Ecgfrith (c. 645 May 20, 685) was the King of Northumbria from 670 until his death. He ruled over Northumbria when it was at the height of its power, but his reign ended with a disastrous defeat in which he lost his life. Ecgfrith was the son of his predecessor as king, Oswiu of Northumbria. Bede tells us, in his Historia ecclesiastica gentis Anglorum, that Ecgfrith was held as a hostage "at the court of Queen Cynwise in the province of the Mercians" at the time of Penda of Mercia's invasion of Northumbria in 654 or 655. Penda was, however, defeated and killed by the Northumbrians under Oswiu in the Battle of Winwaed, a victory which greatly enhanced Northumbrian power. Ecgfrith was made king of Deira, a sub-kingdom of Northumbria, in 664, and he became king of Northumbria following his father's death on February 15, 670. He had married Æthelthryth, the daughter of Anna of East Anglia, in 660; however, she took the veil shortly after Ecgfrith's accession, a step which possibly led to his long quarrel with Wilfrid, the Archbishop of York. Ecgfrith married a second wife, Eormenburg, before 678, the year in which he expelled Wilfrid from his kingdom.