The Siege of Ansiseong Fortress

A documentary painting of the Siege of Ansiseong Fortress in the year 645 (fourth year in the reign of King Bojang of Goguryeo), where Goguryeo forces stopped the advance of a massive invading army led by Emperor Taizong of Tang China.

The Tang invaders had captured the fortresses of Yodongseong, Gaemoseong, and Baegamseong, seriously compromising Goguryeo defenses around the Yoha (Liaohe) River. The fortresses at Yodongseong and Baegamseong were key strategic locations in Goguryeo’s defense, and the kingdom was at risk of being attacked at positions deep inland south of the Yalu River. Ansiseong Fortress was built on the plains at the southwestern tip of the Yodong (Liaodong) Peninsula, and the battle that occurred here would decide the course of the war to come.

Yeon Gaesomun, generalissimo of Goguryeo, had sent reinforcements 150,000-strong to the fortress, but these forces were defeated, leaving Ansiseong Fortress cut off. Taizong of Tang split his forces into two and attacked the fortress with catapults and battering rams. However, the forces defending the fortress, led by Yang Manchun, repelled the attacks time after time, and Tang losses mounted. The Tang forces then built a rampart around the fortress, in an effort that took 60 days and mobilized upwards of 500,000 laborers. The Goguryeo forces occupied the rampart and thwarted a Tang offensive to recapture it.

The Goguryeo victory at Ansiseong Fortress was significant in the Goguryeo-Tang war not only in that it successfully repelled the Tang forces which were undefeated until then, but also in that by keeping the invaders occupied for so long, it forced the Tang to waste supplies and time they could have otherwise spent attacking other locations, and in that the battle bought the forces of Goguryeo valuable time to regroup.

After committing masses of supplies, men and horses to the effort, Emperor Taizong of Tang China was forced to give up his conquest of Goguryeo and retreat.