The Seleucians had at no time been contented with their position as Parthian subjects.

Whether they supposed that they could stand alone, or whether they looked to enjoying under Roman protection a greater degree of independence than had been allowed them by the Parthians, is uncertain.
They revolted however, in A.D.40, and declared themselves a self-governing community.

It does not appear that the Romans lent them any assistance, or broke for their sake the peace established with Parthia in A.D.37.

The Seleucians had to depend upon themselves alone, and to maintain their rebellion by means of their own resources.

No doubt Artabanus proceeded at once to attack them, but his arms made no impression.