He afterwards commanded an army of ninety-five thousand Arabs and Persians, sent by his father to invade the Eastern Roman Empire, which was then ruled by the Empress Irene (_i-re'ne_). After defeating Irene's famous general, Nicetas (_ni-ce'tas_), Harun marched his army to Chrys-op'o-lis, now Scutari (_skoo'ta-re_), on the Asiatic coast, opposite Constantinople. He encamped on the heights, in full view of the Roman capital. The Empress saw that the city would certainly by taken by the Moslems. She therefore sent ambassadors to Harun to arrange terms; but he sternly refused to agree to anything except immediate surrender. Then one of the ambassadors said, "The Empress has heard much of your ability as a general. Though you are her enemy, she admires you as a soldier." These flattering words were pleasing to Harun. He walked to and fro in front of his tent and then spoke again to the ambassadors. "Tell the Empress," he said, "that I will spare Constantinople if she will pay me seventy thousand pieces of gold as a yearly tribute. If the tribute is regularly paid Constantinople shall not be harmed by any Moslem force." The Empress had to agree to these terms. She paid the first year's tribute; and soon the great Moslem army set out on its homeward march. When Harun was not quite twenty-one years old he became caliph. He began his reign by appointing very able ministers, who carried on the work of the government so well that they greatly improved the condition of the people. Harun built a palace in Bagdad, far grander and more beautiful than that of any caliph before him. Here he established his court and lived in great splendor, attended by hundreds of courtiers and slaves. He was very anxious that his people should be treated justly by the officers of the government; and he was determined to find out whether any had reason to complain. So he sometimes disguised himself at night and went about through the streets and bazaars, listening to the talk of those whom he met and asking them questions. In this way he learned whether the people were contented and happy, or not. In those times Bagdad in the east and the Mohammedan cities of Spain in the west were famed for their schools and learned men. Arabian teachers first introduced into Western Europe both algebra and the figures which we use in arithmetic. It is for this reason that we call these figures the "Arabic numerals." Harun-al-Rashid gave great encouragement to learning. He was a scholar and poet himself and whenever he heard of learned men in his own kingdom, or in neighboring countries, he invited them to his court and treated them with respect. The name of Harun, therefore, became known throughout the world. It is said that a correspondence took place between him and Charlemagne and that, as you have learned, Harun sent the great emperor a present of a clock and an elephant. [Illustration: THE PRESENTS FROM HARUN-AL-RASHID]