In the year A.D. 637 the Arabs again took the offensive.  They had employed the intervening year and a half in the foundation of Busrah and Kufam and in the general consolidation of their sway on the right bank of the Euphrates.  They were now prepared for a further movement.  The conduct of the war was once more entrusted to Sa’ad.  Having collected an army of 20,000 men, this general proceeded from Kufa to Anbar (or Perisabor), where he crossed the Euphrates, and entered on the Mesopotamian region.  Isdigerd. learning that he had put his forces in motion, and was bent upon attacking Ctesiphon, called a council of war, and asked its advice as to the best course to be pursued under the circumstances.  It was generally agreed that the capital must be evacuated, and a stronger situation in the more mountainous part of the country occupied; but Isdigerd was so unwilling to remove that he waited till the Arabian general, with a force now raised to 60,000, had reached Sabat, which was only a day’s march from the capital, before he could be induced to commence his retreat.  He then abandoned the town hastily, without carrying off more than a small portion of the treasures which his ancestors had during four centuries accumulated at the main seat of their power, and retired to Holwan, a strong place in the Zagros mountain-range.  Sa’ad, on learning his movement, sent a body of troops in pursuit, which came up with the rear-guard of the Persians, and cut it in pieces, but effected nothing really important.  Isdigerd made good his retreat, and in a short time concentrated at Holwan an army of above 100,000 men.  Sa’ad, instead of pushing forward and engaging this force, was irresistibly attracted by the reputed wealth of the Great Ctesiphon, and, marching thither, entered the unresisting city, with his troops, in the sixteenth year of the Hegira, the four hundred and eleventh from the foundation of the Sassanian kingdom by Artaxerxes, son of Babek.

Ctesiphon was, undoubtedly, a rich prize.  Its palaces and its gardens, its opulent houses and its pleasant fields, its fountains and its flowers, are celebrated by the Arabian writers, who are never weary of rehearsing the beauty of its site, the elegance of the buildings, the magnificence and luxury of their furniture, or the amount of the treasures which were contained in them.  The royal palace, now known as the Takht-i-Khosru, especially provoked their admiration.  It was built of polished stone, and had in front of it a portico of twelve marble pillars, each 150 feet high.  The length of the edifice was 450 feet, its breadth 180, its height 150.  In the centre was the hall of audience, a noble apartment, 115 feet long and 85 high, with a magnificent vaulted roof, bedecked with golden stars, so arranged as to represent the motions of the planets among the twelve signs of the Zodiac, where the monarch was accustomed to sit on a golden throne, hearing causes and dispensing justice to his subjects.  The treasury and the