Battle of Diu (1509): How Portugal Won the Indian Ocean

The Battle of Diu was a naval battle fought on 3 February 1509 off the port of Diu in Gujarat, western India. A Portuguese fleet under the viceroy Francisco de Almeida defeated a combined force from the Mamluk Sultanate of Egypt, the Gujarat Sultanate and the Zamorin of Calicut. The victory gave Portugal command of the sea routes of the western Indian Ocean and marked the start of a century of European naval power in Asian waters.

Background

After Vasco da Gama’s voyage reached India in 1498, Portugal set out to take over the spice trade, especially in pepper, that had long flowed from India through the Red Sea and Egypt to Venice. Portuguese fleets attacked Muslim merchant shipping and fought the Zamorin of Calicut, the most powerful ruler on the Malabar Coast.

This threatened the Mamluk Sultanate, which earned large revenues from taxing the spice trade through Egypt, and the merchant states of western India. The Mamluk sultan Qansuh al-Ghuri assembled a fleet at Suez, built partly with timber and guns supplied through the Ottoman Empire, and sent it to India under Amir Husain al-Kurdi, governor of Jeddah. Venice, whose trade also suffered, is believed to have encouraged the effort. For Venice and Cairo the stakes were high: if spices went round Africa to Lisbon instead of through Alexandria, both would lose a major source of income built up over centuries.

In March 1508, Husain’s fleet, with help from Malik Ayaz, the governor of Diu, surprised a Portuguese squadron at Chaul. Lourenço de Almeida, the viceroy’s son, was killed. The Mamluk fleet then withdrew to Diu.

The road to Diu

Francisco de Almeida, the first Portuguese viceroy of India, had already been told that Afonso de Albuquerque would succeed him. He refused to hand over power until he had avenged his son. In late 1508 he sailed north from Cochin with a fleet of about 18 ships and, according to most estimates, some 1,200 to 1,800 Portuguese soldiers and sailors, along with several hundred allied Malabar fighters. On the way he sacked the port of Dabul.

At Diu, the allied force included around a dozen larger Mamluk ships and galleys and a much larger number of light Gujarati and Calicut vessels. Estimates of these smaller craft vary widely, from several dozen to over a hundred.

The campaign also had a personal side. Albuquerque had arrived at Cannanore with royal orders to take over as governor, but Almeida refused to step down and later had him detained. Only when a senior noble, Fernando Coutinho, Marshal of Portugal, reached India in October 1509 with the king’s authority was the transfer of power completed.

The battle

On 3 February 1509 Almeida attacked the allied fleet anchored in the channel near Diu. The Mamluk ships stayed close to shore, hoping the town’s guns would support them. Portuguese gunners, firing heavier cannon from carracks such as the large Flor de la Mar, battered the enemy ships, and boarding parties followed.

Malik Ayaz, a shrewd politician who had already been in contact with the Portuguese, did not commit his forces fully. By the end of the day the Mamluk fleet was destroyed or captured and the Gujarati and Calicut vessels had scattered. Portuguese chroniclers report losses of around 30 dead and a few hundred wounded on their side. Losses among the allies are not reliably known but were far higher, running into the hundreds or more.

After the battle Almeida executed many prisoners in brutal ways as a warning, an act recorded by Portuguese chroniclers themselves. Malik Ayaz returned the Portuguese prisoners taken at Chaul and made peace.

Why the Portuguese won

Several factors explain the outcome. Portuguese carracks were tall, strongly built ships designed in the Atlantic to carry heavy guns, and their crews were trained to fight with artillery at a distance before boarding. Many of the Indian Ocean vessels they faced were lighter merchant ships or oared craft, built for trade and coastal warfare rather than artillery duels.

The allied force was also divided. The Mamluk crews were far from home, short of supplies after months at Diu, and dependent on local allies. Malik Ayaz had his own interests: Diu’s prosperity depended on trade, and he wanted to avoid lasting war with a new sea power. The Zamorin’s contingent was smaller than the Portuguese had feared. These divisions allowed Almeida to concentrate his firepower on the Mamluk ships.

Key people

• Francisco de Almeida (c. 1450–1510): first viceroy of Portuguese India, who led the fleet. He died in 1510 in a clash with Khoikhoi people at Table Bay in southern Africa on his way home.
• Amir Husain al-Kurdi: Mamluk commander and governor of Jeddah, who escaped after the defeat.
• Malik Ayaz: Gujarati governor of Diu, who balanced between the Mamluks and the Portuguese.
• Lourenço de Almeida: the viceroy’s son, whose death at Chaul in 1508 helped trigger the battle.

Timeline

• 1498, May: Vasco da Gama reaches Calicut.
• 1505: Francisco de Almeida sails to India as the first viceroy.
• 1508, March: Mamluk and Gujarati ships defeat a Portuguese squadron at Chaul; Lourenço de Almeida is killed.
• 1508, December – 1509, January: Almeida’s fleet sails north and sacks Dabul.
• 1509, 3 February: Battle of Diu; the allied fleet is destroyed.
• 1509, November: Almeida hands over the government to Afonso de Albuquerque.
• 1510, 1 March: Almeida is killed at Table Bay on his voyage home.

Consequences

The Mamluks never sent another large fleet to India, and within a few years their state collapsed when the Ottomans conquered Egypt in 1517. The Ottoman conquest of Egypt brought a new and stronger rival into the Indian Ocean, and Ottoman fleets challenged the Portuguese several times later in the century.

For Portugal, Diu opened the way to a network of fortified bases. Albuquerque took Goa in 1510, Malacca in 1511 and Hormuz in 1515. The Portuguese also imposed the cartaz, a licence system that required Asian merchant ships to carry Portuguese passes. In 1535 Portugal finally obtained a fortress at Diu itself, which it held until 1961.

The fortress quickly became a target. In 1538 an Ottoman fleet under Hadım Suleiman Pasha, sailing from Suez, besieged Diu together with Gujarati forces, but withdrew after several weeks. In 1546 Gujarat besieged the fortress again for months before a relief fleet under the governor João de Castro broke the siege. Both attempts showed that the struggle begun in 1509 continued for decades.

By the numbers

Legacy

Historians often describe Diu as one of the decisive naval battles of history, because it showed that ships armed with cannon could defeat larger numbers of traditional vessels. At the same time, recent scholarship emphasises the limits of Portuguese power: Asian merchants continued to trade widely, and Portugal’s control rested on a handful of ports and constant warfare rather than full mastery of the ocean.

Why it matters

The Battle of Diu was the first major victory of a European navy in Asian waters. It shaped the balance of power in the Indian Ocean for most of the sixteenth century and prepared the ground for the Portuguese seaborne empire.