Li Siyuan
Gao was still serving under Li Siyuan in 926, when the Later Tang realm was overrun with mutinies in light of Emperor Zhuangzong's recent killing of major generals Guo Chongtao and Zhu Youqian without justification. When Li Siyuan was sent to combat mutineers at Yedu (鄴都, in modern Handan, Hebei), according to traditional accounts, his own soldiers mutinied and forced him to join the Yedu mutineers. Subsequently, he tried to send a number of officers, including Gao, to nearby Li Shaorong, to try to get Li Shaorong to join him in jointly acting against the mutineers, but Li Shaorong, suspecting Li Siyuan's intentions, did not respond, and subsequently reported to Emperor Zhuangzong that Li Siyuan had joined the mutiny. Unable to show himself to be still faithful to Emperor Zhuangzong, Li Siyuan headed south toward the capital Luoyang, where Emperor Zhuangzong was then killed in a mutiny before Li Siyuan reached there. When Li Siyuan arrived, he declared himself regent, and later emperor (as Emperor Mingzong).