Battle of Ansi

Siege of Ansi
Part of the First campaign in the Goguryeo–Tang War
Map showing the invasion of Tang forces to Goguryeo
Date 20 June – 18 September 645 CE Location Ansi Result Goguryeo victory
Belligerents
Goguryeo Mohe	Tang
Commanders and leaders
In Ansi: Yang Manchun At Jupilsan: Go yeon-su (POW) Go hye-jin (POW)	Emperor Taizong of Tang Li Shiji Zhangsun Wuji Li Daozong (WIA) Xue Rengui
Strength
In Ansi: ~5,000 (garrison) At Jupilsan: ~150,000 (reinforcements)	In Ansi: Unknown At Jupilsan: ~30,000 soldiers
Casualties and losses
20,000+ killed 36,800 surrendered[1]	2,000+ killed or injured

The siege of Ansi took place between Goguryeo and Tang forces in Ansi, a fortress in the Liaodong Peninsula, and the culmination of the First campaign in the Goguryeo–Tang War. The confrontation lasted for about three months from 20 June 645 to 18 September 645.

The initial phase of combat resulted in the defeat of a Gorguryeo relief force of 150,000 and resulted in the Tang troops laying siege to the fortress. After a siege lasting around two months, the Tang forces constructed a rampart. However, the rampart was on the brink of completion, when a section of it collapsed and was taken over by the defenders. This, along with the cold winter approaching as well as arriving Goguryeo reinforcements and the lack of supplies, forced Tang troops into a retreat. Over 20,000 Goguryeo troops were killed during the siege.