In the face of these invasions by European Christian powers, the Ottoman Caliphate aided the beleaguered Southeast Asian Sultanates by making Aceh a protectorate and sending expeditions to reinforce, train and equip the local mujahideen.
Spain declared war in 1578, planning to attack and capture Kota Batu, Brunei's capital at the time.
Brunei briefly rose to prominence in Southeast Asia when the Portuguese occupied Malacca and thereby forced the wealthy and powerful but displaced Muslim refugees there to relocate to nearby Sultanates such as Aceh and Brunei.
However, European influence gradually brought an end to the regional power, as Brunei entered a period of decline compounded by internal strife over royal succession.
During the 15th century, Po-ni had seceded from Majapahit and then converted to Islam.
Thus transforming into the independent Sultanate of Brunei.
Economic growth during the 1990s and 2000s, with the GDP increasing 56% from 1999 to 2008, transformed Brunei into an industrialised country.Nevertheless, by the 16th century, Islam was firmly rooted in Brunei, and the country had built one of its biggest mosques.