to the Cornish border at Exeter, together with the portion of Mercia
south-west of Watling Street. The former kingdom passed into the hands
of his son Eadward; the latter was still held by the ealdorman Æthelred,
who had married Ælfred's daughter Æthelflæd. The departure of the Danish
host, led by Hæsten, left the English time to breathe and to recruit
their strength. Henceforth, for nearly a century, the direct wicking
incursions cease, and the war is confined to a long struggle with the
Northmen already settled in England. Four years later, the east Anglian
Danes broke the peace and harried Mercia and Wessex; but Eadward overran
their lands in return, and the Kentish men, in a separate battle,
attacked and slew Eric their king with several of his earls. In 912,
Æthelred the Mercian died, and Eadward at once incorporated London and
Oxford with his own dominions, leaving his sister Æthelflæd only the
northern half of her husband's principality. Thenceforth Æthelflæd, "the
Lady of the Mercians," turned deliberately to the conquest of the North.
She adopted a fresh kind of tactics, which mark again a new departure in
the English policy. Instead of keeping to the old plan of alternate
harryings on either side, and precarious tenure of lands from time to
time, Æthelflæd began building regular fortresses or _burhs_ all along
her north-eastern frontiers, using these afterwards as bases for fresh
operations against the enemy. The spade went hand in hand with the
sword: the English were becoming engineers as well as fighters. In the
year of her husband's death, the Lady built _burhs_ at Sarrat and
Bridgnorth. The next year "she went with all the Mercians to Tamworth,
and built the _burh_ there in early summer; and ere Lammas, that at
Stafford." In the two succeeding years she set up other strongholds at
Eddesbury, Warwick, Cherbury, Wardbury, and Runcorn. By 917, she found
herself strong enough to attack Derby, one of the chief cities in the
Danish confederacy of the Five Burgs, which she captured after a hard
siege. Thence she turned on Leicester, which capitulated on her