However Taizong died before the conquest of Goguryeo was completed , and his successor Gaozong reneged on the promise .
Originally Emperor Taizong of Tang promised to exchange Baekje and the lands south of Peonyang in return for Silla's military cooperation.
Taizong died before the conquest of Goguryeo was completed , and his successor Gaozong reneged on the promise .
Originally Emperor Taizong of Tang promised to exchange Baekje and the lands south of Peonyang in return for Silla's military cooperation.