Portuguese India Armadas

The Carreira da Índia ("India Run") was the sea route and trade between the Kingdom of Portugal and India around the Cape of Good Hope, first opened by Vasco da Gama in 1497–99. The armadas da Índia ("Indian armadas") were organized by the crown and dispatched on an annual basis, being among the first recorded voyages on the European-Asian sailing route.

For a long time after its discovery by Vasco da Gama in 1497–1499, the sea route to India via the Cape of Good Hope was dominated by the Portuguese India armada – the annual fleet dispatched from Portugal to India. Between 1497 and 1650, there were 1033 departures of ships at Lisbon for the Carreira da Índia ("India Run").

Each leg of the voyage took approximately six months. The critical determinant of the timing was the monsoon winds of the Indian Ocean. The monsoon was a southwesterly wind (i.e. blew from East Africa to India) in the Summer (between May and September) and then abruptly reversed itself and became a northeasterly (from India to Africa) in the Winter (between October and April). The ideal timing was to catch the late summer monsoon to India, and return with the early winter monsoon, minimizing the time at sea.

The India armada typically left Lisbon in the early Spring (March–April). That would bring it to the Cape of Good Hope around June–July, and to the East African middle coast by August, just in time to catch the summer monsoon winds to India. Arrival in India was usually around early September. The return trip from India would typically begin in January, taking the winter monsoon across the Indian Ocean and down East Africa, double the Cape in reverse around April, and arrive in Lisbon by the Summer (June–August). Overall, the round trip took a little over a year.

The critical step was ensuring the armada reached East Africa on time. Ships that failed to reach the equator latitude on the East African coast by late August would be stuck in Africa and have to wait until next Spring to undertake an Indian Ocean crossing. And then they would have to wait in India until the Winter to begin their return. So any delay in East Africa during those critical few weeks of August could end up adding an entire extra year to a ship's journey.

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