The Spaniards embarked on a policy of forced conversion, in a seemingly continued version of the Christian crusade against the Islamic jihad that was seen in the past century in Europe. It was the Spaniards that first termed the Filipino muslims as "moros- after the Muslim Moors back in Europe.
The arrival of the Spaniards marked the start of the decline of Islam in the Philippines. Over the previous three centuries before the Spaniards had arrived, Islam, as well as the Muslim sultanates originating in Jolo, had gained increasing influence, to the extent that even Manila was ruled by an Islamic sultanate when the Spaniards arrived. However, with their superior firepower and technology, the Spaniards destroyed and captured Manila and other settlements in the northern island of Luzon and its surrounding islands, forcibly converting many of its inhabitants to Christianity. These Christian Filipinos were referred to by the Spaniards as "indios-. While the Spanish technical superiority was put to good use in the northern Philippines, their constant attempts to conquer the Muslim sultanates to the south were met with failure. For the next 300 years, until Spain left the Philippines in 1899, the Spanish were engaged in prolonged periods of warfare and uneasy peace with the Muslim sultanates to the south, having explored all means of defeating them, even to the extent of economic starvation through the blockage of marine and land trade routes. .
It is important to note two main points about the Spanish conquest:.
Firstly, the Spaniards first created the animosity between the Christian Filipinos and the Muslim Filipinos. During the Spanish-Moro war, the Spaniards occasionally included Christian Filipinos in their offensives against the Muslims, as they burnt towns and villages, and killed hundreds of Muslim villagers, regardless of men, women or children. This same treatment was often returned by the Muslims, as they too conducted raids on Christian villages.