Nabonidus, whose relationship with the previous Chaldean Kings of Babylon is unclear, came to the throne in 556 BC by overthrowing the youthful king Labashi-Marduk. In 549 BC he left Babylon to live in Arabia leaving his son Belshazzar behind to rule the empire in his stead.
In 539 BC while Belshazzar and the nobles of the empire were feasting and drinking from the chalices from the Temple of God in Jerusalem, a hand wrote an unknown text on the wall: mene, mene, tekel, ufarsin.
None of Belshazzar's soothsayers could translate the words written and then the Jew Daniel, known for his accurate prophecies was called to translate the text and he said: "God has numbered your kingdom and brought it to an end. You are weighed in the balances and are found wanting. your kingdom is divided and given to the Medes and Persians." These words indicated the arrival of the Persian king Cyrus the Great who rode out to conquer Babylon
King Nabonidus returned to save his kingdom but he came to late. The Persians took the city and the kingdom without any resistance (they even got support from Gobryas, a local provincial governor) and King Cyrus was greeted as a liberator.
The fate of Nabonidus is uncertain. King Cyrus was known for sparing the lives of the kings whom he had defeated, King Croesus of Lydia lived after his defeat at king Cyrus's court as an advisor. But it is presumed that Cyrus made an exception in Nabonidus's case.
see also: Kings of Babylon, Babylonia