The ephemeral kingdom of Palmyra was in its origin as in its fall closely bound up with the relations of the Romans to the non-Roman East, but not less a part of the general history of the empire. For, like the western empire of Postumus, the eastern empire of Zenobia was one of those masses into which the mighty whole seemed then about to resolve itself. If during its subsistence its leaders endeavoured earnestly to set limits to the onset of the Persians, and indeed the development of its power was dependent on that very fact, not merely did it in its collapse seek deliverance from those same Persians, but probably in consequence of the revolt of Zenobia Armenia and Mesopotamia were lost to the Romans, and after the subjugation of Palmyra the Euphrates again for a time formed the frontier. The queen, when she arrived at it, hoped to find a reception among the Persians; and Aurelian omitted to lead the legions over it, seeing that Gaul, along with Spain and Britain, still at that time refused to recognise the government. He and his successor Probus were not able to take up this struggle. But when in the year 282, after the premature end of the latter, the troops proclaimed the commander next in rank, Marcus Aurelius Carus, as emperor, it was the first saying of the new ruler that the Persians should remember this choice, and he kept it. Immediately he advanced with the army into Armenia and re-established the earlier order there. At the frontier of the land he was met by Persian envoys, who declared themselves ready to grant all that was reasonable;[117] but they were hardly listened to, and the march went on incessantly. Mesopotamia too became once more Roman, and the Parthian residential cities Seleucia and Ctesiphon were again occupied by the Romans without encountering lengthened resistance--to which the war between brothers then raging in the Persian empire contributed its part.[118] The emperor had just crossed the Tigris, and was on the point of penetrating into the heart of the enemy’s country, when he met his death by violence, presumably by the hand of an assassin, and thereby the campaign also met its end. But his successor obtained in peace the cession of Armenia and Mesopotamia;[119] although Carus wore the purple little more than a year, he re-established the imperial frontier of Severus. [Sidenote: Persian war under Diocletian.]