challenged him to engage in civil war.  So long as Sapor threatened invasion he did not like to quit Mesopotamia, lest he might appear to have sacrificed the interests of his country to his own private quarrels; but he must have been anxious to return to the seat of empire from the first moment that intelligence reached him of Julian’s assumption of the imperial name and dignity; and when Sapor’s retreat was announced he naturally made all haste to reach his capital.  Meanwhile the desire of keeping his army intact caused him to refrain from any movement which involved the slightest risk of bringing on a battle, and, in fact, reduced him to inaction.  So much is readily intelligible.  But what at this time withheld Sapor, when he had so grand an opportunity of making an impression upon Rome—­what paralyzed his arm when it might have struck with such effect it is far from easy to understand, though perhaps not impossible to conjecture.  The historian of the war ascribes his abstinence to a religious motive, telling us that the auguries were not favorable for the Persians crossing the Tigris.  But there is no other evidence that the Persians of this period were the slaves of any such superstition as that noted by Ammianus, nor any probability that a monarch of Sapor’s force of character would have suffered his military policy to be affected by omens.  We must therefore ascribe the conduct of the Persian king to some cause not recorded by the historian—­same failure of health, or some peril from internal or external enemies which called him away from the scene of his recent exploits, just at the time when his continued presence there was most important.  Once before in his lifetime, an invasion of his eastern provinces had required his immediate presence, and allowed his adversary to quit Mesopotamia and march against Magnentius.  It is not improbable that a fresh attack of the same or some other barbarians now again happened opportunely for the Romans, calling Sapor away, and thus enabling Constantius to turn his hack upon the East, and set out for Europe in order to meet Julian.

The meeting, however, was not destined to take place.  On his way from Antioch to Constantinople the unfortunate Constantius, anxious and perhaps over-fatigued, fell sick at Mopsucrene, in Cilicia, and died there, after a short illness, towards the close of A.D. 361.  Julian the Apostate succeeded peacefully to the empire whereto he was about to assert his right by force of arms; and Sapor found that the war which he had provoked with Rome, in reliance upon his adversary’s weakness and incapacity, had to be carried on with a prince of far greater natural powers and of much superior military training.

CHAPTER X.