Fernando and Isabel, armed though they were with the tremendous authorities and responsibilities conferred by this Bull, did not hasten to brandish it over the heads of the Conversos, and to light the vast and lonely horizons of Castile with bonfires; as they would have done, had they been the bigots they have been accused of being. On the contrary, they decided to consider the matter further, and put the document away for nearly two years. They were influenced in this by the counsels of Cardinal Mendoza, who reminded them that if many of the Conversos were ignorant of the truths of the Catholic Faith, it might be because they had not been taught them by those whose business it was to do so. The Cardinal prepared a catechism for all the parishes of his own diocese.
The results, after several months, were discouraging…Toward the end of the second year of futile catechizing, all Christendom was thrown into a panic by the ruthless victories of the Grand Turk, Mohammed II, who, angered by his failure to storm Rhodes, sent his fleet westward, ravaged the coast of Apulia, and on August 11, 1480, took the city of Otrano in the Kingdom of Naples. Nearly half the civil population of 22,000 were butchered in cold blood, while the Archbishop and all the priests were slaughtered after the most brutal tortures.
The reaction in Spain when the news of these outrages arrived, sometime in September, probably had something to do with the decision of King Fernando and Queen Isabel to put into effect, without further delay, the powers granted to them by Sixtus. On the twenty-sixth, at Medina del Campo, they published a decree making the Inquisition effective, and appointing as members of the first tribunal in Castile, Cardinal Mendoza, Fray Tomas de Torquemada, and two other Dominicans, Fray Miguel Morillo and Fray Juan de San Martin.
William Thomas Walsh, Characters of the Inquisition (1940)