What sea battle in 1509 secured Portuguese dominance in the Indian Ocean?

The sea battle in 1509 that secured Portuguese dominance in the Indian Ocean was the Battle of Diu.

Fought on 3 February 1509 near Diu, on India’s Gujarati coast, the battle pitted a Portuguese fleet led by Francisco de Almeida against a coalition involving the Mamluk Sultanate of Egypt, the Gujarat Sultanate, and the Zamorin of Calicut. Portuguese cannon-armed carracks and disciplined naval tactics defeated the allied fleet.

The victory protected Portugal’s developing sea route around the Cape of Good Hope and weakened rival control of trade through the Red Sea and Persian Gulf. Portugal subsequently strengthened its position at ports including Goa, Malacca, and Ormuz. The battle is often described as a turning point in the rise of European naval power in Asian waters.

A common mix-up is the Battle of Chaul, fought in 1508. Chaul preceded Diu and involved Portuguese losses, but Diu was the decisive 1509 victory that established Portuguese strategic dominance.