There are many famous naval battles in history: the Battle of Midway in World War II, the Battle of Trafalgar during the Napoleonic Wars, the Battle of Salamis between Greece and the invading Persians in 480 BC, etc. However, probably the most important naval battle that most people have never heard of is the Battle of Diu, which took place on February 3, 1509 off the coast of India. Ending with a complete victory for the Portuguese, it effectively handed them control of the Indian Ocean for the next hundred years before other Europeans barged into the "Portuguese lake".
The broader context for the battle was a trade war over spices, but it was spiced up by a very personal loss for a vengeful leader. After Constantinople fell to the Ottoman Turks in 1453, European imports of spices like pepper from Asia, previously controlled by the Mediterranean maritime republics, were disrupted. This prompted the Portuguese to find a sea route to the source, which they thought was India. In 1498, Vasco da Gama became the first European to lead an expedition that sailed from Europe around the Cape of Good Hope to India, landing near Calicut, one of the hubs of the pepper trade then controlled by Muslim traders. According to one analysis, pepper bought for 4.64 ducats in Calicut fetched 25 ducats in Alexandria, Egypt. For the Mamluks that controlled Egypt at the time, this profitable trade was one of the main sources of public revenue. The 25 ducats worth of pepper would be sold for 56 ducats in Venice, and by the time it reached Lisbon, the price would be 80 ducats.
The Portuguese attempt to insert themselves into this trade after Vasco da Gama's expedition naturally threatened many stakeholders. Indian merchants, the Muslim Marakkar from Kerala and the Bania from Gujarat, were immediately impacted and incited local attacks against Portuguese assets. The Yemeni traders that transported the goods to Egypt as well as the Venetians who bought from them risked being disintermediated. The Zamorin of Calicut, the Sultan of Gujarat, and the Christian Venetians sent envoys to the Mamluk court of Egypt requesting intervention. A decision was made to send a huge armada to deal with the Portuguese. On September 15, 1505, a large flotilla of over a thousand Mamluk, Ottoman, Nubian and Ethiopian fighters, Venetian gunners and Greek sailors, under the command of a Kurdish admiral, set sail from Suez. It took the multinational force two years to reach Diu in India in September 1507.
Diu was then a major trading port controlled by the Sultan of Gujarat. The governor in 1507 was a Mamluk with Dalmatian Christian origins before he converted to Islam. In March 1508, the armada from Suez, reinforced by forces from Diu, sailed south towards the Portuguese who had defeated the Zamorin of Calicut and his Arab allies after resisting a four-month siege in Cannanore, in today's Kerala, India. The two sides met in the harbour of Chaul, near today's Mumbai (or Bombay), where the Portuguese were caught off-guard by the European appearance of the fleet from Egypt, thinking it was the early arrival of Afonso de Albuquerque whom they had been expecting. The Muslim (plus Venetian) alliance technically won the battle by sinking the Portuguese flagship, inflicting the first defeat for the Portuguese in the Indian Ocean. However, the rest of the Portuguese fleet escaped while the alliance suffered heavy losses and returned to Diu.
The personal context was set here: the Portuguese fleet in Chaul was commanded by captain-major Lourenço de Almeida, the son of Dom Francisco de Almeida, the first Viceroy of Portuguese India. Lourenço died in the battle and his body was never found. Dom Francisco grieved alone for three days and swore revenge, supposedly saying that "he who ate the chick must also eat the rooster or pay for it". The monsoon season then started and the Viceroy had to wait and prepare his forces. On December 6, 1508, Afonso de Albuquerque finally arrived in Cannamore to replace de Almeida as Viceroy under the orders of the King of Portugal. De Almeida, wanting revenge, refused to cede control immediately and set sail for Diu three days later on December 9 with the Portuguese fleet he had assembled.
There are quite a few chapters in the lead up to February 1509. One of these involved the Governor of Diu, sensing the imminent catastrophe for his city, sending a message to appease de Almeida. De Almeida responded with a simple message: he was coming for revenge. The Governor of Diu's concerns had also created problems for the Muslim alliance, as the Kurdish admiral perceived the Governor to be less than fully committed to the cause.
On February 3, at around 11am, the Battle of Diu started. Against up to 200 ships from the Mamluk-Gujarat-Calicut alliance, the Portuguese fielded 18 ships, ranging from a brigantine to five large naus. The Governor of Diu had already retreated inland, leaving the Kurdish admiral in charge. Through strategic and tactical competence, as well as superior firepower and more seasoned sailors, the Portuguese won a decisive victory in a battle of annihilation. Every ship of the alliance was sunk with the exception of six that were captured. To finish off the violent day, the alliance had at the end only one ship left, the largest vessel of the battle that was anchored too close to shore for the deep-draft Portuguese ships to reach. With a reinforced hull it was resistant to Portuguese cannon fire, so de Almeida ordered a continuous bombardment from his entire fleet. It finally sank just before nightfall, a movie-style end to the Battle of Diu.
De Almeida exacted brutal revenge for the death of his son Lourenço. He ordered most of the captured Mamluks to be hanged, burned alive or tied to the mouths of cannons and blown apart. De Almeida then ceded the role of Viceroy to Afonso de Albuquerque and sailed for Portugal in November the same year. Unfortunately for him, he was killed near the Cape of Good Hope in a skirmish with a local tribe in December. De Almeida's legacy would be Portuguese control of the Indian Ocean, especially with the fall of the Mamluk Sultanate in Egypt to the Ottomans in 1517. Some would characterize this as the start of Western European hegemony over the Indian Ocean, as the Portuguese were followed by the Dutch, English and French. Interestingly, the Chinese under Admiral Zheng He had sailed in the other direction to the Indian Ocean with large armadas, but these naval expeditions ended in the 15th century after the death of the Admiral and the rising threat of Mongol overland invasions from the north.
I just finished Roger Crowley's "Conquerors: How Portugal Forged the First Global Empire" about the Portuguese expansion to east and especially about the exploits of de Almeida and de Albuquerque. According to the book what the Portuguese had in mind was not just some friendly business competition, but a monopoly of the spice trade in the Indian Ocean, effected by cannons and violence. Starting from the murder of the pilgrims on the ship Miri by Vasco da Gama (https://en.wikipedia.org/wiki/4th_Portuguese_India_Armada_(Gama,_1502)#Massacre_of_the_pilgrim_ship), the Portuguese forces executed an effective terror campaign against all the muslims in the area.
So, based on reading one book, I assume that the Portuguese were not just a commercial threat to the different Muslim nations, but an existential threat…