dynasty had come into existence. The T'u-chüeh, the Turks, much the
strongest people of the north, had given support now to one and now to
another of the northern kingdoms, and this, together with their many
armed incursions, had made them the dominant political factor in the
north. But in the first year of the Sui period (581) they split into two
sections, so that the Sui had hopes of gaining influence over them. At
first both sections of the Turks had entered into alliance with China,
but this was not a sufficient safeguard for the Sui, for one of the
Turkish khans was surrounded by Toba who had fled from the vanished
state of the Northern Chou, and who now tried to induce the Turks to
undertake a campaign for the reconquest of North China. The leader of
this agitation was a princess of the Yü-wen family, the ruling family of
the Northern Chou. The Chinese fought the Turks several times; but much
more effective results were gained by their diplomatic missions, which
incited the eastern against the western Turks and vice versa, and also
incited the Turks against the Toba clique. In the end one of the
sections of Turks accepted Chinese overlordship, and some tribes of the
other section were brought over to the Chinese side; also, fresh
disunion was sown among the Turks.

Under the emperor Yang Ti, P'ei Chü carried this policy further. He
induced the Tölös tribes to attack the T'u-yü-hun, and then himself
attacked the latter, so destroying their power. The T'u-yü-hun were a
people living in the extreme north of Tibet, under a ruling class
apparently of Hsien-pi origin; the people were largely Tibetan. The
purpose of the conquest of the T'u-yü-hun was to safeguard access to
Central Asia. An effective Turkestan policy was, however, impossible so
long as the Turks were still a formidable power. Accordingly, the
intrigues that aimed at keeping the two sections of Turks apart were
continued. In 615 came a decisive counter-attack from the Turks. Their