Declining Indian populations, a Spanish disdain for manual labor, and the defense requirements of an extended empire had created an early demand for additional workers. Blacks cleared land and planted crops, built fortifications and domestic structures, and provided a wide variety of skilled labor for Spanish colonists. By the 16th century, they had become the main labor force in Mexican mines and on Caribbean plantations. Also by that time, the Spanish had organized them into militia companies in Hispanola, Cuba, Mexico, Cartagena, and Puerto Rico. (Landers FM 9)