“In 1493 Pope Alexander VI, while granting Spain the right to colonize the New World, mandated that the indigenous people be converted to Catholicism and prohibited their enslavement. However, he added a “catch 22” by going on to say that those who did not accept Christianity or reverted to their old religion, should be punished and could be enslaved. More positively, in 1500, Queen Isabella of Spain had expressly ordered, “all the Indians of the Spaniards were to be free from slavery.” This order had no ifs or buts. When she died in 1504, her will instructed her successors to continue these policies.
Thus, when in 1519 Cortes and the Conquistadors invaded Mexico, both Spanish and Papal Law seemingly protected the Indians from enslavement. It is not surprising that Cortes, whose very invasion of Mexico was an illegal rebellion against the order of his superior, the Governor of Cuba, ignored the order of the Queen, and used the aforementioned “catch 22” to remain in compliance with the Papal order. As they moved toward Tenochtitlan, the Spaniards went through the motions of converting the Indians but offered them no religious instruction. The erection of a Cross, a speech outlining the virtues of Christianity by La Malinche and the destruction of the local idols was the standard procedure.
It was not until 1524, after the Aztecs had been conquered and enslaved, that 10 Franciscan Priests and 2 lay brothers arrived. Now, real religious instruction was offered to the Indians. In 1526, 12 Dominicans followed them. The first Jesuits who ultimately were to carry the main burden of religious instruction, did not arrive until 1572. Thus, in 1521 when Cortes gave his followers vast tracts of land called encomiendas,all indigenous people living within the boundaries of these land grants were bound to the land as slaves. Simply baptized, without follow up, it was easy to claim they had reverted to the worship of their old Gods. Thus the ecomienderos could claim they were in compliance with the second part of the Pope’s directive. Recognized by the Spanish Crown as the military governor of New Spain, largely unsupervised, Cortes ran Nueva Espagna until 1526.”http://www.mexconnect.com/articles/666-slavery-in-mexico