Knowing that he had provoked a powerful enemy by this bold act, and ignorant how soon he might be called upon to defend his kingdom, from the entire force of his foe, which might be suddenly hurled against him almost at any moment, Nabonadius seems to have turned his attention at once to providing means of defence.  The works ascribed by Herodotus to a queen, Nitocris, whom he makes the mother of Nabonadius (Labynetus) must be regarded as in reality constructions of that monarch himself, undertaken with the object of protecting Babylon from Cyrus.  They consisted in part of defences within the city, designed apparently to secure it against an enemy who should enter by the river, in part of hydraulic works intended to obstruct the advances of an army by the usual route.  The river had hitherto flowed in its natural bed through the middle of the town.  Nabonadius confined the stream by a brick embankment carried the whole way along both banks, after which he built on the top of the embankment a wall of a considerable height, pierced at intervals by gateways, in which were set gates of bronze.  He likewise made certain cuttings, reservoirs, and sluices at some distance from Babylon towards the north, which were to be hindrances to an enemy’s march, though in what way is not very apparent.  Some have supposed that besides these works there was further built at the same time a great wall which extended entirely across the tract between the two rivers—­a huge barrier a hundred feet high and twenty thick—­meant, like the Roman walls in Britain and the great wall of China, to be insurmountable by an unskillful foe; but there is ground for suspecting that this belief is ill-founded, having for its sole basis a misconception of Xenophon’s.

Nabonadius appears to have been allowed ample time to carry out to the full his system of defences, and to complete all his preparations.  The precipitancy of Croesus, who plunged into a war with Persia single-handed, asking no aid from his allies, and the promptitude of Cyrus, who allowed him no opportunity of recovering from his first false step, had prevented Nabonadius from coming into actual collision with Persia in the early part of his reign.  The defeat of Croesus in the battle of Pteria, the siege of Sardis, and its capture, followed so rapidly on the first commencement of hostilities, that whatever his wishes may have been, Nabonadius had it not in his power to give any help to his rash ally.  Actual war was thus avoided at this time; and no collision having occurred, Cyrus could defer an attack on the great kingdom of the south until he had consolidated his power in the north and the northeast, which he rightly regarded as of the last importance.  Thus fourteen years intervened between the capture of Sardis by the Persian arms and the commencement of the expedition against Babylon.