Their exodus from their true homeland seem to have been an escape from the wars reffered to in the Mahabaratha/Ramayana.
Actually Their exodus from their true home land was an escape from the Bharatha clan as mentioned in Rigveda after the Battle of Ten Kings or 'Dasa Rajna' in Which the Trtsu(Bharatha) clan and its King Sudas became Victorius.
Other Clans who were defeated and forced to leave Being
1) Alinas or Allenes or The Hellenes(greeks)
2) Anus or Anouvas (Persians as called by greeks)
3) Bhrigus or Phrygians(who lived in southern Balkans as Bryges or Briges and changed it to Phruges after their final migration to Anatolia)
4) Bhalanas the inhabitants of Bolan passes of Eastern Kabulistan
5) Dasas or Dasyus or Dahae/Dahi/Saka or Scythians
6) Druhyus of Gandhara or later called the 'Druids'(Celtic Druids) who later Migrated to far north west
7)Matsya of Madra desa North west of Punjab
8) Parsu or Assyrian 'Parsa' or Persians
9) Purus the descendants of Yayati - King Porus against whom the battle of Hydaspes was fought by Alexander is the descendent of Puru..
10) Pani or Parni or Parnoi related to scythians who later migrated to North west and came to be known as the Vanir of the Nordic Aesir Vanir Mythology