Battle of Diu

At Diu a single European fleet defeated a combined Mamluk Egyptian, Gujarati and Calicut coalition, backed by Ottoman and Venetian guns, that had been assembled to drive the Portuguese out of Asian waters. The victory broke the old Muslim and Venetian hold on the Indian Ocean spice trade and opened the sea lanes to Portuguese domination for a century. The viceroy, Francisco de Almeida, fought partly for revenge, since his son had been killed the year before when the same coalition beat the Portuguese at Chaul. He won by using heavier ships and superior broadside gunnery to stand off and pound a fleet built around galleys rather than let it close and board. Diu confirmed Portugal's blue-water supremacy and cemented its emerging maritime empire in Asia.

Historians treat Diu as a hinge of world history, the point at which European ship-mounted artillery and ocean-going hulls overturned the established Indian Ocean trading order and began the age of European seaborne empire in Asia. The debate is over how decisive a single day really was, against a longer Portuguese campaign of fortress-building and blockade, and over how far Diu prefigured the gunpowder-and-sail template of later colonial expansion. It is also a reminder that the coalition it beat was itself a wide alliance, Egyptian, Gujarati, Ottoman and Venetian, defending a trade system centuries old. The winners wrote most of the surviving accounts, so the numbers favour them.