April, the Pope made Charles imperial vicar of Tuscany "during the vacancy of the empire", a move of dubious legality. Charles marched to southern Italy and laid siege to Lucera, but he then had to hurry north to prevent Conradin's invasion of Abruzzo in late August. At the Battle of Tagliacozzo, on 23August 1268, it appeared that Conradin had won the day, but a sudden charge by Charles's reserve routed Conradin's army. The burghers of Potenza, Aversa and other towns in Basilicata and Apulia massacred their fellows who had agitated on Conradin's behalf, but the Sicilians and the Saracens of Lucera did not surrender. Charles marched to Rome where he was again elected senator in September. He appointed new officials to administer justice and collect state revenues. New coins bearing his name were struck. During the following decade, Rome was ruled by Charles's vicars, each appointed for one year. Conradin was captured at Torre Astura. Most of his retainers were summarily executed, but Conradin and his friend, Frederick I, Margrave of Baden, were brought to trial for robbery and treason in Naples. They were sentenced to death and beheaded on 29October. Conrad of Antioch was Conradin's only partisan to be released, but only after his wife threatened to execute the Guelph lords she held captive in her castle. The Ghibelline noblemen of the Regno fled to the court of Peter III of Aragon, who had married Manfred's daughter, Constance. Mediterranean empire Italy Charles's wife, Beatrice of Provence, had died in July 1267. The widowed Charles married Margaret of Nevers in November 1268. She was co-heiress to her father, Odo, the eldest son of Hugh IV, Duke of Burgundy. Pope Clement died on 29November 1268. The papal vacancy lasted for three years, which strengthened Charles's authority in Italy, but it also deprived him of the ecclesiastic support that only a pope could provide. Charles returned to Lucera to personally direct its siege in April 1269. The Saracens and the Ghibellines who had escaped to the town resisted until starvation forced them to surrender in August 1269. Charles sent Philip and Guy of Montfort to Sicily to force the rebels there into submission, but they could only capture Augusta. Charles made William l'Estandart the commander of the army in Sicily in August 1269. L'Estandart captured Agrigento, forcing Frederick of Castile and Frederick Lancia to seek refuge in Tunis. After L'Estandart's subsequent victory