He drew a fortification from sea to sea, consisting of a stone wall on the north, and lines of earthen ramparts on the south, with a military way between them. In connection with these lines of defence he built stationary camps, mile-castles, and turrets for the accommodation of his soldiery whether in camp or keeping guard. The line of fortification was not intended as a mere fence to shut out a northern foe; it was intended to protect the troops from surprise either from the north or south, and it was intended to form a basis of operation against an enemy in whatever quarter he might show himself (p. 9).