The King being desirous of bringing into notice his natural son Ferdinando Duke of Calabria, the destined heir of his crown, now placed him at the head of 8000 cavalry, and half that number of foot soldiers, but bestowed on Federigo the rank and title of Captain-general. Entering Tuscany by Cortona, this army penetrated by the valleys of Chiana and Arno, carrying terror almost to the gates of Florence, and overrunning a vast extent of country. But no permanent impression was made, for, trusting to the artillery of Siena, which was refused him, Alfonso had not provided his troops with the means of taking any strong places. It accordingly cost them six weeks to reduce Foiano, and after spending as long before Castellina, the bursting of their only battering-gun rendered further perseverance useless. Thus when they betook themselves to winter quarters at Aquaviva on the Mediterranean coast, they could boast no important result of the campaign. A colourable pretext was thus afforded for murmurs from the captains, many of whom served reluctantly under a commander so much their junior. Although these complaints reached Alfonso, they no way diminished his confidence in Federigo, whom he encouraged to meet such jealousy by redoubled exertions. In order to arrange a plan of operations, the Count repaired to Naples, and received from him a cordial welcome. As spring advanced, the pestilent air of the Maremma, which had formerly compromised the Neapolitan army in "That sun-bright land of beauty," again proved their scourge. Many officers and men were attacked by fever, and among them the Captain-general, who was removed to Siena whilst his troops fell back upon Pitigliano. The following letter, written by him during an earlier stage of his malady, and probably in reply to pressing invitations from the priors of that city, proves his reluctance to leave his post:-- "Mighty and potent Lords, dearest Fathers;