Persia from the Earliest Period to the Arab

HISTORY OF PERSIA. 145
that ultimately befell her invaders. In Babylonia a dis-
ease, alike unwonted and wasting, was contracted by
the soldiers; a scourge, indeed, so terrible that their
deaths were numbered by thousands; and, what was
worse, the survivors, on their homeward march, car-
ried the infection with them, till the pestilence had
swept over Italy and reached even the shores of the
Atlantic Ocean. If Eutropius can be believed, nearly
one-half of the whole population and almost all the
Roman army were carried off by it. Yet by this war,
fatal as it had been to the conquerors, a province
of Parthia, that between the Euphrates and the Khabur,
became Roman, and was long held by the em-
perors as part of the Roman territory. The struggle
ended in A.D. 165, and, though Vologases survived
another twenty-five years, he did not make any
effective effort to recover the ground he had lost.
Indeed, the Parthian system was now on its decline,
and the time was fast maturing for the substitution
in its place of a revived religion. The next time
we find the Parthians at war with Rome was, when,
on the death of Commodus, the empire was claimed
by Pescennius Niger, Clodius Albinus, and Severus,
respectively. During these disturbances, the Parthians
naturally gave their aid where it was likely
to be most
damaging to the Roman empire ; probably caring
little enough which individual became emperor, so
only he entered on his government with diminished
forces and strength.
In the progress of these commotions, Sept. Severus
marched twice across Mesopotamia; in his second
expedition, perhaps hoping to surpass Trajan, he built