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The 840s

250 sourced entries across 10 years, inside the 9th century. Each year below opens its own page; the lines under it are that year’s highest-ranked entries.

840 CE34 entries

  • February 10 – Chinese Tang dynasty Emperor Wenzong (Li Ang) dies after a 13-year reign. Through the intervention of his powerful palace eunuchs, he is succeeded by his brother Wuzong.
  • June 20 – Louis the Pious, Emperor of the Romans and King of the Franks, falls ill and dies at his hunting lodge, on an island in the Rhine, near the Ingelheim Imperial Palace in Francia, while suppressing a revolt. He proclaims his eldest son Lothair I as his successor as Emperor. Lothair tries to seize all the territories of his late grandfather Charlemagne. Louis' son by his second wife, Charles, 17, becomes King of the Franks, and joins with his half-brother Louis the German in resisting Lothair.
  • The Yenisei Kirghiz settle along the Yenisei River, and sack with a force of around 80,000 horsemen the Uyghur capital, Ordu-Baliq (driving the Uyghurs out of Mongolia). This ends the Uyghur Khaganate.

841 CE26 entries

  • June 25 – Battle of Fontenay: Frankish forces of Emperor Lothair I, and his nephew Pepin II of Aquitaine, are defeated by allied forces of King Louis the German, and his half-brother Charles the Bald, at Fontenoy (Eastern France), in a civil war among the three surviving sons of the former emperor Louis the Pious. A total of 40,000 men are killed, including the Frankish nobles Gerard of Auvergne and Ricwin of Nantes, fighting on the side of Charles.
  • December 17 – Comet X/841 Y1 is first sighted in Chang'an by the Japanese monk Ennin.
  • A pro-Umayyad rebellion, led by al-Mubarqa in Palestine, breaks out against caliph al-Mu'tasim of the Abbasid Caliphate (ending in 842).

842 CE24 entries

  • January 5 – Caliph Al-Mu'tasim dies at Samarra (modern Iraq), after an eight year reign. He is succeeded by his son Al-Wathiq, as ruler of the Abbasid Caliphate.
  • February 14 – Oaths of Strasbourg: King Louis the German, ruler of East Francia, and his half-brother Charles the Bald, ruler of West Francia, meet with their armies at Strasbourg. They agree to swear allegiance (recorded in vernacular languages) to each other, and to support each other against their brother Lothair I (nominal emperor of all the Frankish kingdoms and the Holy Roman Empire).
  • February 19 – The Medieval Iconoclastic Controversy ends, as a council in Constantinople formally reinstates the veneration of icons in the churches.

843 CE21 entries

  • March 11 – Feast of Orthodoxy – Official end of Iconoclasm: Empress Theodora II restores the veneration of icons in the Orthodox churches in the Byzantine Empire.
  • May 24 – Battle of Blain: Breton forces under Erispoe, count of Vannes, defeat the Franks led by Renaud d'Herbauges, near the town of Messac, at the River Vilaine. This battle marks a Breton war between Charles the Bald and Nominoe, duke of Brittany.
  • Al-Andalus: The city of Zaragossa rises against the Umayyad Emirate of Córdoba in modern-day Spain.

844 CE25 entries

  • January 25 – Pope Gregory IV dies after a 16-year reign, in which he has supported the Frankish policy of late emperor Louis the Pious, and established the observance of All Saints' Day. He is succeeded by Sergius II, as the 102nd pope of Rome. Sergius imprisons the antipope John VIII, and is elected by popular acclamation.
  • June 15 – Louis II, eldest son of Emperor Lothair I, is crowned king at Rome by Pope Sergius II, and becomes co-ruler of Middle Francia, and over Lombardy, Friuli, and Tuscany in Italy.
  • September 25–November 11 or 17 – Viking raid on Seville (844): Vikings arrive in Seville by the Guadalquivir, taking the city on October 1 or 3 and pillaging it; but are expelled by forces of the Emirate of Córdoba.

845 CE23 entries

  • March 6 – 42 captured Byzantine officials from Amorium are executed at Samarra, then the capital of the Abbasid Caliphate, after they repeatedly refuse attempts to convert them to Islam.
  • November 22 – Battle of Ballon: Frankish forces (3,000 men) led by Charles the Bald are defeated by Nominoe, count of Vannes, near Redon, Ille-et-Vilaine. After the battle, Brittany becomes a regnum 'kingdom' within the Frankish Empire.
  • John Scotus Eriugena, Irish theologian, travels to France and takes over the Palatine Academy in Paris, at the invitation of Charles the Bald (approximate date).

846 CE30 entries

  • April 22 – Emperor Wu Zong (Li Chan) dies after a 6-year reign. He is succeeded by his uncle Xuān Zong, as Chinese ruler of the Tang Dynasty.
  • Frankish forces led by Louis the German invade Moravia. They encounter little resistance, and depose King Mojmir I from the throne. His relative, Rastislav, is set up as the new client ruler.
  • Prince Pribina becomes a vassal of the Frankish Empire. King Louis the German grants him land near Lake Balaton (modern Hungary). He establishes Blatnohrad, capital of Balaton Principality.

847 CE29 entries

  • January 24 – Pope Sergius II dies of gout after a 3-year reign.
  • April 10 – Leo IV is consecrated 103rd pope of Rome (where he was born c.790). Because of the sense of urgency driven by the previous year's Arab raid against Rome, he is consecrated without waiting for the consent of the Holy Roman Emperor. He will reign until 855.
  • August 10 – Abbasid Caliph Al-Wathiq dies of dropsy after a five-year reign. He is succeeded by his brother al-Mutawakkil.

848 CE20 entries

  • Pope Leo IV builds (on the opposite of the Tiber River) the Leonine City, a fortified three-kilometre wall that encircles the Vatican Hill and Borgo, to defend Rome.
  • Frankish forces under Count (comté) William of Septimania assume authority over the counties of Barcelona and Empúries (modern Spain).
  • The Saracens conquer Ragusa (Sicily), after its Byzantine garrison is forced by severe famine to surrender. The city and its castle are razed to the ground.

849 CE18 entries

  • In the Chinese capital city of Chang'an, an imperial prince is impeached during the Tang Dynasty from his position by officials at court, for erecting a building that obstructs a street in the northwesternmost ward in South Central Chang'an.
  • King Pyinbya of Burma founds the city of Bagan, located in the Mandalay Region, and fortifies it with walls.
  • Frankish forces under King Charles the Bald invade southern France, and conquer the territory of Toulouse. He appoints Fredelo as count (comté) of Toulouse, who founds the Rouergue dynasty. Aquitaine is submitted to the West Frankish Kingdom.