870

By place

Europe

• August 8 - Treaty of Meerssen: King Louis the German forces his half-brother Charles the Bald to accept a peace treaty, which partitions the Middle Frankish Kingdom into two larger east and west divisions. Louis receives most of Austrasia, and Charles receives territory in Lower Burgundy. However, large parts of the Frisian coast are under Viking control.
• Charles the Bald marries Richilde of Provence, after the death of his first wife, Ermentrude of Orleans. He intends to secure his rule in Lotharingia through the powerful Bosonid family and the connection to Teutberga, widow-queen of Lothair II.
• Rastislav, ruler of Great Moravia, dies in prison after he is condemned to death for treason, by Louis the German. He is succeeded by his nephew Svatopluk I, who becomes a vassal of the East Frankish Kingdom.
• Bořivoj I, duke of Bohemia, makes Levý Hradec his residence. Around this time Prague Castle is founded.
• Wilfred the Hairy, a Frankish nobleman, becomes count of Urgell and Cerdanya.

  Britain

• Autumn - The Great Heathen Army, led by Ivar the Boneless and Ubba, invades East Anglia and plunders Peterborough. King Edmund the Martyr is captured, tortured, beaten and used for archery practice.
• The Danes, led by Ivar the Boneless and King Olaf of the Dublin Vikings, besiege Dumbarton in Scotland, the capital of King Artgal of Stratchlyde. After a siege of four months, the citadel is captured and destroyed.
• The Danes, led by Halfdan Ragnarsson and Bagsecg, invade Wessex and take the royal estate at Reading, which Halfdan makes his headquarters. A naval Viking contingent sails up the Thames River.
• December 31 - Battle of Englefield: The Vikings clash with ealdorman Æthelwulf of Berkshire. The invaders are driven back to Reading; many of the Danes are killed.

  Abbasid Caliphate

• January 29 - Anarchy at Samarra: The rebel Salih ibn Wasif is hunted down and killed in Abbasid Samarra by troops of Musa ibn Bugha al-Kabir.
• June 21 - Caliph Al-Muhtadi is deposed and killed by the Turks, after a brief reign. He is succeeded by Al-Mu'tamid as ruler of the Abbasid Caliphate, who moves his court to Baghdad. End of the Anarchy at Samarra.
• Byzantine–Arab War: A Muslim expeditionary force, led by Halaf al-Hadim, Arab governor of Sicily, conquers Malta. He is welcomed by the local Christian inhabitants as liberator of the agonizing Byzantine yoke. The Muslims sign a treaty with the Christians to live in peace after liberating the island from the Byzantines.
• The Zanj Rebellion: The Zanj capture the Abbasid seaport of Al-Ubullah at the Persian Gulf, and cut off communications with Basra.

  By topic

Religion

• February 28 - The Fourth Council of Constantinople ends. The Bulgarians are granted an autocephalous archbishopric. with its seat in the capital of Pliska.