Achaemenid Empire (First Persian Empire) expansion 559-486 BCE

"After (re)taking Babylon, Darius himself marched against the Scythians. For since Asia was bursting with men and vast revenues were coming in, Darius desired to punish the Scythians for the wrong they had begun when they invaded Media first and defeated those who opposed them in battle. For the Scythians, as I have said before, ruled upper Asia for twenty-eight years; they invaded Asia in their pursuit of the Cimmerians, and ended the power of the Medes, who were the rulers of Asia before the Scythians came."

-Herodotus, The Histories 4.1

Source:

https://en.wikipedia.org/wiki/File:Achaemenid_Empire_under_different_kings_(flat_map).svg

Quote:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0126%3Abook%3D4&force=y