What does Isaiah 13:17 mean?
Looking ahead from his own time to events that had not yet happened, Isaiah wrote that the Lord would summon multiple nations and kingdoms to destroy Babylon (Isaiah 13:2–5). The fact that those nations don't realize the Lord is using them for His own purposes is irrelevant to their divine purpose for being there. They will be the Lord's weapon. Now Isaiah mentions one people specifically: the Medes.The Medes occupied the region of what is now central Iran, east of the region of Mesopotamia. The Medes would join forces with Nebuchadnezzar and the Babylonians to defeat the Assyrians in 609 BC (Isaiah 10:12–14). Later, though, they would participate in the destruction of Babylon. Some scholars believe that Isaiah is describing the overthrow of Babylon by the Medes and the Persians in 539 BC. However, the city was not fully destroyed at that time, so other scholars are not confident that this is the correct interpretation.
It was common during these times for a city under siege to pay a huge sum to the attacking army to convince them to give up and go away. Isaiah writes that the Medes wanted to defeat Babylon more than they wanted silver or gold. They would not take a payoff from wealthy Babylon in exchange for mercy. They were merciless (Isaiah 13:9) and savage (Isaiah 13:16), out for blood and stopping at nothing short of destroying the city.