15 events the sources record for this year, grouped by region.
What happened
China (10)
Li Shimin, alleging that Crown Prince Jiancheng and Qi Prince Yuanji plotted to harm him, led troops and executed them (the Xuanwu Gate Incident). (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷1 武德9年 6月)
Emperor Taizong went to the Weibian Bridge at Xianyang, sacrificed a white horse with Jieli, and made an oath; the Turks withdrew. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷2 武德9年 8月)
Prince Shimin killed Crown Prince Jiancheng and Li Yuanji, Prince of Qi; Shimin then became crown prince. (New Book of Tang (Xin Tangshu), Annals 新唐書 卷001 高祖 武德9年6月)
In 626 (Gengshen day), Shimin leads Zhangsun Wuji and others in and sets an ambush at the Xuanwu Gate. (Zizhi Tongjian (Comprehensive Mirror) 권191 626년 항)
In June 626, the gate guards and Wan Che fight a long battle; Wan Che beats the drum and attacks the enemy line, and the officers and men are greatly frightened; but Yuchi Jingde raises the heads of Jiancheng and Yuanji, the palace garrison collapses, and Wan Che flees with a few dozen riders to Zhongnan Mountain. (Zizhi Tongjian (Comprehensive Mirror) 권191 626년 항)
In August 626 (Xinsi day), Yuchi Jingde, commander of the Jingzhou march, fights the Turks at Jingyang and routs them, capturing the rear commander Ashide Wumochuo and beheading more than a thousand. (Zizhi Tongjian (Comprehensive Mirror) 권191 626년 항)
In 626 (Yiyou day), the emperor goes out west of the city, sacrifices a white horse, and swears a covenant with Xieli Khan on the Bianqiao bridge. (Zizhi Tongjian (Comprehensive Mirror) 권191 626년 항)
Japan (1)
In the fifth month of the thirty-fourth year, Soga no Umako dies and is buried at the Momohara tomb (Nihon Shoki (Chronicles of Japan) 日本書紀 卷第廿二 推古紀 34年 단락170)
An assassin sent by Cwichelm, named Eomer, tried to kill King Edwin, killed the thegn Lilla, and wounded the king. (Anglo-Saxon Chronicle Giles/Ingram 1847 A.D. 626 항 (pg657.txt 줄 1406))