From “Undoing Manifest Destiny: Settler America, Christian Colonists, and the Pursuit of Justice” by L. Daniel Hawk
Beginning in the fifteenth century, Portuguese mariners ventured into the Atlantic Ocean and along the coast of Africa, looking for new territories for agriculture, access to gold and ivory from West Africa, and a sea route to the lucrative eastern spice trade. By the 1440’s they had established trading posts and forts along the African coast and began trafficking in slaves. Anxious to establish his rights over his African possessions, Portuguese King Alfonso V answered a call by Pope Nicholas V for assistance against the Turks, who were threatening Christian lands in the East. Sometime later, Pope Nicholas issued a papal bull titled Dum Diversas. The bull, published in 1452, authorized Alfonso and his successors “to invade, search out, capture, vanquish, and subdue all Saracens and pagans whatsoever, and other enemies of Christ,” to take whatever they owned, and to subject them to “perpetual slavery.” It further decreed that his acquisitions had been “justly and lawfully” acquired and permitted him to appropriate the lands and goods “for his and [his heirs’] use and profit.”