856

Events

March 15 - Emperor Michael III overthrows the regency of his mother Theodora. He appoints his uncle Bardas as the de facto regent and co-ruler of the Byzantine Empire.

King Charles the Bald cedes the county of Maine to Erispoe, ruler of Brittany—this in return for an alliance against the Vikings.
King Ordoño I of Asturias is said to have begun the repopulation of the town of León in the northwest of Spain.

October 1 - King Æthelwulf of Wessex marries the 12- or 13-year-old Judith, daughter of Charles the Bald, at Verberie. She is crowned queen and anointed by Hincmar, archbishop of Reims. The marriage is a diplomatic alliance between Wessex and the West Frankish Kingdom.
Winter - Æthelwulf returns to Wessex to face a revolt by his eldest son Æthelbald, who usurps the throne. Æthelwulf agrees to give up the western part of his kingdom, in order to avoid a civil war. He keeps control over Sussex, Surrey, Essex and Kent, over which Prince Æthelberht has presided.

November - An earthquake in Corinth, Greece kills an estimated 45,000 people.
December 3 - Another earthquake strikes the Abbasid Caliphate, also killing an estimated 45,000 people.
December 22 - Another 856 [Damghan earthquake|earthquake] strikes Damghan, killing an estimated 200,000 people.