Battle of Ansi

In the year 644, Taizong of Tang decided to invade Goguryeo in the face of opposition inside the Tang dynasty. The assassination of Yongnu of Goguryeo and other officials by Yŏn Kaesomun was used to justify invasion. For the next year, he began preparations for an invasion, preparing troops, ships, and siege engines, and conducting reconnaissance. On 1 April 645, under the pretext of marching to camp Huaiyuan, Tang forces led by Li Shiji suddenly turned to invade Goguryeo. In response to the Tang invasion, Yŏn Kaesomun, Generalissimo of Goguryeo, sent about 150,000 forces with Ko Yŏnsu and Ko Hyejin to rescue Ansi. ==Development==

The battle to rescue Ansi On 20 July, the two sides descended into battle. The Tang dynasty sent Li Shiji leading 15,000 infantry and cavalry to fight the Goguryeo army directly. But Tang general Zhangsun Wuji led 11,000 elite cavalry across the canyon from the north of the mountain to hit the rear of Goguryeo forces. In the battle, Taizong personally led 4,000 infantry and cavalry to fight. The Tang army came out victorious in the end, decimating the Goguryeo forces. At least 20,000 Goguryeo soldiers were killed and 36,800 Goguryeo soldiers, including their generals Ko Yŏnsu and Ko Hyejin, surrendered. The Tang army captured 50,000 horses, over 50,000 cattle, and over 10,000 iron suits of armor. After the battle, Tang had succeeded in isolating Ansi fortress from other Goguryeo territory. One night, hundreds of Goguryeo soldiers climbed out of the fortress and attempted to attack the Tang army. When Taizong heard about it, he called up soldiers to make an emergency joint attack which killed dozens of Goguryeo soldiers, and the rest fled back to the fortress. It overlooked the city. Fu Fuai, one officer of the Tang Army, stationed his troops on the top of the rampart. However, Fu Fuai left the camp privately and the rampart suddenly fell, and the Goguryeo army occupied it. Taizong was very angry and put Fu Fuai to death. After that, Tang tried to regain the rampart for three days but failed. On the third day, the Goguryeo army reinforcements arrived and Taizong had still not captured the Ansi Fortress. In addition, because the battle was fought in the Liaodong peninsula, winter approached as early as October. This made the situation even worse for the Tang forces as the weather got considerably colder and food ran out, so the Emperor Taizong unavoidably ordered retreat. Taizong's retreat was difficult and many of his soldiers died as they were hit by a snowstorm. Taizong himself tended to the injuries of his Turkic generals Qibi Heli and Ashina Simo, who were both wounded during the campaign against Goguryeo. ==Aftermath==

In 645, Emperor Taizong founded the Minzhong Temple, the oldest temple in Beijing, to commemorate his soldiers who died in Goguryeo. Emperor Taizong prepared another invasion in 648, but died, possibly due to an illness he contracted during his Goguryeo campaigns. The Goguryeo forces lost over 20,000 people, with over 36,800 troops being taken prisoner during the early stage of combat. The casualties of the Goruryeo troops during the siege itself are unknown. Tensions between Goguryeo and Tang continued, until Goguryeo was finally defeated by a joint Silla-Tang force in the year 668. ==In popular culture==

The 2018 South Korean film The Great Battle is based on this siege. ==References==