In 878, the Great Heathen Army struck Anglo-Saxon England with its usual fury. By this point, the Vikings controlled much of England. King Alfred emerged from hiding to defend his kingdom. At Ethandun, he inflicted a decisive defeat on the heathens. The Vikings retreated, Alfred saved his kingdom, and the two sides partitioned England.
Viking raids on England became a regular event following the attack on Lindisfarne in 793 A.D. The pressure escalated with the arrival of the Great Heathen Army in 865. The army reflected an alliance between a number of Viking warriors from Norway, Denmark, and Sweden. Anglo Saxon resistance disintegrated under the Northmen’s ferocity. With little to fear, the chieftain Guthrum began attacking Wessex in 875. Three years later, the Vikings controlled the east and England’s last hope sought refuge in the Somerset marsh.
While the Vikings waited for the English to pay extortion money, King Alfred followed the Norse army. In January 878, the impatient Vikings struck the Anglo Saxon forces inflicting a hideous defeat at Chippenham. A humiliated Alfred fled with the survivors. Sometime after the so-called Twelfth Night attack, Alfred spent several months preparing and skirmishing. He called for all able bodied men to rally to his flag, moved to Ethandun at modern day Edington, and awaited Guthrum’s force. Sometime in May 878, the two armies met with Alfred inflicting a “great slaughter” upon Guthrum. The Vikings fled to a nearby fortress, but it proved no refuge. The Anglo-Saxons removed all food sources from the countryside and simply waited for the surrender.
It seems as though Alfred’s force greatly outnumbered Guthrum’s. A storm decimated a Viking fleet en route to England. Additionally, other Norse warlords refused to join Guthrum’s raid. Plus, some Vikings decided to settle the land and retire from fighting. As a result, Guthrum’s Great Heathen Army may have been severely diminished for the attack. Alfred used his advantage in inflicting a decisive defeat on the Vikings.
As part of the Treaty of Wedmore, Guthrum was baptized as a Christian and forced to flee Wessex. His army abandoned Chippenham and settled with their king in East Anglia. Essentially, Alfred split England with the Vikings. Despite the treaty, fighting continued for years. Alfred created the English navy and developed a system of defensive fortifications to combat the raiders. Eventually, the Vikings looked to raid elsewhere rather than tangle with Alfred.