In the second half of the first century A.D., the sea route to China was known, though vaguely, even to the author of the Periplus whose trading activities extended only to the west coast of India. From the second century A.D. onwards, we have more than one line of evidence pointing to the use of the sea route to Tonkin by Indians as well as others voyaging from India’s shores.
In the first century A.D., there was a regular overland trade in Chinese raw silk, as well as silk yarn and silk cloth from This (the state of in North-west China) to the Malabar ports byway of the lower Ganga. The extensive trade in these articles led to the issue of a gold coin (caltis) in the lower Ganga region.
The rise of the Greek kingdom of Bactria, and still more the formation of the Kushana empire, combined with the persistent efforts of the Chinese from the second century B.C. onwards to extend their political influence westward across the Tarim basin, led to the growth of conditions favourable to the fostering of Indian trade with Central Asia and beyond.
In the latter half of the first century A.D., furs (Seric skins) and silks from China were being sent by way of Bactria to Barbaricum, silks being carried to Barygaza as well for export to the West. This trade must have been diverted from the usual silk route from China to the West, probably because of the antagonism between the Parthian and the Roman empires.
In the early centuries of the Christian era, northwestern India was connected with China by some famous routes. Proceeding from the north-west frontier, the road ran by way of Kapisa and Bamiyan across the Hindukush to Bactria where it joined the great silk route from China to the Western world.
Of these, the northern route passed north of the Taklamakan desert across Kucha and Karashar, while the southern one marched south of the desert through Khotan and Yarkand, both converging on the Chinese frontier near Tunhuang. A shorter and more difficult route led by way of the upper Indus through Gilgit and Yasin to Kashgar and thence onward to China.