Portuguese authorities instituted the cartaz licensing system, requiring many vessels operating in the Indian Ocean to carry Portuguese-issued passes or face seizure/attack. The cartaz became a core administrative tool for taxing trade, compelling port calls at Portuguese feitorias, and projecting naval authority beyond directly held territory.
Portuguese forces established a fortified base at Cochin (Kochi) on the Malabar Coast. Fortification and protected anchorage underpinned early efforts to police shipping and channel commerce toward Portuguese-controlled ports—an institutional precursor to later Indian Ocean-wide licensing and convoy practices.
King Manuel I appointed Francisco de Almeida as the first viceroy and formalized the Estado da Índia framework. This strengthened centralized command over forts, fleets, and customs collection—key to enforcing Portuguese maritime control and the regulation of trade routes.
Afonso de Albuquerque attacked Hormuz Island, seeking leverage over Gulf traffic and the India–Persian Gulf corridor. Although Portuguese control fluctuated until a more durable takeover in 1515, this move signaled a strategy of controlling chokepoints to steer shipping into Portuguese-supervised channels.
A Portuguese fleet defeated a coalition force at Diu, a decisive early demonstration of Portuguese sea power in the western Indian Ocean. The victory helped underpin later enforcement measures—escorts, seizures, and licensing—against rival shipping and hostile ports.
Afonso de Albuquerque seized Goa, which became the principal administrative and logistical center for Portuguese India. From Goa, the Estado da Índia could more effectively issue passes, collect dues, and dispatch naval forces to enforce compliance across major sea-lanes.
Portuguese forces conquered Malacca, targeting control over a key choke point for trade between the Indian Ocean and the South China Sea. This expanded the geographic reach of Portuguese maritime regulation and strengthened their ability to redirect Asian commerce toward Portuguese-controlled nodes.
Albuquerque’s unsuccessful assault on Aden left the Red Sea entry largely outside Portuguese control. The failure limited Portugal’s capacity to fully block competing spice routes via the Red Sea and reinforced reliance on policing shipping through patrols and pass systems elsewhere.
Portuguese power at Hormuz was reasserted and fortified, including construction of the main fortress on the island. Control at Hormuz supported regulation of Persian Gulf traffic and enhanced the broader strategy of combining forts, fleets, and documentation requirements to shape trade flows.
An agreement with the Sultan of Gujarat in October 1535 allowed the Portuguese to build a fortress at Diu, strengthening their position near the Gulf of Cambay. Diu became a strategic point for controlling shipping and trade along India’s northwest coast—complementing cartaz enforcement with permanent fortification.
Work on the Diu fortress complex moved from agreement to implementation, with formal construction beginning on Saint Thomas’s Day. The fortress became central to Portuguese defense and to enforcing maritime control in the region, especially against Ottoman- and Gujarati-backed challenges.
A large Ottoman- and Gujarati-supported force besieged Portuguese-held Diu but failed to capture the fortress. The successful defense demonstrated the resilience of Portugal’s fort-and-fleet system and helped preserve Portuguese leverage over shipping lanes and customs collection in the northwestern Indian Ocean.
English East India Company ships defeated Portuguese forces off Suvali (Swally), marking a key early setback to Portuguese naval dominance on India’s west coast. The battle signaled the rising capacity of European rivals to contest Portuguese enforcement practices, including pass-and-blockade pressures on regional trade.
Safavid forces with English East India Company naval support captured Hormuz after siege operations in early 1622. The loss removed a critical Portuguese choke-point in the Persian Gulf, undermining their ability to regulate Gulf shipping and contributing to the broader erosion of Portuguese Indian Ocean supremacy.
After a prolonged siege, Dutch East India Company forces allied with Johor took Malacca, ending Portuguese rule there. Losing this strategic strait node weakened Portuguese capacity to police trans-Straits traffic and curtailed their influence over Southeast Asian segments of Indian Ocean trade networks.
Indian Ocean trade networks, the cartaz system, and Portuguese naval control (1500–1650)
