It was, perhaps, on account of the repulse from Nisibis, and in the hope of recovering his lost laurels, that Sapor, in the next year but one, A.D. 348, made an unusual effort. Calling out the entire military force of the empire, and augmenting it by large bodies of allies and mercenaries, the Persian king, towards the middle of summer, crossed the Tigris by three bridges, and with a numerous and well-appointed army invaded Central Mesopotamia, probably from Adiabene, or the region near and a little south of Nineveh. Constantius, with the Roman army, was posted on and about the Sinjax range of hills, in the vicinity of the town of Singara, which is represented by the modern village of Sinjar. The Roman emperor did not venture to dispute the passage of the river, or to meet his adversary in the broad plain which, intervenes between the Tigris and the mountain range, but clung to the skirts of the hills, and commanded his troops to remain wholly on the defensive. Sapor was thus enabled to choose his position, to establish a fortified camp at a convenient distance from the enemy, and to occupy the hills in its vicinity--some portion of the Sinjar range--with his archers. It is uncertain whether, in making these dispositions, he was merely providing for his own safety, or whether he was laying a trap into which he hoped to entice the Roman army. Perhaps his mind was wide enough to embrace both contingencies. At any rate, having thus established a _point d’appui_ in his rear, he advanced boldly and challenged the legions to an encounter. The challenge was at once accepted, and the battle commenced about midday; but now the Persians, having just crossed swords with the enemy, almost immediately began to give ground, and retreating hastily drew their adversaries along, across the thirsty plain, to the vicinity of their fortified camp, where a strong body of horse and the flower of the Persian archers were posted. The horse charged, but the legionaries easily defeated them, and elated with their success burst into the camp, despite the warnings of their leader, who strove vainly to check their ardor and to induce them to put off the completion of their victory till the next day. A small detachment found within the ramparts was put to the sword; and the soldiers scattered themselves among the tents, some in quest of booty, others only anxious for some means of quenching their raging thirst. Meantime the sun had gone down, and the shades of night fell rapidly. Regarding the battle as over, and the victory as assured, the Romans gave themselves up to sleep or feasting. But now Sapor saw his opportunity--the opportunity for which he had perhaps planned and waited. His light troops on the adjacent hills commanded the camp, and, advancing on every side, surrounded it. They were fresh and eager for the fray; they fought in the security afforded by the darkness; while the fires of the camp showed them their enemies, worn out with fatigue, sleepy, or drunken.