In 300 the colony of Tripoli revolted. There, as in Kairawan, there had been riots between the Berbers and Arabs. When Abu l-Qasim returned from punishing the tribes he advanced to attack Tripoli, whilst the Mahdi at the same time sent a fleet against it, and after some delay it was reduced. Then Sicily revolted, and this proved to be a permanent loss to the Fatimid Khalifs. At first the Sicilians invited Ahmad, a son of Ziadat Allah, the former emir of Kairawan, to take charge. He refused, but after some time, as the invitation was repeated, he consented to be recognised as emir of Sicily. As soon as he was established he sent a letter to the Khalif of Baghdad professing loyalty and asking to be confirmed as emir by the Khalif. Thus Sicily broke away from the Fatimid dominions and became once more a part of the empire of the ʿAbbasid Khalif. In 301 the Mahdi founded a new city on the coast near Kairawan, and gave to it the name of al-Mahadiya. The site was very badly chosen, and the place afterwards decayed completely, although it served as the Fatimid capital for some generations. At the same time he commenced building a fleet, by the help of which he hoped to make an attack upon Egypt in due course; no doubt he was by this time convinced that his kingdom in North Africa was not likely to be a stable one, just as it had been held precariously by the Arab rulers who preceded him: in fact it was an unsettled and savage country, which could be under control only so long as under actual military occupation. Probably, also, he hoped that the prospect of conquering Egypt would attach the Berbers to him more successfully. The weak point in these plans was that the building and manning of a fleet depended almost entirely on what Greek help he could hire. Soon afterwards he sent his general Khubasa eastwards and extended his authority, somewhat precariously, to Barqa. In the summer of 302 he made his first attempt against Egypt, sending forces by land under his son Abu l-Qasim, and Khubasa against Alexandria. The inhabitants of that city were obliged to take refuge in the ships in the harbour, whilst the invaders plundered their houses. The invading army then passed southwards to the Fayyum, but here they were met by an Egyptian army strongly reinforced from Baghdad, and compelled to retire. The effort, however, had brought the invasion of Egypt within the sphere of practical politics, and the plunder of Alexandria raised much enthusiasm amongst the Mahdi’s followers. At that time the ʿAbbasid Khalifate was in its decline: in Baghdad the government was in the hands of the military guard, the commander of that guard was the real ruler, the Khalif being no more than a figure head liable to be deposed and replaced at the will of the soldiery. The provinces were semi-independent, in most cases ruled by hereditary emirs who paid no more than a formal tribute of respect to the Khalif; indeed, in many cases it meant simply that his name was