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.

唐太宗征讨高句丽 发生在645年（唐太宗贞观十九年）。642年（贞观十六年），渊盖苏文杀害荣留王之后，拥立荣留王的侄子高宝藏为王，并自封为“大莫离支”摄政。唐太宗为了声讨渊盖苏文弑君、帮助与高句丽作战的新罗，准备与高句丽开战。644年（贞观十八年），太宗带领李世𪟝、李道宗、长孙无忌诸将率军亲征高句丽。645年（贞观十九年），唐军冲破高句丽的防线，似乎大功在即，准备直接攻打高句丽国都平壤。但在安市城（今辽宁省海城市）受阻，再也无法推进。当年秋季，唐军班师。从此之后，太宗对高句丽的进攻，仅保持在一些小规模的袭击。647年（贞观二十一年），唐太宗派牛进达率兵从海路、李世𪟝率兵从陆路攻打辽东半岛。648年（贞观二十二年），太宗再派薛万彻率军从海路攻打鸭绿江口。唐朝与回纥等铁勒诸部击灭薛延陀，设立燕然都护府后，开始集结水陆大军，准备在649年（贞观二十三年）再一次大规模攻打高句丽。不过由于太宗于同年驾崩，使唐朝再攻高句丽的战役搁浅。直到668年（总章元年），才由太宗的儿子唐高宗派军联合新罗灭亡了高句丽。

The Battle of Mount Jupil, also known as Battle of Jupil-san and Battle of Mount Zhubi was a battle between Tang Chinese and Goguryeo Korean forces that took place in Mount Jupil at the south of the fortress city of Ansi. It took place on July 11, 645 AD. The small but elite Tang army wiped out the Goguryeo relief force trying to come to bolster the defenses of Ansi, achieving a major victory.