Alfred was the youngest son of King Æthelwulf of Wessex. He died in 858 while on pilgrimage when Alfred’s older brother Æthelberht was 'sub-king' of Sussex, Essex, Kent and Surrey, and his brother Æthelbald was ruling Wessex in the King’s absence. Æthelbald ruled from 855 (when King Æthelwulf had left England on his pilgrimage) to his death in 860. His brother Æthelberht then took power. He died in 865 or 866 and another of Alfred’s older brothers, Æthelred, became king. In 866 the Danes invaded Northumbria and East Anglia. The Mercian King Burgred asked Æthelred for assistance. Æthelred and Alfred lead an army to Nottingham but it was not needed. Burgred later negotiated for peace with the Danes. Three years later the Danes attacked Wessex and Burgred did not help. Æthelred and Alfred (who were 25 and 23 respectively at the time) attacked a Danish base at Reading, but failed. Æthelred died after Easter in 871 and the Witenagemot elected Alfred to the throne.

In Alfred's first year as king he waged nine battles and won only two. The first few years of his reign were ones of losses to the Danes. Alfred P. Smith¹ said that "Halfdan and other leaders in his Great Army were now defacto overlords of all England". The Danes demands for tribute forced Alfred to use church treasury funds to avoid more attacks.

In 878 his home at Chippenham was attacked and he fled to the Somerset Marshes. There he rallied an army of West Saxons and won a battle at Edington in May of the same year. After Alfred's victory the Danes promised to leave his kingdom. In October that year they moved to Cirencester in Mercia, and in late 879 or early 880 they moved again to East Anglia, where they settled.

After his victory against the Danish army, Alfred extended the burghal defenses and set up permanent garrisons within them. The extent of the defensive fortresses is detailed in the Burghal Hidage, which contains a list of the forts protecting Wessex and the number of hides needed to maintain each section of the wall. He also reorganised the army so that only half of the men were on duty at any one time. Alfred commissioned a newly designed ship and set up an aggressive policy towards Vikings in southern England. This policy allowed him to take London from the Vikings and claim in annals which would later become part of the Anglo-Saxon Chronicle, that 'all the English people that were not under subjection to the Danes submitted to him'. He gave London to his son-in-law Æthelred who was already the ruler of western Mercia. The alliance between the Mercians and the West Saxons kept the Danish army on the move between 892 and 896.

Alfred is described by his biographer Asser as a pious man who could nonetheless be ruthless and harsh when necessary. He was an educated man, who wanted his people to benefit from religious writings as he had. He translated four religious texts from Latin during his life, and made a new law code in the style of the Old Testament, which extended his and his lords' power. He founded a nunnery and a monastery, reformed coinage and opened two new mints. Michael Lapidge² claims that 'Alfred provided the springboard for his successors of the tenth century to become kings of England'. Alfred the Great died on October 26, 899, and is buried in Winchester.