arabian peninsula, to ports on the Red Sea in Roman Egypt. They deliberately omitted mentioning a more direct overland route across the Fertile Crescent to Antioch in Roman Syria. Gan Ying, who was now nearly five thousand miles from home, feared, like many of his countrymen, venturing out to sea. He decided to retrace his steps and to report to Ban Chao his findings. Based on his informants, he brought back to his fellow Chinese the first description of the Roman Empire. The historians of the Hou Hanshu summarized the report as follows:

Their kings are not permanent. They select and appoint the most worthy man. If there are unexpected calamities in the kingdom, such as frequent extraordinary winds or rains, he is unceremoniously rejected and replaced. The one who has been dismissed quietly accepts his demotion, and is not angry. The people of this country are all tall and honest. They resemble the people of the Middle Kingdom and that is why this kingdom is called Da Qin [or “Great China”]. This country produces plenty of gold [and] silver, [and of] rare and precious [things] they have luminous jade, “bright moon pearls,” Haiji rhinoceroses, coral, yellow amber, opaque glass, whitish chalcedony, red cinnabar, green gemstones, gold thread embroideries, rugs woven with gold thread, delicate polychrome silks painted with gold, and asbestos cloth. They also have a fine cloth which some people say is made from the down of “water sheep,” but which is made, in fact, from the cocoons of wild silkworms. They blend all sorts of fragrances, and by boiling the juice, make a compound perfume. [They have] all the precious and rare things that come from the various foreign kingdoms. They make gold and silver coins. Ten silver coins are worth one gold coin. They trade with Anxi [Parthia] and Tianzhu [Northwest India] by sea. The profit margin is ten to one... The king of this country always wanted to send envoys to Han, but Anxi [Parthia], wishing to control the trade in multi-colored Chinese silks, blocked the route to prevent [the Romans] getting through [to China].44

Historians have long speculated about what would have happened if Ying Gan had pressed on, for he would have reached Rome in the year 98. He would have gained an audience from the emperor Trajan, arguably the greatest emperor after Augustus, who enjoyed the singular distinction of being more popular at his death than at his accession. Trajan would have been most receptive to an alliance against the Parthians, who challenged Rome for mastery of the Near East and charged outrageously high customs duties on silks carried by caravans bound for Rome.45 The Han court, however, would have wanted an alliance against the Kushans. It is extremely unlikely that the negotiations would have resulted in any effective cooperation. When the two courts finally did exchange envoys in 166, they remained respectfully, and distantly, on cordial terms.46

The Han dynasty reached its apex at the opening of the second century AD, at the same time when the emperor Trajan had brought the Roman Empire to its greatest extent. Yet the Han court feared appointing effective protector generals who might challenge the dynasty’s Mandate of Heaven. Within a generation of the death of Ban Chao, the Han armies were withdrawn from the Western Regions.47 The greatest Kushan emperor, Kanishka I, soon asserted control over the Tarim Basin.48 The Tocharian-and Iranian-speaking residents of the cities and the nomads of the Tarim Basin preferred Kushan hegemony over a Chinese one. Even more significantly, as Han power weakened from the mid-second century on, Xiongnu allies moved south of the Great Wall and settled in northern China. There, Xiongnu princes began to carve out their own states. In time, they would assume Chinese throne names and, with the aid of mandarin bureaucrats, rule as regional lords over the northern provinces of the former Han Empire.49 Ultimately, Han victory proved to be Pyrrhic, for it ironically benefited the Xiongnu allies far more than the dynasty. In 220, the Han Empire did not so much fall as fragment for the next three hundred fifty years.50 The wars between the Xiongnu and Han emperors also drove west Tocharian-and Iranian-speaking nomads to seek new homes in Transoxiana, Iran, and northern India. Foremost among these were the Kushans, descendants of the Yuezhi.