with it the great fortress of Nisibis, was somewhat in the position of the holder of Alsace-Lorraine. It had control of a gate which might admit its armies into the territory of the enemy, or which might be effectively shut in the face of an invader. Hence both parties claimed the five small, and otherwise not very important, provinces into which this country was divided, and neither could be content to see them in the hands of the other.
With all these causes for war ready to hand, it is not surprising that only unusual combinations of circumstances, like the simultaneous accession of two peace-loving monarchs, or simultaneous invasion of both empires by the barbarians who threatened the northern frontiers of either, could keep their relations friendly.
It was not only as an empire that Persia thus rose from the dead in the third century; it rose also as a religion, of a definite and militant type. The Persia of Achæmenid days had accepted Zoroaster's reforms of the ancient fire-worship as a national faith; and that religion had been preserved by the nation as its heritage, and treasured as only a subject nation can treasure its national faith (if, indeed, it had not been, as is possible, the force that had kept the nation alive) during the 500 years of dependence. Now, when Persia rose to power once more, their religion rose with them; and the Sassanian Empire had a definitely established Magian Church, loyal membership of which was the test and condition of loyalty to the empire.
This religion had its system of theology and its Sacred books. It had its priestly caste, the Magians; who were at once one of the seven great clans of the nation, and an organized hierarchy under their "Mobeds" or prelates, with the "Mobed Mobedan" at the head of all. The fire-temple
