Their colonies existed by the sufferance of their foes. The feudal barons, in most instances, detested their Christian neighbors--not infrequently connected with them by ties of blood as well as by the obligations of a common religious belief--far more than the blaspheming Moslems. In vain was the aid of the Emperor of Germany invoked; his plans were thwarted by the discord and treachery of his allies. The forces he despatched for the relief of the Italians were constantly at variance with the Byzantines, and armies, almost equal to the conquest of an empire, were fruitlessly employed in the quarrels of petty sovereigns, whose union was indispensable to the expulsion of a crafty and audacious enemy. The Pope, either through weakness or from motives of policy, seems to have generally kept aloof from this crusade, prosecuted in his behalf as the head of Christendom, as well as to assure the stability of his temporal power. During the course of these events, Ibrahim-Ibn-Ahmed, a prince of rare administrative talents, of vast accomplishments, of boundless ambition, and of a character remarkable for barbarity even in an age of tyrants, had ascended the throne of Kairoan. Desirous of signalizing his accession by the successful prosecution of an enterprise which his predecessors had in vain attempted, he determined to capture Syracuse. A numerous army was raised. In accordance with the favorite policy of the sovereigns of Africa, special care was exercised that the malcontents who had manifested hostility towards the government should be enrolled in the expedition. When pecuniary inducements failed to tempt these disturbers of the peace, they were seized and forced to embark. The preparations were worthy of the importance and difficulties of the undertaking. The fleet consisted of the swiftest and largest vessels of the Moorish navy. The army was provided with the most formidable engines ever constructed by the Arabs for the siege of any city. The command was intrusted to Giafar-Ibn-Mohammed, the newly appointed Emir of Sicily, an officer of ability, experience, and courage.