8 “Assyria will fall by no human sword; a sword, not of mortals, will devour them. They will flee before the sword and their young men will be put to forced labor.

Read Isaiah 31:8 Using Other Translations

Then shall the Assyrian fall with the sword, not of a mighty man; and the sword, not of a mean man, shall devour him: but he shall flee from the sword, and his young men shall be discomfited.
"And the Assyrian shall fall by a sword, not of man; and a sword, not of man, shall devour him; and he shall flee from the sword, and his young men shall be put to forced labor.
“The Assyrians will be destroyed, but not by the swords of men. The sword of God will strike them, and they will panic and flee. The strong young Assyrians will be taken away as captives.