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, with Liu defending the city capably. Shi had Sang write a letter requesting 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 — despite Liu's misgivings. Emperor Taizong agreed, arriving in Hedong territory in fall 936. He quickly engaged Zhang's Later Tang imperial army, defeating Zhang. The remnants of Zhang's army was subsequently surrounded by the Khitan/Hedong troops at Jin'an Base (晉安寨, near Taiyuan).