John Piper, in “A Hunger for God” p 166:
Israel had been taken into Babylonian exile. They had been there for decades. Now the time had come, in God’s reckoning, for their restoration. But how could this happen? They were a tiny, obscure ethnic minority in the massive Persian empire. The answer is that God rules empires. And when it is his time for his people to move, he moves empires. That’s the point of the first eight chapters of this book of Ezra. And it is massively hope-giving for the people of God every time we slip back into a mentality of siege.
Now in the first year of Cyrus king of Persia, in order to fulfill the word of the Lord by the mouth of Jeremiah, the Lord stirred up the spirit of Cyrus king of Persia, so that he sent a proclamation throughout all his kingdom, and also put it in writing, saying, “Thus says Cyrus king of Persia, ‘The Lord, the God of heaven, has given me all the kingdoms of the earth, and He has appointed me to build Him a house in Jerusalem, which is in Judah.’”
Do not miss the sovereign rule of God over the mind and will of Cyrus, the most powerful king in the world. God had prophesied by Jeremiah that the people would come back to their own land. “For thus says the LORD, ‘When seventy years have been completed for Babylon, I will visit you and fulfill My goodword to you, to bring you back to this place’” (Jeremiah 29:10).
God never leaves his prophesies dangling uncertainly in the will of man. He does not merely predict; he acts to fulfill the predictions he makes.This is why his predictions are as sure as he is powerful.