‘In the third year of Cyrus, king of Persia, a word was revealed to Daniel, whose name was called Belteshazzar, and the word was true. It was about a great warfare (literally ‘even a great warfare'). And he understood the word and had understanding of the vision.”
The change of method of dating suggests either that Darius the Mede was Cyrus, or more likely that Darius the Mede was no longer the ruler of Babylon, having died or been replaced. Note that Cyrus is not called the king of Babylon, whereas Darius had been (Daniel 9:1). Daniel makes clear distinctions. ‘King of Persia' is an attested title for such a ruler.
It is noteworthy that Daniel has not returned with the exiles. If the account was fictitious we would expect that he would be depicted as so returning, so that this is a strong affirmation of the genuineness of the account.
Here we learn that ‘a word' from God was revealed to Daniel, a word that was true. The latter statement, which is unusual, suggests that on this occasion Daniel felt the need to emphasise the truth of what he had seen. This may also explain his reference to himself as Belteshazzar. He wanted his credentials to be appreciated, and most knew him as Belteshazzar. What was revealed was a great warfare. This most probably refers to the supernatural warfare described in the chapter, which parallels warfare on earth. Others see it as referring to a struggle within Daniel himself. ‘Understood' may mean simply that he apprehended it and was able to write it down (compare Daniel 12:8).