Wolfram Eberhard,
A history of China., [3d ed. rev…
“ 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. ”
