Cyrus was advancing in years before he undertook the conquest of Babylon, the most important of all his undertakings, and for which his other conquests were preparatory. At the age of sixty, Cyrus, 538 B.C., advanced against Narbonadius, the proud king of Babylon,--the only remaining power in Asia that was still formidable. The Babylonian Empire, which had arisen on the ruins of the Assyrian, had lasted only about one hundred years. Yet what wonders and triumphs had been seen at Babylon during that single century! What progress had been made in arts and sciences! What grand palaces and temples had been erected! What a multitude of captives had added to the pomp and wealth of the proudest city of antiquity! Babylon the great,---"the glory of kingdoms," "the praise of the whole earth," the centre of all that was civilized and all that was corrupting in the Oriental world, with its soothsayers, its magicians, its necromancers, its priests, its nobles,--was now to fall, for its abominations cried aloud to heaven for punishment. This great city was built on both sides of the Euphrates, was fifteen miles square, with gardens and fields capable of supporting a large population, and was stocked with provisions to maintain a siege of indefinite length against any enemy. The accounts of its walls and fortifications exceed belief, estimated by Herodotus to be three hundred and fifty feet in height, with a wide moat surrounding them, which could not be bridged or crossed by an invading army. The soldiers of Narbonadius looked with derision on the veteran forces of Cyrus, although they were inured to the hardships and privations of incessant war. To all appearance the city was impregnable, and could be taken only by unusual methods. But the genius of the Persian conqueror, according to traditional accounts, surmounted all difficulties. Who else would have thought of diverting the Euphrates from its bed into the canals and gigantic reservoirs which Nebuchadnezzar had built for purposes of irrigation? Yet this seems to have been done. Taking advantage of a festival, when the whole population were given over to bacchanalian orgies, and therefore off their guard, Cyrus advanced, under the cover of a dark night, by the bed of the river, now dry, and easily surprised the drunken city, slaying the king, with a thousand of his lords, as he was banqueting in his palace. The slightest accident or miscarriage would have defeated so bold an operation. The success of Cyrus had all the mystery and solemnity of a Providential event. Though no miracle was wrought, the fall of Babylon--so strong, so proud, so defiant--was as wonderful as the passage of the Israelites across the Red Sea, or the crumbling walls of Jericho before the blasts of the trumpets of Joshua.