The most difficult challenges for the missionaries were the dispersion of the Filipinos and the wide variety of languages and dialects. The geographical isolation forced the Filipino population into numerous small villages, and every other province supported a different language. Furthermore, frequent privateering from Japanese Wokou pirates and slave-raiding by Islamic Moros blocked Spanish attempts to Christianize the archipelago, and to offset the disruption of continuous warfare with them, the Spanish militarized the local populations, importing soldiers from Latin America, and constructed networks of fortresses across the islands. As the Spanish and their local allies were in a state of constant war against pirates and slavers, the Philippines became a drain on the Vice-royalty of New Spain in Mexico City, which paid to maintaining control of Las Islas Filipinas in lieu of the Spanish crown.