The strength of metropolitan development in Central Asia has a long history with urban development that can be traced back to the Bronze Age and continuing under the Achaemenids and the Greeks, following Alexander's brief incursion. The full flourishing of these ancient cities, however, next seems to have taken place as a consequence of the lengthy peace brought about by Kushan imperial rule. This millennium was one of considerable prosperity in Central Asia, reflected by the remains of numerous large cities, such as Merv, Toprak kala, Ayaz kala, Afrasiab, Varakhsha, Panjikent, Termez, etc. Following is a computer-aided reconstruction of the Hellenistic city of Ai Khanum:
For most classicists of the Mediterranean world, Central Asia is known essentially for its Hellenistic past, beginning with the expedition of Alexander in 329-327 BC.] However, north of the Hindu Kush, this period, which ended between about 145 and 130 BC, was only a brief event in the history of the region. Since the beginning of the Iron Age, Central Asian oases have known endless invasions and migrations, and a permanent interaction between sedentary, semi-mobile and nomadic populations is evident.
The position of the frontier between Bactria and Sogdiana appears to have changed between the Iron Age and the Kushan period, with a progressive reduction northward of the territory of Sogdiana from the region of the Darya-i Pandj to the Baysun and Hissar ranges. The geography of the Oxus and the Ochus as presented in the sources for Alexander's expedition indicates that in the late Achaemenid and Hellenistic periods the northern Bactrian frontier probably lay along the Amu-darya and the Wakhsh, rather than at the Iron Gates or along the Amu-darya and the Darya-i Pandj. This research has no implications for the archaeology, since before the Kushans the cultural context was very similar on both sides of the Oxus; it is doubtful that the now traditional term 'Northern-Bactrian' for the right bank of the Oxus-the classical Oxiana region-will ever be changed, but subtleties should not be forgotten when historical interpretations focus on defined 'ethnic' locations along the frontiers or peripheral regions.
As can be inferred from the discoveries of Ai Khanum, Bactria was, in the Hellenistic period, a major cultural centre, from which Greek culture radiated throughout Central Asia. But, from an economic point of view, nothing appears to prove that the GraecoBactrians were interested economically by their position on the main crossroads of Asia. The scarcity of coins on the site of Afrasiab and in its region is probably due to the short time of Hellenistic power, but it also suggests that in the Hellenistic period, trade in northern Sogdiana was not based on a developed monetary system (GraecoBactrian coins were mainly diffused in the form of imitations only by later nomad authorities). In Bactria, on the other hand, the monetary finds do not present such concentration as in the Indian area. So far as international commerce is concerned, the imports to Ai Khanum are limited to a few 'occidental' products, like Mediterranean plaster mouldings on metallic vases for the Graeco-Bactrian artists, olive oil for the gymnasium activities, or books for the library, whereas the Indian objects collected mainly in the treasury of the palace have simply been identified as booty from Eucratides' Indian expeditions against Menander. (After Alexandrer: Central Asia before Islam, 2007, p.63.)
Another constant of Central Asian life has been 'Invasion', either of expanding imperial powers, such as Alexander and his successors or the Sasanian empire, or by nomads, such as the Saka or Yuezhi.
Despite their direct links represented, for example, by the eastern imports identified at Nisa (Bactrian royal gifts or war booty?), the Parthians were probably partially responsible for the economic isolation of the Graeco-Bactrians from the western world. Before their disappearance, the Graeco-Bactrian economy appears therefore to have been based more on local natural resources and regional crafts than on any international commercial potential, whereas the links perceived with the Indo-Greek world tended to be of an ideological, political and military nature. Therefore, it is important to underline the role of the nomads in the renewal of cultures and in the development of international trade in Central Asia. The network of commercial routes between China, India and the western world through the steppe and later through the Indian Ocean corresponds to the so-called 'Silk Road'. Its real beginning is difficult to date, and this event is not necessarily a direct consequence of the disappearance of the Graeco- Bactrian rulers. The first links with China in the last third of the second century Be are related to the initiative of its emperor, who sent his ambassador Zhang Qian. The main information provided by the report of this envoy is that all the roads between China and Central Asia were controlled by mobile nomads. The identity of the merchants active in Lan-shi (see above) is difficult to determine. Their presence does coincide with the period of the plundering of the Graeco-Bactrian kingdom, and does not imply the involvement of a wide commercial system. Trade on a large scale probably begins later, when the Scythian and Kushan power in northern India appears well established and connected to the northern regions through roads affording sufficient security to travellers. The opening of international trade is therefore to be dated around the beginning of the first century AD, 57 in the period represented by the rich nomad burials of Tillya Tepe and Koktepe.
The ethnic and cultural identities and migration routes of Central Asian nomadic tribes present one of the most disputed questions of those related to the Kushans. The tribes appear in literary sources preserved mainly in Chinese chronicles and in scarce references in the works of Greek and Latin authors. The migration of Central Asian nomads, particularly into Transoxiana can be divided into two categories. The long 'trans-regional' route is ascribable to the Yuezhi migration from the valley of Gansu, on the northern borders of China, to the territory north of the Oxus River (Amu Darya), while the migration of tribes like the Dahae, Sakaraules, Appasiakes, Parnes etc. can be classified as 'local' movements.
After being defeated by the Xiongnu, the Yuezhi migrated westwards. The first to clash with them were the Wusun. According to the Chinese chronicles, the Wusun initially inhabited territory in eastern Turkestan prior to being defeated by Xiongnu in 176 BC. In about 160 BC, the Wusun moved to the area of Semirech'e following the same path as the Yuezhi. According to this version of events the locally found Wusun cultural remains must be dated no earlier than the second century BC. However, some investigators also attribute monuments of both earlier and later periods to the Wusun culture. They identify as Wusun most of the necropolis remains of the third century BC to fifth century AD in Semirech'e, Tian Shan, the valley of Ta1as, and at the foot of Karatau. This interpretation is not sufficiently substantiated as it is based on the absence of reliable chronology and a contradictory interpretation of literary sources. According to Kazim Abdullaev a leading Researcher at the Institute of Archeology of Uzbekistan, literary sources recount how the Yuezhi on their long journey from the valley of Gansu met different peoples. The first were the Wusun. After their defeat by the Wusun in the region of Semirech'e, the Yuezhi migrated further in a westerly direction. Passing through Da Yuan, they reached the region between the two rivers of Amu Darya and Syr Darya. Here, north of the Oxus River, they found another tribe already settled for some time, whom we can hypothetically identify as the Sakaraules.
This tribe is linked with the culture of the archaeological monuments of lower Syr Darya and is placed in eastern provinces of Khwarezm (Choresmia) and have been identified with the Kangju. In approximately the third to first half of the second century BC, these tribes migrated in a southern direction and settled around the Samarkand and Bukhara oases. In all probability, one can connect the representatives of the culture of the Orlat kurgans (tumuli) with the tribe of the Sakaraules, who dwelt in former times in the region of Kangju. If we follow this scheme further, the territory of the Sakaraules accords with the description in Strabo, who locates them as coming originally from the region beyond the Jaxartes river.
The discovery of a 'Sasanian' relief published in After Alexandrer: Central Asia before Islam, 2007, found on a cliff in central Afghanistan, rather than Iran, shows a rhinoceros hunt, which appears to symbolize a Sasanian king's conquest of 'India'.
Buddhism spread to Bactria in the Kushan period thanks to its support from the Kushan nobility. In the first to third centuries there is a considerable flowering of Buddhist art to be observed, mainly that of the monumental variety (sculpture, wall-paintings), which was also made possible by support from the Kushan nobility. Most of the work on the decoration of Buddhist monuments at that time was undertaken by professional artists, who did not belong to the Buddhist community. In their work they made use of the iconography of the two main centres of Buddhist art-Gandhara and, to a lesser extent, Mathura. Analysis of the works of art in Bactria of the Kushan period has shown that the influence of Buddhist iconography on non-Buddhist art was minimal.
In the early medieval period certain changes took place in the social composition of the community of Buddhist believers in Bactria-Tokharistan. Buddhism ceased to be merely a religion of the nobility and began to spread among the ranks of the common people and probably not just in the towns. The Buddhist buildings of Tokharistan were being decorated by Buddhist artists by this time, and they were working within the framework of the artistic tradition of the region. Examples have been recorded of the influence of Buddhist iconography on non-Buddhist sculpture in the Early Medieval period. In addition the main influence on the development of Buddhist art in Tokharistan at that time was from Kashmir, which became an important centre of Buddhist teaching and art in the second half of the first millennium. The spread of Islam in Tokharistan put an end to the development of Buddhist art in the region. Yet, the influence of Buddhist iconography is thought still to be discernible in the Islamic art of Transoxania in the tenth and eleventh centuries.