Isaiah 21:3

"Therefore are my loins filled with anguish; pangs have taken hold upon me, as the pangs of a woman in travail: I am pained so that I cannot hear, I am dismayed so that I cannot see. My heart fluttereth, horror hath affrighted me; the twilight that I desired hath been turned into trembling unto me."

It is simply impossible that the news of Babylon's fall in 539 B.C. could have been the occasion of the reaction on Isaiah's part, as described in these two verses. He was so upset, dismayed, astounded, and pained that he could not hear, could not see, and could not rest. Even twilight, when ordinarily he would have rested became a time of trembling. This verse makes it mandatory to see the object of this prophecy in a prior fall of Babylon in 696 B.C., long before the captivity, in the ruin of the city by Sennacherib.