Read Isaiah 21.
Judah looked to any nation that could possibly stay the invasion of Assyria. In His faithfulness, God told Isaiah what was about to happen and then the prophet delivered the word of God.
Looking to the east, there were the desert peoples of Dumah (Elam), Media, and the city of Babylon. Surely, one of these could help.
A rebellion against Assyria did take place from the area of the desert sea, now known as the Persian Gulf. But while Isaiah emotionally and physically felt the awfulness of the coming battle, some sat down to feast as if nothing was going to happen. Then, the prophecy stated the news would come that Babylon had been "shattered to the ground." Isaiah described Judah's dashed hopes as grain that had been threshed.
The message from the LORD even included the time. The rout of the region would happen within one year.
Though a similar wording is used concerning Babylon in Revelation 14 and 18, these are two distinct events. Isaiah wrote concerning the Assyrians' defeat of Babylon. Later, in Daniel's time, the demise of the Babylonian Empire took place at the hands of the Medes and Persians. Then, prior to the return of Christ the new Babylon will be destroyed.
God will be faithful to Judah and protect them from the cruelty of the Assyrians. The lesson here appears to be that they need to stop looking to other sources of help and turn to the only One who can truly protect them. That is a good word for all of us today.
"He who dwells in the shelter of the Most High will abide in the shadow of the Almighty. I will say to the LORD, 'My refuge and my fortress, my God, in whom I trust.'" (Psalm 91:1-2)