Wang Chengzong
In 809, one of the key military governors ("Jiedushi") who had been ruling their circuits in a "de facto" independent manner — Wang Shizhen the military governor of Chengde Circuit (成德, headquartered in modern Shijiazhuang, Hebei) — died. Wang Shizhen's son Wang Chengzong declared himself acting military governor. In the past, these successions were routinely approved by the imperial government, but Emperor Xianzong, wanting to reassert imperial authority, hesitated in doing so and considered taking the control of Chengde back by force. The chancellor Pei Ji opposed military action, but Tutu volunteered to command an army against Wang Chengzong. Meanwhile, Lu Congshi (盧從史) the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi) wanted imperial favor, and offered, through Tutu, to attack Wang as well, causing Emperor Xianzong to consider military action further.