The Portuguese Indian Armadas () were the fleets of ships funded by the Crown of Portugal, and dispatched on an annual basis from Portugal to India. The principal destination was Goa, and previously Cochin. These armadas undertook the () from Portugal, following the maritime discovery of the Cape route, to the Indian subcontinent by Vasco da Gama in 1497–99. During the Dutch occupation of Cochin and the Dutch siege of Goa, the harbour of Bom Bahia, now known as Mumbai (Bombay), off the coast of the northern Konkan region, served as the standard diversion for the armadas.
The India Run
For a long time after its discovery by Vasco da Gama, the sea route to India via the Cape of Good Hope was dominated by the Portuguese Indian armada – the annual fleet dispatched from Portugal to India, and after 1505, the Estado da India. Between 1497 and 1650, there were 1033 departures of ships at Lisbon for the Carreira da Índia ("India Run").
Timing
The India armada typically left Lisbon and 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 pass the Cape of Good Hope around June–July and get to the East African middle coast by August, just in time to catch the summer monsoon winds to India, arriving around early September. The return trip from India would typically begin in January, taking the winter monsoon back to Lisbon along a similar route, arriving by the summer (June–August). Overall, the round trip took a little over a year, minimizing the time at sea.
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.
The circumnavigation of Madagascar opened an alternative route to get to India, which gave more flexibility in timing. The rule that quickly emerged was that if an outbound armada doubled the Cape of Good Hope before mid-July, then it should follow the old "inner route" – that is, sail into the Mozambique Channel, up the East African coast until the equator latitude (around Malindi, Seychelles), then take the southwesterly monsoon across the ocean to India. If, however, the armada doubled the Cape after mid-July, then it was obliged to sail the "outer route" – that is, strike out straight east from South Africa, go under the southern tip of Madagascar, and then turn up from there, taking a northerly path through the Mascarenes islands, across the open ocean to India. While the outer route did not have the support of African staging posts and important watering stops, it sidestepped sailing directly against the post-summer monsoon.
Return fleets were a different story. The principal worry of the return fleets was the fast dangerous waters of the inner Mozambican channel, which was particularly precarious for heavily loaded and less maneuverable ships. In the initial decades, the return fleet usually set out from Cochin in December, although that was eventually pushed forward to January. January 20 was the critical date, after which all return fleets were obliged to follow the outer route (east of Madagascar) which was deemed calmer and safer for their precious cargo. That meant they missed the important watering stop on Mozambique island on the return leg and had to put in elsewhere later, such as Mossel Bay or St. Helena. Between 1525 and 1579, all return fleets were ordered to follow the outer route. This rule was temporarily suspended between the 1570s and 1590s. From 1615, a new rule was introduced whereby return fleets from Goa were allowed to use the inner route, but return fleets from Cochin still had to use the outer route. With the entry of Dutch and English competition in the 1590s, the start of the return legs were delayed until February and March, with the predictable upsurge in lost and weather-delayed ships.
Arrival times in Portugal varied, usually between mid-June and late August. It was customary for return fleets to send their fastest ship ahead to announce the results in Lisbon, before the rest of the fleet arrived later that summer.