The foreign policy of this first period of the T’ang, lasting until about 690, was mainly concerned with the Turks and Turkestan.  There were still two Turkish realms in the Far East, both of considerable strength but in keen rivalry with each other.  The T’ang had come into power with the aid of the eastern Turks, but they admitted the leader of the western Turks to their court; he had been at Ch’ang-an in the time of the Sui.  He was murdered, however, by Chinese at the instigation of the eastern Turks.  The next khan of the eastern Turks nevertheless turned against the T’ang, and gave his support to a still surviving pretender to the throne representing the Sui dynasty; the khan contended that the old alliance of the eastern Turks had been with the Sui and not with the T’ang.  The T’ang therefore tried to come to terms once more with the western Turks, who had been affronted by the assassination; but the negotiations came to nothing in face of an approach made by the eastern Turks to the western, and of the distrust of the Chinese with which all the Turks were filled.  About 624 there were strong Turkish invasions, carried right up to the capital.  Suddenly, however, for reasons not disclosed by the Chinese sources, the Turks withdrew, and the T’ang were able to conclude a fairly honourable peace.  This was the time of the maximum power of the eastern Turks.  Shortly afterwards disturbances broke out (627), under the leadership of Turkish Uighurs and their allies.  The Chinese took advantage of these disturbances, and in a great campaign in 629-30 succeeded in overthrowing the eastern Turks; the khan was taken to the imperial court in Ch’ang-an, and the Chinese emperor made himself “Heavenly Khan” of the Turks.  In spite of the protest of many of the ministers, who pointed to the result of the settlement policy of the Later Han dynasty, the eastern Turks were settled in the bend of the upper Hwang-ho and placed more or less under the protectorate of two governors-general.  Their leaders were admitted into the Chinese army, and the sons of their nobles lived at the imperial court.  No doubt it was hoped in this way to turn the Turks into Chinese, as had been done with the Toba, though for entirely different reasons.  More than a million Turks were settled in this way, and some of them actually became Chinese later and gained important posts.

In general, however, this in no way broke the power of the Turks.  The great Turkish empire, which extended as far as Byzantium, continued to exist.  The Chinese success had done no more than safeguard the frontier from a direct menace and frustrate the efforts of the supporters of the Sui dynasty and the Toba dynasty, who had been living among the eastern Turks and had built on them.  The power of the western Turks remained a lasting menace to China, especially if they should succeed in co-operating with the Tibetans.  After the annihilation of the T’u-yue-hun by the Sui at the very beginning