It was natural that the chief kingdom of Western Asia should note these events, and should seek to promote its own interests by taking advantage of the circumstances of the time.

Sapor, in A.D.
258, determined on a fresh invasion of the Roman provinces, and, once more entering Mesopotamia, carried all before him, became master of Nisibis, Carrhae, and Edessa, and, crossing the Euphrates, surprised Antioch, which was wrapped in the enjoyment of theatrical and other representations, and only knew its fate on the exclamation of a couple of actors "that the Persians were in possession of the town." The aged emperor, Valerian, hastened to the protection of his more eastern territories, and at first gained some successes, retaking Antioch, and making that city his headquarters during his stay in the East.

But, after this, the tide turned.

Valerian entrusted the whole conduct of the war to Macrianus, his Praetorian prefect, whose talents he admired, and of whose fidelity he did not entertain a suspicion.

Macrianus, however, aspired to the empire, and intentionally brought Valerian into difficulties, in the hope of disgracing or removing him.