In his own inscriptions Nabonidus claims to be of noble descent. A tablet found near ancient Haran gives evidence that Nabonidus’ mother or grandmother was a devotee of the moon-god Sin. (Ancient Near Eastern Texts, edited by J. Pritchard, 1974, pp. 311, 312) As king, Nabonidus showed great devotion to the worship of the moon-god, both at Haran and at Ur, where this god occupied a dominant position.​—PICTURE, Vol. 2, p. 324.

Cuneiform tablets of the eighth year of Nebuchadnezzar (Nisan 617-Nisan 616 B.C.E.) list a certain Nabu-naʼid as the one “who is over the city,” and some historians believe this is the same Nabonidus who later became king. However, this would mean that Nabonidus was a very young man when placed in such administrative position and would make him extremely aged at the fall of Babylon, some 77 years later (539 B.C.E.).

Nabonidus’ ascension to the throne followed the assassination of Labashi-Marduk. Yet, the fact that in one of his inscriptions Nabonidus refers to himself as the “mighty delegate” of Nebuchadnezzar and Neriglissar indicates that he claimed that he gained the throne by legitimate means and was not a usurper.

In a number of prisms Nabonidus associates his firstborn son, Belshazzar, with himself in his prayers to the moon-god. (Documents From Old Testament Times, edited by D. W. Thomas, 1962, p. 73) An inscription shows that in his third year, prior to going out on a campaign that resulted in the conquest of Tema in Arabia, Nabonidus appointed Belshazzar to kingship in Babylon. The same text indicates that Nabonidus offended the people of his empire by concentrating worship on the moon-god and by failing to be in Babylon to celebrate the New Year’s festival. The document known as the Nabonidus Chronicle states that in the 7th, 9th, 10th, and 11th years of his reign Nabonidus was in the city of Tema, and in each case the statement is made: “The king did not come to Babylon [for the ceremonies of the month of Nisanu]; the (image of the) god Nebo did not come to Babylon, the (image of the) god Bel did not go out (of Esagila in procession), the fest[ival of the New Year was omitted].” (Ancient Near Eastern Texts, p. 306) Due to the mutilated condition of the text, the record of the other years is incomplete.

Of the oasis city of Tema it is elsewhere recorded: “He made the town beautiful, built (there) [his palace] like the palace in Su·an·na (Babylon).” (Ancient Near Eastern Texts, p. 313) Nabonidus appears to have established his royal residence in Tema, and other texts show that camel caravans carried provisions there from Babylonia. While not relinquishing his position as king of the empire, Nabonidus entrusted the administration of the government of Babylon to Belshazzar. Since Tema was a junction city on the ancient caravan routes along which gold and spices were transported through Arabia, Nabonidus’ interest in it may have been motivated by economic reasons or may have been based on factors of military strategy. The suggestion is also advanced that he considered it politically advisable to administer Babylonian affairs through his son. Other factors, such as the healthful climate of Tema and the prominence of moon worship in Arabia, have likewise been noted as possible motives for Nabonidus’ apparent preference for Tema.

There is no available information as to Nabonidus’ activities between his 12th year and his final year. Anticipating aggression from the Medes and Persians under Cyrus the Great, Nabonidus had entered into an alliance with the Lydian Empire and Egypt. The Nabonidus Chronicle shows Nabonidus back in Babylon in the year of the Medo-Persian assault, with the New Year’s festival being celebrated and the various gods of Babylonia being brought into the city. Regarding Cyrus’ advance, the Chronicle states that, following a victory at Opis, he captured Sippar (c. 60 km [37 mi] N of Babylon) and “Nabonidus fled.” Then follows the account of the Medo-Persian conquest of Babylon, and it is stated that upon Nabonidus’ return there he was taken prisoner. (Ancient Near Eastern Texts, p. 306)