Encouraged by his success in these two lesser contests, Sapor resolved (apparently in A.D. 241) to resume the bold projects of his father, and engage in a great war with Rome. The confusion and troubles which afflicted the Roman Empire at this time were such as might well give him hopes of obtaining a decided advantage. Alexander, his father's adversary, had been murdered in A.D. 235 by Maximin, who from the condition of a Thracian peasant had risen into the higher ranks of the army. The upstart had ruled like the savage that he was, and after three years of misery the whole Roman world had risen against him. Two emperors had been proclaimed in Africa. On their fall two others had been elected by the senate; a third, a mere boy, had been added at the demand of the Roman populace. All the pretenders except the last had met with violent deaths; and after the shocks of a year, unparalleled since A.D. 69, the administration of the greatest kingdom in the world was in the hands of a youth of fifteen. Sapor, no doubt, thought he saw in this condition of things an opportunity that he ought not to miss, and rapidly matured his plans lest the favorable moment should pass away. Crossing the middle Tigris into Mesopotamia, the bands of Sapor first attacked the important city of Nisibis. Nisibis, at the time a Roman colony, was strongly situated on the outskirts of the mountain range which traverses Northern Mesopotamia between the thirty-seventh and thirty-eighth parallels. The place was well fortified and well defended; it offered a prolonged resistance; but the walls were breached and it was forced to yield itself. The advance was then made along the southern flank of the mountains by Carrhæ (Harran) and Edessa to the Euphrates, which was probably reached in the neighborhood of Birehjik. The hordes then poured into Syria, and, spreading themselves over that fertile region, surprised and took the metropolis of the Roman East, the rich and luxurious city of Antioch. But meantime the Romans had shown a spirit which had not been expected from them.