The revolt of Parma, on the 16th of June, 1247, obliged Frederick to resume his arms at a moment when he was least disposed. The friends and relatives of Pope Innocent IV, the Guelf nobles of the houses of Corregio, Lupi, and Rossi, re-entering Parma, whence they had been exiled, triumphed over their adversaries, and in their turn expelled them from the city. Frederick was determined at any price to recover Parma. He sent for a numerous band of Saracens from Apulia, commanded by one of his natural sons, named Frederick, to whom he gave the title of king of Antioch. He assembled the Lombard Ghibellines, under the command of another of his illegitimate sons, named Hans or Hensius, called by him king of Sardinia, and whom he had made imperial vicar in Lombardy. Ezzelino arrived, too, at his camp from the Veronese march, with the militias of Padua, Vicenza, and Verona, and the soldiers whom he had raised in his hereditary fiefs. On the other side, the Guelfs of Lombardy hastened to send succour to a city which had just sacrificed itself for them. The Milanese set the example; the militias of Mantua, Piacenza, and Ferrara followed it; and the Guelfs, who had been exiled from Reggio, Modena, and other Ghibelline cities, thinking they served their country in fighting for their faction, arrived in great numbers to shut themselves up in Parma. Frederick was prevented from hanging the hostages given previous to the revolt, before the walls of the city, by the militia of Pavia, who declared it was with the sword of Ghibelline soldiers only, and not with that of the executioner, that they would secure the throne of the emperor. The siege made little progress; the winter had begun, but Frederick persisted in his attempt. He proclaimed his determination to raze Parma to the ground, and to transfer those of the inhabitants who should be spared into his fortified camp, of which he would make a new town, called Vittoria. This camp, which he quitted on a hawking party, on the 8th of February, 1248, was in his absence surprised by a sortie of a Guelf army from Parma, taken, and pillaged; his soldiers were dispersed, and the emperor had the humiliation of being forced to raise the siege. THE GUELFS EXPELLED FROM FLORENCE; THE BATTLE OF FOSSALTA [Sidenote: [1248-1249 A.D.]]