The Viking Age period began with sporadic incursions and ended with full-scale invasions.
Fifty years before Harald Hardrada, the last Viking, died at Stamford Bridge, a Nordic invasion took the throne of England. This year, 2016, is the 1000th anniversary of that conquest.
Knut of Denmark was the son of Sweyn Forkbeard and grandson of Harald Bluetooth, who had managed to oust Aethelraed in 1013. His mistake then was simply that Aethelraed was exiled, not killed, and when Sweyn died the following year, he came back. Knut, whose brother Harald inherited Denmark’s crown, was elected King by the Vikings and Norsemen of Danelaw, but the English nobility chose to bring Aethelraed back from exile.
Knut, returning to Denmark, marshalled his forces and returned for invasion in 1015. Lots of battles were fought for over a year, with Aethelraed’s men led by his son Edmund Ironside.
And then, in April 1016, Aethelraed died. Edmund kept fighting, but Knut defeated him that October. Didn’t kill Edmund, but they came to an agreement, dividing England into Danelaw (Knut’s) and Wessex (Edmund’s). Edmund died a month later. Maybe it was battle-wounds, maybe it was murder. Not quite sure, but Knut became King of all England. He was crowned at Epiphany 1017.
Six months later, he married Aethelraed’s widow Emma, and he used his base in England to build a North Sea Empire, taking Denmark when his brother died in 1018 and Norway in 1028 when Olaf of Norway’s jarls deserted him and he fled the field. Olaf was killed two years later in 1030 when he attempted to reclaim his crown. Knut also laid claim to parts of Sweden – as far east as Sigtuna.
Knut died in 1035, and his Empire broke up. Within ten years, England was ruled again by the House of Wessex, by Edward the Confessor, son of Aethelraed and Emma.