His own army thus amounted to 100,000 men; and, with the Armenian contingent, his entire force would have been 113,000.

It seems that it was his original intention to cross the Euphrates into Mesopotamia, and thus to advance almost in the footsteps of Crassus but when he reached the banks of the river (about midsummer B.C.

37) he found such preparations made to resist him that he abandoned his first design, and, turning northwards, entered Armenia, determined to take advantage of his alliance with Artavasdes, and to attack Parthia with Armenia as the basis of his operations.

Artavasdes gladly received him, and persuaded him, instead of penetrating into Parthia itself, to direct his arms against the territory of a Parthian subject-ally, the king of Media Atropatene, whose territories adjoined Armenia on the southeast.
Artavasdes pointed out that the Median monarch was absent from his own country, having joined his troops to those which Phraates had collected for the defence of Parthia.

His territory therefore would be open to ravage, and even Praaspa, his capital, might prove an easy prey.