Dum Diversas

Dum Diversas (English: Until different) is a papal bull issued on 18 June 1452 by Pope Nicholas V. It authorized Afonso V of Portugal to conquer Saracens and pagans and consign them to "perpetual servitude".Pope Calixtus III reiterated the bull in 1456 with Inter Caetera (not to be confused with Alexander VI's), renewed by Pope Sixtus IV in 1481 and Pope Leo X in 1514 with Precelse denotionis. The concept of the consignment of exclusive spheres of influence to certain nation states was extended to the Americas in 1493 by Pope Alexander VI with Inter caetera.

By the summer of 1452 Ottoman Sultan Mehmed II had completed the Rumelihisarı fortress on the western or European side of the Bosphorus. Located several miles north of Constantinople, it commanded the narrowest part of the Bosporus. Byzantine Emperor Constantine XI wrote to Pope Nicholas for help. Issued less than a year before the Fall of Constantinople in 1453, the bull may have been intended to begin another crusade against the Ottoman Empire. Nicholas V's nephew, Loukas Notaras, was Megas Doux of the Byzantine Empire. It was not until Alfonso V of Portugal responded to a Papal call for aid against the Turks, that Pope Nicholas V agreed to support the Portuguese claims regarding territory in Africa. Although some troops did arrive from the mercantile city states in the north of Italy, Pope Nicholas did not have the influence the Byzantines thought he had over the Western Kings and Princes. France and England were both weakened by the Hundred Years' War, and Spain was still engaged in conflict with Islamic strongholds in Iberia. Any Western contribution was not adequate to counterbalance Ottoman strength.

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