How a royal assassination triggered a brutal decade of war between Goryeo and Liao
In 1009, the assassination of Goryeo's King Mokjong provided the Khitan-led Liao dynasty with the perfect pretext for invasion. What followed was a devastating conflict that saw the capital city sacked, a king in flight, and a winter retreat that forced an army to abandon its own weapons.
The Second Goryeo-Khitan War, occurring in 1010, emerged from internal instability within the Goryeo dynasty. Following the death of King Seongjong in 997, his successor Wang Song—known as King Mokjong—reigned until his assassination in 1009 by the general Kang Cho. The Liao dynasty, seeking to exert influence over the Korean peninsula, seized upon this political vacuum to launch an offensive the following year. While the Liao initially suffered a defeat, they quickly recovered, winning a second engagement where Kang Cho was captured and executed.
The conflict escalated rapidly as Liao forces pushed deep into Goryeo territory, occupying northern border prefectures. Although the Goryeo monarch initially proposed surrender, the governor of the capital, Kaesong, executed the Liao envoys, choosing instead to resist. The Liao responded by winning a decisive pitched battle at Kaesong, forcing the king to flee south to Naju. The city was subsequently sacked, with its palaces, archives, and official buildings systematically destroyed by the invading forces.
Despite their military success, the Liao faced a precarious situation. As they began their withdrawal, local districts that had previously surrendered rose up against them. The retreating Liao army became mired in mountainous terrain during the harsh winter, forcing them to abandon their armor and weaponry before successfully crossing back north of the Yalu River. While Goryeo agreed to reaffirm its tributary status, the peace was fragile; the Liao emperor’s demand that the king appear in person and cede strategic border territory was rejected, leading to a decade of indecisive border skirmishes in 1015, 1016, and 1017.
