The ruler mentioned in this verse and throughout the 6th chapter is still an obscure figure as far as secular history is concerned. The Additional Note at the end of ch. 6 presents a brief survey of the various identifications proposed by commentators, as well as a possible solution of the various historical problems involved.

 The conjunction “and,” with which the verse begins, shows that the author of the book closely connected the death of Belshazzar, recorded in the preceding verse, with the accession of “Darius the Median” to the throne. In the printed editions of the Hebrew Bible this verse is counted as the first verse of ch. 6. However, most modern versions, following the LXX, connect v. 31 with ch. 5. This is preferable.

 There is no difference between the spelling of the name of the Darius mentioned here and that of “Darius [I] king of Pesia” in Ezra 4:24 (see comments there) and elsewhere, in Aramaic and Hebrew as in English.

 Darius’ advanced age was probably responsible for the brevity of his reign. The book of Daniel mentions only the first regnal year of Darius (chs. 9:1, 2; 11:1). The king’s death occurred “within about two years of the fall of Babylon” (PK 556).

 One of the great puzzles to Bible commentators through the centuries has been the identity of Belshazzar. Until fairly recently no reference in ancient records to such a king had been discovered. The name Belshazzar was known only from the book of Daniel and from works that borrowed the name from Daniel—as, for example, the Apocryphal Baruch and Josephus’ writings. Many attempts were made to harmonize secular history with the Biblical records. The difficulty was accentuated by the fact that several ancient sources gave lists of the kings of Babylon to the end of the history of that nation, all of which mentioned Nabonidus, in different spellings, as the last king before Cyrus, who was the first king of Persia. Since Cyrus conquered Babylon and succeeded its last Babylonian king, there seemed to be no place for Belshazzar in the royal line. The book of Daniel, on the other hand, puts the events immediately preceding the fall of Babylon in the reign of Belshazzar, a “son” of Nebuchadnezzar (see on ch. 5:2), who lost his life during the night of the conquest of Babylon by the invading Medes and Persians (ch. 5:30).

Of the numerous interpretations formerly set forth to explain the apparent discrepancies between the Biblical records and other ancient sources the following are listed (according to Raymond P. Dougherty, Nabonidus and Belshazzar, pp. 13, 14):

Belshazzar was

 (1) another name of Nebuchadnezzar’s son known as Evil-Merodach,

 (2) a brother of Evil-Merodach,

 (3) a son of Evil-Merodach, hence Nebuchadnezzar’s grandson,

 (4) another name for Nergal-shar-usur, Nebuchadnezzar’s son-in-law,

 (5) another name for Labashi-Marduk, Nergal-shar-usur’s son,

 (6) another name for Nabonidus, and

 (7) the son of Nabonidus and a daughter of Nebuchadnezzar.

According to another view, held by the majority of critical scholars prior to the discovery of Belshazzar’s name in cuneiform sources toward the close of the 19th century, the name Belshazzar was an invention of the writer of Daniel, who, these critics assert, lived in the time of the Maccabees in the 2d century B.C.

 This list of divergent views demonstrates the nature and extent of the historical problems confronting interpreters of the book of Daniel, one that seems to abound in more problems than any other OT book of its size. That the identity and office of Belshazzar have now been fully established from contemporary sources, thus vindicating the reliability of ch. 5, is one of the great triumphs of Biblical archeology of the last century. The extreme importance of this achievement calls for a brief review of the subject.

In 1861 H. F. Talbot published certain texts found in the Moon Temple at Ur, in the Journal of the Royal Asiatic Society (vol. 19, p. 195). The texts contained a prayer of Nabonidus pronounced in favor of Bel-shar-uṣur, his eldest son. Several writers, among them George Rawlinson, brother of the famous decipherer of the cuneiform script, identified this Bel-shar-uṣur with the Biblical Belshazzar. Others rejected this identification, among them Talbot himself, who, in 1875, listed his arguments with a new translation of the text mentioning Belshazzar (Records of the Past, vol. 5, pp. 143-148).

Seven years later (1882) Theophilus G. Pinches published a text brought to light in the preceding year, which is now called the Nabonidus Chronicle. This text describes the capture of Babylon by Cyrus, and states also that Nabonidus stayed in Tema for several years while his son was in Babylonia. Although at the time Pinches did not completely understand the text, and incorrectly identified Tema, which lies in western Arabia, he made several accurate deductions concerning Belshazzar. He observed, for example, that Belshazzar “seems to have been commander-in-chief of the army, probably had greater influence in the kingdom than his father, and so was regarded as king” (Transactions of the Society of Biblical Archaeology, vol. 7 [1882], p. 150).

In the succeeding years more texts were discovered that shed light on the various functions and important positions that Belshazzar, Nabonidus’ son, held before and during his father’s reign. However, none of these texts called Belshazzar king as the Bible does. Nevertheless a number of scholars, on the basis of the accumulating evidence, suggested the view—later proved to be correct—that the two men may have been coregents. In 1916 Pinches published a text in which Nabonidus and Belshazzar were jointly invoked in an oath. He claimed that texts like this indicated that Bleshazzar’ must have held a “regal [viceregal] position,” although he stated that “we have yet to learn what was Belshazzar’s exact position in Babylonia” (Proceedings of the Society of Biblical Archaeology, vol. 38 [1916], p. 30).

Confirmation of the conclusion that a coregency between Nabonidus and Belshazzar had existed finally came in 1924, when Sidney Smith published the so-called “Verse Account of Nabonidus” of the British Museum, in which the clear statement is made that Nabonidus “entrusted the kingship” to his eldest son (Babylonian Historical Texts [London, 1924], p. 88; see translation by Oppenheim in Ancient Near Eastern Texts, ed. by Pritchard [Princeton, 1950], p. 313). This text, which settled all doubts about a kingship for Belshazzar, was a severe blow to scholars of the higher-critical schools who claimed that Daniel was a product of the 2d century B.C. Their dilemma is reflected in the words of R. H. Pfeiffer of Harvard University, who states:

“We shall presumably never know how our author learned ... that Belshazzar, mentioned only in Babylonian records, in Daniel, and in Bar. 1:11, which is based on Daniel, was functioning as king when Cyrus took Babylon” (Introduction to the Old Testament [New York, 1941], pp. 758, 759).

The discovery of so many cuneiform texts that shed light on the reign of Nabonidus and Belshazzar led Raymond P. Dougherty of Yale University to collect all source material, cuneiform and classical, in one monograph, which appeared in 1929 under the title Nabonidus and Belshazzar (New Haven, 1929, 216 pp.).

Cuneiform inscriptions indicate that Nabonidus was the son of the prince of Haran, Nabû-balâṭsu-iqbi, and of the priestess of the Moon Temple at Haran. After the Medes and Babylonians captured Haran in 610 B.C. the mother of Nabonidus was possibly taken as a distinguished prisoner to Nebuchadnezzar’s harem, so that Nabonidus grew up in the court under the eyes of the great king. He was most likely the “Labynetus” of Herodotus (i. 74), who acted as peace mediator between the Lydians and Persians in 585 B.C. This appears evident from the following observations: Herodotus calls the king of Babylon who reigned at the time of the fall of Sardis, in 546, Labynetus (i. 77). Later he identifies the father of the ruler of Babylon at the time of its fall in 539 by the same name (i. 188). We know that Nabonidus was king of Babylon in 546, also that he was Belshazzar’s father. That, in 585, Nabonidus was chosen to act as diplomatic representative of Nebuchadnezzar was a high honor, and shows that the young man must have been a favorite of the king at that time. It is possible, as Dougherty thinks, that his wife Nitocris, whom Herodotus describes as a wise woman (i. 185, 188), was a daughter of Nebuchadnezzar by an Egyptian princess.

However, the family relationship between Belshazzar, Nabonidus’ son, and Nebuchadnezzar is not yet definitely established from contemporary records.

 For lack of more complete information it is impossible at present to determine precisely how the repeated statements of ch. 5, that Nebuchadnezzar was Belshazzar’s father, are to be understood. As far as Biblical usage is concerned “father” may mean also “grandfather” or “ancestor” (see on 1 Chron. 2:7). Three interpretations have been offered:

 (1) Nabonidus was a son-in-law of Nebuchadnezzar, and Belshazzar was Nebuchadnezzar’s grandson through his mother.

 (2) Nabonidus was called son because his mother belonged to Nebuchadnezzar’s harem and was therefore his stepson.

 (3) Belshazzar was son only in the sense of the analogous case of Jehu, king of Israel, whom the Assyrian contemporary inscriptions call the “son of Omri.” Jehu was not related by blood to the house of Omri, but Jehu extinguished the dynasty that Omri had founded and became the next king of Israel.

 Cuneiform records have thrown an abundant stream of light on Belshazzar, his office and activities during the years he was coregent with his father. After conferring the kingship upon Belshazzar in 553/552 B.C., or shortly thereafter (see on ch. 5:1), Nabonidus conducted a successful expedition against the Arabian Tema, and made it his residence for many years. During this time Belshazzar was the acting king in Babylon and functioned as commander in chief of the army. Although legal documents continued to be dated according to the regnal years of Nabonidus, the fact that the names of both father and son were pronounced together in oaths, whereas under other kings’ reigns only one name was used, clearly reveals the dual rulership of Nabonidus and Belshazzar.

 Information from the secular sources, briefly sketched above, has, in a positive way, vindicated the historical accuracy of ch. 5. At the conclusion of his monograph on Belshazzar and Nabonidus, Dougherty has forcefully expressed this conviction:

“Of all non-Babylonian records dealing with the situation at the close of the Neo-Babylonian empire the fifth chapter of Daniel ranks next to cuneiform literature in accuracy so far as outstanding events are concerned. The Scriptural account may be interpreted as excelling because it employs the name Belshazzar, because it attributes royal power to Belshazzar, and because it recognizes that a dual rulership existed in the kingdom. Babylonian cuneiform documents of the sixth century B.C. furnish clear-cut evidence of the correctness of these three basic historical nuclei contained in the Biblical narrative dealing with the fall of Babylon. Cuneiform texts written under Persian influence in the sixth century B.C. have not preserved the name Belshazzar, but his role as a crown prince entrusted with royal power during Nabonidus’ stay in Arabia is depicted convincingly. Two famous Greek historians of the fifth and fourth centuries B.C. do not mention Belshazzar by name and hint only vaguely at the actual political situation which existed in the time of Nabonidus. Annals in the Greek language ranging from about the beginning of the third century B.C. to the first century B.C. are absolutely silent concerning Belshazzar and the prominence which he had during the last reign of the Neo-Babylonian empire. The total information found in all available chronologically-fixed documents later than the cuneiform texts of the sixth century B.C. and prior to the writings of Josephus of the first century A.D. could not have provided the necessary material for the historical framework of the fifth chapter of Daniel” (op cit., pp. 199, 200).