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