After the capture of the metropolis, which was followed by the surrender of Borsippa, and the capture of Nabonetus (538 B.C.), Cyrus, so far as we can tell, showed clemency both towards the king, whom he caused to be taken to Carmania, and to the city of Babylon. The kings of Asshur treated besieged princes and conquered cities in a manner very different from that in which Cyrus treated Astyages, Croesus and Sardis, Nabonetus and Babylon. Babylonia was not oppressed; the city was not destroyed. Cyrus stepped into the place of the native king. The Babylonian tablets after the capture of the city and the fall of the kingdom, date from the years of the reign of Cyrus over Babylonia, the years "of Kurus, king of Babylon, king of the lands."[79] The city of Babylon retained her temples and palaces and her mighty walls. Herodotus tells us expressly that Cyrus did no injury to the walls or the gates of Babylon,[80] and twenty years afterwards we find the city in possession of her impregnable works. Xenophon remarks that Cyrus placed troops in the citadels, set captains over them, left behind a sufficient garrison in the city and charged the inhabitants with the maintenance of it; the arrangements then made for keeping guard were in existence still.[81] If, therefore, the excerpt of Josephus from Berosus tells us that Cyrus destroyed the walls "outside the city," this can only refer to the great wall which Nebuchadnezzar had built from the Euphrates to the Tigris above Sepharvaim, as a protection against an attack from the north. It would have been a heavy task to level with the ground this fortification throughout its entire length of from 60 to 75 miles, the Persians therefore contented themselves with making large breaches in it. The wall was in this condition when Xenophon came with the ten thousand to Babylon.[82]