As Charles VIII. was marching through Italy, and was approaching, all unopposed, the sacred city of Rome, Alexander VI., anxious at all hazards to obtain the assistance of his countrymen in the hour of danger, had sent an envoy to the Spanish court representing the critical state of affairs in Italy, assuring the king and queen of his constant goodwill, in spite of certain disputes as to the Papal authority in Spain, and conveying to them, with other less substantial favors, the grant of the Tercias, or two-ninths of the tithes throughout all the dominions of Castile, an impost which, until the middle of the present century, formed a part of the revenues of the Spanish monarchy. He also conceded to the Spanish crown the right of dominion over the whole of northern Africa, except Fez, which had been given to the King of Portugal. A projected marriage between the Duke of Calabria, eldest son of the King of Naples, and the Infanta Maria, daughter of Ferdinand and Isabella, served to give the King of Spain an opportunity for negotiating with the Neapolitan court; and Ferdinand at the same time dispatched the celebrated Garcilaso de la Vega as his embassador, with instructions to return the most comforting assurances to the Pope at Rome. Yet he refrained from making any definite promises, or from committing himself to any definite policy. He was not a man to do anything rashly; and he preferred to await the course of events. Meanwhile, having sent a second mission from Guadalajara to the French court or camp, with good advice for his young friend and ally Charles VIII., Ferdinand betook himself with Isabella to Madrid, where the Spanish sovereigns devoted themselves to the preparation and equipment of an army to be dispatched at an opportune moment to any part of Italy where subsequent events might render its presence necessary. As, for various reasons, it was impossible that either Ferdinand or Isabella should accompany their army abroad, it became necessary to select a general. Among all the skillful leaders and gallant knights who had signalized themselves in the wars of Granada, it was somewhat difficult to decide upon a commander. But Isabella had never lost sight of Gonsalvo de Cordova, in whom she discerned traces of rare military talent; and from the moment the Sicilian expedition was planned she determined that he should be captain-general of the royal forces. The greater experience and apparently superior claims of many who had distinguished themselves in battle against the Moors were urged by Ferdinand without avail. The command was given to Gonsalvo de Cordova.