Æthelflæd, Lady of the Mercians (c. 870 – 12 June 918), ruled Mercia in the English Midlands from 911 until her death. She was the eldest daughter of Alfred the Great, king of Anglo-Saxon Wessex, and his wife Ealhswith. Æthelflæd was born around 870 at the height of the Viking invasions of England. By 878 most of England was under Danish Viking rule, East Anglia and Northumbria having been conquered, and Mercia partitioned between the English and the Vikings, but in that year Alfred won a crucial victory at the Battle of Edington. Soon afterwards the English-controlled western half of Mercia came under the rule of Æthelred, Lord of the Mercians, who accepted Alfred's overlordship. Alfred adopted the title King of the Anglo-Saxons, claiming to rule all English people not living in areas under Viking control. In the mid-880s, Alfred sealed the strategic alliance between the surviving English kingdoms by marrying Æthelflæd to Æthelred.