In October 539 BCE, the Persian king Cyrus took Babylon, the ancient capital of an oriental empire covering modern Iraq, Syria, Lebanon, and Israel. In a broader sense, Babylon was the ancient world's capital of scholarship and science. The subject provinces soon recognized Cyrus as their legitimate ruler. Since he was already lord of peripheral regions in modern Turkey and Iran (and Afghanistan?), it is not exaggerated to say that the conquest of Babylonia meant the birth of a true world empire. The Achaemenid empire was to last for more than two centuries, until it was divided by the successors of the Macedonian king Alexander the Great. A remarkable aspect of the capture of Babylon is the fact that Cyrus allowed the Jews (who were exiled in Babylonia) to return home.
The final redaction of the biblical book of Daniel (called after a Jewish sage at the court of Belshazzar, i.e. Nabonidus' crown prince Bêlsharusur) took place in the second century BCE, but the text contains many older elements. Probably, no less than four authors have contributed to the text. The resulting text cannot be taken as history. Too many elements are too incredible (e.g., about every personal name is wrong).
However, chapter four contains a bit of information that is corroborated by a text known as the Prayer of Nabonidus. According to Daniel, the Babylonian king Nebuchadnezzar suffers from a mental illness, and lives isolated for seven years, until he acknowledges the power of the one God. From cuneiform texts, nothing is known about Nebuchadnezzar's mental health. The original story must have centered on another royal patient: Nabonidus, about whom rumors like this did circulate (see the Verse Account). Moreover, several details return in the Prayer, where Nabonidus is the sad hero: the period of seven years, the isolation, the ultimate recognition of the power of the supreme God. Since the authors of Daniel consistently avoid mentioning Nabonidus, it is likely that one of them is responsible for the change of names.
This means that two elements of the Verse Account are corroborated: the madness of Nabonidus and his monotheistic attitude. Stated differently, we have two sources for the accusations - a Babylonian poem full of insults and a Jewish story.
(Not all editions of this text use the same numbering. There is a change of perspective in lines 33/34.)
Daniel on the Madness of Nebuchadnezzar
[4.29] At the end of the twelve months Nebuchadnezzar was walking about the royal palace of Babylon.
[4.30] The king spoke, saying, "Is not this great Babylon, that I have built for a royal dwelling by my mighty power and for the honor of my majesty?"
[4.31] While the word was still in the king's mouth, a voice fell from heaven: "King Nebuchadnezzar, to you it is spoken: "The kingdom has departed from you!"
[4.32] And they shall drive you from men, and your dwelling shall be with the beasts of the field. They shall make you eat grass like oxen; and seven years shall pass over you, until you know that the Most High rules in the kingdom of men, and gives it to whomever He chooses."
[4.33] That very hour the word was fulfilled concerning Nebuchadnezzar; he was driven from men and ate grass like oxen; his body was wet with the dew of heaven till his hair had grown like eagles' feathers and his nails like birds' claws.
[4.34] And at the end of the time I, Nebuchadnezzar, lifted my eyes to heaven, and my understanding returned to me; and I blessed the Most High and praised and honored Him Who lives forever: for His dominion is an everlasting dominion, and His kingdom is from generation to generation.
[4.35] All the inhabitants of the earth are reputed as nothing; He does according to His will in the army of heaven and among the inhabitants of the earth. No one can restrain His hand or say to Him, "What have You done?"
[4.36] At the same time my reason returned to me, and for the glory of my kingdom, my honor and splendor returned to me. My counselors and nobles resorted to me, I was restored to my kingdom, and excellent majesty was added to me.
[4.37] Now I, Nebuchadnezzar, praise and extol and honor the King of heaven, all of whose works are truth, and His ways justice. And those who walk in pride He is able to put down.