A Comparative Study of the Military Tactics of the Mongol Empire and Goguryeo Kingdom (Goryeo)

2.1.1 Arrow Storm Tactics

The arrow storm was the most common tactic practiced by the Mongols. During the course of an arrow storm, the Mongol forces simply kept their distance from the enemy and showered them with arrows; archers did not aim at specific targets, but released their arrows at a high trajectory into a predetermined killing zone or target area. The aim of this tactic was to break up the enemy formation enough to allow the Mongolian lancers to finish the job. The range of attack varied; at 200 or 300 yards, their shooting was still accurate enough to disrupt an enemy formation, and once it broke, the Mongol army charged.^[8]

Our chief source of information is the Chinese general Mêng Hung. According to him as soon as the scouting screen of an advancing Mongol army made contact with the enemy, the main body extended its front over as great a distance as possible. This was done to outflank the hostile force. Accounts of the battle formation of the Mongol army are very imperfect, but probably it resembled that of the Jürchät (Chin) in their early days, and consisted of five ranks, two clad in iron scale armor and three in lacquered hide armor. A jaghun (100 men) of these, with the heavy armored ranks in front and the light armored behind, were arranged so as to allow intervals between them. Throughout the action all maneuvers were directed from the station taken up by the senior commander, who rarely if ever participated in the mêlíe. His orders were transmitted by flag signals and bugle calls or at night by lamp and fire signals.

Battle begun, bodies of the light troops, one in support of another, advanced through the jaghun intervals and poured volleys of arrows into the opposing ranks. Simultaneously one or both the wings began an enveloping movement to take the enemy on the flanks and rear. If the first storm of arrows succeeded in disordering his array the shock troops received the command to charge. At times the whole army supported the assault when, says Mêng Hung, even if the enemy numbered 100,000 it was almost impossible to escape defeat. Should the light troops be repulsed by a charge they retired shooting backwards from the saddle, which they could do with deadly effect, and other detachments took their place and repeated the arrow storm.

At Huan-êrh-Tsui (late September or early October, 1211) Genghis Khan, employing this combination of fire and shock action, defeated the most powerful army in the Chin empire. Apparently, the Mongol arrow storm completely disordered the Chin cavalry early in the day, for it was hurled pell-mell back on to its own infantry and involved these in such rout that by noon the Mongols were driving before them a broken and flying enemy.^[9]

Also, this tactic was used by the Mongols in the Goryeo Dynasty, which succeeded Goguryeo. In 1231, the Mongols attacked Goryeo, and at this time, the three armies of Goryeo started fighting the Mongols. At that time, the Mongol army all dismounted and built a large formation, and out of nowhere cavalry rushed and charged the right army of Goryeo. The arrows of the Mongols rained down like rain.^[10] The record in The History of Goryeo (高麗史) can be said to be a case in which the Mongol army invaded Goryeo during the Goryeo Dynasty, which succeeded Goguryeo, and used the arrow storm tactics.

2.1.2 Caracole Tactics

Another tactic employed by the Mongols on the battlefield was the caracole tactic, also called the charge and shoot tactic. Approximately 80 men in each jaghun, or company, participated; the remaining 20 acted as heavy cavalry. Each jaghun sent 20 men per wave of attackers, and each wave fired several arrows as they charged. They released their final shots roughly 40–50 m from the enemy lines before circling back to their own lines. This distance was close enough to pierce armor, yet distant enough to evade a counter charge. Furthermore, on the way back to their line, the Mongols used the Parthian shot, a light horse military tactic, to keep up the barrage. When they reached their own lines, the next wave would move forward and continue the process. Also, they changed horses frequently to keep their mounts fresh. Since each man was equipped with 60 arrows, the Mongols could maintain this barrage for almost an hour, perhaps longer. Marco Polo reported the following concerning the Mongol army’s advance:

When they come to an engagement with the enemy, they will gain the victory in this fashion. [They never let themselves get into a regular medley, but keep perpetually riding round and shooting into the enemy. And] as they do not count it any shame to run away in battle, they will [sometimes pretend to] do so, and in running away they turn in the saddle and shoot hard and strong at the foe, and in this way make great havoc.^[11]

2.1.3 Feigned Retreat Tactics

The feigned retreat was a classic tactic of Mongol steppe warfare. A token force charged the enemy and then retreated in order to attract them. The retreat might extend a great distance in order to stretch the enemy’s ranks and formations. Then, at a prearranged location, other Mongol forces ambushed and attacked the enemy force from the flanks, while the initial force turned around and attacked the enemy’s front.^[12] The ‘Secret History of the Mongols’ described this form of attack in the following passage:

After that, in the Year of the Sheep, Chinggis Qahan rode out against the Kitad people. Taking Wujiu, he crossed the Fox Pass and seized Söndeiwu, sending Jebe and Güyigünek-ba’atur [ahead] as vanguards. On arriving at Chabchiyal, [Jebe and Güyigünek-ba’atur found] that guards had been posted on the Chabchiyal Pass. Then Jebe said: ‘We shall lure them into moving. When they come [after us], we shall fight them.’ He then turned back. The Kitad soldiers decided to pursue him. As they drew nigh, they choked the valleys and mountains. On reaching the provincial capital, Söndeiwu, Jebe reined in [his horses] and turned back. He attacked the advancing enemy, which was growing [ever] bigger, and overcame them.^[13]

2.1.4 Fabian Tactics

Another important tactic utilized by the Mongols was the Fabian tactic. At times the Mongols avoided combat with the enemy until they found an ideal location for battle or had regrouped far-flung forces to confront their opponent. When the Mongols were confronted by an enemy who, for instance, planted spears in the ground to prevent cavalry charges, they responded by withdrawing the bulk of their forces and leaving behind a few detachments to harass the enemy. Eventually, as the enemy emerged from their defenses, the main Mongol force would return to destroy them. The ‘Secret History of the Mongols’ described the Fabian tactic as follows:

After receiving this message, Chinggis Qahan issued a decree: ‘[They] are many and will lose many, [we] are few and will lose few.’ Facing them, he rode out and routed their watchmen. He [and his captains] decided to attack and to [re]organize the soldiers to march in ‘bushclump’ formation, stand in ‘lake array’, and attack with the ‘chisel’. Chinggis Qahan himself [joined] the vanguard. He put Qasar in charge of the main army and Otchigin-noyan in charge of the reserve horses.^[14] The ‘bush clump’ formation entailed dividing the soldiers into numerous small groups that kept contact with each other but maintained a low profile as they advanced. The ‘lake array’ entailed sending waves of men to surround and attack the enemy on all sides. The ‘chisel attack’ entailed direct hand-to-hand combat by a line of soldiers that drives straight through the middle of the enemy ranks.^[15]

Even when the Mongol Empire invaded Goryeo, records of the Mongol army using Fabian tactics can be found. According to the record of December 16, 1232 in the History of Goryeo, the Goryeo army fought against the Mongols in a small castle in Bugok, Cheoin, and shot and killed their enemy general Salyetop. It seems that from this point on, their energy was weakened and they could not comfortably stay in a certain place, so they withdrew their troops. However, it is recorded that they did not gather all at once, or they went first, or they fell behind, and since they are flashing in the east and in the west, it is not known until what day they all disappeared or where they went.^[16]

2.1.5 Open-The-End Tactics

When using open-the-end tactics, the Mongol army sought to encircle their enemies, especially if their flanks and rear were exposed. In this case, the Mongols sometimes confused their enemy by feinting at the front and then unleashing the main attack on their rear. By attacking from several directions, the Mongols gave the enemy the impression that they were surrounded. However, the Mongols opened a gap in their encirclement, encouraging the enemy forces to attempt to flee. In reality, the gap served as a trap. Other Mongol forces appeared on both sides, rode alongside, and attacked them. In their panic and desire to get away, the enemy rarely maintained discipline and often discarded their weapons to flee faster. The escaping troops found themselves hunted down and without the protection of their weapons.

During the Mongolian invasion of Europe, Batu Khan and General Subedei inflicted a crushing defeat on King Béla IV’s Hungarian army, which was renowned for having the best cavalry in Europe. The Mongols burned the city of Pest and seized control of the Hungarian plain. Mongol general Subedei planned an invasion of Europe in which a three-pronged assault on Hungary was supported by a campaign in Poland. The main invasion force destroyed Hungarian defenses in the Carpathians and swept across Hungary, stopping on the banks of the River Sajo. King Béla IV encamped on the opposite bank, his army of 100,000 outnumbering the Mongols by at least 20,000.

On 10 April, Batu Khan attacked: he and his brother, Prince Shiban, led a frontal assault across the river while Subedei rode northward in search of a ford by which his troops could cross and attack the Hungarians from behind. Batu and Shiban struggled to make headway, but then unleashed catapult-fired explosives that drove the Hungarians back. Once across, they wheeled around and turned the Hungarian position so it would be vulnerable to Subedei when he arrived; then Batu ordered his men to retreat and line up in single file.

Subedei’s troops arrived and deployed in the same way behind the Hungarians, who-realizing they were about to be encircled by archers—charged out to regain their camp. Subedei pursued them and bombarded the camp with explosives, finally sending in his heavy cavalry. A column of Hungarians fled back toward Pest but was pursued and shot down by the mounted Mongol archers.^[17]

2.2.1 Iron Armored Cavalry Assault Tactics

Goguryeo craftsmen made weapons as well as agricultural tools using various iron-carbon alloys such as nearly pure iron (with a carbon content of less than 0.02 percent), cast iron (with a carbon content greater than 2 percent), and steel (with a carbon content somewhere between the two). They were fluent enough to freely choose among them. For instance, to make an ax they made only the tip out of steel and the rest of pure iron.^[18]

The Goguryeo army created the iron armored cavalry in the 2nd century to overcome the weakness of light cavalry and to ensure strong protective equipment for the soldiers.^[19] Both soldier and horse wore iron armor and helmets, and fought the enemy with long iron spears.^[20] This tactic spearheaded the iron armored cavalry as the attacking force. In battle, the cavalry broke through the opponent’s line of defense by short, fast, and powerful attacks, and then dislocated the enemy defenders. Their assault was the dominant shock attack.^[21] When the iron armored cavalry broke the enemy’s front line, the infantry and light cavalry immediately reinforced them in their attack.

For example, in the case of the so-called Achasan Fort in Korea, there was a furnace, but no cauldron was left behind and only a few weapons were found. Archaeologists did, however, discover an iron helmet of a Goguryeo soldier inside the furnace-the first of its kind to be found in South Korea. This is a rare artefact, particularly when in all of Korea, only five Goguryeo helmets have been uncovered. The Achasan Fort helmet is what is known as a scale helmet, and is made by connecting many tiny pieces of metal with leather strings. A research team found 52 pieces of metal less than a 10th of an inch thick that would have made up the helmet, as well as 280 pieces that may possibly have been used for scale body armor. This type of flexible armor made it easier for soldiers to move while still being protected. In Goguryeo murals, there are depictions of a soldier, along with his horse, wearing a magnificently intricate scale helmet and armor that covered him from neck to ankle. But so far only two sets of Goguryeo-era scale armor have been found in South Korea, the first in 2011 in Yeoncheon and the second in 2014 in Yangju, both in Gyeonggi Province.

While discoveries of Goguryeo armaments are rare, on Mount Acha a total of 1757 pieces of Goguryeo weapons have been found, which South Korean archaeologists say is a higher number than the total reported to have been found in North Korea and China. Of those, iron arrowheads make up the largest portion, followed by metal pieces of scale armor.

These finds provide an important window into Goguryeo iron-making technology, which is known to have been the most advanced among the Three Kingdoms, and one of the factors that made the Goguryeo military so powerful. A study of Goguryeo-era iron discovered on Mount Acha found that Goguryeo artisans employed the same sophisticated ironworking technologies that were in use in China and the west at the time. Goguryeo openly accepted technologies from Europe, Persia, and China, and this attests to the broad-minded and unrestrained spirit and nature of the dynasty’s people that even contemporary Koreans often admire.^[22]

2.2.2 Ambush Tactics

The terrain of the Goguryeo kingdom was mostly mountainous, and the Goguryeo army took advantage of this rugged terrain. They would use the ambush tactic in rough mountainous areas or valleys. In battle, if the enemy force impatiently pursued the Goguryeo army, they often retreated to a river, passing through a valley. When half of the enemy forces had crossed the river, the Goguryeo army would ambush and make a surprise attack from the riverbanks. Meanwhile, the other Goguryeo force would hide in the valley to prepare for a secondary ambush. The enemy forces who had been attacked at the river retreated to the valley where the other Goguryeo force lay in ambush ahead. Meanwhile, the Goguryeo light cavalry pursued the retreating enemy. Finally, when the enemy passed through the valley, the Goguryeo force cut off the retreat and ambushed them.^[23]

Korean countries have always had an over-amplified influence on their Han Chinese neighbors, perhaps because Korea has almost always been China’s strongest and closest immediate neighbor. Similarly, these tensions between Korean kingdoms in the late 500s affected mainland China. In the 580s, the Sui had succeeded in uniting most of the Han Chinese under their new rule. At the same time, however, a new power was rising in the northern steppes of Siberia, the Gokturks (돌궐, 突厥), who would eventually become the Khitan people (거란, 契丹). They posed a direct threat to the newly-arrived Sui, and they created a great opportunity for Goguryeo.

With its vast kingdom stretching over today’s South Korea, all of North Korea, most of Manchuria, all of Liaoning Province, all of Jilin Province, most of Heilongjiang Province, many parts of eastern Inner Mongolia, and most of Primorsky Krai, Goguryeo saw this as an opportunity. It reached northward to forge ties with the Gokturks, just as its ally, Baekje, reached southward to forge ties across the sea with Wa (왜, 倭), a broad collection of Kofun/Asuka kingdoms (고훈 시대, 古墳時代/아스카 시대, 飛鳥時代).

Thus, a great north–south axis was formed: the Gokturk-Goguryeo-Baekje-Wa (Siberia-Manchuria-Korea-Kyushu). To counter this, Silla teamed up with Sui to form an east-west axis: the Silla-Sui (Korean Peninsula-Mainland China). It is here that we lay our scene.

The final decisive test of strength between these two axes was between Goguryeo and Sui in A.D. 612, and Eulji Mundeok was the Goguryeo general in charge. Goguryeo Army Commander Eulji Mundeok mixed head-on attack with guerrilla tactics, when it suited him, and strategic retreat and deception, when the odds were harsh.^[24]

Goguryeo was the first to open hostilities. In 598, it launched a lightning assault across the Liao River (랴오허, 遼河) in southern Manchuria, just north of the Liaodong Peninsula (랴오둥 반도, 遼東半島). The Sui monarch, Wen (수 문황제 양견, 隋 文皇帝 楊堅) (r. 581–604), launched a retaliatory attack against Goguryeo. He was unsuccessful and had to turn back.

In 612, the next Sui monarch, Yang (수 명황제 양광, 隋 明皇帝 楊廣) (r. 604–618), launched another retaliatory attack. This time, Sui was better prepared. Yang had gathered an unprecedentedly large army to send into Goguryeo-Manchuria. The texts estimate that it involved 1,000,000 soldiers.

The anchor of Goguryeo’s first line of defense was the fortress at the modern-day city of Liaoyang (랴오양시, 遼陽市) in today’s Liaoning Province (랴오닝성, 遼寧省). Splitting his forces and lightening the siege, Yang decisively ordered about a third of his force – say, 300,000 men – to break off southward and to head directly for the Goguryeo heart in Pyeongyang.

Just north of Pyeongyang is where Eulji Mundeok laid his trap. Eulji Mundeok used a strategy similar to that used by the USSR against the Nazi invasion of 1941. Eulji retreated and retreated, strategically, drawing the invading army further and further from its supply lines. Tactically, he used weather to his advantage, in this case the rainy season and a river. Also tactically, he laid ambushes and chose the time and place of his battles.

The Cheongcheongang River (청천강, 淸川江) flows westward into the Seohan man of Korea Bay, through today’s town of Anju-si in Pyeongannam-do Province. In older forms of Romanization, it’s sometimes called the “Salsu River.” The battle is sometimes called the Battle of Salsu (살수대첩, 薩水大捷).

This is where Eulji Mundeok sprung his trap. He made grand feints and thrusts, and made use of his knowledge of the terrain. The story goes that he had dammed the river, swollen with the rainy season, and then at the crucial moment broke the dams to release the raging water, washing away the Sui soldiers. Texts tell us that only 2700 of the 300,000 Sui soldiers survived to find their way back home. The battle was decisive. Yang lifted his siege of the Goguryeo fortress at Liaoyang, packed up his forces, and headed back to mainland China. Yang continued to send smaller armies against Goguryeo-Liaoyang, but to no avail. These losses led directly to the Sui collapse in 618, allowing for the rise of the Tang (당, 唐). Ignoring, or perhaps even fearing, Goguryeo and other Korean kingdoms, the Tang focused their energies elsewhere and managed to reign quite successfully for just under 300 years.^[25]

2.2.3 Defense First and Offense Later Tactics

When the enemy force was strong, the Goguryeo army was stuck inside and defended the fortress first. However, when the enemy force exposed their weakness, the Goguryeo army immediately opened the gate and sent the cavalry outside to attack the enemy. If the enemy forces fled, the Goguryeo cavalry kept up their pursuit, while other Goguryeo forces waited and ambushed them.

Since 2000, a number of fortresses, villages, and Goguryeo tombs have been found in South Korea, supporting the theory that the southern part of the peninsula was, in fact, important to the kingdom. Mount Acha is now understood by scholars to be the largest Goguryeo site in South Korea. During the Three Kingdoms Period (57 B.C.–A.D. 668), the Goguryeo, Silla, and Baekje Kingdoms fought one another fiercely to gain sovereignty over the area, a contest that played out on Mount Acha as it did across the peninsula. For example, the murals show that, after the fourth century, a Goguryeo soldier’s main weapon was a spear. Researchers posit that because 10 spear points were found at the Guui-dong Fort, 10 soldiers were stationed there. Further, based on the size of this fort, they have concluded that the biggest Goguryeo fort on Mount Acha could have accommodated up to 100 soldiers. Arrowheads make up the largest number of the nearly 2000 remnants of weapons found at Mount Ahca. Researchers believe that each Goguryeo soldier was armed with at least 300 arrows.^[26]