During the medieval era, 400 - 1450 CE, trade flourished in the Indian Ocean basin.  The rise of the Umayyad (661 -  750 CE) and Abbasid (750 - 1258) Caliphates on the Arabian Peninsula provided a powerful western node for the trade routes.  In addition, Islam valued merchants (the Prophet Muhammad himself was a trader and caravan leader), and wealthy Muslim cities created an enormous demand for luxury goods.