These were (1) the division of the fyrd or national militia into two parts, relieving each other at fixed intervals, so as to ensure continuity in military operations; (2) the establishment of fortified posts (burgs) and garrisons at certain points; (3) the enforcement of the obligations of thanehood on all owners of five hides of land, thus giving the king a nucleus of highly equipped troops.
When he summoned out the fyrd they came in great force to his aid, not so much because they trusted in the promises of good governance and reduced taxation which he made, but because they saw that a horde of greedy barons would be worse to serve than a single king, however hard and selfish he might be.
The fyrd was gradually superseded by the gathering of the thegns and their retainers, but it was occasionally called out for defensive purposes even after the Norman Conquest.
It is first mentioned in the Anglo-Saxon Chronicle under the date 605.The ealdorman, or sheriff, of the shire was probably charged with the duty of calling out and leading the fyrd, which appears always to have retained a local character, as during the time of the Danish invasions we read of the fyrd of Kent, of Somerset and of Devon.
All through the summcr Harold held a fleet concentrated under the lee of the Isle of Wight, waiting to intercept Williams armament, while the fyrd of Wessex was ready to support him if the enemy should succeed in making a landing.
But Roger, who was to bring his force from the west to join the earl of Norfolk, was held in check at the Severn by the Worcestershire fyrd which the English bishop Wulfstan brought into the field against him.
The old national levy of the fyrd was made somewhat more serviceable by an ordinance which divided it into two halves, one of which must take the field when the other was dismissed.