several severe droughts and also great plagues of locusts, so that they had lost a large part of their cattle.  They were no longer able to assert themselves in Turkestan and at the same time to fight the Chinese in the south and the Hsien-pi and the Wu-huan in the east.  These two peoples, apparently largely of Mongol origin, had been subject in the past to Hsiung-nu overlordship.  They had spread steadily in the territories bordering Manchuria and Mongolia, beyond the eastern frontier of the Hsiung-nu empire.  Living there in relative peace and at the same time in possession of very fertile pasturage, these two peoples had grown in strength.  And since the great political collapse of 58 B.C. the Hsiung-nu had not only lost their best pasturage in the north of the provinces of Shensi and Shansi, but had largely grown used to living in co-operation with the Chinese.  They had become much more accustomed to trade with China, exchanging animals for textiles and grain, than to warfare, so that in the end they were defeated by the Hsien-pi and Wu-huan, who had held to the older form of purely war-like nomad life.  Weakened by famine and by the wars against Wu-huan and Hsien-pi, the Hsiung-nu split into two, one section withdrawing to the north.

The southern Hsiung-nu were compelled to submit to the Chinese in order to gain security from their other enemies.  Thus the Chinese were able to gain a great success without moving a finger:  the Hsiung-nu, who for centuries had shown themselves again and again to be the most dangerous enemies of China, were reduced to political insignificance.  About a hundred years earlier the Hsiung-nu empire had suffered defeat; now half of what remained of it became part of the Chinese state.  Its place was taken by the Hsien-pi and Wu-huan, but at first they were of much less importance.

In spite of the partition, the northern Hsiung-nu attempted in the years between A.D. 60 and 70 to regain a sphere of influence in Turkestan; this seemed the easier for them since the king of Yarkand had been captured and murdered, and Turkestan was more or less in a state of confusion.  The Chinese did their utmost to play off the northern against the southern Hsiung-nu and to maintain a political balance of power in the west and north.  So long as there were a number of small states in Turkestan, of which at least some were friendly to China, Chinese trade caravans suffered relatively little disturbance on their journeys.  Independent states in Turkestan had proved more profitable for trade than when a large army of occupation had to be maintained there.  When, however, there appeared to be the danger of a new union of the two parts of the Hsiung-nu as a restoration of a large empire also comprising all Turkestan, the Chinese trading monopoly was endangered.  Any great power would secure the best goods for itself, and there would be no good business remaining for China.