35. =The Roman Defence.=--The Romans had always been weak at sea, and they were weaker now than they had been in earlier days. They were therefore obliged to content themselves with standing on the defensive. Since the time of Severus, Britain had been divided, for purposes of defence, into Upper and Lower Britain. Though there is no absolute certainty about the matter, it is probable that Upper Britain comprised the hill country of the west and north, and that Lower Britain was the south-eastern part of the island, marked off by a line drawn irregularly from the Humber to the Severn.[1] Lower Britain in the early days of the Roman conquest had been in no special need of military protection. In the fourth century it was exposed more than the rest of the island to the attacks of the Saxon pirates. Fortresses were erected between the Wash and Beachy Head at every point at which an inlet of the sea afforded an opening to an invader. The whole of this part of the coast became known as the Saxon Shore, because it was subjected to attacks from the Saxons, and a special officer known as the Count of the Saxon Shore was appointed to take charge of it. An officer known as the Duke of the Britains (_Dux Britanniarum_) commanded the armies of Upper Britain; whilst a third, who was a civilian, and superior in rank over the other two, was the Count of Britain, and had a general supervision of the whole country. [Footnote 1: There were also four smaller divisions, ultimately increased to five. All that is known about their position is that they were not where they are placed in our atlases.]