The Lord sends Assyria against “a hypocritical nation.” As is clear in the text of this prophecy, Isaiah is now speaking about Jerusalem. After Assyria’s conquest of Jerusalem’s neighbors, the army turns towards Jerusalem (see verse 10). The destruction of their attack is no doubt accurate, and the purpose here it to note that it comes with not only the Lord’s approval, but by his direction. Assyria is only the tool of the Lord’s vengeance.