From 'A History of the British Nation' by AD Innes, 1912
Then for a brief moment appeared on the scene a national hero, Edmund Ironside, AEthelred's son, a prince who seemed fitted to revive the older glories of his house. While the young Knut was making ready to enforce his claim, AEthelred returned, showing no sign of any intention of changing his old evil courses.
Where AEthelred's direct influence could be felt Edmund could do nothing; but the North was ready to follow a bold leader, having before yielded in sheer despair over AEthelred's incompetence. The South was helpless. AEthelred's death in 1016 came too late.
The Battle of Assandun
Edmund made a splendid stand against Knut; but sheer treachery brought about his defeat at the battle of Assandun. Even then Knut realised that with such an antagonist victory was by no means certain, and a treaty was made dividing the kingdom on the old lines of the treaty of Wedmore, though the southern portion of the Danelagh went to Edmund's share. But the heroic prince was not destined to be a second Alfred.
The treaty had hardly been concluded when he died, being then but five and twenty, while his rival was only twenty-one. It was perhaps inevitable that Edmund's death should have been attributed to foul play on the part of Knut, who succeeded to the entire kingdom without opposition.