The second and third waves of castle building were led by the major magnates, and then by the more junior knights on their new estates. The apportionment of the conquered lands by the king influenced where these castles were built. In a few key locations the king gave his followers compact groups of estates including the six rapes of Sussex and the three earldoms of Chester, Shrewsbury and Hereford; intended to protect the line of communication with Normandy and the Welsh border respectively. In these areas a baron's castles were clustered relatively tightly together, but in most of England the nobles' estates, and therefore their castles, were more widely dispersed. As the Normans pushed on into South Wales they advanced up the valleys building castles as they went and often using the larger castles of the neighbouring earldoms as a base.