Before it was finished the legions might be beyond his reach, and so the campaign would end, and he would have gained no advantage from it.

Under these circumstances he determined to open negotiations with the Romans, and to see if he could not extract from their fears some important concessions.

They were still in a position of great peril, since they could not expect to embark and cross the stream without suffering tremendous loss from the enemy before whom they would be flying.

And it was uncertain what perils they might not encounter beyond the river in traversing the two hundred miles that still separated them from Roman territory.

The Saracenic allies of Persia were in force on the further side of the stream; and a portion of Sapor's army might be conveyed across in time to hang on the rear of the legions and add largely to their difficulties.