Commentaries:
God stirred up the spirit of quite a number of people to set the Medo-Persians at war against Babylon to take away its authority and destroy it. God is Sovereign in His creation. He has the last word, and in most every case, He had the first word as well. He does things on His own initiative, because He knows the exact direction for which He is heading, yet He seems to give nations a great deal of latitude within the purpose He is working out. There are times, though, that He needs to tweak events to return them to the purpose and timing in which He wants them to occur. He then stirs up the spirit of the man He chooses to make those changes. He interfaces with him, and he may not even be aware it is happening. The history books record that Cyrus said the same words about Marduk that he said about the true God of heaven, suggesting that he attributed his inspiration to his false god. Cyrus was not converted, so he probably did not know that God was stirring up his spirit to do this.
John W. Ritenbaugh
The Holy Spirit and the Trinity (Part Three)