The Rise and Decline of Goryeo

Founded in 918 by King Taejo (Wang Geon), the Goryeo Dynasty 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. Corruption plagued the royal court, and weak leadership left the kingdom vulnerable to external threats.

This internal instability coincided with the rise of the Mongol Empire under Genghis Khan, whose conquests would soon reshape Eurasia. As Mongol power expanded, Goryeo found itself caught between the remnants of the crumbling Khitan Liao Dynasty and the advancing Mongol juggernaut.

The Khitan Invasion and Goryeo’s Desperation

In 1216, a rogue Khitan army led by commanders including Qinu, Jinshan, Tonggu, Ya’er, and Hansha crossed the Yalu River into Goryeo. These rebels, fleeing retribution from their former leader Yelü Liuge, exploited Goryeo’s military weakness, sacking cities like Pyongyang and Hwangju with little resistance. By 1217, they had split into factions, ravaging the countryside and seizing key fortresses.

Goryeo’s military, led by the capable general Kim Chwi-ryeo, managed temporary victories, but infighting among the Khitan commanders—culminating in Hansha’s rise to power—only prolonged the crisis. With the Khitan entrenched in Gangdong Fortress and Goryeo’s government paralyzed by indecision, the kingdom faced collapse.

The Mongol Gambit: A Calculated Intervention

Desperate, Goryeo turned to an unlikely savior: Genghis Khan. Initially dismissive, the Mongol ruler was persuaded by his advisor Yelü Chucai, who recognized Goryeo’s strategic value in securing the eastern flank of the Mongol Empire. In 1218, Genghis Khan dispatched generals Jalairtai Qorchi and Wanyan Aguda with 20,000 troops, supplemented by forces from the Eastern Xia Kingdom under Puxian Wannu.

Puxian Wannu, a former Jin Dynasty general turned warlord, saw the campaign as an opportunity to test his troops. The Mongol-led coalition advanced into Goryeo, where they demanded supplies and reinforcements from the terrified Korean court. Reluctantly, Goryeo contributed troops under Kim Chwi-ryeo, though tensions flared when the general recognized Yelü Liuge among the Mongol allies.

The Siege of Gangdong and Mongol Victory

By December 1218, the combined forces besieged Gangdong Fortress. Harsh winter conditions stalled progress, and initial attempts at negotiation failed when Hansha defiantly rejected Yelü Liuge’s surrender demands. When spring arrived in 1219, the Mongols and their allies launched a coordinated assault. Puxian Wannu’s Eastern Xia troops breached the walls first, leading to Hansha’s suicide and the surrender of the remaining Khitan forces.

The victory came at a cost. The Mongols, now Goryeo’s de facto overlords, imposed heavy tributes—including furs, silk, and raw materials—that strained the kingdom’s economy. When Goryeo assassinated a Mongol envoy in 1225, relations ruptured until Ögedei Khan’s reign reignited conflict, forcing Goryeo back into submission.

Cultural and Political Aftermath

The Mongol intervention left an indelible mark on Goryeo:
– Vassalage and Tribute: Goryeo’s forced subjugation under the Mongol Yuan Dynasty reshaped its foreign policy, integrating it into the broader Mongol world order.
– Military Reforms: The invasion exposed Goryeo’s military weaknesses, prompting later reforms to fortify defenses.
– Diplomatic Leverage: Paradoxically, Goryeo’s ties to the Mongols granted it a degree of protection against other regional threats.

Legacy: Between Resistance and Adaptation

Goryeo’s experience under Mongol dominance illustrates the precarious balance between resistance and survival. While the tributes were oppressive, the dynasty endured by navigating Mongol demands—a strategy that preserved Korean autonomy until the rise of the Joseon Dynasty in 1392. Today, this period is remembered as a testament to resilience, a chapter where a weakened kingdom faced the storm of an empire and emerged transformed.

The Mongol-Goryeo conflict also foreshadowed Korea’s later struggles with foreign powers, echoing themes of sovereignty and adaptation that resonate throughout its history.