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-yü-hun by the Sui at the very beginning of the seventh century, a new political unit had formed in northern Tibet, the T'u-fan, who also seem to have had an upper class of Turks and Mongols and a Tibetan lower class. Just as in the Han period, Chinese policy was bound to be directed to preventing a union between Turks and Tibetans. This, together with commercial interests, seems to have been the political motive of the Chinese Turkestan policy under the T'ang.
3 Conquest of Turkestan and Korea. Summit of power
The Turkestan wars began in 639 with an attack on the city-state of Kao-ch'ang (Khocho). This state had been on more or less friendly terms with North China since the Toba period, and it had succeeded again and again in preserving a certain independence from the Turks. Now, however, Kao-ch'ang had to submit to the western Turks, whose power was constantly increasing. China made that submission a pretext for war. By 640 the whole basin of Turkestan was brought under Chinese dominance. The whole campaign was really directed against the western Turks, to whom Turkestan had become subject. The western Turks had been crippled by two internal events, to the advantage of the Chinese: there had been a tribal rising, and then came the rebellion and the rise of the Uighurs (640-650). These events belong to Turkish history, and we shall confine ourselves here to their effects on Chinese
history. The Chinese were able to rely on the Uighurs; above all, they were furnished by the Tölös Turks with a large army, with which they turned once more against Turkestan in 647-48, and now definitely established their rule there.
The active spirit at the beginning of the T'ang rule had not been the emperor but his son Li Shih-min, who was not, however, named as heir to the throne because he was not the eldest son. The result of this was tension between Li Shih-min and his father and brothers, especially the heir to the throne. When the brothers learned that Li Shih-min was claiming the succession, they conspired against him, and in 626, at the very moment when the western Turks had made a rapid incursion and were once more threatening the Chinese capital, there came an armed collision between the brothers, in which Li Shih-min was the victor. The brothers and their families were exterminated, the father compelled to abdicate, and Li Shih-min became emperor, assuming the name T'ai Tsung (627-649). His reign marked the zenith of the power of China and of the T'ang dynasty. Their inner struggles and the Chinese penetration of Turkestan had weakened the position of the Turks; the reorganization of the administration and of the system of taxation, the improved transport resulting from the canals constructed under the Sui, and the useful results of the creation of great administrative areas under strong military control, had brought China inner stability and in consequence external power and prestige. The reputation which she then obtained as the most powerful state of the Far East endured when her inner stability had begun to deteriorate. Thus in 638 the Sassanid ruler Jedzgerd sent a mission to China asking for her help against the Arabs. Three further missions came at intervals of a good many years. The Chinese declined, however, to send a military expedition to such a distance; they merely conferred on the ruler the title of a Chinese governor; this was of little help against the Arabs, and in 675 the last ruler, Peruz, fled to the Chinese court.
The last years of T'ai Tsung's reign were filled with a great war against Korea, which represented a continuation of the plans of the Sui emperor Yang Ti. This time Korea came firmly into Chinese possession. In 661, under T'ai Tsung's son, the Korean fighting was resumed, this time against Japanese who were defending their interests in Korea. This was the period of great Japanese enthusiasm for China. The Chinese system of administration was copied, and Buddhism was adopted, together with every possible element of Chinese culture. This meant increased trade with Japan, bringing in large profits to China, and so the Korean middleman was to be eliminated.
T'ai Tsung's son, Kao Tsung (650-683), merely carried to a conclusion what had been begun. Externally China's prestige continued at its zenith. The caravans streamed into China from western and central Asia, bringing great quantities of luxury goods. At this time, however, the foreign colonies were not confined to the capital but were installed in all the important trading ports and inland trade centres. The whole country was covered by a commercial network; foreign merchants who had come overland to China met others who had come by sea. The foreigners set up their own counting-houses and warehouses; whole quarters of the capital were inhabited entirely by foreigners who lived as if they were in their own country. They brought with them their own religions: Manichaeism, Mazdaism, and Nestorian Christianity. The first Jews came into China, apparently as dealers in fabrics, and the first Arabian Mohammedans made their appearance. In China the the foreigners bought silkstuffs and collected everything of value that they could find, especially precious metals. Culturally this influx of foreigners enriched China; economically, as in earlier periods, it did not; its disadvantages were only compensated for a time by the very beneficial results of the trade with Japan, and this benefit did not last long.