In the 860s a large Danish army, known as the "Great Heathen Army," invaded England. At its head were the brothers Ivar the Boneless, Halfdan, Bjorn Ironside, Sigurd Snake-in-the-Eye, and Ubba, sons of Ragnar Lothbrok.
According to the Anglo-Saxon Chronicles, in the fall of 865 the "Great Heathen Army" landed in East Anglia and wintered there. In the spring of the following year the Vikings, on horses derived from the local population, invaded the kingdom of Northumbria, where there was an internecine struggle for power between the co-ruler kings, brothers Aella II and Osbert.
In late 866 the Danes captured York, one of the richest trading towns in England. In 867, the Northumbrian kings Aella II and Osbert, joining their forces, decided to take York back and were defeated under the walls of the city. In the battle Aella and Osbert were killed. The Danes put their puppet Egbert I (died 873) on the royal throne in Northumbria.
According to Anglo-Saxon chronicles, in 867 the Great Army attacked the neighboring kingdom of Mercia, where the Vikings captured the city of Nottingham, which became their winter quarters.
King Burgred of Mercia (died 874) and King Ethelred I of Wessex (died 871) combined their forces and besieged Nottingham, but could not defeat the Vikings. The opponents only negotiated a temporary truce, during which the Danes replenished their forces to further conquer the island.
In 869, the Great Heathen Army descended on the kingdom of East Anglia. The Anglo-Saxon chronicles report that the Vikings encamped for the winter at Thetford, where they defeated the army of King Edmund of East Anglia, who died in battle.
According to other accounts, King Edmund was captured by the Danes and executed for refusing to worship pagan idols. According to the Anglo-Saxon chronicles, the kings Ivar the Boneless and Ubba were involved in the murder of King Edmund.
After Edmund's death and the conquest of East Anglia, Danish King Ivar the Boneless disappears from English sources. In the 870s his brother Halfdan became commander of the "Great Army" and led the invasion of the Kingdom of Wessex.
The Anglo-Saxon chronicles report that the Vikings established themselves at Reading in 871 and had nine battles with the West Anglo-Saxons. The most important of the battles was the Battle of Ashdown[en].
As a result, the Danes were forced into a truce with the new king of Wessex, Alfred the Great.
According to the Anglo-Saxon Chronicle, after the truce the Vikings retreated to London, where they camped out for the winter. In 873 the Danes moved north into Northumbria, where they crushed a rebellion against their puppet king, Egbert I. In 874 the Vikings subjugated the kingdom of Mercia.
The Vikings deposed King Burgred of Mercia and installed a puppet king, Keolwulf (874-879). "Historia Regum" reports that the "Great Army of the Gentiles" then divided into two parts.
One, led by Halfdan, marched northward against the Picts and Britons at Strathclyde. "The Ulster Annals," in 875, reports a bloody battle between the Vikings and the Picts.
According to the Anglo-Saxon Chronicles, in 876 Halfdan settled his warriors in the lands of Northumbria, where the Scandinavian kingdom of Jorvik was established.
While Halfdan fortified himself in Northumbria, a second part of the "Great Pagan Army" under King Guthrum moved southward against the kingdom of Wessex. "The Anglo-Saxon Chronicle reports that in 875 the Danes, having established themselves at Cambridge, waged hostilities against Wessex.
The following year the Danes took Wareham. King Alfred of Wessex made a new truce with the Vikings, but they broke it and captured Exeter in 877.
The approaching Viking fleet, with which Guthrum had planned to join, was forced to retreat to Mercia because of a storm. Despite this, the Anglo-Saxon Chronicle reports that many of the warriors in Guthrum's army began to settle in the northeastern part of England, later to become known as Danelagh.
In the winter of 877-878 Guthrum undertook a surprise campaign against the West Saxons. From their base at Gloucester, the Vikings invaded deep into Wessex, captured London, and stood on the River Avon to spend the winter there.
In 878 a flotilla of Vikings (23 ships) commanded by Ubba landed on the north coast of Somerset, near the mouth of the Parrett River.
At the Battle of Kinwint, the Anglo-Saxons, under the command of Odda, the Eldorman of Devon, defeated the Vikings. In this battle Ubba was killed, and the famous banner of Ragnar Lothbrok's sons with the raven was captured by the Anglo-Saxons. "The Anglo-Saxon Chronicle does not name the Viking leader by name, but he was described in it as the brother of Ivar and Halfdan.
But the twelfth-century Anglo-Norman chronicler Geoffrey Guymar, in his History of the Angles, names Ubba as the Viking commander at the Battle of Kinwint.
According to the Anglo-Saxon Chronicle, in May 878 King Alfred the Great of Wessex gathered his forces and defeated the Danish Vikings under the command of the King Guthrum at the Battle of Edington.
After his defeat, Guthrum was forced to accept the peace terms Alfred offered him. At Alfred's demand, Guthrum converted to Christianity.
East Anglia, Essex, Northumbria and eastern Mercia were left under Guthrum's control, while Alfred the Great gained Wessex, Sussex, Kent and western Mercia.