sentences:  In response to Welsh advances, William established a series of earldoms in the borderlands, specifically at Chester, under Hugh d'Avranches; Shrewsbury, under Roger de Montgomerie; and Hereford, under William FitzOsbern.He instilled a great deal of power into each earldom, allowing them control of the surrounding towns and land, rather than retaining it within the kingship.The inspiration for such an action seems to have been the overextended nature of the Norman troops, thus preventing William from exercising his own power in the area.