Though Wessex managed to contain the Vikings by defeating them at Ashdown in 871, a second invading army landed, leaving the Saxons on a defensive footing. At much the same time, Æthelred, king of Wessex died and was succeeded by his younger brother Alfred. Alfred was immediately confronted with the task of defending Wessex against the Danes. He spent the first five years of his reign paying the invaders off. In 878, Alfred's forces were overwhelmed at Chippenham in a surprise attack.

It was only now, with the independence of Wessex hanging by a thread, that Alfred emerged as a great king. In May 878 he led a force that defeated the Danes at Edington. The victory was so complete that the Danish leader, Guthrum, was forced to accept Christian baptism and withdraw from Mercia. Alfred then set about strengthening the defences of Wessex, building a new navy—60 vessels strong. Alfred's success bought Wessex and Mercia years of peace and sparked economic recovery in previously ravaged areas.

Alfred's success was sustained by his son Edward, whose decisive victories over the Danes in East Anglia in 910 and 911 were followed by a crushing victory at Tempsford in 917. These military gains allowed Edward to fully incorporate Mercia into his kingdom and add East Anglia to his conquests. Edward then set about reinforcing his northern borders against the Danish kingdom of Northumbria. Edward's rapid conquest of the English kingdoms meant Wessex received homage from those that remained, including Gwynedd in Wales and Scotland. His dominance was reinforced by his son Æthelstan, who extended the borders of Wessex northward, in 927 conquering the Kingdom of York and leading a land and naval invasion of Scotland. These conquests led to his adopting the title 'King of the English' for the first time.

The dominance and independence of England was maintained by the kings that followed. It was not until 978 and the accession of Æthelred the Unready that the Danish threat resurfaced.