 Shi, in fear, rebelled.Li Congke commissioned Zhang Jingda to lead the imperial troops against Shi, and Zhang quickly put Taiyuan under siege, but was unable to capture it quickly.Shi sought aid from Khitan's Emperor Taizong, promising that if Emperor Taizong agreed to support him as emperor, he would cede 16 prefectures to the north (the entire Lulong Circuit and the northern prefectures of Hedong Circuit) to Khitan.