851 - Battle of Aclea

England
Vikings plundered London and Canterbury.
350 Viking ships came into the Thames and stormed Canterbury and London and put to flight Beorhtwulf, King of Mercia with his army, and then went south over the Thames to Surrey and King Aethelwulf and his son Aethelbald with the West Saxon army fought against them at Oak Field Aclea, and there made the greatest slaughter of a heathen raiding-army that we have heard tell of up to the present day, and there took the victory.
"The Anglo-Saxon Chronicle"

One of the few victories for the West Saxons in Wessex, which made the viking raids decrease for 14 years. The exact location of the Battle of Aclea has never been identified. Although the Old English Aclea could be the modern Oakley there a number of settlements with the same name. Suggested locations include the Oakley that lies some four miles to the north west of Bedford on the Great Ouse and the village of Water Oakley in Berkshire.
Linguistic evidence of Scandinavian settlement in England

Ireland
Danes captured Dublin.
Netherlands
Annales Bertiniani tells of viking pillaging in Frisia