Many of you are long time followers of my meager blog—deeply appreciated by yours truly, let me assure you—and so it won’t come as a surprise that a current writing project has me spending a lot of time researching the Mongol conquests. In examining the military history of Korea, in all its dynastic forms, I’ve found myself absolutely engrossed by the accounts from the mid-to-late Goryeo Period and the Korean struggle to ward off the inexorable flood of Mongol aggression. It really is a David versus Goliath kind of story, and I find the details surrounding that episode in Northeast Asian history absolutely fascinating.
Let’s start off with the obvious. It was the Mongols—at the height of their power, no less—against the diminutive, if tough, kingdom of Goryeo, occupying the entirety of the Korean Peninsula as well as small parcels of Manchuria and what is today Northeastern China. The military balance in the mid-13th Century would certainly have argued for the type of engagement most people mistakenly believe took place: the Mongols rolled over the small Korean kingdom and simply took over. After all, the Mongols destroyed two separate dynasties in China (one of which, the Southern Song, was actually Chinese), subjugated innumerable Jurchen and Turkish tribes, utterly destroyed the powerful Central Asian Khwarezmian Empire, cut through Russia, Poland, Hungary, and Bohemia, obliterated the Abbassid Persian Empire—destroying Baghdad in the process—the list of achievements by that uber-aggressive nomadic peoples goes on and on!
And yet, that’s not at all how things played out on the mountainous peninsula we know today as Korea. In fact, the Mongols never achieved the conquest they sought over the Kingdom of Goryeo, settling instead for an alliance with their recalcitrant foes. Now, make no mistake, the character of that relationship increasingly favored the Mongol side of the alliance for the 86 years of the arrangement, to the degree that conscripted Korean sailors and soldiers would help invade Japan, on Kublai Khan’s order, in 1274 and 1281. Yet what is not widely understood is that it took SEVEN campaigns, seven separate invasions of the Korean Peninsula, to reach that negotiated settlement.
The Mongols. Conquerors of much of Asia by this time and casting hungry glances toward Europe. Masters of the steppe, destroyers of a hundred cities, heirs to the largest empire the world had or has ever seen—lined up against little Goryeo—took seven campaigns and twenty-six years to bring the Koreans to a final negotiating table. Not to conquer them, but to get the King of Goryeo to agree to stop fighting and support the Mongol cause. That’s … well … the word “impressive” just doesn’t quite seem to do it justice. It’s incredible!! And it raises the immediate question in my mind … how?
First, let’s never forget what the terrain between Manchuria and the Korean Peninsula looks like. Steep mountains, often separated by deep, fast-moving rivers, with little in the way of forage for a predominantly horse-mounted army. This terrain—I’m fond of calling it a “Defender’s Paradise”—is truly tough going and has, at times with only the slightest assistance from the region’s inhabitants, turned back invading armies and ruined well-planned incursions. This is not a fun place to fight, offering innumerable opportunities to ambush long, strung-out columns of horsemen all but incapable of chasing their assailants back up into the rocky terrain. The difficulty involved, simply from the perspective of military logistics and geography, was truly daunting and was partially or wholly responsible for turning back four invasions by Sui Dynasty China and one by the Tang Dynasty between 598 and 645 A.D. That brutal terrain would continue to serve successive Korean states well into the Joseon period.
Second, while the Mongols were everywhere proving themselves adept at knocking down city walls, they seemed to falter at the fortifications in Korea. Don’t get me wrong, they certainly had their successes, though these were generally limited to locations protected by Chinese-style city walls. The Mongols had long before begun employing Chinese and Persian siege experts in the reduction and subsequent conquests of massive cities like Kiev, Merv, and Baghdad, with predictable, and bloody, results. The mountain fortresses of Korea, called sanseong, and fortified islands like Ganghwa-do, however, proved a tougher nut for the Mongols to crack. That these sites were large enough—often linking multiple high peaks with long masonry walls—to shelter the local populace meant the civilian population couldn’t be used as leverage against Goryeo’s largely military rulers. The militarization of the population, a concurrent development, meant these sieges became more and more difficult for the Mongols to prosecute, and failed attempts to take these fortified sites twice led to the withdrawal of Mongol forces from the kingdom.
Third, the Goryeo military was a largely professional force with a sturdy cavalry arm that was well-versed in fighting the horse-mounted Jurchen tribes to the northeast. Yet these tough veterans found themselves—like most of the civilized world—outmatched by the hard-riding Mongol cavalry. Unable to stand up to the invaders in the open field, the military units of Goryeo increasingly broke into smaller, more maneuverable elements, based at unassailable regional sanseong. These units not only leavened the resistance by civilian defenders of the fortresses, they also maintained the flexibility and military training to conduct small-scale harassment of the larger Mongol armies, especially as the invaders transited the rocky Korean terrain. This effected a continuous drain on Mongol manpower that added up over time and greatly contributed to the invaders’ desire to vacate the Peninsula whenever a lull in the fighting presented itself.
Finally, and this is truly interesting, the Goryeo court proved itself adept at supplemental—if not downright Machiavellian—diplomacy with the Mongols. Agreeing to submit, then killing off Mongol overseers when the army departed, agreeing to terms, then refusing to provide the required tribute, Goryeo diplomats always seemed to be one step ahead of their otherwise experienced and skilled Mongol counterparts. Goryeo’s willingness to wield military force in one hand, and diplomacy in the other, made for a powerful opponent to Mongol intentions, and frustrated attempts to bring the unruly kingdom into line. In the end, Goryeo diplomatic efforts tied down large numbers of Mongol troops who seem to have spent much of their military careers riding back and forth through the treacherous mountain gauntlet. The majority of these forces would return home with little to show for their effort beyond the slaves they managed to round up and lead North. But that limited booty hardly made up for the constant trickle of skilled veteran manpower lost to small-scale hit-and-run-style Korean attacks, difficult sieges, and natural attrition.
In the end, the Mongols achieved their goals only through the destruction of Korean fields and agricultural infrastructure, starving the citizens hiding safely within their mountain and island strongholds. The sixth and seventh invasions are a catalogue of fire and mayhem, and many a Goryeo farmer must have looked on from the walls of his high mountain refuge in apprehension as his home and fields down below were set alight by invaders on horseback. The Mongols, in this way, starved Korea into submission and in 1258 the King sued for peace, negotiating both alliance and tribute.
This state of affairs would last through the establishment of the Mongol-dominated Yuan Dynasty in China in 1271, to the rise of the Ming in 1368. As Mongol power waned, however, Goryeo refused to sit around waiting for their frenemy to depart the Peninsula on their own. Goryeo rebelled and, in loose confederation with the growing power of Ming China, pushed the unwanted foreign influence back across the Yalu River, recovering full independence in 1356.
Once again master of its own fate, the Korean people nonetheless suffered greatly from the effects of their far-ranging and destructive resistance to repeated Mongol incursions. Simmering tensions within the government led to a coup and Goryeo’s military class was overthrown by men who supported the royal court, reinstituting civilian rule and initiating a suppression of Korea’s traditional military families that would continue well into the Joseon period which followed. While this, perhaps, sowed the seeds for the military calamities that would so impact the Yi Dynasty, these terrible events lay well into the future and Goryeo’s final rulers might be forgiven for those fateful decisions given all they’d seen and experienced in the previous three decades.
In the end, the ever-victorious Mongols honored Goryeo’s defiant resistance, allowing for the negotiated settlement. Yet it’s not hard to imagine that concession came as a great relief to Mongol leaders tired of campaigning in such an inhospitable environment.
In a very real sense Goryeo seemed to play the immovable object set against the irresistible force of Mongol conquest … yet the small kingdom had paid dearly for that honor. An honor that today is unfortunately overlooked as simply a minor footnote in the illustrious history of the Mongol conquests. Considering the odds stacked against them, Goryeo deserves better than that.
M. G. Haynes