The Indian Ocean Trade World

The Indian Ocean trading world was structured, more than any other premodern maritime network, by a single predictable natural phenomenon: the seasonal reversal of the monsoon winds, blowing from the southwest roughly from June to September and from the northeast roughly from November to March, which allowed sailing ships to make reliably timed round trips across open ocean stretches that would otherwise have required hugging the coastline. Knowledge of this pattern is described in the anonymous Greek Periplus of the Erythraean Sea (mid-1st century CE), which credits — with likely legendary compression — a Greek navigator named Hippalus with having "discovered" the direct monsoon crossing from the Red Sea to India, even though Arab, Persian, and Indian sailors had almost certainly exploited the pattern independently and earlier. This wind system linked an immense arc of coastline: East Africa's Swahili coast, the Arabian Peninsula, the Persian Gulf, western India's Malabar and Gujarat coasts, the Bay of Bengal, and the Southeast Asian archipelago, feeding ultimately into Chinese maritime trade at its eastern extreme.