The origins of the campaign are not attested in historical sources, but it was probably in response to a revolt of the Cadusii and the refusal of paying tribute.

[1] The Cadusii people lived in a mountainous district of Media Atropatene on the south-west shores of the Caspian Sea, between the parallels of 39° and 37° North latitude, called for its inhabitants Cadusia.

They are described by Strabo[2] as a warlike tribe of mountaineers, fighting chiefly on foot, and well skilled in the use of the short spear or javelin.

[4] The mountainous terrain offered little food but some pears, apples, and other tree-fruits insufficient to feed such a host of fighting men.

[4] Both Tiribazus and his son convinced the Cadusii chiefs that the other had sent envoys to the Persian King and sought an advantageous peace.