846

By place

Byzantine Empire

• Byzantine–Bulgarian War: The Bulgarians violate the peace treaty, and invade Macedonia along the River Struma. The cities of Serres and Philippi are devastated.

Europe

• Summer - Breton forces under Nominoe occupy the Frankish cities of Nantes and Rennes. He makes raids in Anjou and threatens Bayeux. King Charles the Bald recognizes him as duke of Brittany.
• Prince Pribina becomes a vassal of the Frankish Empire. King Louis the German grants him land near Lake Balaton. He establishes Blatnohrad, capital of Balaton Principality.
• 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.
• Muslim forces attempt to raid Rome but only pillage the countryside around the city before being beaten back by Duke Guy I of Spoleto. In the aftermath, Pope Leo IV starts walling the area around the Vatican hill, creating the Leonine City.
• The Mozarabs, Iberian Christians who live under Moorish rule, try to repopulate León in Al-Andalus. The city is recaptured by the Muslim Arabs.

Britain

• King Æthelred II of Northumbria sends military assistance to the Picts, in their fight against the invading Scots.

Ireland

• Máel Sechnaill mac Máele Ruanaid becomes the first High King of Ireland.

Arabian Empire

• A Saracen Arab expeditionary force from Africa, consisting of 11,000 men and 500 horses, raid the outskirts of Rome, sacking the basilicas of Old St. Peter's and Basilica of [Saint Paul Outside the Walls|St. Paul's Outside the Walls].

Asia

• April 22 - Emperor Wu Zong dies after a 6-year reign. He is succeeded by his uncle Xuān Zong, as Chinese ruler of the Tang Dynasty.
• Chang Pogo, a powerful maritime hegemon of Silla, is assassinated by aristocratic elements at his garrison headquarters by Yŏm Chang.