To that monarch, when some years afterwards (B.C. 23) he demanded the surrender of his subject and the restoration of his young son, Octavian answered that he could not give Tiridates up to him, but he would restore him his son without a ransom.  He should expect, however, that in return for this kindness the Parthian king would on his part deliver to the Romans the standards taken from Crassus and Antony, together with all who survived of the Roman captives.  It does not appear that Phraates was much moved by the Emperor’s generosity.  He gladly received his son; but he took no steps towards the restoration of those proofs of Parthian victory which the Romans were so anxious to recover.  It was not until B.C. 20, when Octavian (now become Augustus) visited the East, and war seemed the probable alternative if he continued obstinate, that the Parthian monarch brought himself to relinquish the trophies which were as much prized by the victors as the vanquished.  In extenuation of his act we must remember that he was unpopular with his subjects, and that Augustus could at any moment have produced a pretender, who had once occupied, and with Roman help might easily have mounted for a second time, the throne of the Arsacidse.

The remaining years of Phraates—­and he reigned for nearly twenty years after restoring the standards—­are almost unbroken by any event of importance.  The result of the twenty years’ struggle between Rome and Parthia had been to impress either nation with a wholesome dread of the other.  Both had triumphed on their own ground; both had failed when they ventured on sending expeditions into the enemy’s territory.  Each now stood on its guard, watching the movements of its adversary across the Euphrates.  Both had become pacific.  It is a well-known fact that Augustus left it as a principle of policy to his successors that the Roman Empire had reached its proper limits, and could not with advantage be extended further.  This principle, followed with the utmost strictness by Tiberius, was accepted as a rule by all the earlier Caesars, and only regarded as admitting of rare and slight exceptions.  Trajan was the first who, a hundred and thirty years after the accession of Augustus, made light of it and set it at defiance.  With him re-awoke the spirit of conquest, the aspiration after universal dominion.  But in the meantime there was peace—­peace indeed not absolutely unbroken, for border wars occurred, and Rome was tempted sometimes to interfere by arms in the internal quarrels of her neighbors—­but a general state of peace and amity prevailed—­neither state made any grand attack on the other’s dominions—­no change occurred in the frontier, no great battle tested the relative strength of the two peoples.  Such rivalry as remained was exhibited less in arms than in diplomacy and showed itself mainly in endeavors on either side to obtain a predominant influence in Armenia.  There alone during the century and a half that intervened between Antony and Trajan did the interests of Rome and Parthia come into collision, and in connection with this kingdom alone did any struggle between the two countries continue.