When Jehovah no longer has use for the Assyrian king, Jehovah will turn his ire upon Assyria, and as a prophecy of the last days, upon all nations who rise against Jehovah. Where previously the fire had burned Israel, in this reversal, the “light of Israel shall be for a fire, and his Holy One for a flame.” Thus, Jehovah becomes the defender of Israel and lights the fire of destruction against those who oppose Israel. The imagery of devouring thorns and briers had previously been applied to Israel, but is now reversed and it is the opposing nations that are cleansed through fire.
In verse 19 the trees of the forests will burn and leave so few trees that even a child could count them. This may also be a reversal using the image of the child, which had previously been said to be the ruler in Israel. This too is reversed and the child image is used against the opposing nations.
Finally, verse 21 notes that a “remnant will return.” This is a reference to Isaiah’s son’s name, Shearjashub, which means “a remnant will return.” Jehovah has therefore given prophecy, and declares how those prophecies will be fulfilled. There will be a time when the Lord ceases to use other nations as a tool against Israel, and a repentant Israel will become the dominant force rather than the one dominated.
The idea that a remnant would return will become an important theme for Nephi and Jacob in their sermons to their new people in the New World.