been sent in 138 to conclude an alliance with the Yüeh-chih against the
Hsiung-nu. The Yüeh-chih had formerly been neighbours of the Hsiung-nu
as far as the Ala Shan region, but owing to defeat by the Hsiung-nu
their remnants had migrated to western Turkestan. Chang Ch'ien had
followed them. Politically he had no success, but he brought back
accurate information about the countries in the far west, concerning
which nothing had been known beyond the vague reports of merchants. Now
it was learnt whence the foreign goods came and whither the Chinese
goods went. Chang Ch'ien's reports (which are one of the principal
sources for the history of central Asia at that remote time)
strengthened the desire to enter into direct and assured commercial
relations with those distant countries. The government evidently thought
of getting this commerce into its own hands. The way to do this was to
impose "tribute" on the countries concerned. The idea was that the
missions bringing the annual "tribute" would be a sort of state
bartering commissions. The state laid under tribute must supply
specified goods at its own cost, and received in return Chinese produce,
the value of which was to be roughly equal to the "tribute". Thus Chang
Ch'ien's reports had the result that, after the first successes against
the Hsiung-nu, there was increased interest in a central Asian policy.
The greatest military success were the campaigns of General Li Kuang-li
to Ferghana in 104 and 102 B.C. The result of the campaigns was to bring
under tribute all the small states in the Tarim basin and some of the
states of western Turkestan. From now on not only foreign consumer goods
came freely into China, but with them a great number of other things,
notably plants such as grape, peach, pomegranate.

In 108 B.C. the western part of Korea was also conquered. Korea was
already an important transit region for the trade with Japan. Thus this
trade also came under the direct influence of the Chinese government.