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. [Illustration: 347.jpg DOOR OF AN ARABIAN HOUSE.] 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: