However, Emperor Gaozong, too, was unable to defeat Goguryeo led by Yeon Gaesomun; one of Yeon Gaesomun's most notable victories came in 662 at the Battle of Sasu (蛇水), where he annihilated the Tang forces and killed the invading general Pang Xiaotai (龐孝泰) and all 13 of his sons.
Men kejser Gaozong var ligeledes ude af stand til at besejre Goguryeo ledet af Yeon Gaesomun; en af Yeon Gaesomuns mest bemærkelsesværdige sejre kom i 662 i slaget ved Sasu (蛇 水), hvor han tilintetgjorte Tang styrker og dræbte den invaderende general Pang Xiaotai (龐孝泰) og alle hans 13 sønner.