2.24. History of the Mongols: Invasions of Korea

Had you to guess a kingdom to offer decades of resistance to the Mongols at the height of their power, Korea might not have been high on your list. Situated close to Mongol dominated North China and first coming to Mongol attention at the start of the 1220s, it took until the beginning of the 1260s for the peninsula to be firmly under Mongol rule. Today’s episode will detail the long and devastating Mongol war in Korea and the final subjugation during the reign of Great Khan Mongke. I’m your host David, and this is Kings and Generals: Ages of Conquest.

 

By the 13th century the Korean peninsula had been ruled by the house of Wang since 918. Their kingdom was called Koryo [also written Goryeo (Gor-yeo)], a shortened form of the name of the more ancient Korean Kingdom of Kokuryeo (kok-ur-yeo) [also written Goguryeo] which fell in 668 CE. Both terms are the origin of the modern name for the peninsula. Smaller in scale than the empire of Kokuryeo, the 13th century Koryo kingdom’s territory did not extend much past the Yalu river. Staunch Buddhists, the Kingdom of Koryo was a major player in regional trade and commerce, and a centre of art and culture, and was a proud state. Successfully resisting invasions by the Khitan Liao and Jurchen Jin, Koryo entered into tributary relationships with both but maintained its internal autonomy, and unique worldview where the Korean King was essentially also son of Heaven, alongside the Chinese monarch who traditionally held the title. Similar to the contemporary Song Dynasty, military roles were subservient to the civilian classes and excluded from powerful civil positions. Despite the military being key to repulsing the Jurchen invasion of the 1120s, they gained no recognition, or promotions, for their efforts. Conditions worsened over the 12th century when revolts needed the military to be crushed. During the reign of King Uijong from 1146-1170, matters came to a head. More interested in visiting Buddhist temples than governing, under Uijong, corruption peaked. Government institutions were controlled by aristocratic families competing with the central government, the court was divided among factional lines and critics were exiled. These grievances fed into existing frustrations of the military leaders, ultimately culminating in a coup by the general Chong Chungbu in 1170. The King was dethroned in favour of a brother, and military leaders assumed most of the top offices. This was the beginning of a century of military dictatorship in Korea, its kings reduced to puppets. It was a system remarkably similar to the shogunate established at nearly the same time by Minamoto no Yoritomo in Japan, wherein the Japanese Emperor still head his title and conducted ceremonial roles, but real power was held by the shogun- though after Yoritomo’s death in 1199, real power was held by regents, the shikken of the Hojo clan. 

 

Chungbu struggled to exercise his authority and could not fix the problems facing Koryo; revolts across the country continued and Chungbu was ousted by rivals in 1178, followed in turn by a succession of generals vying for power. It was not until 1196 when the general Ch’oe Ch’unghon assassinated the military dictator. A skilled and brave warrior, Ch’oe Ch’unghon was also a patriot, and saw the years of failed military rule as a disaster for his career, and for Koryo. Ch’oe was adept at political maneuvering. After assassinating the current dictator, he met the King and explained his actions. Gaining royal approval, his authority was established quickly. With support of the Korean King- whom Ch’oe Ch’unghon soon replaced- as well as key military figures, Ch’oe rooted out rivals, skillfully threw bones to military officers, civil leaders and literati, and revitalized the dynasty. Authority was extended through existing dynastic institutions, reformed to weed out corruption but ensured loyal men were in control of those institutions. Marriage ties cemented political alliances, and Ch’oe Ch’unghon essentially established his own dynasty alongside the royal dynasty. He was careful to ensure that alternate power bases to his own were undermined: government military forces weakened while he built up his own private army. Knowing how to champion Zen Buddhism and Confucianism, Ch’oe Ch’unghon masterfully manipulated his public image and public works. Allowing the King to focus on ceremonial and religious roles, Ch’oe’s tight lease on government meant that, over the first decade of the thirteenth century, he felt his position on HIS peninsula to be quite secure.

 

But like so many others, Ch’oe Ch’unghon’s plans were upset by a little someone named Chinggis Khan. The Great Khan’s invasion of the Jin Empire began in 1211, during which the Korean ambassador to the Jin was killed in the fighting. We have little information on what the Koreans and Ch’oe Ch’unghon thought of the rapid Mongol conquest of the Jin. During these centuries, the Korean kingdoms were always concerned with their northern border with Manchuria, where the Manchurian tribesmen, be they Khitan or Jurchen, invariably proved dangerous foes, crossing to raid in small parties or conquer with full armies. As Jin Dynastic authority collapsed in their Manchurian homeland, the Koreans watched the north uneasily. There, aside from the ongoing warfare, two new states were formed: the first was a Khitan Kingdom in central Manchuria, a “restored” Liao Dynasty made subject to the Mongols in 1212. The second was in Eastern Manchuria and Russia’s Primorsky Krai, founded by the Jin defector Puxian Wannu in 1215, which soon submitted to the Mongols. The latter is often called the Kingdom of Ta-chen, Tung-chen or the Eastern Xia. The frontiers north of Korea were unstable, and Ch’oe Ch’unghon expected trouble would spill over his borders sooner or later.

 

In 1216 as many as 90,000 rebel Khitans displaced by Jin forces overran Wannu’s southern territory. A few months later, Mongols accompanied by loyal Khitans chased these rebel Khitans from Wannu’s borders. The rebels’ requests to Koryo for aid were denied, and stuck between the Mongols and Korea, the Khitans chose Korea. In autumn 1216 the Khitans blazed through the Korean border defences. Skilled horse archers, the Khitans drove deep into Korea, menacing the capital, modern Kaesong. Korean military resistance contained them to the northern half of the country. Aside from a brief foray back over the border to gain reinforcements in autumn 1217, the Khitans spent most of 1217 and 1218 pillaging and plundering in the northeast. 

 

Unexpectedly, in winter 1218 10,000 Mongols under the command of Qacin and Jala, with 20,000 troops provided by Wannu, arrived in Korea. The Mongols sent a simple message to the Koreans: they would crush the rebel Khitans, requested troops and provisions from the Koreans to assist with this, and then would enter into the same tributary relationship the Koreans had with Liao and Jin. After a brief delay in answering the Koreans acquiesced, sending 1,000 picked troops and 1,000 bushels of rice. The rebels Khitans were crushed, and Korea began sending tribute to the Mongols in 1219. 

 

Korea’s first Mongol experience was relatively peaceful. Though forced to send tribute, their cities had not suffered. Ch’oe Ch’unghon’s advancing age, failing health, and desire to pass his rule onto his son stopped him from taking any provocative actions. A keen observer, he had judged the danger of this new foe, expecting the relationship would differ little from Liao or Jin tribute demands. Ch’oe Ch’unghon died in late 1219, and was succeeded by his oldest son, Ch’oe U. A military man like his father, an effective administrator and decisive leader, though not quite as cautious, Ch’oe U helmed Koryo for the next two decades. Ch’oe U found Mongol demands were downright rapacious, especially for otter skins, highly desired for their water resistant properties. For a people who lived their entire lives outdoors, an otter-skin cap was a valuable product. The chief Mongol envoy to Korea, Ja’uyu (Chao-ku-yu), was said to have abandoned the rest of the tribute at the border and just kept the otter skins!

 

As we’ve noted in episodes past, when Chinggis Khan marched west against the Khwarezmian Empire in 1219 his general Mukhali was left to maintain pressure on the Jin Dynasty. With Mukhali’s death in 1223, the reduced Mongol military presence in north China and with Chinggis still in Central Asia, the political situation across the region changed dramatically. The end of hostilities between the Jin, Xi Xia and Song Dynasties around 1225 we’ve dealt with already, but changes occurred even in Manchuria and Korea. There, Puxian Wannu renewed his independence and asked for alliance with Koryo. The Koreans declined, but made their own moves. In 1225 the chief Mongol envoy to Korea, the aforementioned Ja’uyu (Chao-ku-yu), mysteriously disappeared while transporting the annual tribute north. The Koreans insisted it was bandits, but the Mongols put the blame square on Koryo. 

 

Ogedai Khaan was enthroned in 1229 and immediately set about bringing the region to heel. The Jin Dynasty took his personal attention and was destroyed by 1234. Both Puxian Wannu and the Koreans were also to be punished. Initially the new Khaan demanded Korea aid in an attack against Wannu. With the failure of the Koreans to comply, Ogedai ordered an invasion of the peninsula, the first of six Mongol invasions. Led by Sartaq-Qorchi, the army crossed the Yalu River in autumn 1231. The attack was overwhelming; the government armies were annihilated in the field and the capital surrounded. There was some notable resistance at a few fortified cities, none more famous than the defence of Kuju. Famed for a victory over the Khitans in 1018, in late 1231 through early 1232 under the command of Pak So, the city withstood weeks of constant Mongol assault. The most famous event occurred early in the siege. The southern wall of the city was defended by Kim Kyongson and a skilled unit of pyolch’o, translated as Defense Command Patrol, Extraordinary Watches or Night Patrol. These were local troops from outside the regular army, an elite militia specializing in guerilla warfare. Sending most of the unit inside the city, Kim Kyongson led a group of 12 picked men before the south gate. Telling them “not to think of their lives and accept death as their fate,” Kim and his men withstood four or five Mongol charges. Taking an arrow to the arm, Kim and his forces stood proudly and girded the city to further resistance;  Attacks were launched on the walls day and night: carts of dry grass and wood were pushed to the gates to burn them, only to be destroyed by Korean catapults; a tower built before the walls to protect sappers was destroyed when the Koreans dug holes through their own walls to pour molten iron onto it. 15 large catapults were driven off by the Korean counter artillery; scaling ladders were toppled by Korean polearms. Bundles of sticks soaked allegedly in human fat, set aflame and hurled into the city could not be put out with water, but were smothered with mud and earth. Another catapult team through constant barrage made 50 breaches in the walls, which the defenders filled back in as the holes were made. After a month of terrible destruction but no success, the Mongol siege was lifted, deciding the city was protected by heaven.

 

Kuju city and other select settlements outlasted the central government. Military ruler Ch’oe U came to terms with the Mongols in January 1232, and was so frustrated that Kuju had continued to resist that he wanted to have its commanders, Pak So and Kim Kyongson, executed fearing Mongol retaliation. Here the Mongols are said to have interceded, saying: “Although he went contrary to our orders, he is a loyal subject of yours. We are not going to kill him now that you have already pledged peace with us. Would it be proper to kill the loyal subjects of all your cities?”

 

Still, Koryo had submitted to Sartaq-qorchi in the first month of 1232. The tribute demands were massive. 20,000 horses, 20,000 otter skins, slaves, royal hostages and clothing for 1 million men were demanded, alongside gold, silver and other treasures. The demands were impossible to meet; within a few months the Koreans had procured barely 1,000 otter skins. 72 Mongol darughachin were appointed to oversee Koryo, and Sartaq withdrew his forces, considering the peninsula conquered. 

 

The Koreans were less keen to comply, however. The demands were onerous; while they sent much in gifts, they were unwilling to send royal hostages. Ch’oe U organized sambyolch’o units, a sort of paramilitary police force of the house of Ch’oe. By the end of spring 1232, Ch’oe held a meeting of his top ministers to decide the course of action. In June and July, the plan was struck. Ch’oe U, the King and the court moved from the capital at Kaesong to Kanghwa island offshore, making it the new administrative centre of Korea, protected by the experienced Korean navy. Mongol officials in Korea were murdered and the peninsula was in open revolt. Sartaq returned in fall 1232, blazing a trail of destruction across the northern half of the country until he was killed during a siege by a Buddhist monk turned archer, Kim Yunhu. On Sartaq’s death, the Mongol army withdrew.

 

The Mongols were not done with Korea. The defection of one Korean commander, Hong Pogwon, gave them control of Korea stretching north from Pyongyang, which Hong was made the overseer of. In early 1233 a Mongol envoy came with a list of grievances and demands, among them that Koreans had to fight against Puxian Wannu- though this came to naught, as Wannu’s kingdom, and the connection between his head and his neck, were removed from the scene later that year by armies under Ogedai’s son Guyuk. After the fall of the Jin Dynasty in 1234, a quriltai was held in Mongolia in 1235 to determine the next campaigns. Attacks were ordered against the Song Dynasty, Guyuk, Subutai and Batu were sent on the great western campaign, and another army, this time under Tangut Ba’atar, was sent to Korea. 

 

Tangut Ba’atar’s invasion in summer 1235 was hugely destructive; with the assistance of Hong Pogwon by winter 1236, he had penetrated some 470 kilometres into Korea. The Koreans were unable to field armies against them, and alternative strategies were developed to respond. Just as the court had fled to Kanghwa Island, most of the population outside of fortified settlements was ordered to flee to coastal islands or mountain refuges, where they could escape Mongol riders. Offensives were limited to guerilla warfare, pyolch’o units launching surprise night raids, ambushes through mountain passes and striking small parties. Hitting quick and hard and making use of their excellent knowledge of local terrain, these small units were actually more mobile than the Mongols. It was a frustrating way of war for the Mongols, and when the Mongols got frustrated, the devastation only increased. Fortified settlements were left to fend for themselves, and when they did fall, the destruction was horrific. The countryside was ravaged, the death toll horrendous. The guerilla tactics could harass but not stop the Mongols, who in turn, unable to strike directly at the royal court or military dictator, could not immediately bring the country to submission. Korean defections to the Mongols were enormous; and in many respects the Ch’oe rulers had chosen a strategy to bring the most damage to their people.

 

By winter 1238, the Korean court was willing to come to talks with the Mongols to halt the destruction.  Tangut Ba’atar withdrew his forces with talks ongoing and it seemed the Koreans would pledge eternal submission. As the Koreans feared, the Mongolian idea of negotiated settlement was a bit different from their own. Alongside the expected tribute demands, the Mongols required a census, the court could no longer stay on Kanghwa Island, and the Korean King, at that time Kojong, had to present himself to the Mongol court. For the military ruler Ch’oe U, this presented an issue. His legitimacy rested on him being the one to control the King; Mongol demands would remove him from power. Peace on the terms the Mongols wanted could not be accepted as long as the Ch’oes wanted to remain in control. For two years the Koreans made excuses on not sending the King, Ch’oe U trying to find some room to maneuver. Finally, a ploy was decided on: a distant relation of the King was made up to be the Crown Prince, and thus Wang Sun was sent to Karakorum in 1241. The Mongols found out about the deception…. Some 14 years later. By then, he was a loyal member of the Mongol court and even married a daughter of Great Khan Mongke.

 

With the royal hostage sent in 1241 and resumption of tribute, Ch’oe U achieved a six year truce. The Mongols still wanted the royal court to return to the mainland though, and their envoys grew ever more insistent on the matter. Ch’oe U spent the next six years preparing defenses, building elaborate fortifications on Kanghwa Island and readying militia units.  Buddhist projects were consecrated to secure heavenly favours; the most famous was the recarving of the Tripitaka, the Buddhist scriptures, begun in 1237. Often called the Tripitaka Koreana, this was a massive project, over 80,000 wooden printing blocks carved, requiring thousands of scholars and 12 years to complete.

 

Guyuk was elected as Great Khan in 1246, and decided the Koreans had stalled long enough on returning the court to the mainland.  In Autumn 1247 an army under the general Amukhan and Hong Pogwon invaded. Official orders were sent for the countryside to be abandoned for coastal islands and mountain fortresses; guerilla attacks were launched; the northern half of the peninsula was desolated. The death of Guyuk in summer 1248 and Ch’oe U in winter 1249 brought a relative calm. Ch’oe U was succeeded by his son, Ch’oe Hang, who proved not the equal of his father or grandfather. More arrogant and hasty than his father, he struggled to maneuver the complicated politics of Koryo and Mongol attacks. Within a few months there was an attempted coup against him, and his reaction alienated major allies, at a time when they couldn’t afford to lose a single one.

 

In 1251 Mongke was confirmed as Great Khan; driven by the need to complete the conquests, the continued independence of Koryo was not something he could abide. Again, envoys demanded the Korean King visit the Mongol court and abandon Kanghwa island. Again, excuses were made.  King Kojong was too old and sickly for such a trip, but they could discuss the possibility of considering sending the Crown Prince. At the same time, the Koreans prepared for the expected invasion. At the quriltai in 1252 wherein Kublai was ordered against Dali and Hulegu against the Caliph in Baghdad, forces were organized to attack Korea. Prince Yeku invaded in August 1253 alongside Amukhan and Hong Pogwon. Envoys preceded him stating he was there to find out if King Kojong was as sick as he said he was. He had six days to comply and meet Mongol representatives on the mainland. Kojong actually met with Mongol envoys on the straits across from Kanghwa island, and achieved precisely nothing. Mongol forces rode and burned across the peninsula, inland settlements were abandoned for coastal and mountain defenses. Pyolch’o raids attacked Mongol parties, and Mongols destroyed the cities which fell to them. Yeku was held up and fell ill during the long siege of Ch’ungju, ably defended by Kim Yunhu, the same Buddhist Monk who had killed Sartaq some 20 years prior. Ultimately, Mongke recalled Yeku before the end of the year due to his feuding with another prince. Amukhan and Hong Pogwon continued the campaign for a few more weeks, organizing a brief effort at amphibious warfare: seven captured Korean ships landed troops on Kal Island in early 1254, to no great result. Amukhan pulled the troops back in spring, returning in August with reinforcements under Jalayirtai Qorchi.

 

Jalayirtai brought a variation on the Mongol demands for submission. Now ministers and people had to shave their heads in the Mongol style: leaving only a tuft on the forehead between the eyes, and over the ears to be braided into loops. He also demanded Ch’oe Hang and King Kojong come to the mainland. Predictably, Ch’oe Hang was unwilling to do so. Early in summer 1255 Jalayitrai and Amukhan fell back to the northern border; by then, aside from years of destruction and abandonment of farmland, the peninsula was also in the midst of an ongoing drought. We are told in the first year of Jalayirtai’s command in Korea an estimated 206,8000 persons were taken captive. The suffering was horrific. Jalayirtai’s forces attacked again in autumn 1255, beginning a ship building program. Frustrated with continued resistance from the Korean court, the Mongols were considering assaulting the well defended Kanghwa Island. A sense of Jalayirtai’s frustration is evident in his response to Korean envoys in mid-1256. The envoys came asking for peace and Mongol withdrawal, to which Jalayirtai, incensed with pyolch’o attacks in the night, snapped “if you desire peace and friendship, then why do you kill our soldiers in great numbers?”

 

Jalayirtai’s movement of troops back north in autumn 1256 was no respite: in spring 1257, famine gripped even Kanghwa island. As Jalayirtai returned in the spring, it must have been apparent that the Ch’oes were hanging by a thread. Ch’oe Hang soon died, succeeded by his son Ch’oe Ui, who proved a very poor choice. His attempts to win favour by grants of food to the populace and court did not offset bad advisers enriching themselves and his own poor decisions. Alienating just about everyone in the court, the pressure of the situation finally led to a coup. Officers led by Kim Injun assaulted Ch’oe’s palace in May 1258. Ch’oe Ui tried to escape over the walls, but was too fat to get himself over. Caught by the assassins, Ch’oe Ui’s death ended six decades of Ch’oe military rule in Korea. Gaining the support of the elderly Kojong and handing out the wealth of the Ch’oe’s, Kim Injun made himself the new military governor. However, his position was much weaker than the Ch’oe’s had been, and still refused to submit to the Mongols. Mongol envoys who arrived in summer 1258 brought threats that they would storm Kanghwa Island, and in August Jalayirtai received further reinforcements under the command of Yesuder. Refusal to supply either the Crown Prince or the King was met with unchecked destruction across the Korean peninsula. If the Royal court would not come to then, then the Mongols would impose direct rule.  No matter how bloody the pyolch’o attacks were, they could not stop the Mongols.

 

Resistance broke in 1259. Revolts against military rule began across the country, towns and cities surrendered on the arrival of the Mongols rather than continue fighting. With food supplies exhausted, their military forces ground nearly to dust, in the spring of 1259 a peace deal was reached. The Crown Prince, Wang Chon, was to travel to the Mongol court as a royal hostage, the court move back to the mainland, and the defences of Kanghwa be demolished. Kim Injun was not removed but his power was considerably lesser to that of the Ch’oes. Organized Koryo resistance to the Mongol Empire was over. In May 1259, Prince Wang Chon set out for the imperial court, which met a hiccup when Mongke died in August 1259. Wang Chon decided to head for the court of Mongke’s younger brother in China, Kublai. There, he became the first foreign ruler to officially recognize Kublai as the next Great Khan of the Empire. In turn, Kublai provided Wang Chon an armed escort to return to Korea and be installed as the new king, as the venerable Kojong had died in July 1259. Kojong had reigned through the entire Mongol-Korean war, and it was fitting he died only weeks after it ended.

 

Wang Chon, known better by his temple name, Wonjong, proved a loyal vassal to Kublai Khan, marrying his son and eventual successor to one of Kublai’s daughters. Military rule in Korea ended in 1270 after a series of assassinations, and the Korean court finally returned to the mainland. With that, Koryo was a fully incorporated client kingdom. The King ruled in earnest, though with Mongol backing; when briefly ousted by a coup, Kublai’s forces came in and reinstalled him. Yet Mongol demands upon Korea did not grow any less burdensome; rather,. Wonjong had to mobilize the Koreans for another war, this time fighting alongside the Mongols. Koreans ships, food supplies and men were needed by Kublai Khan against the island of Japan, which had spurned his demands for submission. Korea was to be a launchpad for the first Mongol Invasion of Japan of 1274. To coincide with the release of the new SuckerPunch game Ghost of Tsushima which covers that very same invasion, we will have a few special episodes discussing this area, so be sure to subscribe to the Kings and Generals Podcast. To help us keep bringing you content, consider supporting us on Patreon, at (inset patreon link here). I’m your host David, and we’ll catch you on the next one.