During the 15th century, Boni had seceded from Majapahit and then converted to Islam. Thus transforming into the independent Sultanate of Brunei. Brunei became a Hashemite state when she allowed the Arab Emir of Mecca, Sharif Ali, to become her third sultan. Scholars claim that the power of the Sultanate of Brunei was at its peak between the 15th and 17th centuries, with its power extending from northern Borneo to the southern Philippines (Sulu) and even in the northern Philippines (Manila) which Brunei incorporated via territorial acquisition accomplished through royal marriages. For political reasons, the historical rulers of Maynila maintained close cognatic ties through intermarriage with the ruling houses of the Sultanate of Brunei, but Brunei's political influence over Maynila is not considered to have extended to military or political rule. Intermarriage was a common strategy for large thalassocratic states (maritime states) such as Brunei to extend their influence, and for local rulers such as those of Maynila to help strengthen their family claims to nobility. Sultan Bolkiah had extended Brunei's power to its greatest extent when it conquered Manila and Sulu as he even attempted but failed to conquer the Visayas islands even though Sultan Bolkiah was half-Visayan himself being descended from a Visayan mother and he was famously known as Sultan Ragam "The Singing Captain", his powerful musical voice was a trait he inherited from his Visayan lineage since Visayans were culturally obsessed with singing, with the best Visayan singers often also being members of their warrior castes too. However, Islamic Brunei's power was not uncontested in Borneo since it had a Hindu rival in a state founded by Indians called Kutai in the south which they overpowered but didn't destroy. Brunei's dominance in the Philippines was also challenged by two Indianized kingdoms, the Rajahanates of Cebu and Butuan which were also coincidentally allied with Kutai and were also at war with Brunei's dependencies; Sulu and Manila as well as their mutual ally, the Sultanate of Maguindanao. The Kedatuans of Madja-as and Dapitan were also belligerent against Brunei due to them being the targets of constant Muslim attacks organized from Maguindanao and Ternate, a Papuan speaking state in the vicinity of Oceania that grew wealthy by monopolizing spice production. Nevertheless, by the 16th century, Islam was firmly rooted in Brunei, and the country had built one of its biggest mosques. In 1578, Alonso Beltrán, a Spanish traveller, described it as being five stories tall and built on the water.