The Arab Conquests in Central Asia

The Oxus is a boundary of tradition rather than of history. Lying midway between the old frontier of Aryan civilisation formed by the Jaxartes and the Pamīr and the natural strategic frontier offered by the north-eastern escarpment of the plateau of Īrān, it has never proved a barrier to imperial armies from either side. It was not on the Oxus but on the Jaxartes that Alexander’s strategic insight fixed the position of Alexander Eschate, and when the outposts of Persian dominion were thrust back by the constant pressure of the Central Asian hordes, their retreat was stayed not on the Oxus but on the Murghāb. Thus when the tide of conquest turned and the Arabs won back her ancient heritage for Persia, they, like Alexander, were compelled to carry their arms ever further to the East and all unknowing re-establish the frontiers of the Achaemenid Empire. It was from the legends of Sāsānian times, enshrined in the pages of the historians and the national epic of Firdawsī, that the Oxus came to be regarded as the boundary between Īrān and Tūrān.

Through all the centuries of invasion, however, the peoples of Sogdiana and the Oxus basin remained Iranian at bottom, preserving an Iranian speech and Iranian institutions. But the political conditions of the country at the period of the Arab conquests were so complex that it is necessary to trace briefly the course of their development.

The second century B.C. was a period of upheaval in Central Asia: the powerful Hiung-Nu peoples were dispossessing weaker tribes of their pasture lands and forcing them to migrate westwards. Between 150 and 125 B.C. a succession of nomadic tribes, the last and most powerful of which were a branch of the Yueh-Chi, were driven down into Sogdiana. It is now generally held that these tribes were of Aryan origin, though the question is not perhaps settled with absolute certainty. Before long, however, a second group, the K’ang, possessed themselves of Sogdiana, driving the Yueh Chi on into Bactria and the Afghan mountains. In these districts they found, alongside the Iranian peasantry, a settled population of Tukhari (in Chinese, Ta-Hia), already noted in the Chinese annals for their commercial enterprise, and while at first the nomad tribes introduced complete confusion, it would seem that they rapidly absorbed, or were absorbed by, the native elements, and thus assimilated the Hellenistic civilisation of Bactria. From this fusion arose, about 50 A.D., the powerful Kushan Empire which spread into India on the one side and probably maintained some form of suzerainty over the K’ang kingdoms of Sogdiana on the other. Under the new empire, Buddhism was acclimatised in Turkestan, and Sogdiana developed into a greatentrepôt for Chinese trade with the West. Towards the close of the third century the Kushan Empire, weakened by attacks from the new national dynasties in India and Persia, reverted to its primitive form of small independent principalities, which, however, retained sufficient cohesion to prevent a Persian reconquest. It is practically certain that Sāsānian authority never extended beyond Balkh and rarely as far. In the fourth and fifth centuries references are made to a fresh horde of nomads in the north-east, the Juan-Juan (Chionitae, Avars), but it does not appear that any new settlements were made in the Oxus countries.