Pedro was overjoyed at this opportunity of extending his dominions; but to fight against the pope, the king of France, brother to Charles of Sicily, and the whole party of the Guelfs, was too momentous an undertaking to be lightly commenced. He first secured a considerable sum from the Greek emperor, to whom the Sicilian usurper was obnoxious; he next collected a fleet, assembled his barons, gave liberty to his rebel subjects, whom he had placed in confinement; but took care to conceal his purpose. It seems, however, to have been divined both by the pope and the French king, who, alarmed at the extent of his preparations, demanded for what object they were intended. By pretending that his expedition was to be directed against Barbary, and by even sending an ambassador to the pope (Martin IV), soliciting an indulgence for all who joined him in warring against the infidels, he hoped to lull the suspicions of Europe. But Martin, who was not to be deceived, contumeliously dismissed the ambassador. This circumstance did not discourage Pedro, whose armament was prosecuted with an alacrity inspired by the hope of success. An accident which, operating like a spark on the inflammable temper of the Sicilians, forced them into open insurrection, hastened his departure. The citizens of Palermo rose as one man, and destroyed every Frenchman on whom they could lay hands. Their example was followed by other towns--by none more heartily than Messina; so that scarcely a Frenchman was left alive from one extremity of the island to another. Such is the famous massacre which posterity has called the Sicilian Vespers. [Burke[g] estimates the number of slain at 28,000.] When Pedro learned that the Messenians were courageously repelling the assaults of Charles of Anjou, who had passed over from Naples to reduce them, and when a deputation from Palermo arrived, beseeching him to accept the crown, he laid aside his extreme caution, and proceeded towards the western coast of the island. In August he landed at Trapani, where his reception was enthusiastic; he hastened to Palermo, where he was joyfully proclaimed king of Sicily. The inhabitants of Messina, still invested by Charles, besought the new monarch to relieve them, and to receive their homage. Pedro hastened to their aid. Charles now raised the siege, and conducted his powerful armament towards the ports of Calabria; it was pursued by that of Aragon, headed by Don James, a son of Pedro, who took twenty vessels, with four thousand prisoners. But the young prince, listening only to his ardour, instead of returning to Messina, pursued Charles to a fort in Calabria, which he attempted to take; where, being repulsed with some loss, he re-embarked his troops. His father, indignant at his failure, deprived him of the naval command, which was intrusted to a more experienced chief, Roger de Lauria.