When Darius heard these things, he gathered all his host together, and marched to Babylon and besieged it. But the Babylonians took no heed of the siege, but went up on the bulwarks of the wall and danced, scoffing at Darius and his army. And as they did so, one of them cried aloud, saying, "Why sit ye here, ye Persians, and depart not? For Babylon ye shall not take till mules shall bring forth foals." These words said one of the Babylonians, thinking that mules should never bring forth foals. And after the space of a year and seven months, King Darius was sore troubled and his army with him, because they could not take the city of Babylon. Yet had Darius used all manner of devices and stratagems against them, and among them the device which King Cyrus had used aforetime, even turning the stream of the river Euphrates; but the men of Babylon ceased not to watch, and he prevailed nothing. Now there was in the army of the Persians one Zopyrus; and this Zopyrus was the son of Megabyzus, who was of the seven that conspired against the Magian. To this Zopyrus it happened in the twentieth month of the siege that one of the mules that carried provender for him bare a foal. But when the tidings of this thing was brought to him, at the first Zopyrus would not believe it. But when he had seen the foal with his own eyes and so was persuaded, bidding his servants tell the matter to no one, he considered it with himself. And when he remembered the words which the man of Babylon had spoken, when the siege was hardly begun, that the Persians might take the city when mules should bring forth foals, it seemed that now Babylon should indeed be taken, for it was of the Gods both that the man had spoken and that the mule had brought forth. Seeing then that the matter had been decreed by Heaven, he came near to Darius, and enquired of him whether the King counted it a great thing that Babylon should be taken. And when he heard that it was indeed so, he considered with himself how he might take the city and gain this glory for himself; for such good deeds are held in high account among the Persians. But after he had weighed the matter for a long time, it seemed that he could by no means bring it to pass, unless he should desert to the Babylonians, having first mutilated himself. After this, thinking it of no account what he should himself suffer, he wounded himself in such fashion as was past all healing, for he cut off his nose and his ears, and laid many stripes upon his back, and so stood before Darius. And when the King saw him so shamefully ill-treated he had great indignation, for this Zopyrus was a man of great repute; and he leapt up from his throne and cried out, asking him, "Who is the man that hath dealt so shamefully with thee?" Then Zopyrus made answer, "There is no man save thee only, O King, that hath power to deal with me after this fashion. And indeed no other man hath done this deed, but I myself have done it. And I have done it because I judged it to be a dreadful thing that these Assyrians should laugh the Persians to scorn." Then the King said, "This is a fair name that thou givest to a very dreadful deed, saying that thou hast thus hurt thyself beyond all healing, because of these Assyrians that we are besieging. For how shall they be vanquished the sooner because thou hast suffered this thing? Surely thou art besides thyself, thinking that this loss shall be our gain." Then said Zopyrus, "I doubt not, O King, that if I had told thee the thing that was in my heart to do, thou hadst not suffered it, for which cause I took counsel with myself alone, and so did it. Now, therefore, if thou fail not on thy part, Babylon is taken. For I will desert to their city, and will say to them that it is thou that hast dealt with me in this fashion. And I think that I shall so work with them that they shall give over to me a part of their army. But thou must do what I now tell thee. Reckon ten days from the day whereon I shall enter their city, and on the tenth day set a thousand men of thy army, being such as thou carest not if they perish, and set them in order by the gates that are called the gates of Semiramis. And on the seventh day after the tenth set two thousand in like manner by the gates that are called the gates of the Ninevites. And on the twentieth clay after the seventh set four thousand others by the gates of the Chaldĉans. And let these have no other arms but short swords only; these let them have. And when the twentieth day is past, then cause thy army to compass the city round about, but bring thy Persians near to the gates of Belus. For I judge that when I shall do great deeds for them, the men of Babylon will commit many things to my hands, and among these the keys also of the gates. But after this the Persians and I will order the matter as thou wouldst have it."

Then Zopyrus, having thus instructed the King what he should do, went to the gates, turning himself to see if any pursued, as though he were in truth a deserter. Then they that stood upon the towers, whose business it was to deal with this matter, when they saw the man come near, ran down, and having opened one of the gates a little space, enquired of him who he was and what he wanted, that he came to them. Then he answered that his name was Zopyrus, and that he had deserted from the King to them. Then the keepers of the gates, when they heard these things, took him into the assembly of the Babylonians, wherein standing up he sought to move the pity of them that sat there, affirming that he had suffered from the hands of the King the things which he had in truth done unto himself, and that he had suffered them because he had counselled him to take away his army from before Babylon, seeing that the city could not by any means be taken. "Now, therefore," he said, "O men of Babylon, my coming shall be no small advantage to you and to your city, but to Darius and to his army and to the whole nation of the Persians no small harm, seeing that I know all their goings out and comings in." Zopyrus said this, and when the Babylonians saw the man, how being of great account among his own people, he had had his ears cut off and his nose also, and was marked with many stripes on his body, and covered with blood, they doubted not that the things which he spoke were true, and that he was ready to help them; and so were willing to commit to him all that he asked. Then he asked them to give him an army, which, when he had reviewed, he did according as he had agreed beforehand with Darius, for on the tenth day after that he entered the city, he led forth the army of the Babylonians, and having surrounded the thousand whom Darius had sent from this end, he slew them. But when the men of Babylon perceived that his deeds were like unto his words, they rejoiced exceedingly, and were ready to give all things into his hands. Then again when the appointed days were passed, he chose certain of the Babylonians and marched out of the city and slew the two thousand soldiers that Darius had set in the appointed place. But when the men of Babylon saw this second thing that he did they all praised Zopyrus with one voice. Then the third time, after the twenty days had passed as was agreed, he led the Babylonians to the appointed place, and surrounded the four thousand, and slew them. But after this the Babylonians would have no one but Zopyrus, making him captain of the host and keeper of the wall. Then Darius made his attack as had been agreed; and the men of Babylon went up on to the wall and fought against the Persians, but while they were busy doing this, Zopyrus performed the device which he had devised against them, for he opened the gates that are called the gates of Belus and of Cissus, and let the Persians into the city. And such of the men of the Babylonians as saw that which was done, fled to the temple of Belus, but such as saw it not remained each in his place till these also knew that they had been betrayed. Thus was the city of Babylon taken for the second time. And when Darius had conquered the Babylonians, he threw down their walls and took away their gates; for Cyrus when he took Babylon the first time had done neither of these things. After this he took three thousand of the chief men among the people and slew them; as for the rest of the Babylonians, he gave them back their city to dwell in; also that they might have wives, for their own they had strangled that their food might not be consumed, he commanded the nations round about to send some of their women to Babylon, appointing a certain number to each, the sum of the whole being fifty thousand.

As for Zopyrus Darius held that no man had done better service to the state, save Cyrus only, for with Cyrus no man among the Persians compares himself. And indeed the King would oftentimes say that he had sooner Zopyrus was healed of his wounds than that he should have twenty Babylons over and above that which he had. And he honoured him greatly, giving him such gifts year by year as are most accounted of among the Persians. Also he gave him the city of Babylon for his dwelling free of tribute.