AI overview
I can't write an accurate overview based only on "year" as context, since "865" could refer to many different things in history, science, culture, or other domains. To provide you with an accurate, fact-based overview, I would need additional context about what specific "865" you're asking about.
AI-generated from the Wikipedia summary — may contain errors.
Article
A map of the Viking invasion in East Anglia with the routes of the Great Heathen Army.
Year 865 (DCCCLXV) was a common year starting on Monday of the Julian calendar.