What does Jeremiah 28:14 mean?

This is what the Lord Almighty, the God of Israel, says: I've put an iron yoke on the necks of all these nations to make them serve Nebuchadnezzar king of Babylon, and they'll have to serve him. I've even given him control over the wild animals.' Jeremiah 28:14 - Modern Text Bible

(God declares that Babylon's power is absolute for now, and resisting it is pointless.)