Edmund II (the exact date of Edmund's birth is unclear, but it could have been no later than 993; he died 30 November 1016), usually known as Edmund Ironside, was King of England from 23 April to 30 November 1016. He was the son of King Æthelred the Unready and his first wife, Ælfgifu of York. Edmund's reign was marred by a war he had inherited from his father, his cognomen "Ironside" was given to him "because of his valour" in resisting the Danish invasion led by Cnut the Great.
Edmund was not expected to be King of England; however, by 1014 two elder brothers had died, making him the oldest male heir. His father, Æthelred, was usurped by Sweyn Forkbeard in that same year, but Sweyn died shortly thereafter, paving the way for Æthelred and his family to return to the throne, which they did but not without opposition. In the process they forced Sweyn's son, Cnut, back to Denmark, where he assembled an invasion force to re-conquer England. It would not arrive for another year.
After regaining the throne, the royal family set about strengthening its hold on the country with the assistance of Eadric Streona (Edmund's brother-in-law). People who had sided with the Danes in 1014 were punished, and some were killed. In one case, two brothers, Morcar and Sigeferth, were killed and their possessions, along with Sigferth's wife, were taken by Edmund. Edmund unofficially became the Earl of the East Midlands; however, it was against his father's wishes that he marry Ealdgyth.
Cnut returned to England in August 1015. Over the next few months, Cnut conquered most of England, and Edmund joined Æthelred to defend London, but Æthelred died on 23 April 1016, making Edmund King. It was not until the summer of 1016 that any serious fighting was done: Edmund fought five battles against the Danes, ending in his defeat on 18 October at the Battle of Assandun, after which they agreed to divide the kingdom, Edmund taking Wessex and Cnut the rest of the country. Edmund died shortly afterwards on 30 November, leaving two sons called Edward and Edmund; however, Cnut became the king of all England.