The Battle of Ashdown, fought on 8th January 871 in southern England, saw the Kingdom of Wessex defeat the Great Heathen (Viking) Army. This was the first major defeat of the Viking army, which had arrived in England in 865 and had conquered several Anglo-Saxon kingdoms. While the conflict between the Wessex and the Vikings continued for several months into 871 and beyond, Ashdown demonstrated that the Viking army could be defeated, giving the English hope for future battles.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/2829/battle-of-ashdown/.