What would become the city of Manila in Spanish times was previously the small kingdom of Maynila ruled by Datus who had ties to the royal family of the Kingdom of Brunei. It was established early in the 16th century through an attack by Bornean forces on the Filipino principality at the mouth of the Pasig river.

The Spanish in turn attacked and conquered the walled fort they found there in 1570, and returned in force to permanently occupy Manila the following year. But in the years following the Spanish conquest of Manila in 1571, the Castilians remained wary of possible military expeditions being sent out from the Kingdom of Brunei to recover Manila. The situation culminated in the Spanish themselves, accompanied by ships of the Filipino allies they had cultivated, sending a large expedition south to Brunei in 1578. Sailing into the harbor, the Spaniards and Filipinos attacked and overwhelmed the city, which was then subjected to a sacking. The sultan of Brunei fled inland and eventually the Spanish themselves withdrew back to the Philippines.