It is hard to say whether the author of the Book of Daniel was a prophet. Rather, one could suggest that he was one of those...
It is hard to say whether the author of the Book of Daniel was a prophet. Rather, one could suggest that he was one of those active opponents of the religious policy of Antiochus Epiphanes who in the end found themselves among the participants in the anti-Syrian uprising raised by the Maccabees. But there can be no doubt that among the inspirers and ideologists of the anti-Syrian movement there were both prophets and apocalyptic visionaries. Apparently the author collected and wrote down some of their prophecies and visions, placing them in the mouth of Daniel, one of the figures of ancient Jewish traditions, whom he made the main hero of his book, transferring its action to times that in his day had already become almost legendary: the times of the Babylonian exile and the first years of the reign of Cyrus the Great, whose victory over Babylonia became liberation for the Jews.
For completeness, it should be added that this victory and this liberation caused in the Synagogue a powerful surge of messianism, similar to the one that in the time of the author of the book was caused by the persecutions of Antiochus and the Maccabean wars, which were fought under religious and messianic slogans. And if the first of the prophecies placed in Daniel's mouth, the one concerning Nebuchadnezzar, sounded like a call to come to one's senses, the second was a direct warning, especially relevant in the context of those actions of the authorities that led to the defilement of the Jerusalem Temple.
In essence, Belshazzar does something similar: he does not defile the Temple and does not destroy it, but he continues the work of those who defiled and destroyed it by using the sacred vessels in a blasphemous way (vv. 1-4). The issue here is not only the drinking of wine in itself, but the fact that it was accompanied, as was customary in antiquity among all peoples, by libations to the gods, a kind of small but entirely real pagan sacrifice. The use of vessels and cups dedicated to God for pagan sacrifices was precisely blasphemy, and demonstrative blasphemy at that. It was meant to demonstrate not only the absolute power of the ruler, but also the triumph of his gods over the God of Israel. It is no wonder that immediately after his blasphemous act Belshazzar receives a warning whose meaning, however, remains unclear to him, although he sees plainly the scene unfolding before his eyes (vv. 5-9).
As in the case of Nebuchadnezzar, Belshazzar needs the testimony of a prophet in order to understand what has been revealed to him (vv. 10-16). And Daniel indeed explains to the king the meaning of what he has seen, emphasizing that Belshazzar's sin was committed knowingly, because he knew the story of his father Nebuchadnezzar and what happened to him because of his disregard for the God of Israel (vv. 17-29). And the speed with which the prophecy was fulfilled (vv. 30-31) was undoubtedly meant to make not only the contemporaries of the last Babylonian king think, but also the contemporaries of the author of the Book of Daniel.