Editing Yeon Gaesomun (section)

===Wars with China===
{{See also|First conflict of the Goguryeo–Tang War}}
{{See also|Goguryeo–Tang War}}

The series of wars between [[Goguryeo]] and [[Tang dynasty|Tang China]] comprise some of the most important events in the ancient history of Northeast Asia, leading to the Tang–Silla alliance, the ultimate demise of powerful Goguryeo, and the unification of the [[Korean Peninsula]] under [[Silla]] control. Yeon Gaesomun was a central protagonist in this series of conflicts, as well as its primary cause.

At the outset of his rule, Yeon Gaesomun took a brief conciliatory stance toward Tang China. For instance, he supported [[Taoism in Korea|Taoism]] at the expense of [[Korean Buddhism|Buddhism]], and to this effect in 643, sent emissaries to the Tang court requesting Taoist sages, eight of whom were brought to Goguryeo. This gesture is considered by some historians as an effort to pacify Tang and buy time to prepare for the Tang invasion Yeon thought inevitable given his ambitions to annex Silla.

Relations with Tang deteriorated when Goguryeo launched new invasions of Silla. In 645, the [[first conflict of the Goguryeo–Tang War]] began and [[Emperor Taizong of Tang|Emperor Taizong]]'s noted military acumen enabled him to conquer a number of major Goguryeo border fortresses.

Eventually, however, Emperor Taizong's invasion was met with two major setbacks. First, his main army was stymied and bogged down for several months at [[Ansi Fortress]] due to the resistance of the celebrated commander [[Yang Manchun]].<ref name="Lee" /><ref name="Kim" /> Second, the elite marine force that he sent to take [[Pyongyang]], Goguryeo's capital, was defeated by Yeon Gaesomun who, according to the ''[[Joseon Sanggosa]]'', then immediately marched his legions to relieve Yang Manchun's forces at Ansi Fortress.

[[Emperor Taizong of Tang|Emperor Taizong]], caught between Yang Manchun's army in the front and Yeon Gaesomun's counter-attacking forces closing in from behind, as well as suffering from the harsh winter and dangerously low food supplies, was forced to retreat homeward.<ref>{{cite book|last1=Sima|first1=Guang|title=Zizhi Tongjian}}</ref> Before setting off, Emperor Taizong left behind 100 bolts of silk cloth out of respect to Yang Manchun.<ref name="Kim" /> The retreat was difficult and many of his soldiers died.<ref>{{cite book|last1=Graff|first1=David|title=Medieval Chinese Warfare 300–900|date=2 September 2003|publisher=Routledge|isbn=9781134553532|page=168|url=https://books.google.com/books?id=gpmBAgAAQBAJ&pg=PA198|access-date=2 November 2016|language=en}}</ref> Emperor Taizong's campaign against Goguryeo was unsuccessful.<ref name="Maps">{{cite book|last1=Lee|first1=Injae|last2=Miller|first2=Owen|last3=Park|first3=Jinhoon|last4=Yi|first4=Hyun-Hae|title=Korean History in Maps|date=15 December 2014|publisher=Cambridge University Press|isbn=9781107098466|page=29|url=https://books.google.com/books?id=46OTBQAAQBAJ&pg=PA29|access-date=17 July 2016|language=en}}</ref><ref name="Tucker">{{cite book |last1=Tucker |first1=Spencer C. |title=500 Great Military Leaders |date=2014 |publisher=ABC-CLIO |isbn=9781598847581 |page=447 |url=https://books.google.com/books?id=SZHgBQAAQBAJ&pg=PA447 |access-date=12 October 2019 |language=en}}</ref> However, he succeeded in inflicting heavy casualties on Goguryeo. Upon returning home, Emperor Taizong founded the [[Fayuan Temple|Minzhong Temple]], the oldest temple in Beijing, to commemorate his soldiers who died in Goguryeo.<ref>{{cite web|title=Record of Restoring the Buddha Relic at Minzhong Temple|url=http://museum.sinica.edu.tw/exhibition_item.php?id=2&item=397&lang=en-us|website=Museum of the Institute of History and Philology|publisher=Academia Sinica|quote=The Minzhong Temple is known today as the Fayuan Temple in Beijing.  The temple was built by Emperor Li Shimin to mourn and salvage the lost souls in his failed attempt to conquer Goguryeo.}}</ref><ref>{{cite book|last1=Haw|first1=Stephen G.|title=Beijing – A Concise History|date=22 November 2006|publisher=Routledge|isbn=9781134150335|page=171|url=https://books.google.com/books?id=J8J8AgAAQBAJ&pg=PA171|access-date=2 November 2016|language=en}}</ref><ref>{{cite book|last1=Perkins|first1=Dorothy|title=Encyclopedia of China: History and Culture|date=19 November 2013|publisher=Routledge|isbn=9781135935696|url=https://books.google.com/books?id=tsIeAgAAQBAJ&pg=PT112|access-date=2 November 2016|language=en}}</ref><ref>{{cite book|last1=Jaivin|first1=Linda|title=Beijing|date=15 May 2014|publisher=Reaktion Books|isbn=9781780233000|url=https://books.google.com/books?id=SJAOBQAAQBAJ&pg=PT23|access-date=2 November 2016|language=en}}</ref> He invaded Goguryeo again in 647 and 648, but was defeated both times, and thus was unable to accomplish his ambition of conquering Goguryeo in his lifetime.<ref name="Kim" /><ref name="Tucker" />

Conquering Goguryeo had been an obsession with Emperor Taizong,<ref>{{cite book|last1=Walker|first1=Hugh Dyson|title=East Asia: A New History|date=20 November 2012|publisher=AuthorHouse|isbn=9781477265178|page=161|url=https://books.google.com/books?id=GBvRs-za0CIC&pg=PA161|access-date=4 November 2016|language=en}}</ref> and after his death in 649, his son [[Emperor Gaozong of Tang|Emperor Gaozong]] continued his ambition. After the Tang-Silla alliance conquered [[Baekje]], Emperor Gaozong invaded Goguryeo in 661 and 662.<ref name="Maps" /><ref>{{cite book|last1=Ring|first1=Trudy|last2=Watson|first2=Noelle|last3=Schellinger|first3=Paul|title=Asia and Oceania: International Dictionary of Historic Places|date=12 November 2012|publisher=Routledge|isbn=9781136639791|page=486|url=https://books.google.com/books?id=voerPYsAB5wC&q=stalwart+defenses|access-date=16 July 2016|language=en}}</ref> One of Yeon Gaesomun's greatest victories came in 662, when his forces defeated Tang general Pang Xiaotai ({{lang|zh|龐孝泰}}) and his [[Lingnan]] army at the Sasu River ({{script|Hani|蛇水}}, probably [[Pothong River|Botong River]]). Pang Xiaotai and all his 13 sons were killed in combat.<ref>{{cite book|script-title=ko:옆으로 읽는 동아시아 삼국지 1|date=2 September 2013|publisher=EASTASIA|isbn=9788962620726|url=https://books.google.com/books?id=GfevAwAAQBAJ&pg=PT348|access-date=5 November 2016|language=ko}}</ref><ref>{{cite web|script-title=ko:통일기|url=http://www.culturecontent.com/content/contentView.do?search_div_id=CP_THE003&cp_code=cp0901&index_id=cp09010004&content_id=cp090100040001&search_left_menu=1|website=한국콘텐츠진흥원|publisher=Korea Creative Content Agency|access-date=5 November 2016}}</ref> Famed Tang general [[Su Dingfang]], who was instrumental in conquering Baekje, was unable to overcome [[Pyongyang]]'s defenses and was forced to withdraw due to harsh snowstorms. With increasing domestic turmoil in China, Tang was once again forced to retreat.

However, Goguryeo's population and economy were severely damaged due to the long years of continuous warfare.<ref name="Lee2"/> Yeon Gaesomun died in 666 of a natural cause, and Goguryeo was thrown into chaos and further weakened by a succession struggle among his sons and younger brother,<ref name="Kim" /><ref>{{cite book|last1=Kim|first1=Djun Kil|title=The History of Korea, 2nd Edition|date=30 May 2014|publisher=ABC-CLIO|isbn=9781610695824|page=49|url=https://books.google.com/books?id=IgxvBAAAQBAJ&pg=PA49|access-date=17 July 2016|language=en}}</ref> with his eldest son defecting to Tang and his younger brother defecting to Silla.<ref name="Lee2">{{cite book|last1=Lee|first1=Ki-Baik|title=A New History of Korea|date=1984|publisher=Harvard University Press|location=Cambridge, Massachusetts|isbn=067461576X|page=67}}</ref> Tang mounted a fresh invasion in 667, aided by Silla and the defector [[Yeon Namsaeng]], and was finally able to conquer Goguryeo in 668.<ref name="Lee2" />