Wu Ti’s active policy had not been directed only against the Hsiung-nu.  After heavy fighting he brought southern China, with the region round Canton, and the south-eastern coast, firmly under Chinese dominion—­in this case again on account of trade interests.  No doubt there were already considerable colonies of foreign merchants in Canton and other coastal towns, trading in Indian and Middle East goods.  The traders seem often to have been Sogdians.  The southern wars gave Wu Ti the control of the revenues from this commerce.  He tried several times to advance through Yuennan in order to secure a better land route to India, but these attempts failed.  Nevertheless, Chinese influence became stronger in the south-west.

In spite of his long rule, Wu Ti did not leave an adult heir, as the crown prince was executed, with many other persons, shortly before Wu Ti’s death.  The crown prince had been implicated in an alleged attempt by a large group of people to remove the emperor by various sorts of magic.  It is difficult to determine today what lay behind this affair; probably it was a struggle between two cliques of the gentry.  Thus a regency council had to be set up for the young heir to the throne; it included a member of a Hsiung-nu tribe.  The actual government was in the hands of a general and his clique until the death of the heir to the throne, and at the beginning of his successor’s reign.

At this time came the end of the Hsiung-nu empire—­a foreign event of the utmost importance.  As a result of the continual disastrous wars against the Chinese, in which not only many men but, especially, large quantities of cattle fell into Chinese hands, the livelihood of the Hsiung-nu was seriously threatened; their troubles were increased by plagues and by unusually severe winters.  To these troubles were added political difficulties, including unsettled questions in regard to the succession to the throne.  The result of all this was that the Hsiung-nu could no longer offer effective military resistance to the Chinese.  There were a number of shan-yue ruling contemporaneously as rivals, and one of them had to yield to the Chinese in 58 B.C.; in 51 he came as a vassal to the Chinese court.  The collapse of the Hsiung-nu empire was complete.  After 58 B.C. the Chinese were freed from all danger from that quarter and were able, for a time, to impose their authority in Central Asia.

5 Impoverishment.  Cliques.  End of the Dynasty

In other respects the Chinese were not doing as well as might have been assumed.  The wars carried on by Wu Ti and his successors had been ruinous.  The maintenance of large armies of occupation in the new regions, especially in Turkestan, also meant a permanent drain on the national funds.  There was a special need for horses, for the people of the steppes could only be fought by means of cavalry.  As the Hsiung-nu were supplying no horses, and the campaigns were not producing horses enough as booty,