812

By place

Byzantine Empire

• January 11 - Ex-emperor Staurakios, a son of Nikephoros I, dies of putrefaction in his wounds in a monastery. He has reigned only two months and eight days, before being exiled by senior officials in Constantinople.
• Emperor Michael I re-opens peace negotiations with the Franks, and recognizes Charlemagne as emperor of the Frankish Empire. In exchange for this recognition, Venice is returned to the Byzantine Empire.
• Byzantine–Bulgarian War: The Bulgars, led by Krum, ruler of the Bulgarian Empire, launch an invasion against the Byzantines. They capture the fortress cities of Develt and Mesembria, near the Black Sea.

  Europe

• Charlemagne conquers Catalonia, as far south as the River Ebro and the Balearic Islands. The counties come under the rule of Bera, count of Barcelona. He signs a three-year peace treaty with the Emirate of Córdoba.
• Charlemagne issues the Capitulare de villis, concerning the rights of a feudal landholder and the services owed by his dependents. It also contains the names of some 89 plants, of which most are used medically.
• The Republic of Amalfi sends galleys to support the Byzantine general of Sicily, Gregorio, against the Aghlabid invaders. It is one of the earliest evidences of the independence of the city.

  Britain

• King Sigered of Essex is reduced to the rank of duke, by his Mercian overlords.

  Abbasid Caliphate

• Fourth Fitna: Forces loyal to al-Ma'mun, led by Tahir ibn Husayn, blockade Baghdad, which is loyal to al-Ma'mun's brother, Caliph al-Amin, and begin the year-long Siege of Baghdad.

  China

• The Chinese government takes over the issuing of paper bank drafts, the ancestor of paper money.