The third source of weakness which we have named—the scarcity of well-fortified strongholds—was felt both on this and on the other side of the Channel. Neither Frank nor Anglo-Saxon had made any systematic attempt to keep up the great fortresses which they had inherited from the Romans. But here again the English were at a greater disadvantage than their continental neighbours. They had neglected scientific fortification even more than the Franks. They mostly dwelt in open towns and villages; even the ancient Roman walls of great cities like London and York had been allowed to fall into decay. At most they surrounded important positions with a ditch and a stockade; of the building of an actual wall we hear only at one place, the Northumbrian capital of Bamborough. The Franks, among whom city life was far more important than in England, seem to have done somewhat more in the way of keeping up the old Roman _enceintes_ of their great towns. They had also taken of late to the building of strongholds destined to hold down conquered territory. Charlemagne had warred down the obstinate Saxons mainly by rearing line after line of _burgs_ among their heaths and forests. No great English king had yet tried to maintain his control over his vassal-states by such an expedient. Even if the Frankish _burgs_ were but concentric rings of ditch, mound, and palisade, they were by no means lacking in importance in the day of danger. In the matter of naval defence, on the other hand, there was more hope for England than for her continental neighbours. The Saxons and Angles had always been seafarers: the Franks had never taken to the water. Neither of the nations possessed any regular war-fleet, but in the one the national genius was favourable to its creation; in the other it was not. We hear, indeed, long before Alfred’s day, of intermittent attempts of English kings to do something on the seas. The most notable was the assault on Ireland which the Northumbrian Ecgfrith made in 684. In the days of Alfred’s own father, Ethelwulf, there was at least one endeavour to meet the Danes upon the water: the Anglo-Saxon Chronicle tells how the Kentish alderman Ealhere “fought in ships” at Sandwich, and “took nine ships of the heathen, and put the rest to flight” (851). It is possible that the same chief was engaged in a second naval battle two years later, for in an unsuccessful attempt which he made to turn the Vikings out of Thanet “there was much slaughter and many men _drowned_ upon both sides.” Thanet being then separated from the Kentish mainland by a broad estuary, it is conceivable that there was some fighting on shipboard on this occasion also.