Goguryeo–Tang War: Led by Emperor Taizong, the Tang army was forced to abandon a siege of Ansi Fortress. Emperor Taizong of Tang: Emperor Taizong of Tang, previously Prince of Qin, personal name Li Shimin, was the second emperor of the Tang dynasty of China, ruling from 626 to 649. He is traditionally regarded as a co-founder of the dynasty for his role in encouraging his father Li Yuan to rebel against the Sui dynasty at Jinyang in 617. Taizong subsequently played a pivotal role in defeating several of the dynasty's most dangerous opponents and solidifying its rule over China proper. October 13, 645. Wiki link