Arethas, the chief of the Saracens who fought on the side of Rome, was sent still further in advance.

The orders given him were to cross the Tigris into Assyria, and begin to ravage it, but to return within a short time to the camp, and bring a report of the strength of the Persians beyond the river.

If the report was favorable, Belisarius intended to quit Mesopotamia, and take the whole Roman force with him into Assyria.

His plans, however, were frustrated by the selfish Arab, who, wishing to obtain the whole Assyrian spoil for himself, dismissed his Roman troops, proceeded to plunder the rich province on his own account, and sent Belisarius no intelligence of what he was so doing.

After waiting at Sisauranon till the heats of summer had decimated his army, the Roman general was compelled to retreat by the discontent of the soldiery and the representations of his principal officers.