There was some discussion earlier in this thread about Aethelflaed, the Lady of Mercia, and her place in history. The purpose of this post is to give a brief look at what her accomplishments were.

Source: Women Warriors in Ancient History

A daughter of Alfred the Great, King of Wessex, Aethelflaed was married to Aethelred, King of Mercia. Mercia and Wessex were adjoining Saxon kingdoms at a time when the Saxons in Britain were threatened by Danish invaders. After Alfred's death in 899 A.D., Aethelflaed's brother Edward succeeded to the kingship in Wessex. In 911 A.D., Aethelred died, and Aethelflaed became queen of the Mercians.

Coordinating their efforts, the sister and brother began a new strategy against the Danes, building a chain of fortifications across southern and midland Britain. In 916 A.D., the Welsh raided, and in a counter-attack, Aethelflaed captured a Welsh king's wife and 33 members of his court, leading to the Welsh king's submission to her authority.

The next year Danish war-bands raided Mercia, and Aethelflaed and Edward planned a coordinated attack into Danish territory. Edward led an attack on Danish forts and forced their submission in Northampton and Huntingdon. In East Anglia, and Essex, the Danish army swore allegiance to Edward. Meanwhile, Aethelflaed led her army against Derby, taking it without a siege. She then moved on to Leicester and York, getting pledges of loyalty from both.

As she moved her troops toward the remaining Danish forts, she became sick and died, in 918 A.D., at the height of her success. Edward took control of her armies and conquered the last of the Danes. Aethelflaed's strategy and military support made the final victory for the Saxons possible.