878

By place

Britain

• January 6 - King Alfred the Great is surprised by a Viking attack at Chippenham. He is forced to flee, with his family, into the Somerset Levels for safety. From his headquarters at Athelney, Alfred wages a guerrilla war against the Vikings.
• May - Battle of Edington: Supported by all the levies of Somerset, Wiltshire and Hampshire, Alfred the Great decisively defeats the main body of Danish Vikings, led by King Guthrum, at present-day Edington.
• Treaty of Wedmore: Guthrum agrees to a peace treaty and is baptised, taking the name of Aethelstan. England is divided between Wessex in the south, and the Vikings in the Danelaw up north. Guthrum returns to East Anglia.
• Battle of Cynwit: Viking raiders, led by Ubba Ragnarsson, land on the coast at Combwich with 23 ships, and besiege a hillfort at Cannington. Ealdorman Odda launches a surprise attack, and kills Ubba in battle.
• King Rhodri the Great of Gwynedd, Powys and Seisyllwg, returns to his kingdoms, but is killed fighting the Mercians of King Ceolwulf II. His kingdoms are divided amongst his three sons: Anarawd, Merfyn and Cadell.
• King Áed I of Scotland is killed in battle, by his rival Giric mac Dúngal. Giric becomes king of the Picts, and allies himself with Eochaid. The two rule all of Alba together as joint-kings.

  Arabian Empire

• May 21 - Siege of Syracuse: The Aghlabids capture the Byzantine fortress city of Syracuse, after a nine-month siege. Most of the population is massacred by the Arabs.
• Zanj Rebellion: The Zanj in Mesopotamia seize Wasit, and establish a presence in the Persian province of Khuzestan.
• King Alfonso III of Asturias conquers the city of Coimbra, which is under Umayyad reign.

  By topic

Religion

• April 16 - The city of Belgrade is first mentioned in a papal letter to Boris I, ruler of the Bulgarian Empire.
• September 7 - Pope John VIII crowns Louis the Stammerer as king of the West Frankish Kingdom, in the cathedral at Troyes.
• The excommunication of the later pope Formosus is lifted, after he has promised never to return to Rome.