So well did he manage the defence that after a while Cyrus despaired, and as a last resource ventured on a stratagem in which it was clear that he must either succeed or perish.
Withdrawing the greater part of his army from the vicinity of the city, and leaving behind him only certain corps of observation, Cyrus marched away up the course of the Euphrates for a certain distance, and there proceeded to make a vigorous use of the spade.

His soldiers could now appreciate the value of the experience which they had gained by dispersing the Gyndes, and perceive that the summer and autumn of the preceding year had not been wasted.

They dug a channel or channels from the Euphrates, by means of which a great portion of its water would be drawn off, and hoped in this way to render the natural course of the river fordable.
When all was prepared, Cyrus determined to wait for the arrival of a certain festival, during which the whole population were wont to engage in drinking and revelling, and then silently in the dead of night to turn the water of the river and make his attack.

It fell out as he hoped and wished.

The festival was held with even greater pomp and splendor than usual; for Belshazzar, with the natural insolence of youth, to mark his contempt of the besieging army, abandoned himself wholly to the delights of the season, and himself entertained a thousand lords in his palace.