XX. After this he advanced along the river, with seven legions and
nearly four thousand horsemen, and almost as many light-armed troops
as horsemen. Some of the scouts now returned from their exploration
and reported that the country was clear of men, and that they had
fallen in with the tracks of many horses, which indicated that they
had turned about and were retreating. This gave Crassus still better
hopes, and made the soldiers completely despise the Parthians, who, as
they supposed, would not come to close quarters. However, Cassius
again had some conversation with Crassus, and advised him at least to
give his troops rest in some of the garrisoned cities, till he should
get some certain information about the enemy; but if he would not do
this, to advance towards Seleukeia along the river. He urged that the
boats which carried the provisions would furnish them with supplies by
stopping at the places of encampment, and that, by having the river as
a protection against being hemmed in by the enemy, they would always
be able to fight them on fair terms.

XXI. While Crassus was considering and reflecting on these matters,
there comes an Arab chieftain, Ariamnes[67] by name, a cunning and
faithless man, and of all the misfortunes that were by chance combined
to ruin the Romans the chief and crowning mischief. Some of them who
had served with Pompeius knew him as one who had received favours from
Pompeius, and was supposed to be a friend to the Romans; but he now
came to Crassus with a treacherous intent, and with the privity of the
royal generals, to try if he could draw him far away from the river
and the foot of the hills, into a boundless plain, where he might be
surrounded by the enemy; for nothing was further from the intentions
of the Parthians than to attack the Romans right in front.
Accordingly, the barbarian coming to Crassus (and he was a plausible
talker), spake in high terms of Pompeius as his benefactor, and