The onslaught of the righteous army of the Lord will strike fear into the armies of evil. In the dualistic imagery Isaiah favors in his prophetic statements, Israel would certainly interpret this as a temporal victory against their worldly enemies, as well as a prediction of the ultimate and final victory of the Lord.
Verse 8 appears to describe this vengeance of the Lord as unexpected. for “they shall be amazed one at another’ The ”faces shall be as flames" may refer to the redness and burning one feels with shame.
Variant: In verse 8, the Book of Mormon contains a deletion. The KJV Isaiah text reads: “Isa. 13:8 And they shall be afraid: pangs and sorrows shall take hold of them; they shall be in pain as a woman that travaileth: they shall be amazed one at another; their faces shall be as flames.”
There is no reason for the removal of the text from the Book of Mormon. It can be explained as two missing words on the brass plates (Tvedtnes 1981, p. 53) but that doesn’t have a reason behind it. It serves as an explanation, but not as a reason, and certainly not the same kind of reasoning that provided the plausible reason for the difference in verse 3. Neither is there any reason that would depend upon Joseph Smith’s participation as a translator. This is not the general type of change that Joseph Smith make in the Inspired version. This text remains a variant, without a specific explanation.