After expelling the Sakas, and the remnant of the Græco-Bactrians,[40] the Yué-Chi settled in that part of Central Asia which is named Tokhāristān, after their tribal appellation, and which included Balkh, Kunduz, Hisār, Bolor, Wakhān, and Badakhshān. Meanwhile the Sakas retreated southwards, and occupied in turn Kiphin, Soghdiana, Arachosia (Kandahār), and Drangiana (Sīstān).[41]
Their invasion of India was directly due to the usurpation of their country by the Yué-Chi. The latter parcelled Bactria out among their five clans.[42] Each had its own capital, but the only Yué-Chi headquarters which has been identified is Bamian, at the foot of the northern slope of the Hindu Kush.
The partition continued in force for nearly a century, during which repeated collisions occurred between the Yué-Chi and the Parthians. In B.C. 30 the chief of one of the clans, the Kwei-shuang, subdued the rest, and assumed sovereignty over the whole race. They became thenceforward known by the name of the conquering clan, which in course of time was modified to Kushan, and appears so inscribed on their coins. The recent overthrow of their most persistent enemies the Hiung-nu rendered the more easy the task of consolidating their power, for in the year B.C. 71 the reigning Chinese emperor had administered a crushing defeat on the Huns, who were in B.C. 60 finally enrolled into the Chinese Empire. They thus became masters of all those countries which go to form Turkestan, Eastern Iran, and Afghanistan. The Yué-Chi, or Kushans, relieved of this incubus, turned their arms towards the south, crossed the Paropanisus, and overran Kabul, which belonged in part to the Arsacidæ, and in part to the Sakas, driving the latter out of their kingdom of Kiphin.[43]
At the dawn of the Christian era the Kushans were a foremost power in Central Asia. The Romans deigned to treat with them as an established empire. Mark Antony, for example, sent ambassadors to Bactria, whose chiefs (all Kushans) were represented at Rome by an envoy under Augustus; while later, in the reign of Trojan and Adrian, they sent ambassadors to solicit an alliance against the Parthians.[44]
From Chinese sources we learn that in the year A.D. 98 their general Panchao[45] was received during an expedition to the Caspian by the Yué-Chi, and that they recognised the imperial sovereignty by annual presents.