The Medes will be allied with the enemy. This might help to clarify the original prophecy with the Assyrian invasion. At that time, the Medes were part of the Assyrian empire, but they were among those who attached and destroyed Assyria later.
As we have the prophecy, it indicates that Babylon would overthrow the children of Israel just as when Jehovah overthrew Sodom and Gomorrah, both cities seen has having sinned against Jehovah. Israel’s sins are, therefore, implied to be similarly worthy of destruction.
The image of wild beasts feeding where there was once cultured pasture is the same image that Isaiah had used in the last unit.