863

By place

Byzantine Empire

• September 3 - Battle of Lalakaon: A Byzantine army confronts an invasion by Muslim forces, led by Umar al-Aqta, Emir of Malatya. The Muslims raid deep into Byzantine territory, reaching the Black Sea coast at the port city of Amisos. Petronas annihilates the Arabs near the River Lalakaon, in Paphlagonia.

  Europe

• January 25 - Emperor Louis II claims Provence, after the death of his brother Charles. King Lothair II receives Lower Burgundy and a part of the Jura Mountains.
• King Louis the German suppresses the revolt of his son Carloman, who wants a partition of the East Frankish Kingdom.
• Viking raiders again plunder Dorestad, a Frankish port on the mouth of the river Rhine. It thereafter disappears from the chronicles.
• Danish Vikings loot along the Rhine. They settle on an island close by Cologne, but are driven off by the combined forces of Lothair II and the Saxons.
• The Christianization of Kievan Rus begins, ceasing the 63-year-long dominance of the Rus' Khaganate.
• The first written record is made of Smolensk.

  Britain

• King Osberht of Northumbria engages in a dispute for royal power, with a rival claimant named Ælla. After Osberht is replaced, Ælla wields power in Northumbria, but the civil war continues.

  Asia

• Duan Chengshi, Chinese author and scholar, writes about the Chinese maritime trade and the Arab-run slave trade in East Africa.

  By topic

Religion

• Pope Nicholas I sends archbishops Gunther and Theotgaud to a synod of Metz, which confirms the permission given to King Lothair II of Lotharingia to remarry.
• The Byzantine missionaries Cyril and Methodius arrive with a few disciples in Moravia, by request of Prince Rastislav.
• Nicholas I excommunicates Patriarch Photios I of Constantinople.