14 events the sources record for this year, grouped by region.
What happened
China (5)
Emperor Muzong died, and the next day the crown prince Li Tan (Jingzong) ascended the throne before the bier. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷17上 長慶4年 1月)
Zhang Shao and more than a hundred others reached Youyin Gate, killed the gatekeeper, entered Qingsi Hall, climbed the throne and ate food there. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷17上 長慶4年)
Fifty-four Silla people, including Sin Ryang, Kim Gwi, Ha Ryang and Su Baek, are settled in Mutsu province; under the law they are exempted from labor service and allotted kubunden land from public jōden fields. (Nihon Kōki (Later Chronicles of Japan) 日本後紀 卷32)
Retired Emperor Heijō is buried at the Yōryū mausoleum. The compilers remark that he had a broad mind but was jealous, and that at the start of his reign his punishment of his brothers and their mothers was excessively severe. (Nihon Kōki (Later Chronicles of Japan) 日本後紀 卷32)
Southeast Asia (1)
Li Yuanjia moved the city to its present site, claiming there was reverse water at the city gate. (Đại Việt sử ký toàn thư 外紀卷之五 「甲辰冬十一月，李元嘉以城門有逆水」)
Southern Europe (1)
Pope Paschal dies and Eugenius is consecrated; the emperor sends Lothair to Rome after mid-August to settle matters with the new pope and the Romans. Lothair is received by Eugenius and restores order in Rome (Royal Frankish Annals ARF a.824, Kurze 1895 p.166)
Western Europe (4)
When the Bulgar king sends envoys with a letter asking for peace, the emperor, calling it unprecedented, sends Makelmus of Bavaria to the Bulgar king to find out the situation (Royal Frankish Annals ARF a.824, Kurze 1895 p.164)
Counts Ebolus and Ashinarius go to Pamplona with the Vascon army, and on their way back are ambushed at the Pyrenees crest through the betrayal of the mountain men; the army is nearly annihilated. Ebolus is sent to Córdoba, while Ashinarius is released because he is a kinsman (Royal Frankish Annals ARF a.824, Kurze 1895 p.166)
Because of famine, the Britannia expedition is postponed to early autumn; the emperor gathers all the army and comes to Redonas on the Britannia border, divides his army into three, giving two parts to his sons Pippin and Ludovicus, and enters Britannia himself, devastating it with fire and sword. It takes over 40 days; he takes hostages and returns (Royal Frankish Annals ARF a.824, Kurze 1895 p.165)
Having finished the expedition, the emperor returns to Rouen on November 17, where his wife had asked him to wait, and receives the envoys of Emperor Michael of Constantinople and Patriarch Fortunatus (Royal Frankish Annals ARF a.824, Kurze 1895 p.165)