Muhammed el-Mahdi, son of El-Mansur, succeeded his father and was the third caliph of the house of Abbas. He was at Baghdad when his father expired near Mecca, but, despite his absence, was immediately proclaimed caliph. El-Mahdi betrayed in his deeds that same fickleness which had signalised the caliphate of his father, El-Mansur. He appointed a different governor of Egypt nearly every year. These many changes resulted probably from the political views held by the caliph, or perhaps he already perceived the tendency shown by each of his provinces to separate itself from the centre of Islamism. Perhaps also he already foresaw those divisions which destroyed the empire about half a century later. Thus his prudence sought, in allowing but a short period of power to each governor, to prevent their strengthening themselves sufficiently in their provinces to become independent.
Egypt remained calm and subdued under these constant changes of government. Syria and the neighbouring provinces followed suit, and the Caliph el-Mahdi profited by this peaceful state of things to attack the Emperor of the Greeks. His second son, Harun, undertook the continuation of this war, and the young prince displayed such talent and bravery that he gained brilliant victories, and returned to Baghdad after having captured several cities from the Greeks, overthrown their generals, and forced Constantinople to pay an annual tribute of seventy thousand dinars (about $180,000). The Caliph el-Mahdi rewarded Harun by solemnly naming him the future successor of his eldest son, Musa el-Hadi, whom he had just definitely declared his heir to the throne. Shortly after this decision, el-Mahdi died, in the year 785, having reigned ten years and two months.
Musa el-Hadi, his eldest son, succeeded him, being the fourth caliph of the race of Abbasids. On ascending the throne, he withdrew the government of Egypt from Fadl ibn Salih, appointing in his place Ali ibn Suleiman, also a descendant of Abbas. El-Hadi plotted against the claims of Harun to the succession, but he died before his plans had matured, and Harun became caliph in the year 786.
The reign of Harun er-Rashid was the most brilliant epoch of the empire of Islamism, and his glory penetrated from the far East to the western countries of Europe, where his name is still celebrated.
Harun seems to have been as reluctant as his father and grandfather were before him to leave a province too long in the hands of a governor, and he even surpassed them in his precautionary measures. In the year 171 of the Hegira, he recalled Ali ibn Suleiman, and gave the government of Egypt to Musa ibn Isa, a descendant of the Caliph Ali.
Thereafter the governors were changed on an average of once a year, and their financial duties were separately administered. Musa ibn Isa, however, held the appointment of Governor of Egypt on three separate occasions, and of his third period Said ibn Batrik tells the following anecdote:
“While Obaid Allah ibn el-Mahdi was ruling in Egypt,” he relates, “he sent a beautiful young Koptic slave to his brother, the caliph, as a gift. The Egyptian odalisk so charmed the caliph that he fell violently in love with her. Suddenly, however, the favourite was laid prostrate by a malady which the court physicians could neither cure nor even diagnose. The girl insisted that, being Egyptian, only an Egyptian physician could cure her. The caliph instantly ordered his brother to send post haste the most skilful doctor in Egypt. This proved to be the Melchite patriarch, for in those days Koptic priests practised medicine and cultivated other sciences. The patriarch set out for Baghdad, restored the favourite to health, and in reward received from the caliph an imperial diploma, which restored to the orthodox Christians or Melchites all those privileges of which they had been deprived by the Jacobite heretics since their union with the conqueror Amr ibn el-Asi.”
If this story be true, one cannot but perceive the plot skilfully laid and carried out by the powerful clergy, to whom any means, even the sending of a concubine to the caliph, seemed legitimate to procure the restoration of their supremacy and the humiliation of their adversaries.