The allied army crossed the Euphrates below Circesium, and ascended the right bank of the river till they neared the latitude of Antioch, when they struck westward and reached Gabbula (the modern Jabul), on the north shore of the salt lake now known as the Sabakhah. Here they learned to their surprise that the movement, which they had intended to be wholly unknown to the Romans, had come to the ears of Belisarius, who had at once quitted Daras, and proceeded by forced marches to the defence of Syria, into which he had thrown himself with an army of 20,000 men, Romans, Isaurians, Lycaonians, and Arabs. His troops were already interposed between the Persians and their longed-for prey, Belisarius having fixed his headquarters at Chalcis, half a degree to the west of Gabbula, and twenty-five miles nearer to Antioch. Thus balked of their purpose, and despairing of any greater success than they had already achieved, the allies became anxious to return to Persia with the plunder of the Syrian towns and villages which they had sacked on their advance. Belisarius was quite content that they should carry off their spoil, and would have considered it a sufficient victory to have frustrated the expedition without striking a blow. But his army was otherwise minded; they were eager for battle, and hoped doubtless to strip the flying foe of his rich booty. Belisarius was at last forced, against his better judgment, to indulge their desires and allow an engagement, which was fought on the banks of the Euphrates, nearly opposite Callinicus. Here the conduct of the Roman troops in action corresponded but ill to the anxiety for a conflict. The infantry indeed stood firm, notwithstanding that they fought fasting; but the Saracenic Arabs, of whom a portion were on the Roman side, and the Isaurian and Lycaonian horse, who had been among the most eager for the fray, offered scarcely any resistance; and, the right wing of the Romans being left exposed by their flight, Belisarius was compelled to make his troops turn their faces to the enemy and their backs to the Euphrates, and in this position, where defeat would have been ruin, to meet and resist all the assaults of the foe until the shades of evening fell, and he was able to transport his troops in boats across the river. The honors of victory rested with the Persians, but they had gained no substantial advantage; and when Azarethes returned to his master he was not unjustly reproached with having sacrificed many lives for no appreciable result. The raid into Syria had failed of its chief object; and Belisarius, though defeated, had returned, with the main strength of his army intact, into Mesopotamia. The battle of Callinicus was fought on Easter Eve, April 19.