India’s link with West Asia was maintained by a few land routes. These land routes beyond the north-west frontier were usually the continuation of trade routes emerging from and passing through various seats of industry and trade inside India.
The main trunk route proceeded from Pushkalavati, further through the Khyber Pass, the Kabul valley and the Hindukush, and terminated at Bactria.
Bactria was an important centre of transit trade between India, China, Central Asia and the Mediterranean world. From Bactria, the route proceeded westward through the northern part of the Persian desert covering places such as Aria (Herat) and Margiana (Merv), the Zagros valley across the Tigris and the Euphrates to Antioch in Syria.
There were two other outlets to Western Asia from the Indus Valley. One of them passed through Bolan or the Mulla Pass and opened into the vast Plateau between Herat and Kandahar. The other route passed through the narrow Makran coast of Baluchistan, which joined the lower Indus plain with southern Persia.
The most imporant of these routes, i.e. the one passing through Khyber Pass, was generally preferred by the traders because it was less hazardous and nearer to the international trade route. This route, passing through Kandahar, Herat and Ecbatana (Hamadan) was linked to Seleusia and the ports on the eastern Mediterranean. One route branched off from Kandahar linking it with Persepolis and Susa.
It was the participation of the Roman Empire which gave considerable impetus to the sea-borne trade between India and the Mediterranean world. When this sea-borne trade was combined with the discovery of monsoons by Hippalus in AD 46, the Indian foreign trade began on a large scale. It is believed that the Arabs knew of it earlier.
Ships travelling to western ports generally took two routes: they either followed the coast up the Persian Gulf to Babylon or travelled across the Arabian sea to Aden or Socotra and from there they went to the Red sea.
Goods were landed at Suez and from there sent overland to Alexandria, which was an entrepot of the Mediterranean region. The Periplus refers to Indian settlements in Dioscorida (Socotra) alongwith those of Arabs and Greeks. This island served as the half-way station in the commerce between India and east Africa, as Eudaemon Arabia (Aden) did in the case of Indo- Egyptian trade.