<P> The well - armed Fourth Armada of 1502, under Vasco da Gama again, came in a more mean - spirited mood, indisposed to take no for an answer . Having secured separate treaties with Malindi, Mozambique and all - important Sofala, the Portuguese brought their menacing fleet to bear on Kilwa itself, and extorted a sizeable tribute from emir Ibrahim . </P> <P> Some have speculated whether Emir Ibrahim missed a golden opportunity to restore his fortunes, that had a treaty with Cabral been reached back in 1500, he might have secured the assistance of the Portuguese navy in bringing the half - independent vassals back under his sway . At least one Kilwan nobleman, a certain Muhammad ibn Rukn ad Din (known to the Portuguese as Muhammad Arcone), certainly advised Emir Ibrahim to strike up an alliance with the Portuguese (and for his pains, was given up as a hostage to the Portuguese by the Emir, who then refused ransom him back - allowing him to be subjected to Gama's wrath .) </P> <P> As it turns out, the vassals used the Portuguese, one by one, to secure their permanent break from the Sultanate . The ruler of Malindi was the first to embrace the Portuguese, forging an alliance in 1497 (largely to be directed against Mombassa). After Emir Ibrahim's coup, it was certainly not hard to persuade the ruling sheikh Isuf of Sofala (Yçuf in Barros, Çufe in Goes) (apparently a nephew of the late Emir Muhammad) to break away . He signed a treaty with the Portuguese in 1502, and followed it up by allowing the construction of a Portuguese factory and fort in Sofala in 1505 . </P> <P> It was in 1505 that Francisco de Almeida brought his fleet into the harbor of Kilwa, and landed some 500 Portuguese soldiers to drive Emir Ibrahim out of the city . Almeida installed the aforementioned Muhammad Arcone on the throne, as a Portuguese vassal . Remembering constitutional proprieties, Arcone insisted that Micante, the son of the late sultan al - Fudail be his designated successor . The Portuguese erected a fortress (Fort Santiago) on Kilwa and left a garrison behind, under the command of Pedro Ferreira Fogaça to keep an eye on things . </P>

Factors that led to the decline of kilwa