Gaebelein's Annotated Bible
In the third year of Cyrus king of Persia a thing was revealed unto Daniel, whose name was called Belteshazzar; and the thing was true, but the time appointed was long: and he understood the thing, and had understanding of the vision.CHAPTER 10 The Preparation for the Final Prophecy
This chapter contains the preface to the final great prophecies as found in the last two chapters of this book. The certain man who appeared unto Daniel at the banks of the river Hiddekel (Tigris) was the Lord. Compare with Revelation 1:1-20, where John, the beloved disciple, beheld Him in a vision of glory. Daniel’s vision is a pre-incarnation vision of the same One whom John beheld after His resurrection and in His glorified humanity.
The delayed answer by the angelic messenger is explained by the power of darkness. A powerful demon-prince, a satanic agency, having control over Persia, so that he claimed the title the prince of Persia, kept back the answer. Then the prophet was strengthened.