Æthelflæd was the was the eldest child of a great king, Alfred of Wessex. She jointly ruled Mercia with her husband, leading the battle against the Danes in the Midlands and the North and working to unite England. After her husband’s death in 911, she became the sole ruler of Mercia and became known as ‘The Lady of the Mercians’.
She personally led expeditions against the Vikings. The threat that the Danes would take over all of Mercia and Wessex was very real and, without her input, all could have been lost. The military alliance between Æthelflæd and her brother King Edward was an outstanding success.
Like her father, she proved to be an objective and discerning leader, raising fortifications, refortifying crumbling Roman strongholds and building a number of fortified towns along the border. The association of Æthelflæd and her brother Edward saw the Saxon forces push further into Danish-held territory, until little of Mercia remained under Viking control.
She was not only a great warrior but also a clever tactician and negotiator. Formidable and warrior-like but just and fair, she won the admiration and respect of the people of Wessex and Mercia. Both English and Danes mourned her death.
All info from this site > http://historysheroes.e2bn.org/hero/whowerethey/4292