Indeed already in 306 it is rather as a refuge than as a great and active naval base that Ravenna appears to us, when Severus, destitute of force, "retired or rather fled" thither from the pursuit of Maximian. He flung himself into Ravenna because it was impregnable and because he expected reinforcements from Illyricum and the East, but though he held the sea with a powerful fleet he made no use of it, and the emissaries of Maximian easily persuaded him to surrender. Already perhaps, a century later, when Honorius retired from Milan on the approach of Alaric and the first of those barbarian invasions which broke up the decaying western empire had penetrated into Cisalpine Gaul, the great works of Augustus and Trajan at Ravenna, the canals, the mighty Fossa, and the port itself had fallen into a sort of decay which the fifth century was to complete, till that marvellous city, once the base of the eastern fleet and one of the great naval ports of the world, became just a decaying citadel engulfed in the marshes, impregnable it is true, but for barbarian reasons, lost in the fogs and the miasma of her shallow and undredged lagoons. IV THE RETREAT UPON RAVENNA HONORIUS AND GALLA PLACIDIA When Honorius left Milan on the approach of Alaric he went to Ravenna. Why? Gibbon, whom every writer since has followed without question, tells us, in one of his most scornful passages, that "the emperor Honorius was distinguished, above his subjects, by the pre-eminence of fear, as well as of rank. The pride and luxury in which he was educated had not allowed him to suspect that there existed on the earth any power presumptuous enough to invade the repose of the successor of Augustus. The acts of flattery concealed the impending danger till Alaric approached the palace of Milan. But when the sound of war had awakened the young emperor, instead of flying to arms with the spirit, or even the rashness, of his age, he eagerly listened to those timid counsellors who proposed to convey his sacred person and his faithful attendants to some secure and distant station in the provinces of Gaul.... The recent danger to which the person of the emperor had been exposed in the defenceless palace of Milan urged him to seek a retreat in some inaccessible fortress of Italy, where he might securely remain while the open country was covered by a deluge of barbarians." No historian of Ravenna, and certainly no writer upon the fall of the empire, has cared to understand what Ravenna was. Gibbon complains that he lacks "a local antiquarian and a good topographical map;" yet it is not so much the lack of local knowledge that leads him unreservedly to censure Honorius for his retreat upon Ravenna, as the fact that he has not perhaps really grasped what Ravenna was, what was her relation to Italy and Cisalpine Gaul, and especially how she stood to the sea, and what part that sea played in the geography and strategy of the empire.