Li Shimin (pictured) led his forces to assassinate his rival brothers in a coup for the imperial throne of Tang China. Xuanwu Gate Incident: The Xuanwu Gate Incident was a palace coup for the throne of the Tang dynasty on 2 July 626. During the incident, Prince Li Shimin and his followers assassinated his brothers Crown Prince Li Jiancheng and Prince Li Yuanji. July 2, 626. Wiki link