Page:Political History of Parthia.pdf/284

238 In the late spring of 117 Trajan retreated northward along the Tigris, which he followed to the vicinity of Hatra. A siege of this desert city, which was perhaps the headquarters of the Parthian opposition, was undertaken, but after several days the Emperor was forced to abandon the attempt. The surrounding country offered nothing in the way of food for man or beast, and water was both scarce and bad. As Dio says, the Sun-god made a siege impossible, and the Romans were troubled by clouds of flies, which settled with maddening tenacity on food and drink. Trajan himself mixed in the fighting and had a narrow escape from death when his cavalry was driven back in disorder. A part of the wall was broken down, but the Roman troops failed to occupy the breach thus created, and the whole affair had to be abandoned. A general withdrawal of the Roman forces then took place, not only from the Tigris and the lower Euphrates, but even from towns as far north as Dura-Europus.