Tian Hongzheng
In spring 820, Emperor Xianzong died and was succeeded by his son Emperor Muzong. Soon thereafter, Li Su was given the honorary chancellor title of "Tong Zhongshu Menxia Pingzhangshi" (). Further, in anticipation of potential further actions against two other circuits governed "de facto" independently — Chengde (成德, headquartered in modern Shijiazhuang, Hebei) and Lulong (盧龍, headquartered in modern Beijing) — Emperor Muzong made Li Su the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi). Later that year, when Wang Chengzong the military governor of Chengde died, his brother Wang Chengyuan offered to return control of the circuit to the imperial government. Emperor Muzong, in response, moved Tian Hongzheng the military governor of Weibo Circuit (魏博, headquartered in modern Handan, Hebei) — itself having previously been semi-independent from imperial rule but which had submitted to imperial command during Tian Hongzheng's governance — to Chengde, Wang Chengyuan to Yicheng, Liu Wu from Yicheng to Zhaoyi, Li Su from Zhaoyi to Weibo, and Tian Hongzheng's son Tian Bu to Heyang Circuit (河陽, headquartered in modern Jiaozuo, Henan).