Hvakhshathra or Cyaxares (625 - 585 BC) was the most capable king of Media (Iran).
He reorganized and modernized the Median Army, then joined with King Nabopolassar of Babylon. The allies overthrew the Assyrian Empire and destroyed Nineveh in 612 BC.
After this victory, the Medes conquered Northern Mesopotamia, Armenia and some important parts of Asia Minor especially Lydia.