Although the personal attention of the Conqueror was necessarily confined to the chief cities and central towns of England, to Exeter, Gloucester, Nottingham, Lincoln, York, or Durham, his western frontier was not neglected, although he was obliged to depute its ordinary defence to others. The Welsh, hardened by centuries of constant warfare, held with tenacity their strip of mountain land between Offa’s Dyke and the sea, and were ever on the watch to spoil that other more fertile tract which lay between the Dyke and the Severn and the Dee, known as the March. Foremost among the barons of the March were Roger of Montgomery and Hugh D’Avranches, Earl of Chester, to whom later generations gave the surname of the “Wolf.” The _caput_ of this latter earldom, protected by the deep and rapid Dee, was posted at one angle of the old Roman enclosure; and the castle of Earl Roger, girdled by the convolutions of the Severn, was an almost impregnable citadel. From these fortresses these great earls exercised more than regal power over the counties of Salop and Hereford, composing the Middle March. The border barons, their feudatories, succeeded to no peaceful heritage; but by degrees they possessed themselves of the older English possessions upon the border, and along with them of the fortresses by which in Mercian times the Welsh had been held so long at bay. That these were numerous is evident from the remains of their earthworks; and that they were strong and well held against the Welsh is evident from the English names along and beyond the frontier. “Domesday,” however, though compiled after Earl Roger had held the Earldom of Shrewsbury about twelve years, only mentions four castles upon his border,—Oswestry, Montgomery, Shrewsbury, and Stanton or Castle Holgate, and the Earl’s house at Quatford. Bridgenorth and Carreghova were built a few years later, in the reign of Rufus; but Bridgenorth represented the burgh of Æthelflæda, the remains of which are possibly seen at Oldbury, as are earthworks of still stronger type, actually employed by Earl Roger at Quatford. Besides these, Wattlesborough and Clun exhibit rectangular Norman keeps; and eleven or twelve more castles in those districts are mentioned in records as early as the reign of Henry I. Altogether, by the close of the twelfth century there were from fifty to sixty castles in the county of Salop alone. Now, although the masonry of these castles, or of such of them as remain, can very rarely indeed be attributed to the Norman period, the earthworks show that they existed as fortresses long before that time; and it seems, therefore, certain that here, as in other parts of England, Earl Roger and his barons made the most of such works as they found ready to their hands; and this applies equally to the Palatinate of Chester and to the southern Marches, where also Norman castles took the place, with more or less of interval, of strongholds of the English type.