As a result of the dishonorable death of the legendary Viking king Ragnar Lothbrok by the hands of king Aella of Northumbria, his sons had amassed an army, seeking revenge. They waged a war on the Anglo-Saxon Heptarchy kingdoms in England, thus ushering in an era of pillage, rape, bloodshed as well as seeing the immigration of Viking settlers on the English Isles and Ireland. Note that the Anglo-Saxons refer to every Nord Viking as a Dane, not to confuse them all being from historical Denmark, as Vikings were from all over Scandinavia.
Great Heathen Army:
This was an army not of traditional definition, rather a coalition of armies and raiding parties that were led by Ivar the Boneless alongside his half brothers Sigurd Snake in the Eye, Ubba, Halfdan Ragnarsson and Bjorn Ironside, who, together with other Viking jarls landed off the eastern shores of the Kingdom of East Anglia and begun their vendetta against the Englishmen in 865 A.D.
The size and exact numbers of men as well as ships brought by the Vikings is debatable, but it is certain that the mere sight of them had brought king Edmund of East Anglia to surrender immediately and give provisions and horses to the Vikings in exchange for peace,as well as allowing them to erect settlements and begin owning land. Wintering out in East Anglia, the army began its march northward toward the Kingdom of Northumbria by the end of 866 A.D. They had managed to seize the city of York, while the Northumbrians had payed the Danegeld, or Danish tax in 867 A.D. They failed to halt the pillaging of the Vikings. They lost a battle by being encircled and forced to surrender their king Aella, who had begun the mess the Englishmen found themselves into.
Aella was considered guilty by the Vikings of dishonorable killing and had the blood eagle punishment judged upon him. With that, he prompted the Vikings of leaving a puppet leader in their passing and setting sights on the Kingdom of Mercia. Capturing the town of Nottingham, the Vikings had then successfully defended against the combined forces of the English kingdoms of Mercia and Wessex, who were led by kings Burgred and king Aethelherd respectfully. Coming to mutual agreement after a truce, they were forced to pay the Danegeld that drove the Vikings away to York in the autumn of 868. They stayed there until the next year, reorganizing their leadership and gathering their strength. It is during this period that a change in the leadership occurred, as most of the half brothers began to split from their positions in their army – some settled down peacefully, while others sought riches in different lands leaving Halfdan to become the leader of the Great Heathen Army accompanied by his brother Ubba. The army had returned to East Anglia in the winter of 869-70 where they waited out the harsh weather in Thetford and had fought the army of East Anglia, which lost and had its king Edmund captured. He had the blood eagle judged upon him for treason and first became a martyr, but later a saint for his valiant effort against the Vikings. With the addition of the Great Summer Army that came from Scandinavia led by king Bagsecg in 871 A.D., the Vikings turned their attention once more to the Kingdom of Wessex, but were repelled by the brother of king Aethelred in the battle of Ashdown that took place in January 8th 871 A.D.
Alfred the Great
He later assumed the kingdom and became known as Alfred the Great. The Great Heathen army then returned to London where it stayed during the winter. Their attention was caught by the Kingdom of Northumbria. Setting up their winter quarters in the town of Torksey in the Kingdom of Lindsey in 872 – 873 A.D, they were once more payed in Danegeld to be kept out by the Kingdom of Mercia by the end of 873, where they wintered in Repton, Derbyshire. They had managed to conquer the Kingdom of Mercia in the following year of 874 A.D. establishing once more a puppet king to govern the lands, after they had forced the king Burgred in exile. After splitting England in two parts, east and west, Halfdan led his army northward of Northrumbia to wage war against the Picts and the Britons of Strathclyde in 875 A.D., returning the next year in 876 A.D, thus sharing the land between the Viking’s army. They settled peacefully, enacting the Danelaw and ending the Great Heathen Army.