Asia

• The Byzantine emperor Theophilos
  Theophilos (emperor)
  Theophilos was the Byzantine emperor from 829 until his death in 842. He was the second emperor of the Phrygian dynasty, and the last emperor supporting iconoclasm...
  
   is heavily defeated at the Battle of Anzen
  Battle of Anzen
  The Battle of Anzen or Dazimon was fought on July 22, 838 at Anzen or Dazimon between the Byzantine Empire and the forces of the Abbasid Caliphate...
  
   by the Abbasids. Caliph al-Mu'tasim
  Al-Mu'tasim
  Abu Ishaq 'Abbas al-Mu'tasim ibn Harun was an Abbasid caliph . He succeeded his half-brother al-Ma'mun...
  
   then proceeds to capture and raze
  Sack of Amorium
  The Sack of Amorium by the Abbasid Caliphate in mid-August 838 was one of the major events in the long history of the Byzantine–Arab Wars. The Abbasid campaign was led personally by the Caliph al-Mu'tasim , in retaliation to a virtually unopposed expedition launched by the Byzantine emperor...
  
   Amorium
  Amorium
  Amorium was a city in Phrygia, Asia Minor which was founded in the Hellenistic period, flourished under the Byzantine Empire, and declined after the Arab sack of 838. Its ruins are located near the village of Hisarköy, Turkey....
  
  , the native city of the Byzantine Empire
  Byzantine Empire
  The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...
  
  's reigning Amorian dynasty.
• Discovery of a conspiracy to assassinate Caliph Mu'tasim and place his nephew Al-Abbas ibn al-Ma'mun
  Al-Abbas ibn al-Ma'mun
  Al-Abbas ibn al-Ma'mun was an Arab prince and general, the son of the Abbasid Caliph al-Ma'mun . A distinguished military leader in the Byzantine–Arab Wars, he was passed over in the succession in favour of his uncle al-Mu'tasim...
  
   on the throne. A widespread purge of the army follows, which cements the leading role of the Turkish ghilman
  Ghilman
  Ghilman Ghilman Ghilman (singular ghulam describes either young servants in paradise or slave-soldiers in the Ottoman, Mughal and Persian Empires.-Islamic Theology:...
  
  in the Abbasid military establishment.

Europe

• At Hingston Down
  Hingston Down
  Hingston Down is a hill not far from Gunnislake in Cornwall in the United Kingdom.-History:This is possibly the Hingston Down mentioned in the Anglo-Saxon Chronicle which says that in 835 Egbert king of the West Saxons defeated an army of Vikings and Cornish at Hengestdun = "Stallion Hill"...
  
  , Egbert of Wessex
  Egbert of Wessex
  Egbert was King of Wessex from 802 until his death in 839. His father was Ealhmund of Kent...
  
   beats the Danish and the West Welsh.
• The Stone of Destiny
  Stone of Scone
  The Stone of Scone , also known as the Stone of Destiny and often referred to in England as The Coronation Stone, is an oblong block of red sandstone, used for centuries in the coronation of the monarchs of Scotland and later the monarchs of England, Great Britain and the United Kingdom...
  
   is placed at Scone Palace
  Scone Palace
  Scone Palace is a Category A listed historic house at Scone, Perthshire, Scotland. It was constructed in 1808 for the Earls of Mansfield by William Atkinson...
  
  , Scotland
  Scotland
  Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
  
  .
• Rheine
  Rheine
  Rheine is a city in the district of Steinfurt in Westphalia, Germany. It is the largest city in the district and the location of Rheine Air Base.-Geography:Rheine is located on the river Ems, approx. north of Münster, approx...
  
   is founded on the Ems River.
• According to the Annals of Inisfallen
  Annals of Inisfallen
  The Annals of Inisfallen are a chronicle of the medieval history of Ireland. There are more than 2,500 entries spanning the years between AD 433 and AD 1450, but it is believed to have been written between the 12th and 15th centuries...
  
  , a royal meeting between Feidlimid mac Cremthanin
  Feidlimid mac Cremthanin
  Fedelmid mac Crimthainn was the King of Munster between 820 and 846. He was numbered as a member of the Céli Dé, an abbot of Cork Abbey and Clonfert Abbey, and possibly a bishop...
  
  , King of Cashel and Niall, King of the Southern Uí Neill and Tara at Cluain-Conaire-Tommain, results in Feidlimid becoming High-King of Ireland
  Ireland
  Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
  
  .

Births

• Al-Tabari
  Muhammad ibn Jarir al-Tabari
  Abu Ja'far Muhammad ibn Jarir al-Tabari was a prominent and influential Sunni scholar and exegete of the Qur'an from Persia...
  
  , physician, philosopher, mathematician, and astronomer
• Alfonso III of Leon
  Alfonso III of León
  Alfonso III , called the Great, was the king of León, Galicia and Asturias from 866 until his death. He was the son and successor of Ordoño I. In later sources he is the earliest to be called "Emperor of Spain"...
  
  

Deaths

• Al-Abbas ibn al-Ma'mun
  Al-Abbas ibn al-Ma'mun
  Al-Abbas ibn al-Ma'mun was an Arab prince and general, the son of the Abbasid Caliph al-Ma'mun . A distinguished military leader in the Byzantine–Arab Wars, he was passed over in the succession in favour of his uncle al-Mu'tasim...
  
  , Abbasid prince and general
• Pepin I, son of Louis the Pious, King of the Frankish Empire