The Rise and Decline of Goryeo

The Goryeo dynasty, founded in 918 by Wang Geon, unified the Korean Peninsula in 936 after conquering the rival kingdoms of Silla and Baekje. By the 13th century, Goryeo had endured for nearly three centuries—a longevity that brought with it systemic decay. The kingdom suffered from weak leadership, rampant corruption, and military ineptitude, leaving it vulnerable to external threats.

This internal decline coincided with the rise of the Mongol Empire under Genghis Khan, whose conquests would soon extend into East Asia. Goryeo’s strategic position made it an inevitable target for Mongol expansion, setting the stage for a dramatic confrontation.

The Khitan Invasion and Goryeo’s Desperation

In 1216, a rogue Khitan army led by commanders such as Qinu, Jinshan, Tonggu, Ya’er, and Hanshe crossed the Yalu River into Goryeo. These Khitan rebels, fleeing retribution from their former leader Yelü Liuge, found Goryeo’s defenses shockingly weak. They sacked Pyongyang, massacred civilians in Hwangju, and terrorized the countryside with impunity.

Goryeo’s military, paralyzed by incompetence, could only cower behind city walls. The situation grew dire until General Kim Jwi-ryeok emerged as a rare competent commander, reclaiming lost territory through swift counterattacks. Yet even his efforts were hampered by illness, allowing the Khitans to regroup.

Facing annihilation, Goryeo’s court—unable to rely on its crumbling Jin dynasty allies—made a fateful decision: they appealed to Genghis Khan for help.

Genghis Khan’s Calculated Intervention

Initially, Genghis Khan showed little interest in Korea, preoccupied with campaigns in Central Asia. However, his advisor Yelü Chucai recognized Goryeo’s geopolitical value—securing the peninsula would stabilize Mongolia’s eastern flank for future campaigns against the Jin and beyond.

In 1218, Genghis Khan dispatched 20,000 troops under generals Hasar and Jochi, alongside forces from the puppet Eastern Xia regime led by Puxian Wannu. The Mongol-led coalition advanced into Goryeo, where they demanded provisions and reinforcements from the terrified Korean court.

The alliance was uneasy. When General Kim Jwi-ryeok recognized Yelü Liuge—whose rogue Khitan forces had ravaged Goryeo—he nearly sparked a violent confrontation. Only Hasar’s intervention prevented disaster, relegating Goryeo’s troops to a supporting role in the siege of Gangdong Fortress.

The Fall of Gangdong and Mongol Domination

The siege culminated in early 1219. Despite harsh winter conditions, the Mongols and their allies overwhelmed the Khitan stronghold. Hanshe, the last rebel leader, committed suicide rather than surrender. The surviving Khitans were handed over to Yelü Liuge, effectively ending the rebellion.

With Goryeo “liberated,” the Mongols swiftly imposed harsh terms: annual tributes of furs, silk, paper, and other resources. The demands grew increasingly oppressive, culminating in the 1225 assassination of a Mongol envoy—an act that severed relations until Ögedei Khan’s reign reignited hostilities.

Legacy and Modern Reflections

Goryeo’s subjugation marked the beginning of decades of Mongol dominance, shaping Korea’s political and cultural landscape. The dynasty survived as a Mongol vassal until the 14th century, but the experience left deep scars.

Historically, this episode illustrates the Mongol Empire’s ruthless efficiency in exploiting regional instability. For modern scholars, it serves as a case study in the interplay between internal decay and external conquest—a theme echoing across empires throughout history.

Genghis Khan’s brief Korean campaign, though a minor footnote in his vast conquests, underscores a critical truth: in geopolitics, weakness invites domination. Goryeo’s struggle remains a poignant reminder of how fragile sovereignty can be when faced with an unstoppable force.