Indian Monsoon Current

Sailing across the Indian Ocean depended on knowing when a route could be attempted as well as where it led. Arab, Persian and Indian mariners combined seasonal monsoon winds with observations of the stars. Their knowledge distinguished particular passages and sailing windows, allowing voyages between ports separated by open water rather than continuous coastlines.

Late-fifteenth- and sixteenth-century navigators recorded parts of this knowledge in guides. Ahmad ibn Majid assembled his Book of Useful Information on navigation in 1490; Sulayman al-Mahri also described routes and seasons. The surviving instructions set different dates for journeys from Hormuz to Calicut, Aden to India, and India toward Malacca. These were practical choices for particular crossings, not a single departure season applying everywhere in the ocean. Written guidance worked alongside skills passed between generations of seafarers. The monsoon waters consequently belonged to an experienced navigational world in which astronomy, seasonal judgement and knowledge of individual routes made long-distance passage possible.