Spanish–Moro conflict
The Spanish initiated the conflict by conquering the Philippines and invading Moro territory in an effort to subjugate the region to their rule since the 1500s. When the Spanish conquered the Muslim Kingdom of Maynila, a vassal of the Sultanate of Brunei, the Islamic rajah, Rajah Sulayman resisted the Spanish. Manila then became the capital of the Spanish Philippines after the conquest, with the Spanish forcibly converting people to Catholicism. The Spanish–Moro Wars started with the Castille War, a war between Spaniards and the Sultanate of Brunei. (The term "Moro" at this time included Muslim Tagalogs who were ruled by the Sultanate of Brunei).
Western imperialism in Asia
The Spanish war against Brunei failed to conquer Brunei but it totally cut off the Philippines from Brunei's influence, the Spanish then started colonizing Mindanao and building fortresses. In response, the Bisayas, where Spanish forces were stationed, were subjected to retaliatory attacks by the Magindanao in 1599-1600 due to the Spanish attacks on Mindanao.