14 events the sources record for this year, grouped by region.
What happened
China (9)
Li Guangyan defeated Wu Yuanji's thirty-thousand men at Yancheng and seized a thousand horses and thirty thousand suits of armor. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷15 元和12年 4月)
Li Su captured Caizhou; Wu Yuanji was executed in the eleventh month, pacifying Huaixi. (New Book of Tang (Xin Tangshu), Annals 新唐書 卷007 德宗·順宗·憲宗 元和12年10月)
The commanders of Yancheng, Dong Changling and Deng Huaijin, surrender, and Li Guangyan enters the city. (Zizhi Tongjian (Comprehensive Mirror) 資治通鑑 卷240)
Emperor Xianzong receives the captives at Xing'an Gate, and Wu Yuanji is beheaded beneath the Duliu. (Zizhi Tongjian (Comprehensive Mirror) 資治通鑑 卷240)
Japan (1)
Report from Mutsu: 61 rebel prisoners, including Kimiyakōbe no Oyashibe, were all captured. Because he requested to stay below the castle while summoning his wife and children, permission was granted. (Nihon Kōki (Later Chronicles of Japan) 日本後紀 卷26)
Western Europe (4)
Envoys of Abdirraman, son of the Saracen king Abulaz of Zaragoza, come to ask for peace; they are received at Compiègne and ordered to go to Aachen first. After being detained for three months they are sent back. Envoys of Emperor Leo of Constantinople also come to Aachen on the Dalmatian question (Royal Frankish Annals ARF a.817, Kurze 1895 p.145)
At the June assembly at Aachen the emperor crowns his eldest son Lothair, making him co-emperor and a name of the realm, and installs his other two sons as kings of Aquitaine and Bavaria. Earlier, on Maundy Thursday, a wooden gallery collapsed and he suffered slight injuries but soon recovered (Royal Frankish Annals ARF a.817, Kurze 1895 p.146)
Slaomir, angered at the order to share royal power with Ceadragus, starts an Abodrite revolt and allies with Godofrid's sons. Their fleet sails up the Elbe to Esesfeld castle and devastates the bank of the Stura, but they give up attacking the castle and withdraw (Royal Frankish Annals ARF a.817, Kurze 1895 p.147)
News that his nephew Bernard, king of Italy, plots rebellion by blocking the Alpine passes makes the emperor hurry into Italy with a great army; in December at Cavilonum Bernard surrenders, and his accomplices confess everything (Royal Frankish Annals ARF a.817, Kurze 1895 p.147)