Cut off to the north by desert, to the south by the Mapuche, to the east by the Andes Mountains, and to the west by the ocean, Chile became one of the most centralized, homogeneous colonies in Spanish America. Serving as a sort of frontier garrison, the colony found itself with the mission of forestalling encroachment by both the Mapuche and Spain's European enemies, especially the English and the Dutch. Buccaneers and pirates menaced the colony in addition to the Mapuche, as was shown by Sir Francis Drake's 1578 raid on Valparaíso, the colony's principal port. Chile hosted one of the largest standing armies in the Americas, making it one of the most militarized of the Spanish possessions, as well as a drain on the treasury of the Viceroyalty of Peru.