Four years after this Marcus Aurelius died, and was succeeded in the purple by his youthful son, Lucius Aurelius Commodus.  It might have been expected that the accession of this weak and inexperienced prince would have induced Volagases to resume his warlike projects, and attempt the recovery of Mesopotamia.  But the scanty history of the time which has come down to us shows no trace of his having entertained any such design.  He had probably reached the age at which repose becomes a distinct object of desire, and is infinitely preferred to active exertion.  At any rate, it is clear that he made no effort.  The reign of Gommodus was from first to last untroubled by Oriental disturbance.  Volgases III. was for ten years contemporary with this mean and unwarlike prince; but Rome was allowed to retain her Parthian conquests unmolested.  At length, in A.D. 190 or 191, Volagases died,56 and the destinies of Parthia passed into the hands of a new monarch.

CHAPTER XX.

Accession of Volagases IV.  His Alliance sought by Pescennius Niger, Part taken by Parthia in the Contest between Niger and Severus, Mesopotamia revolts from Rome.  First Eastern Expedition of Severus.  Its Results.  Second Expedition.  Successes of Severus.  His Failure at Hatra.  General Results of the War.  Death of Volagases IV.

On the death of Volagases III., in A.D. 190 or 191, the Parthian crown fell to another prince of the same name, who was probably the eldest son of the late monarch.  This prince was scarcely settled upon the throne when the whole of Western Asia was violently disturbed by the commotions which shook the Roman Empire after the murder of Commodus.  The virtuous Pertinax was allowed to reign but three months (A.D. 193, January—­March).  His successor was scarcely proclaimed when in three different quarters the legionaries rose in arms, and, saluting their commanders as “Emperors,” invested them with the purple.  Clodius Albinus, in Britain; Severus, in Pannonia; and Pescennius Niger, in Syria, at one and the same time claimed the place which the wretched Julianus had bought, and prepared themselves to maintain their rights against all who should impugn them.  It seems that, on the first proclamation of Niger, and before it had become evident that he would have to establish his authority by force of arms, either the Parthian monarch, or at any rate princes who were among his dependants, sent to congratulate the new Emperor on his accession and to offer him contingents of troops, if he required them.  These spontaneous proposals were at the first politely declined, since Niger expected to find himself accepted joyfully as sovereign, and did not look to have to engage in war.  When, however, the news reached him that he had formidable competitors, and that Severus, acknowledged Emperor at Rome, was about to set out for the East, at the head of vast forces, he saw that it would be