809

Year 809 was a common year starting on Monday of the Julian calendar, the 809th year of the Common Era and Anno Domini designations, the 809th year of the 1st millennium, the 9th year of the 9th century, and the 10th and last year of the 800s decade.

Events

Spring - Siege of Serdica: Krum, ruler of the Bulgarian Empire, captures the fortress of Serdica, after a long siege. According to Byzantine sources, he massacres the garrison, sacks the city, and razes the city walls, before returning with much loot to Bulgaria. In the following years, Serdica will serve as a base for the expansion of the Bulgars to the south of the Balkans.
Europe
A Byzantine fleet lands in the Venetian Lagoon, and attacks a Frankish flotilla at Comacchio, but is defeated. Doge Obelerio degli Antenori marries a Frankish bride, Carola; she becomes the first dogaressa of Venice.
Aznar Galíndez I succeeds Aureolus, as count of Aragon. He is installed by King Louis the Pious, and remains a Frankish vassal.
A rebellion in Gharb al-Andalus is crushed by the Emirate of Córdoba.
Abbasid Caliphate
March 24 - Caliph Harun al-Rashid dies at Tus, on an expedition to put down an uprising in Khorasan. He is succeeded by his son Muhammad ibn Harun al-Amin.
Asia
Emperor Heizei becomes ill, and abdicates the throne in favor of his brother Saga, who is installed as the 52nd emperor of Japan.
Emperor Govinda III defeats his rival Nagabhata II, and obtains the submission of the Pala Empire.
By topic

Council of Aachen : Frankish bishops adopt the filioque addition in the Creed. Pope Leo III intervenes, and refuses to recognize it as valid.