Charles Ellicott Commentary Daniel 9:1

"In the first year of Darius the son of Ahasuerus, of the seed of the Medes, who was made king over the realm of the Chaldeans," — Daniel 9:1 (ASV)

On Darius the Mede see Excursus D.

Was made king. —The phrase corresponds with took the kingdom (Daniel 5:31), and shows that Darius was not king by his own right, but that he received his authority from another— i.e., Cyrus.