more than three months.

Perhaps he would not have departed so soon, but would have turned
the siege into a blockade, and endeavored to starve the garrison into
submission, had not alarming tidings reached him from his north-eastern
frontier. Then, as now, the low flat sandy region east of the Caspian
was in the possession of nomadic hordes, whose whole life was spent in
war and plunder. The Oxus might be nominally the boundary of the empire
in this quarter; but the nomads were really dominant over the entire
desert to the foot of the Hyrcanian and Parthian hills. Petty plundering
forays into the fertile region south and east of the desert were no
doubt constant, and were not greatly regarded; but from time to time
some tribe or chieftain bolder than the rest made a deeper inroad and
a more sustained attack than usual, spreading consternation around,
and terrifying the court for its safety. Such an attack seems to have
occurred towards the autumn of A.D. 350. The invading horde is said to
have consisted of Massagatae; but we can hardly be mistaken in regarding
them as, in the main, of Tatar, or Turkoman blood, akin to the Usbegs
and other Turanian tribes which still inhabit the sandy steppe. Sapor
considered the crisis such as to require his own presence; and thus,
while civil war summoned one of the two rivals from Mesopotamia to
the far West, where he had to contend with the self-styled emperors,
Magnentius and Vetranio, the other was called away to the extreme East
to repel a Tatar invasion. A tacit truce was thus established between
the great belligerents--a truce which lasted for seven or eight years.
The unfortunate Mesopotamians, harassed by constant war for above twenty
years, had now a breathing-space during which to recover from the ruin
and desolation that had overwhelmed them. Rome and Persia for a time
suspended their conflict. Rivalry, indeed, did not cease; but it was
transferred from the battlefield to the cabinet, and the Roman
emperor sought and found in diplomatic triumphs a compensation for the
ill-success which had attended his efforts in the field.

CHAPTER IX.

_Revolt of Armenia and Acceptance by Arsaces of the Position of a Roman
Feudatory. Character and Issue of Sapor's Eastern Wars. His negotiations
with Constantius. His Extreme Demands. Circumstances under which he
determines to renew the War. His Preparations. Desertion to him of
Antoninus. Great Invasion of Sapor. Siege of Amida.