Prophetic Historical Accuracies: Elam

“Yet I will restore the fortunes of Elam
    in days to come,”
declares the Lord.
Jer. 49:39

A dire vision has been shown to me:
    The traitor betrays, the looter takes loot.
Elam, attack! Media, lay siege!
    I will bring to an end all the groaning she caused.
Isa. 21:2

Who or what was Elam?

They were the ancient, pre-Persian, pre-Iranian people that lived on the East side of the Tigris River along the Persian Gulf.  They were among the earliest people known to have inhabited that region.

Source: https://en.wikipedia.org/wiki/Elam

Now in 559 BC Cyrus II (who was the grandson of Cyrus I) became king.  In 549 BC he overthrew the Median overlord (who happened to be his mother's father) and took new titles unto himself:

King of Medes

&

King of Elam

On October 16, 539 BC, his army entered Babylon by way of the stream bed under the wall.  Seventeen days later,  Cyrus II himself entered Babylon amid great celebration.  

Thus Elam, nearly completely wiped out by Babylon, returned to wipe out Babylon.  The looted became the looter.  All to advance God's purposes for His people, because it was in the first year of Cyrus II that he issued decrees resettling the captives of Babylon back to their homelands and made an effort to repatriate the "local gods" among their native peoples.  None of this would have happened if Babylon remained in power.  All of it to the praise of His glorious grace who works out all things in conformity to the purpose of His will (Eph. 1:11).