Migration of the Yuezhi and the Conquest of Bactria
The Kushans were descended from a pastoral-nomadic confederation known as the Da Yuezhi to the Chinese, and as the Tocharians to a range of contiguous peoples, because they most probably spoke the Indo-European language of Tocharian.
The identification of the Yuezhi as the Tocharians is aided by the fact that Ptolemy, the second-century ce Greco-Roman geographer, names five separate Tocharian variant groups, located at different places (and with different spellings) across a large swath of Central Asia. The location of each of these groups seems to align with Han Chinese accounts of the route that the Yuezhi followed during their 30-year migration from the Gansu Corridor through Central Asia to Bactria between ca. 166 and ca. 130 bce. However, although Ptolemy's references to groups with names seemingly derived from the word Tocharian have long been used to offer incidental support of the Chinese evidence for that migration, Etienne de la Vaissiere has argued that while some of Ptolemy's Tocharian locations do appear accurate, others are less plausible.[935] The ancestors of the Yuezhi were probably Indo-European pastoral nomads who had migrated eastward during the Bronze Ages (possibly associated with the Afanasevo Culture first identified by Russian archaeologists), who settled eventually in the Gansu Corridor and Tarim Basin regions of western China.[936]The Afanasevo were just one of many significant pastoral nomadic groups whose impact on the sedentary states of ancient Eurasia was so profound. Pastoral nomads are communities that live primarily from the exploitation of domestic animals such as cattle, sheep, camels, or horses. The exact chronology of the origins and spread of pastoralism remains obscure, but certainly by the mid- to late fourth millennium bce the appearance of burial mounds across the steppes of Inner Asia indicates that some communities that were dependent upon herds or flocks of domestic animals had become semi-nomadic.
There were varying degrees of nomadism, ranging from groups that had no permanent settlements at all to communities like the Andronovo that were largely sedentary and lived in permanent settlements. The highly mobile, militarized pastoralism of Inner Asia, associated with the riding of horses by Saka, Yuezhi, Xiongnu, and other groups, probably did not emerge until early in the first millennium bce.In addition to Ptolemy and the Han sources, the Yuezhi/Tocharians are also noted, often tangentially, in the literature of a number of other contemporary states during the first millennium bce. Centuries before they came to the attention of Han historians, the Yuezhi were mentioned in Zhou dynasty texts such as the Zhou Shu and the Guanzi, where they are described as tribute bearers and wealthy suppliers of jade and steppe horses to the Zhou Court. The Yuezhi are also mentioned in the Indian epics the Mahabharata and Ramayana, and are also named in several Tibetan, Khotanese-Sakan, and Persian manuscripts.[937] Early Han Dynasty historians Sima Qian and Ban Gu introduce the Yuezhi as the most powerful of several militarized nomadic groups dwelling along the northwestern borders of China in the third century bce.
The Han references to these various militarized nomads are evidence of increased pastoral nomadic mobility in the steppes more generally, perhaps focused on an epicenter in eastern Kazakhstan and southern Siberia, from which these movements seem to emanate.[938] The principal cause of this increased activity was probably climate change, with the arrival of cooler and drier weather making both pastoralism and agriculture more difficult in the steppes. The pastoralists reacted by grazing their herds over larger areas, and by seeking new pasturelands further south, leading to an increase in nomadism and a consequent increase in pressure along the borders of sedentary societies like China.[939]
But explanations of more restive nomadic activity must also take other factors into account, including overpopulation, an intensification of trade, and an increased military technological capacity through the development of a more powerful compound bow.
Pulleyblank argues that the development of the compound bow was the most significant factor in explaining enhanced nomadic militarized activity in the mid- to late-first millennium bce.[940] It was this enhancement of the military power of mounted archers following the development of this powerful bow that became the principal distinguishing characteristic of the classic horse nomadism of the era. This in turn allowed for “the formation of steppe empires as powerful as the agrarian empires that had emerged on the fringes of the steppes in Outer Eurasia.”[941] The relationship between the Yuezhi, the Xiongnu, and the Han is a striking example of this technologically induced redistribution in the balance of power between militarized semi-nomadic pastoralists and a sedentary agrarian civilization.The Early Han sources describe the Yuezhi as “a nation of nomads,” moving around “in company with their stock animals,” and their customs and way of life were similar to those of the Xiongnu,[942] but it is more likely that both the Yuezhi and the Xiongnu followed a semi-sedentary oasis-based agriculturist/pastoralist lifeway. The Yuezhi and Xiongnu coexisted in the region with other smaller nomadic confederations, including the Wusun, who may, like the Yuezhi, have also been Indo-European speakers.[943] With a military force, according to the probably inflated Han sources, of some 100,000 trained archer warriors, the Yuezhi were powerful and relied on their military strength to maintain their sway over both the Xiongnu and Wusun. But the dynamics of this relationship changed dramatically late in the third century bce with the accession of Modu as Shanyu (supreme ruler) of the Xiongnu.
In 209 bce Modu assassinated his father and established himself as the new Shanyu. Modu immediately set about increasing Xiongnu power by launching raids on the Yuezhi and other rival confederations. Modu eventually massed a force, again according to the no doubt inflated Han sources, of over 300,000 skilled archer warriors, and the Xiongnu were able to treat even the Han forces with disdain.
As Sima Qian put it: “When Modu came to power... the Xiongnu reached the peak of their strength and size, subjugating all other barbarian tribes of the north and turning south to confront China as a rival nation.”[944] Further raids upon the Yuezhi followed in 176 and 166 bce, with the latter attack proving decisive. Reports received by the Han more than two decades after the event (so in ca. 140 bce) indicated that Modus son and successor Jizhu had utterly defeated the Yuezhi and turned their king's skull into a drinking cup.[945] The only option that had apparently remained to the Yuezhi was to migrate far away from the Gansu, leaving the Xiongnu and the Han to sort out a new balance of power in the region. The migration of the Yuezhi was destined to take them far from Western China, but in the process of relocating they were able to carve out for themselves a new and even more significant role in the history of ancient Central Asia.Once modern historians began to consider the consequences of this migration, its significance was immediately apparent. In 1931 G. F. Hudson described it as “the most important ethnic movement in Central Asia since the great Scythian migration some six centuries before,” and this conclusion has only strengthened since.[946] From the evidence of the Han sources, and Ptolemy's knowledge of some Tocharian groups noted earlier, it seems that the various tribes that constituted the Yuezhi confederation followed the ruling dynasty to the north and west, taking up residence in the valley of the Ili River for three decades before being uprooted and forced westward again by an invasion of hostile Wusun and Xiongnu forces late in the 130s. After passing through parts of the Ferghana and Zeravshan valleys, the Yuezhi turned south and eventually concluded their “long march” along the border between modern Uzbekistan and Afghanistan, settling in the Surkhan Darya and neighboring valleys just to the north of the Amu Darya in about 130 bce.
The significance of the Yuezhi migration is also apparent in the wider impact it had on the geopolitics of Inner Eurasia. As they moved into regions already occupied by pastoralists or agriculturists, the vast migrating horde created a domino effect that forced various groups of Saka in particular to uproot and undertake their own substantial migrations. Some headed south through the western Tarim Basin, crossed the so-called Hanging Pass (possibly the Khunjerab Pass along the route of the modern Karakorum Highway), and settled in Kashmir. Others were forced into Bactria, where they settled for a while in Sakastan (present-day Seistan Province), before later being forced, perhaps as a result of the expansion of early Kushan power, to move to the southeast into the Upper Indus and Punjab. Here they established a series of powerful Saka or Shaka kingdoms that remain important enough to early Indian history that an entire era is dated from their formation (the Shaka Era of 78 ce).
Beyond these regional ramifications, the migration of the Yuezhi is of further consequence to world history in that it was directly responsible for the expansion of trans-Eurasian material and cultural exchange that occurred during the First Silk Roads Era. Silk Roads trade was greatly facilitated by the eventual establishment of the Kushan Empire, but it only became possible after the migration of the Yuezhi brought China into extensive engagement with Central Asia for the first time. Soon after coming to power in 141 bce, the vigorous young Han emperor Wudi (141-87 bce) decided to reverse decades of political appeasement with the Xiongnu and pursue a new strategy in which the Chinese military would directly confront the powerful horde. As a first step in this plan, the emperor recruited and dispatched special envoy Zhang Qian to follow the long-departed Yuezhi deep into Central Asia in an attempt to persuade them to form an alliance against the Xiongnu. Although Zhang Qian (after an epic 13-year journey from ca.
138 to ca. 126 bce that included a decade as captive of the Xiongnu) was ultimately unsuccessful in eliciting support from the now happily resettled Yuezhi, the information he brought back to the Han court about the possibilities of imperial and commercial expansion in Central Asia persuaded Wudi to adopt an expansionist policy that led eventually to the incorporation of dozens of states of the Western Regions into the Han Empire by the early first century bce. And this in turn brought Han commercial interests into contact for the first time with the traders of Central Asia, Parthia, and eventually Rome.The century and a half between the visit of Zhang Qian and the emergence of a new ruling Yuezhi/Kushan dynasty (so from roughly 128 bce to 25 ce) might be described as the Kushan “Dark Ages,” because evidence is so sparse. Sometime in the first two decades of the first century bce the Yuezhi left their strongholds in northern Bactria, crossed the Amu Darya, and occupied much of Bactria en masse. At about the same time they divided (for reasons we can only surmise) into five ethnic or tribal subdivisions called xihou (princes, so princedoms[947]), each of which occupied a strategic location in Bactria. One of the five xihou, that of the Guishuang (from whence the name Kushan is derived), remained in occupation of the original Yuezhi stronghold along the present-day border between Uzbekistan and Afghanistan. Eventually, by perhaps 25 ce, Kujula Kadphises, a prince of the Guishuang xihou, reunited the fragmented princedoms into one powerful confederation and began to expand territorially, essentially creating the embryonic Kushan Empire.