Pope Pius II reportedly sent a letter to Sultan Mehmed II, which included among a plea to convert to Catholicism, an exhaustive refutation of the teachings of Islam. What exactly did this Pius say, what were his main arguments?
Followup question: What reasons would Pius have had to send such a (potentially insulting) letter? Might he have had any indication it might actually work (e.g. Has Mehmed II entertained the idea of Christianity in some capacity previously?)