 Roman Catholic teaching began to turn more strongly against forms slavery from 1435.When the Age of Discovery greatly increased the number of slaves owned by Christians, the response of the clergy, under strong political pressures, was confused and ineffective in preventing the establishment of slave societies in the colonies of Catholic countries.Earlier Papal bulls such as Pope Nicholas V's 1452 Dum Diversas, or Romanus Pontifex from 1454, permitting the "perpetual servitude" of saracens and pagans in Africa, were used to justify enslavement of natives and the appropriation of their lands during this era.