Fall of Goguryeo

Overview

Goguryeo fell in the ninth lunar month of 668 (27th year of King Bojang), when its capital, Pyongyang Fortress, was captured by the Silla-Tang allied forces. For more than twenty years after 645, Goguryeo repelled Tang invasions, but after the Fall of Baekje in 660 it faced attacks from both north and south, and the power struggle among the sons of Yeon Gaesomun after his death became a decisive weakness. The dates in this article are lunar dates.

Background

Fatigue from a Prolonged War

During the Goguryeo–Tang War, the Tang repeatedly attacked Goguryeo each year with small units, waging a war of attrition that ruined its farming. In 661–662, Su Dingfang directly besieged Pyongyang Fortress, but he withdrew after defeat in the Battle of Sasu. Nevertheless, the grain supplied by Silla showed that the campaign could continue even in winter.

Division among the Yeon Brothers

In 665 (666 according to the Samguk sagi), Yeon Gaesomun died, and his eldest son Yeon Namsaeng (男生) succeeded him as Daemakriji. While Namsaeng was away inspecting the fortresses of the provinces, his younger brothers Yeon Namgeon (男建) and Yeon Namsan (男産) heard the rumor that "the elder brother plans to eliminate the two younger brothers," and seized control of Pyongyang. Namsaeng fled to Gukneseong and sent his son Heonseong (獻誠) to the Tang to request aid, and then surrendered. In June 666, the Tang sent Gye Pilhalyeok to receive Namsaeng. In the same year, Yeon Jeongto, a younger brother of Yeon Gaesomun, led 12 fortresses, 763 households, and 3,543 people in surrender to Silla.

Course of the War

The Tang Great Offensive (666–668)

In December 666, Emperor Gaozong of Tang appointed Li Shiji (Yi Jeok) as Grand Commander of the Liaodong Campaign Army and sent a large force. Namsaeng led troops from the area around Gukneseong and served as a guide for the Tang army.

• Fall of Sinseong (September 667): Li Shiji attacked Sinseong (present-day Gaogushan Fortress in Fushun), a key stronghold in Liaodong. Sabugu and others within the fortress bound the fortress commander and opened the gates in surrender, and the surrounding sixteen fortresses fell in succession.
• Battle of Geumsan (667): The Goguryeo army met the Tang forces at Geumsan and won for a time, but was badly defeated by Seol Inkwi's counterattack.
• Fall of Buyeo Fortress (February 668): When Seol Inkwi attacked and captured Buyeo Fortress, more than forty fortresses in the area along the Buyeo River all surrendered. Yeon Namgeon sent an army of 50,000 to relieve Buyeo Fortress, but it was defeated at the Seol River.