The peace made between Philip and Sapor was followed by an interval of fourteen years, during which scarcely anything is known of the condition of Persia. We may suspect that troubles in the northeast of his empire occupied Sapor during this period, for at the end of it we find Bactria, which was certainly subject to Persia during the earlier years of the monarchy, occupying an independent position, and even assuming an attitude of hostility toward the Persian monarch. Bactria had, from a remote antiquity, claims to preëminence among the Aryan nations. She was more than once inclined to revolt from the Achæmenidæ, and during the later Parthian period she had enjoyed a sort of semi-independence. It would seem that she now succeeded in detaching herself altogether from her southern neighbor and becoming a distinct and separate power. To strengthen her position she entered into relations with Rome, which gladly welcomed any adhesions to her cause in this remote region. Sapor's second war with Rome was, like his first, provoked by himself. After concluding his peace with Philip he had seen the Roman world governed successively by six weak emperors, of whom four had died violent deaths, while at the same time there had been a continued series of attacks upon the northern frontiers of the empire by Alamanni, Goths, and Franks, who had ravaged at will a number of the finest provinces, and threatened the absolute destruction of the great monarchy of the West. 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, Carrhæ, 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 head-quarters during his stay in the East.