After An Lushan Rebellion, the Tang Dynasty turned from prosperity to decline. Local military governors exercised undisputed authority, controlling the best troops in the world. Li Chun, Emperor Xianzong of the Tang Dynasty, ascended the throne in turbulence. He intended to restore the imperial power and began to weaken the separatist forces in a planned and orderly way. At that time, the military governors of three towns in Hebei Povince, namely Youzhou, Chengde and Weibo, were the most domineering and became the primary target of Xianzong. Kong Konger and Nie Yinniang, military officers of Weibo, were also deeply involved and unable to extricate themselves. The contradiction between military governors and the imperial court intensified day by day. With frequent battles, rangers run amuck. In 815, Xianzong's attack on Huaixi came at a critical moment. Prime Minister Wu Yuanheng was assassinated on the way to the court, becoming the first prime minister to be assassinated in the street. His horse ran to the Jianfu Gate of Daming Palace on its own, mysteriously lingering. All the officials were frightened, Xianzong dared not to go to court, sitting in Yanying Hall in tears. The atmosphere of terror quietly covered the whole Chang'an City. Bai Juyi, accompanying the Crown Prince in his studies, submitted a written statement the Emperor. He advocated that the killers and those behind them be hunted down, but he was immediately demoted to Jiangzhou Sima. The truth was difficult to be found...
