The Battle of Diu sometimes referred as the Second Battle of Chaul was a naval battle fought on 3 February 1509 in the Arabian Sea, near the port of Diu, India, between the Portuguese Empire and a joint fleet of the Sultan of Gujarat, the Mamlûk Burji Sultanate of Egypt, the Zamorin of Calicut with support of Ottomans, the Republic of Venice and the Republic of Ragusa .
The Portuguese victory was critical: Mamluks and Arabs retreated, easing the Portuguese strategy of controlling the Indian Ocean to route trade down the Cape of Good Hope, circumventing the traditional spice route controlled by the Arabs and the Venetians through the Red Sea and Persian Gulf. After the battle, Portugal rapidly captured key ports in the Indian Ocean like Goa, Ceylon, Malacca and Ormuz, crippling the Mamluk Sultanate of Egypt and the Gujarat Sultanate, greatly assisting the growth of the Portuguese Empire and setting its trade dominance for almost a century, until it was taken during the Dutch-Portuguese Wars and the Battle of Swally won by the British East India Company in 1612. It marks the beginning of the European colonialism in Asia. It also marks the spillover of the Christian-Islamic power struggle, in and around the Mediterranean Sea and the Middle East, into the Indian Ocean which was the most important region for international trade at the time.
Background
Since Vasco da Gama arrived in 1498, the Portuguese had been fighting Calicut while allying with its local rival Kingdom of Cochin, where they established their headquarters. The northern region of Gujarat, mainly Khambhat, was even more important: the Gujarat Sultanate was an essential intermediary in east–west trade, between the Red Sea, Egypt and Malacca: Gujarati were important middlemen bringing spices from the Maluku Islands as well as silk from China, and then selling them to the Egyptians and Arabs.