契丹
Having conquered [[Northern Han]] in 979, Emperor Taizong took advantage of the momentum and launched another military campaign against the [[Khitan people|Khitan]]-led [[Liao dynasty]]. In May 979, Emperor Taizong embarked on his campaign from [[Taiyuan]] and took Zhuo and Yi Prefectures easily. He besieged Yanjing (present-day [[Beijing]]) after the success. However, the siege failed when the Liao defending general [[Yelü Xuegu]] defended the fortress firmly.