(Isa. 14:25; 36)
It is difficult to determine whether Isaiah is prophesying about the destruction of Sennacherib’s Assyrian army in 701 b.c. or the defeat of the army of the nations led by King Gog in the last days. (Compare Isa. 36–37 with Ezek. 38–39.) In both cases, the Lord’s punishment is felt by the wicked nations of the earth.
(Victor L. Ludlow, Isaiah: Prophet, Seer, and Poet [Salt Lake City: Deseret Book Co., 1982], 189.)
The Lord has not only determined to destroy Babylon in due time, but he has already programmed the means by which a more immediate threat to Israel will be eliminated. This was the Assyrian Empire, which preceded Babylon and was the terror of the world in Isaiah’s day. In this verse the King James Version says the Lord will “break” the Assyrians, but in the brass plates it says the Lord will “BRING” the Assyrians into the promised land (2 Ne. 24:25). This makes the rest of the verse more sensible. For it says these Assyrians will pour into the mountains of Israel and tread them under foot (conquer them). It turned out that the Assyrians did not storm the mountains of Judah but only the mountains of Ephraim, where the Ten Tribes were located. These were trodden under foot from around 735 to 721 b.c., when the surviving remnants were carried off to Assyria. There they remained as virtual captives or hostages until Babylon came along in 605 b.c. and virtually annihilated the Assyrian people as a nation. This allowed the Ten Tribes to escape from their Assyrian captors and flee northward over the Caucasus Mountains, where they disappeared and became known as the lost tribes.
(W. Cleon Skousen, Isaiah Speaks to Modern Times [Salt Lake City: Ensign Publishing Co., 1984], 284.)