<P> The Portuguese under Vasco da Gama discovered a naval route to the Indian Ocean through the southern tip of Africa in 1497--98 . Initially, the Portuguese were mainly active in Calicut, but the northern region of Gujarat was even more important for trade, and an essential intermediary in east - west trade . </P> <P> Venetian interests were directly threatened as the traditional trade patterns were eliminated and the Portuguese became able to undersell the Venetians in the spice trade in Europe . Venice broke diplomatic relations with Portugal and started to look at ways to counter its intervention in the Indian Ocean, sending an ambassador to the Egyptian court . Venice negotiated for Egyptian tariffs to be lowered to facilitate competition with the Portuguese, and suggested that "rapid and secret remedies" be taken against the Portuguese . The Mamluks sent a fleet in 1507 under Amir Husain Al - Kurdi, which would fight in the Battle of Chaul . </P> <P> The Ottomans tried to challenge Portugal's hegemony in the Persian Gulf region by sending an armada against the Portuguese under Ali Bey in 1581 . They were supported in this endeavor by the chiefs of several local principalities and port towns such as Muscat, Gwadar, and Pasni . However, the Portuguese successfully intercepted and destroyed the Ottoman Armada . Subsequently, the Portuguese attacked Gwadar and Pasni on the Mekran Coast and sacked them in retaliation for providing aid and comfort to the enemy . </P> <P> During the 16th century the Portuguese had established bases in the Persian Gulf . In 1602, the Iranian army under the command of Imam - Quli Khan Undiladze managed to expel the Portuguese from Bahrain . In 1622, with the help of four English ships, Abbas retook Hormuz from the Portuguese in the capture of Ormuz . He replaced it as a trading centre with a new port, Bandar Abbas, nearby on the mainland, but it never became as successful . </P>

About how long did the portuguese trading empire in the indian ocean flourish