[Ancient East Asian History] Goguryeo–Sui War: How Eulji Mundeok Defeated Emperor Yang’s 1.13 Million-Strong Army at Salsu

The Goguryeo–Sui Wars (598–614) were far more than a series of border conflicts.

After conquering the Chen dynasty (陳) in 589 and reunifying China, the Sui dynasty (隋) established a powerful unified empire. The Sui sought to incorporate neighboring states and peoples into an international order centered on the authority of the Chinese emperor. Yet in Northeast Asia, Goguryeo had already established an independent sphere of influence of its own.

Goguryeo had no intention of simply accepting Sui expansion.

At the time, Goguryeo exercised considerable influence across the northern frontier by drawing on the mobility of neighboring nomadic peoples such as the Khitans. As part of its military preparations against the Sui, Goguryeo secretly recruited Sui specialists skilled in the manufacture and use of crossbows and employed their expertise in developing weapons. It also dispatched cavalry forces deep into the Sui’s northern borderlands.

After reunifying China, Emperor Wen of Sui (Yang Jian) attempted to bring Goguryeo into submission. When Goguryeo refused to comply with his demands, the emperor angrily rebuked the Goguryeo king:

“If the king truly required such men, you could have submitted a request to me. Yet in previous years, you secretly distributed wealth to entice petty men and privately induced crossbow specialists to flee to your country. Was this not because your purpose in preparing weapons arose from hostile intentions, and because you feared that others might discover them?”

王必須之，自可聞奏。昔年潛行財貨，利動小人，私將弩手逃竄下國

“Moreover, you have repeatedly dispatched cavalry to kill people along the frontier, repeatedly pursued deceitful schemes, and spread false and improper claims. In your heart, you have shown no intention of submitting.”

又數遣馬騎，殺害邊人，屢騁姦謀，動作邪說，心在不賓。朕於蒼生悉如赤子，賜王土宇，授王官爵，深恩殊澤，彰著遐邇

— Book of Sui (Sui Shu), Vol. 81, “Biographies of the Eastern Barbarians: Goguryeo”

Ultimately, the Sui dynasty’s universal imperial worldview following the reunification of China collided with Goguryeo’s determination to preserve its own independent sphere of influence in Northeast Asia. This geopolitical confrontation eventually escalated into a massive war.

Fought from 598 to 614, the Goguryeo–Sui Wars were among the largest international conflicts of ancient East Asia in terms of the number of troops mobilized, the geographical scale of the campaigns, and the enormous resources committed by both states.

Why, then, did these two powers become locked in such a massive conflict?

1. The Beginning of the War — Goguryeo’s Preemptive Attack on Liaoxi

The first major military confrontation between Goguryeo and the Sui dynasty occurred in 598.

After reunifying China in 589, the Sui expanded its influence toward the northeast. Goguryeo, in turn, regarded the expansion of Sui power as a serious threat to its own security and regional position.

In 598, King Yeongyang of Goguryeo mobilized approximately 10,000 Mohe troops and launched an attack on the Sui dynasty’s Liaoxi region, west of the Liao River.

Goguryeo had chosen to act first rather than wait for a Sui invasion.

Rather than a simple border raid, this attack can be understood as a military response to the Sui dynasty’s expansion into the northeastern frontier.

At the time, Goguryeo was a formidable military power in Northeast Asia and was unwilling to stand by as Sui influence continued to expand.

The attack, however, marked the beginning of a much larger war.

2. The First Goguryeo–Sui War — Emperor Wen’s 300,000-Strong Army

In response to Goguryeo’s attack on Liaoxi, Emperor Wen of Sui immediately launched a massive retaliatory campaign.

In 598, the Sui dynasty appointed Yang Liang, Prince of Han, as commander of an invasion force of approximately 300,000 soldiers and sailors, mobilizing both land and naval forces for a major campaign against Goguryeo.

However, the campaign ran into serious difficulties from the very beginning.

The Sui land forces suffered from heavy rains, supply shortages, and disease during their long-distance march, severely weakening their combat effectiveness.

The Sui navy, commanded by Zhou Luohou, also attempted to attack Goguryeo by sea, but suffered heavy losses due to violent storms and resistance from the Goguryeo navy.

Ultimately, the Sui forces were forced to withdraw without even mounting a major siege against Goguryeo.

According to the Book of Sui (Sui Shu), the expedition suffered catastrophic losses, with only about 10 to 20 percent of the original force returning.

Later accounts also claim that the Goguryeo general Gang I-sik (姜以式), serving as supreme military commander, defeated Sui forces near Linyu Pass (臨渝關), a strategic gateway leading toward the Central Plains of China.

Ultimately, the Sui dynasty’s first major invasion of Goguryeo ended in a disastrous failure.

3. Another Trigger — The 607 Incident at Qimin Khagan’s Camp

Following the war of 598, Goguryeo and the Sui dynasty avoided another large-scale direct confrontation for some time.

The fundamental conflict between the two powers, however, remained unresolved.

In particular, the regional order of Northeast Asia changed significantly as the Sui dynasty weakened and divided the once-powerful Göktürks and brought some of their factions into its sphere of influence.

Then, in 607, a decisive incident occurred.

Emperor Yang of Sui visited Qimin Khagan (啓民可汗) of the Eastern Göktürks, who had submitted to Sui authority.

There, however, the emperor discovered something unexpected: a Goguryeo envoy was present at Qimin Khagan’s camp.

From the perspective of the Sui emperor, this was an extremely sensitive situation.

Goguryeo was maintaining contact with the Göktürks, whom the Sui had only managed to bring under control after considerable effort.

It remains uncertain how far Goguryeo actually intended to pursue a military alliance with the Göktürks. Nevertheless, to Emperor Yang, the very fact that Goguryeo and the Göktürks were in contact could have been perceived as a serious security threat.

Emperor Yang summoned the Goguryeo envoy and demanded that King Yeongyang personally appear at the Sui imperial court.

“Return and tell your king that he ought to come personally and pay homage at court. He should neither be afraid nor harbor doubts. If he treats the empire with proper ritual respect and observes the laws of the imperial court, he will thereby be able to preserve the security of his own kingdom. But if the king of Goguryeo does not come to court, I shall lead Qimin against your country.”

— Samguk Sagi (History of the Three Kingdoms), Vol. 20, “Annals of Goguryeo,” Book 8, 18th Year of King Yeongyang

Goguryeo, however, refused to submit to this demand.

The so-called “Incident at Qimin Khagan’s Camp” became one of the major diplomatic events that contributed to Emperor Yang’s decision to launch a massive invasion of Goguryeo.

A few years later, a military mobilization on a scale rarely seen in the history of ancient East Asia began.

Pei Ju (裴矩, 547–627) was one of the highest-ranking statesmen of the Sui and early Tang periods, as well as a prominent diplomat and geographer. He is particularly remembered for strongly urging Emperor Yang to invade Goguryeo and for providing an ideological and historical justification for the campaign, making him one of the key figures behind the escalation of the Goguryeo–Sui conflict.

Taking advantage of the encounter with the Goguryeo envoy, Pei Ju advised Emperor Yang:

“The land of Goguryeo was originally the state of Guzhu. During the Zhou dynasty, it was granted as a fief to Jizi. Under the Han dynasty, it was divided into three commanderies, and the Jin dynasty likewise governed Liaodong. Yet now Goguryeo refuses to fulfill the duties of a subject and has set itself apart as a foreign realm. For this reason, the late emperor [Emperor Wen] resented it and had long desired to conquer it. It was only because Yang Liang was incompetent that the army was dispatched without achieving success.

“Now, in Your Majesty’s reign, how could this matter be left unresolved, allowing this land of civilized dress and customs to remain among the ranks of the barbarians? The Goguryeo envoy has personally witnessed Qimin Khagan and his entire realm submitting to Your Majesty’s transforming influence. Taking advantage of their fear of imperial power, you should instruct them to come and pay homage at court.”

矩因奏狀曰 : “高麗之地, 本孤竹國也. 周以之封於箕子, 漢世分爲三郡, 晉氏亦統遼東. 今乃不臣, 別爲外域, 故先帝疾焉, 欲征之久矣. 但以楊諒不肖, 師出無功. 當陛下之時, 安得不事, 使此冠帶之境, 仍爲蠻貊之列乎? 今其使者親見啓民擧國從化, 可因其畏威, 諭以朝覲.”

— Book of Sui (Sui Shu), Vol. 67, “Biography of Pei Ju”

Pei Ju (裴矩) Urging Emperor Yang of Sui to Invade Goguryeo

4. The Second Goguryeo–Sui War — The Invasion of 1.13 Million Troops

In 612, Emperor Yang of Sui finally mobilized the full resources of his empire in an attempt to conquer Goguryeo.

According to the Book of Sui (Sui Shu), the expeditionary combat force numbered 1,133,800 troops.

When the enormous number of personnel responsible for logistics, transportation, and other supporting duties is taken into account, the total number of people involved in the campaign was likely far greater.

However, the often-cited figure of approximately three million people when logistical personnel are included should be regarded as a later estimate rather than a precise figure recorded in official contemporary statistics.

Even so, the recorded mobilization of more than 1.13 million combat troops alone demonstrates the extraordinary scale of the campaign.

The Sui army stretched across such an enormous distance that it took a considerable amount of time for all of its units simply to depart for the front.

During the Second Goguryeo–Sui War of 612, Emperor Yang’s massive army of 1,133,800 troops did not simply advance along a single invasion route.

According to the Book of Sui (Sui Shu), one of China’s official dynastic histories, the army was divided into 24 corps—12 forming the Left Wing and 12 forming the Right Wing. The Annals of Emperor Yang records the designated routes of these forces, naming the areas of Goguryeo toward which each corps was ordered to advance.

# The 12 Routes of the Left Wing (左翼)

The Left Wing was assigned routes intended to pressure northern and western Liaodong as well as several of Goguryeo’s major strategic strongholds.

- Loufang Route (鏤方道): Advancing toward the area associated with northern Lelang Commandery

- Changcen Route (長岑道): Advancing toward an old Goguryeo district in the direction of present-day Pyeongan and Hwanghae provinces

- Haiming Route (海冥道): Advancing through territories near the coast

- Gaima Route (蓋馬道): Advancing toward the western approaches of the Gaema Plateau and major defensive positions in Liaodong

- Liaodong Route (遼東道): A direct advance against Liaodong Fortress, one of Goguryeo’s most important strategic strongholds

- Xuantu Route (玄菟道): Advancing toward the Xuantu region, a major strategic area on Goguryeo’s northern frontier

- Tongding Route (通定道): An advance beginning from a forward base near the Liao River

- Lelang Route (樂浪道): Advancing toward the Taedong River basin with the aim of threatening the approaches to Pyongyang

- Lintun Route (臨屯道): Advancing toward northeastern Goguryeo and the eastern coastal region

- Jieshi Route (碣石道): Passing near Mount Jieshi in Liaoxi before entering Liaodong

- Dongti Route (東鯷道): Advancing toward a designated region on the outer reaches of Goguryeo

- Daifang Route (帶方道): Advancing toward the historical Daifang region, associated with the southern Hwanghae and Han River areas

# The 12 Routes of the Right Wing (右翼)

The Right Wing was assigned routes intended to penetrate Goguryeo’s southern, eastern, and interior regions, disrupt its defenses, and contribute to a broader encirclement.

- Zhanchan Route (黏蟬道): Advancing toward the Pyeongan region near the mouth of the Taedong River

- Hanzi Route (含資道): Advancing toward the interior of the Hwanghae region

- Hunmi Route (渾彌道): Advancing along the southern Liaodong coast and nearby river valleys

- Linhuang Route (臨潢道): A flanking route through the northwestern frontier near the Khitan territories

- Lehai Route (樂海道): Advancing toward Goguryeo’s coastal territories

- Tieshan Route (鐵山道): Advancing toward the mountainous defensive zone around present-day Cholsan in North Pyeongan and Liaodong

- Datong Route (大同道): Advancing along a major inland route into Goguryeo

- Shuofang Route (朔方道): Advancing while securing the northern frontier near the Khitan and Mohe territories

- Canghai Route (滄海道): A long advance toward the northeastern and eastern coastal regions

- Fangyu Route (方輿道): A route intended to place pressure on major Goguryeo strongholds

- Mazi Route (馬訾道): Advancing directly toward the Yalu River, historically known as the Mazi River

- Wanghai Route (王海道): A coastal route intended to approach Goguryeo’s southern territories from another direction

# Emperor Yang’s Grand Strategy to Encircle Goguryeo

Emperor Yang divided his enormous army of 1,133,800 troops into 24 corps, intending to attack Goguryeo simultaneously from multiple directions.

Rather than concentrating the entire army along a single axis of advance, the Sui sought to send forces toward numerous regions at the same time. The objective was to disperse Goguryeo’s defensive forces while simultaneously placing pressure on its major strategic strongholds.

In effect, Emperor Yang envisioned a massive multi-front encirclement and annihilation campaign, attempting to envelop Goguryeo’s vast territory with a network of 24 advancing armies and overwhelm its defenses from multiple directions.

Yet an army of such extraordinary size also possessed a potentially fatal weakness.

"Logistics."

Despite their overwhelming numerical superiority, the Sui forces were unable to capture Goguryeo’s major fortresses quickly. As the campaign dragged on, the enormous size of the Sui army transformed from an advantage into a tremendous burden, requiring a continuous flow of food, equipment, and other supplies.

5. The Impregnable Liaodong Fortress (遼東城) — The Stronghold That Halted the Sui Advance

To penetrate deeper into Goguryeo territory, the Sui army first had to cross the Liao River and break through Goguryeo’s defensive line in Liaodong.

At the heart of this defensive system stood Liaodong Fortress (遼東城), located around present-day Liaoyang in Liaoning Province, China. Situated on relatively open terrain, Liaodong Fortress was one of Goguryeo’s key strongholds, protected by formidable walls and defensive installations. It served as a crucial position in the Liaodong defensive network that blocked the advance of the enormous Sui army.

Emperor Yang committed large numbers of troops and extensive siege equipment to the assault on Liaodong Fortress.

The Goguryeo defenders, however, mounted a determined resistance from behind the fortress walls.

Liaodong Fortress (遼東城)

Goguryeo’s defensive system relied on a network of interconnected fortresses and strongholds designed to delay the enemy’s advance.

While the Sui army concentrated on attacking one fortress, other Goguryeo strongholds continued to resist, placing additional pressure on both the Sui advance and its supply lines.

Another factor that made rapid siege operations difficult was Emperor Yang’s highly centralized command system. Field commanders were restricted in making independent decisions and were required to report important military matters to the emperor for approval.

Despite its overwhelming numerical superiority, the Sui army failed to capture Liaodong Fortress.

As the campaign dragged on, the enormous size of the Sui army increasingly became a weakness rather than an advantage.

More than a million troops had to be continuously supplied with food, weapons, equipment, and other necessities.

Transporting enormous quantities of provisions and military supplies from Zhuo Commandery (涿郡), around present-day Beijing, which served as a major concentration point for troops and supplies, through the Liaoxi region and onward to the front lines in Liaodong was an immense logistical challenge.

Ultimately, Emperor Yang abandoned the idea of breaking through Goguryeo’s Liaodong defensive line fortress by fortress and instead made a bold strategic move.

He decided to strike directly at Pyongyang.

6. The 305,000-Man Strike Force — The March Toward Pyongyang

Emperor Yang organized a special force of approximately 305,000 troops, commanded by generals including Yu Zhongwen (于仲文) and Yuwen Shu (宇文述), and ordered it to advance directly toward Pyongyang, the capital of Goguryeo.

The strategy was to bypass Goguryeo’s defensive positions in Liaodong and strike directly at its capital, potentially bringing the war to a rapid conclusion.

But the plan contained a serious weakness.

The farther the Sui army advanced toward Pyongyang, the farther it moved away from the main army and its supply bases.

The Sui commanders required individual soldiers to carry their own provisions. The loads were so heavy, however, that some soldiers secretly discarded their food supplies along the way.

At the beginning of the march, Sui soldiers were ordered to carry 100 days’ worth of food, together with weapons, equipment, and other military necessities. The resulting burden was enormous. Many soldiers feared that if they continued marching long distances while carrying everything they had been issued, they would collapse from exhaustion before they ever reached their destination.

As a result, some soldiers began secretly burying their food supplies in the ground and abandoning other parts of their loads to reduce the weight they had to carry.

Consequently, as the Sui force advanced deeper toward Pyongyang, its food supplies rapidly dwindled. The logistical problems inherent in sustaining such a massive army on a long-distance expedition became increasingly severe.

It was at this critical moment that Eulji Mundeok (乙支文德), one of Goguryeo’s most renowned generals, emerged as a central figure in the war.

7. Eulji Mundeok’s Strategy of Deception — Exhausting the Enemy Without a Decisive Battle

Eulji Mundeok personally entered the Sui camp in order to assess the condition of the enemy forces.

During his visit, he discovered that the Sui army was suffering from severe food shortages and that many of its soldiers were gradually losing their combat effectiveness due to hunger and exhaustion.

The Sui army had been presented with a rare opportunity to capture Eulji Mundeok.

Before the campaign began, Emperor Yang had issued orders that if the Sui commanders encountered either the king of Goguryeo or Eulji Mundeok, they were to seize them. Yu Zhongwen therefore attempted to detain Eulji Mundeok, but Liu Shilong (劉士龍), who was serving as an imperial pacification commissioner, advised against it. Eulji Mundeok was ultimately allowed to leave.

Soon after Eulji Mundeok departed, however, Yu Zhongwen regretted his decision. He sent a messenger after him, saying that “there are matters that we must discuss further,” in an attempt to lure him back.

Eulji Mundeok had already realized what was happening. He refused to return, crossed the Yalu River, and safely rejoined the Goguryeo forces.

Through this brief visit, Eulji Mundeok was able to assess firsthand the condition of the Sui forces and the severity of their food shortages. He then began to exploit these weaknesses through a deliberate strategy of deception and withdrawal.

In the battles that followed, Eulji Mundeok repeatedly engaged the Sui forces and then deliberately appeared to suffer defeat before retreating.

According to the Book of Sui (Sui Shu), the Goguryeo forces fought the Sui army several times in a single day and repeatedly appeared to be defeated.

These apparent defeats, however, were part of a calculated strategy designed to draw the Sui army deeper into Goguryeo territory and exhaust it completely.

Believing that they were winning battle after battle, the Sui forces continued their advance.

Yet the closer they came to Pyongyang, the more unfavorable the situation became for the Sui army.

The troops were exhausted, food supplies were running dangerously low, and their line of retreat was growing increasingly long.

It was at this moment that Eulji Mundeok sent a famous poem to the Sui general Yu Zhongwen.

8. Eulji Mundeok’s Poem to Yu Zhongwen — A Poem Sent to the Sui General Yu Zhongwen

The Samguk Sagi (History of the Three Kingdoms) preserves a poem that Eulji Mundeok reportedly sent to the Sui general Yu Zhongwen.

# 與隋將于仲文詩 (A Poem Sent to the Sui General Yu Zhongwen)

神策究天文 (Your divine strategy has fathomed the ways of Heaven.)

妙算窮地理 (Your marvelous calculations have mastered the principles of the Earth.)

戰勝功旣高 (Victorious in battle after battle, your achievements are already great.)

知足願云止 (May you know when enough is enough, and now bring your advance to an end.)

A more literal rendering would be:

“Your marvelous strategy has fathomed the principles of Heaven,

Your brilliant calculations have exhausted the principles of the Earth.

Your victories in battle have already brought you great achievement;

May you know when enough is enough and now stop.”

On the surface, the poem appears to praise Yu Zhongwen’s brilliant strategy and military achievements.

Its actual meaning, however, was quite the opposite.

In effect, Eulji Mundeok was telling him:

“Do you not think you have already won enough? If you advance any farther, you will be in danger. Turn back while you still can.”

The poem thus combined mockery with a warning.

The final line in particular—知足願云止, meaning roughly “May you know when enough is enough and stop”—was a subtle form of psychological warfare. It played upon the enemy commander’s pride while simultaneously urging him to withdraw before it was too late.

Eulji Mundeok’s way of war was not simply about confronting the enemy in direct battle.

It combined intelligence gathering, deception, disruption of enemy logistics, feigned retreats, and psychological warfare to bring down an enemy force that possessed overwhelming numerical superiority.

9. The Battle of Salsu — The Collapse of a 300,000-Strong Army

After advancing to the vicinity of Pyongyang, the Sui forces finally recognized the danger of their situation and decided to retreat.

By this point, the soldiers were already severely exhausted from the long-distance march and increasingly weakened by severe food shortages.

Eulji Mundeok had been waiting for precisely this moment.

As the Sui army retreated, the Goguryeo forces relentlessly pursued and attacked it.

Then, as the Sui troops were crossing the Salsu River (薩水), the Goguryeo army launched a massive assault.

The Salsu is generally identified with the present-day Chongchon River (Cheongcheon River) in Korea.

This battle became known as the Battle of Salsu, one of the most famous military victories in Korean history.

The Sui army effectively collapsed under the Goguryeo assault.

The Battle of Salsu (薩水大捷)

According to the Book of Sui (Sui Shu), of the 305,000 troops dispatched toward Pyongyang, only 2,700 returned to Liaodong.

Of course, this figure should not necessarily be interpreted as a precise modern-style count of soldiers killed in battle.

The losses may have included not only those killed in combat but also soldiers who deserted, were captured, went missing, or died from disease and other causes.

Nevertheless, there is little doubt that the Sui expeditionary force sent toward Pyongyang suffered catastrophic losses and was effectively destroyed as a fighting force.

The Battle of Salsu was therefore more than a victory in a single engagement.

It was a strategic victory in which Goguryeo used its fortified defensive system to hold down the main Sui army, drew the enemy’s detached force deep into its territory until its logistical capacity was exhausted, and then launched concentrated attacks as the weakened army retreated.

10. The Third Invasion — 613: Another Assault on Liaodong Fortress

Despite the disastrous defeat at Salsu, Emperor Yang did not abandon his ambition to conquer Goguryeo.

In 613, he once again mobilized a massive army and launched another invasion.

The Sui forces crossed the Liao River once more and renewed their assault on Liaodong Fortress.

This time, however, an unexpected crisis erupted within the Sui Empire itself.

It was the rebellion of Yang Xuangan (楊玄感).

Yang Xuangan was a powerful aristocrat and high-ranking Sui official, but he rose in rebellion against Emperor Yang.

At a time when enormous amounts of manpower and resources had already been committed to the campaign against Goguryeo, a major rebellion erupted within the Sui Empire itself.

For Emperor Yang, preserving his own regime suddenly became more urgent than conquering Goguryeo.

As a result, he abandoned the campaign and hurriedly withdrew his forces.

The crisis demonstrated how the prolonged wars against Goguryeo were contributing to the worsening political and social instability within the Sui Empire.

11. The Fourth Invasion — 614: Both Sides Growing Exhausted

Even then, Emperor Yang refused to give up.

In 614, he launched yet another campaign against Goguryeo.

By this point, however, the situation had changed dramatically.

Rebellions were breaking out across the Sui Empire, while the population was suffering under the enormous burdens imposed by years of massive construction projects and repeated military mobilizations.

Goguryeo, too, was under considerable strain after enduring repeated large-scale wars.

In particular, the scorched-earth tactics Goguryeo employed against the massive Sui armies were effective in denying the enemy access to local supplies and forcing it into a prolonged campaign. Yet these tactics also imposed a substantial cost on Goguryeo itself. Moving civilians, food supplies, and livestock into fortified or safer areas—and destroying or removing resources that could otherwise be used by the enemy—inevitably devastated farmland and damaged local agricultural and economic foundations.

Repeated military mobilizations, prolonged fortress defenses, and continuing losses of both manpower and material resources placed additional pressure on the kingdom. As a result, Goguryeo itself was reaching a point where it could no longer sustain an indefinite war without serious consequences.

By 614, therefore, not only the Sui dynasty but also Goguryeo had exhausted a considerable portion of its national resources after years of warfare.

Ultimately, King Yeongyang handed over Husi Zheng (斛斯政), a former Sui official who had defected to Goguryeo.

Emperor Yang used the surrender of Husi Zheng as a justification for withdrawing his army.

From the Sui perspective, this allowed the emperor to preserve face by presenting Goguryeo as having submitted to his demands. From Goguryeo’s perspective, however, the war could be brought to an end while the kingdom retained its effective independence and political system intact.

Moreover, King Yeongyang never personally appeared at the Sui imperial court, despite Emperor Yang’s earlier demand that he do so.

Ultimately, despite four major military campaigns, the Sui dynasty failed to conquer Goguryeo.

12. The Surrender of Husi Zheng — The High-Level Intelligence Asset Goguryeo Gave Up

A particularly intriguing figure emerged during the negotiations that brought the war to an end in 614.

His name was Husi Zheng (斛斯政), a Sui official who had defected to Goguryeo.

Husi Zheng was no ordinary political refugee. He had served as Vice Minister of the Ministry of War (兵部侍郞), making him a high-ranking military official within the Sui government. Although the position cannot be precisely equated with a modern office, it can roughly be understood as comparable to a vice-ministerial or deputy defense minister-level position. His office would have placed him in a position with access to important aspects of Sui military administration and military information.

After becoming implicated in Yang Xuangan’s rebellion, Husi Zheng fled to Goguryeo in 613.

His defection provided Goguryeo with a significant military advantage.

According to the Book of Sui (Sui Shu), after Husi Zheng defected to Goguryeo, the Goguryeo leadership gained detailed knowledge of the Sui dynasty’s internal circumstances. Using this intelligence, Goguryeo mobilized elite troops and launched attacks against the retreating Sui forces.

In other words, from Goguryeo’s perspective, Husi Zheng was an extremely valuable high-level intelligence asset who possessed detailed knowledge of the Sui army’s internal affairs and military system.

By 614, however, the situation had changed.

The Sui dynasty once again invaded Goguryeo, but rebellions and popular uprisings were spreading throughout the empire. Goguryeo, meanwhile, had also exhausted a considerable portion of its national resources after years of repeated large-scale warfare.

Ultimately, King Yeongyang handed Husi Zheng over to the Sui dynasty as a bargaining chip to bring the prolonged war to an end.

Emperor Yang was greatly pleased and portrayed Husi Zheng’s surrender as evidence of Goguryeo’s submission. Yet King Yeongyang continued to refuse Emperor Yang’s demand that he personally appear at the Sui imperial court.

A tragic fate awaited Husi Zheng.

After being handed over to the Sui dynasty, Husi Zheng incurred the intense wrath of Emperor Yang for his involvement in Yang Xuangan’s rebellion and his subsequent defection to Goguryeo. He was eventually executed in Chang’an in an exceptionally brutal manner.

From a modern perspective, Goguryeo’s decision to surrender a defector whom it had previously accepted—and who had even provided it with valuable military intelligence—may appear extremely harsh.

From Goguryeo’s perspective at the time, however, ending the prolonged war with the Sui dynasty and reducing further damage to the kingdom was probably a more urgent practical concern than protecting a single political refugee.

Even so, the surrender of Husi Zheng was a severe decision from the standpoint of humanitarian responsibility and trust. Goguryeo handed back to his enemy a man who had risked his life to defect and had subsequently provided the kingdom with important military intelligence.

Such a decision could also have created distrust among other potential defectors, giving rise to the perception that “Goguryeo might hand defectors back to their enemies whenever political circumstances made it expedient.”

Goguryeo therefore not only lost a highly valuable intelligence asset in Husi Zheng, but may also have damaged its longer-term reputation as a safe destination for political defectors. It is possible that this, in turn, could have negatively affected Goguryeo’s ability to attract defectors and obtain valuable intelligence in the future.

Since the reigns of King Gwanggaeto the Great and King Jangsu, Goguryeo had taken advantage of periods of political turmoil in China by accepting numerous refugees and defectors—including politicians, technicians, and military personnel—and using their knowledge and skills to strengthen the kingdom.

By handing Husi Zheng back to the Sui so readily, however, Goguryeo may have created the impression that “Goguryeo was a state willing to betray defectors once they were no longer useful.” It may even have encouraged high-ranking Chinese officials and intellectuals to conclude that remaining loyal to a Chinese dynasty was safer than defecting to Goguryeo and cooperating with it.

It cannot be entirely ruled out that, over the long term, such a loss of trust may have weakened Goguryeo’s ability to acquire valuable intelligence and, indirectly, contributed to the strategic disadvantages it faced before its eventual fall in 668. In an age without reconnaissance satellites or modern intelligence-gathering technologies, human intelligence was especially important for understanding the internal political and military conditions of a rival state.

Diplomacy that sacrifices trust may produce short-term benefits, but over the long term it can damage a state’s international credibility and ultimately return like a boomerang, leaving it isolated at a decisive moment.

In particular, the decision to return Husi Zheng (斛斯政) to the Sui can be interpreted as reflecting the influence of a peace-oriented or accommodationist faction within the Goguryeo court. A similar diplomatic tendency would later become more visible during the reign of King Yeongnyu (Go Geonmu), when Goguryeo pursued a comparatively conciliatory policy toward the newly established Tang dynasty.

During King Yeongnyu’s reign, Goguryeo permitted the Tang envoy Zhangsun Shi (長孫師) to enter its territory and dismantle the jingguan (京觀)—victory monuments associated with the remains of Sui soldiers killed during the Goguryeo–Sui Wars—and collect and rebury the remains.

Goguryeo also presented the Tang court with a territorial map known as the Fengyutu (封域圖), which contained information concerning Goguryeo’s territory and geographical boundaries. These actions have often been interpreted as part of King Yeongnyu’s broader policy of accommodation toward the Tang dynasty.

A Moderate Goguryeo Delegation Presenting the Fengyutu (封域圖), a Map of Goguryeo’s Territory, to Emperor Taizong of Tang in September 628, the 11th Year of King Yeongnyu’s Reign

Emperor Taizong of Tang, however, was an ambitious ruler who had no intention of allowing Goguryeo to remain a powerful and independent rival indefinitely. As geographical and military information about Goguryeo flowed into the Tang court, neighboring nomadic powers also increasingly aligned themselves with the Tang, leaving Goguryeo facing a growing security threat.

Ultimately, these developments became one of the important factors contributing to Yeon Gaesomun’s coup in 642, which he launched in the belief that drastic political change was necessary to defend the kingdom.

13. The Four Goguryeo–Sui Wars at a Glance

# First War — 598

Goguryeo launches a preemptive attack on Liaoxi with Mohe troops

→ Emperor Wen of Sui mobilizes approximately 300,000 land and naval forces

→ Heavy rains, disease, logistical difficulties, and Goguryeo resistance

→ The Sui expedition ends in failure

# Second War — 612

Emperor Yang mobilizes an enormous expeditionary army of 1,133,800 combat troops

→ Sui forces attack Goguryeo’s defensive line in Liaodong

→ Sui fails to capture Liaodong Fortress

→ A 305,000-man strike force advances toward Pyongyang

→ Eulji Mundeok employs a strategy of deception and withdrawal

→ Battle of Salsu

→ Catastrophic Sui defeat

# Third War — 613

Emperor Yang launches another invasion of Goguryeo

→ Sui forces attack Liaodong Fortress

→ Yang Xuangan’s rebellion erupts within the Sui Empire

→ Emperor Yang is forced to withdraw his army

# Fourth War — 614

Emperor Yang launches his final campaign against Goguryeo

→ Rebellions spread throughout the Sui Empire

→ Goguryeo also faces increasing strain after years of warfare

→ Goguryeo hands Husi Zheng over to the Sui

→ Emperor Yang withdraws his forces

→ The war effectively comes to an end

14. How Did Goguryeo Hold Off the Mighty Sui Empire?

During the Goguryeo–Sui Wars, the Sui dynasty was a great empire whose overall national power was at least ten times greater than that of Goguryeo.

The difference in national power between Goguryeo and the Sui dynasty was enormous.

Goguryeo was a major regional power in Northeast Asia, with an estimated population of approximately 3.5 million people, or around 690,000 households. The Sui dynasty, by contrast, ruled a vast unified empire with a population estimated at roughly 46 to 50 million people, or around nine million households. In demographic terms alone, the Sui Empire may therefore have possessed a population approximately 13 to 14 times larger than that of Goguryeo.

The difference in military mobilization capacity was also substantial. Under conditions of total national mobilization, Goguryeo may have been capable of fielding approximately 300,000 to 400,000 troops, although such figures should be regarded as estimates rather than precise contemporary statistics.

The Sui dynasty, meanwhile, reportedly mobilized 1,133,800 combat troops for Emperor Yang’s second invasion of Goguryeo in 612. Even when compared with the highest estimates for Goguryeo’s military capacity, the Sui expeditionary force alone was approximately three to four times larger.

The contrast became even more striking when logistics and support personnel are considered.

Goguryeo relied heavily on its own network of fortified strongholds and support from local populations to sustain its defensive operations. The Sui, by contrast, had to transport enormous quantities of food, weapons, equipment, and other military supplies over great distances from China into the Liaodong theater.

Some later estimates suggest that more than two million additional personnel may have been involved in transportation, logistics, and other supporting roles for the massive Sui war effort. If such estimates are accepted, the number of people involved in supporting the Sui military campaigns alone would have approached the scale of Goguryeo’s entire population.

In other words, Goguryeo was confronting an empire whose population, military mobilization capacity, and logistical resources vastly exceeded its own.

For this reason, Goguryeo’s victory cannot be explained solely by the brilliance of a single great commander, Eulji Mundeok.

The first major factor was Goguryeo’s formidable fortress-based defensive system.

Goguryeo used a network of fortresses along its frontier to delay the enemy’s advance in successive stages. Despite its overwhelming numerical superiority, the Sui army was unable to quickly capture key strongholds such as Liaodong Fortress.

The second major factor was defense in depth.

Goguryeo did not concentrate all of its forces in a single location and attempt to confront the Sui’s million-strong army head-on.

Instead, it used its network of fortresses to disperse the enemy, slow its advance, and force the Sui to extend its operations over greater distances. As the campaign dragged on, the logistical burden on the Sui army became increasingly severe.

The third major factor was Goguryeo’s exploitation of the Sui army’s logistical difficulties.

An army of more than 1.13 million troops possessed enormous military power, but it also required extraordinary quantities of food, equipment, and other supplies.

The longer the war continued, the more the enormous size of the Sui army itself became a strategic weakness.

The fourth major factor was the use of deception and feigned retreats.

Eulji Mundeok drew the Sui forces deep into Goguryeo territory toward Pyongyang, stretching their supply lines to the limit. He then concentrated his attacks on the enemy during its retreat, when the exhausted Sui forces were at their most vulnerable.

Ultimately, despite possessing far fewer resources than the Sui Empire, Goguryeo was able to neutralize much of its enemy’s overwhelming numerical superiority by exploiting fortifications, terrain, distance, time, and logistics.

15. The Jingguan (京觀) Built from the Remains of Sui Soldiers

Evidence of the brutality of the Goguryeo–Sui Wars remained even after the fall of the Sui dynasty.

Goguryeo constructed a jingguan (京觀) using the bodies and remains of Sui soldiers who had died during the wars. A jingguan was a type of victory monument created after a military triumph by piling up the bodies or remains of defeated enemy soldiers as a visible display of victory.

Jingguan (京觀)

Even after the Sui dynasty collapsed and was replaced by the Tang dynasty, the jingguan remained standing.

In 631, Emperor Taizong of Tang dispatched the envoy Zhangsun Shi (長孫師) to Goguryeo. He was instructed to collect and properly bury the remains of soldiers who had died during the Sui campaigns against Goguryeo and to dismantle the jingguan erected by Goguryeo.

The fact that this monument still existed more than a decade after the fall of the Sui dynasty demonstrates how the physical legacy of the Goguryeo–Sui Wars remained visible within Goguryeo territory.

At the same time, the episode can also be seen as a symbolic indication of the gradually increasing tensions between Goguryeo and the Tang dynasty. Goguryeo remained wary of Tang intentions and, in the same year, began constructing the Cheolli Jangseong (千里長城, “Thousand-Li Wall”) to strengthen its defenses along the northern and western frontiers.

16. The Goguryeo Campaigns and the Fall of the Sui Empire

The failure of the campaigns against Goguryeo dealt an enormous blow to the Sui dynasty.

Of course, the collapse of the Sui Empire cannot be explained solely by its wars against Goguryeo.

During the reign of Emperor Yang, the population was already burdened by massive state projects, including the construction of the Grand Canal, extensive palace construction, and repeated military mobilizations.

The repeated deployment of enormous armies in attempts to conquer Goguryeo placed even greater pressure on the empire’s finances and society.

Eventually, rebellions erupted throughout the empire, and the Sui political order rapidly disintegrated.

In 618, the Sui dynasty collapsed, and the Tang dynasty (唐) emerged as the new imperial power in China.

In other words, the wars against Goguryeo were not the sole cause of the Sui dynasty’s collapse, but they were an important accelerating factor that intensified the political, economic, and social pressures already accumulating within the empire.

17. The Sui Dynasty Fell, but the Grand Canal Survived

Alongside the massive campaigns against Goguryeo, one of the defining projects of Emperor Yang’s reign was the construction and expansion of the Grand Canal (大運河).

The Sui dynasty connected a number of existing canals while constructing new waterways, creating an enormous transportation network that linked the economic centers of southern China with the Yellow River basin.

Through this network, enormous quantities of grain and other goods produced in the prosperous Jiangnan region of southern China could be transported northward far more efficiently than before. This expanded system of waterways and logistics was also one of the important foundations that enabled Emperor Yang to mobilize armies on an extraordinary scale for his campaigns against Goguryeo, particularly the massive invasion of 612.

Yet the construction of the Grand Canal contained a profound paradox.

The enormous labor demands of large-scale construction projects, combined with the repeated mobilization of manpower and resources for the wars against Goguryeo, placed tremendous burdens on the population. These pressures contributed to the spread of rebellions throughout the empire and became one of the factors behind the rapid collapse of the Sui dynasty.

The Sui dynasty disappeared, but the Grand Canal survived.

After replacing the Sui in 618, the Tang dynasty was able to make use of the canal and transportation networks that its predecessor had left behind. The Grand Canal became particularly important for transporting grain and other resources from the economically prosperous regions of southern China to the north.

Over the long term, this transportation network became one of the logistical foundations that enabled the Tang dynasty to conduct large-scale military operations along its northern frontiers.

Ultimately, the Grand Canal that Emperor Yang had constructed at enormous human and material cost failed to save the Sui dynasty. Paradoxically, however, it survived as an important legacy that strengthened the administrative and military mobilization capabilities of its successor, the Tang dynasty.

The Tang later fought a prolonged series of wars against Goguryeo and eventually contributed to the kingdom’s fall in 668.

Of course, Goguryeo’s collapse cannot be explained by the Grand Canal alone. A combination of factors—including the power struggle following Yeon Gaesomun’s death, internal divisions within Goguryeo, the exhaustion caused by decades of warfare, and the Tang–Silla alliance—all played important roles.

Nevertheless, the transportation and logistical system developed under the Sui was inherited by the Tang and strengthened the long-term military and economic mobilization capacity of the Chinese empire. In this sense, the Grand Canal can be regarded as an important piece of infrastructure that indirectly influenced the later wars between Goguryeo and the Tang dynasty.

18. The Historical Significance of the Goguryeo–Sui Wars

The Goguryeo–Sui Wars were massive conflicts that shook the international order of ancient East Asia.

After reunifying China, the Sui dynasty attempted to bring Goguryeo into submission by drawing upon its enormous population and economic resources. Ultimately, however, it failed.

The scale of the 612 campaign was particularly extraordinary, with more than 1.13 million combat troops reportedly mobilized for the invasion.

Goguryeo, however, did not attempt to match the Sui army in numbers and confront it head-on with an equally massive force.

Instead, Goguryeo used its formidable network of fortresses to slow the enemy’s advance, maximized the logistical difficulties faced by a massive expeditionary army operating far from its supply bases, and employed mobile forces to strike at the enemy’s vulnerabilities at critical moments.

The culmination of this strategy was Eulji Mundeok’s victory at the Battle of Salsu.

By resisting the military expansion of the Sui dynasty, Goguryeo also prevented the emergence of a fully consolidated regional order dominated exclusively by the Sui in Northeast Asia. Political states on the Korean Peninsula, including Baekje and Silla, remained outside direct Sui rule and continued to pursue their own political and cultural development.

However, rather than interpreting Goguryeo simply as a modern-style “bulwark defending the Korean nation,” it is historically more accurate to understand the wars in the context of Goguryeo’s struggle for its own survival and its determination to preserve an independent sphere of influence in Northeast Asia.

Ultimately, the Goguryeo–Sui Wars were far more than a series of military campaigns.

They were among the largest international conflicts of ancient East Asia, fought between a vast empire that had reunified China and a powerful military kingdom in Northeast Asia over regional hegemony and the shape of the international order.

Despite possessing far fewer resources than the Sui Empire, Goguryeo successfully resisted its invasions by making effective use of terrain, fortifications, logistics, time, intelligence, and deception.

What the Sui’s million-strong army failed to overcome was not simply the walls of Goguryeo’s fortresses.

The entire state of Goguryeo had become one vast defensive system.

19. Goguryeo’s Military Power Was Still Remembered Nearly 1,000 Years Later

The wars between Goguryeo and the Sui and Tang dynasties were so extraordinary in their scale and outcome that they continued to be discussed during the Joseon period, some 900 to 1,000 years later.

In 1488, the Joseon scholar-official Choe Bu (崔溥) was shipwrecked while traveling from Jeju. After drifting across the sea, he reached Zhejiang Province in Ming China. With assistance from Ming authorities, he subsequently traveled north along the Grand Canal before eventually returning to Joseon.

Choe Bu’s Pyohaerok (漂海錄, Record of a Castaway’s Journey) reveals that Ming officials were still familiar with the history of Goguryeo’s resistance against the enormous armies of the Sui and Tang dynasties.

The Ming officials asked Choe Bu:

“What strengths did Goguryeo possess that enabled it to defeat the armies of the Sui and Tang dynasties?”

Choe Bu replied that Goguryeo had possessed wise ministers and courageous generals who understood how to command their armies effectively. As a result, the soldiers were devoted to their superiors and were willing to sacrifice their lives for their commanders.

According to Choe Bu, this was how the relatively small kingdom of Goguryeo had been able to defeat armies numbering a million men from an empire that ruled All Under Heaven.

Even after some nine centuries had passed, therefore, Goguryeo’s ability to confront the enormous armies of the Sui and Tang dynasties remained a remarkable episode in the historical memory of Ming officials.

“At noon on the seventeenth day of the second month, two Assistant Censors, one surnamed Wang and the other Song, received me at the Guest House and asked: ‘What strengths did Goguryeo possess that enabled it to defeat the armies of the Sui and Tang dynasties?’

“I replied: ‘It had wise and resourceful ministers and brave generals who knew how to command their troops. Therefore, the soldiers all respected and loved their superiors and were willing to die for their commanders. For this reason, although Goguryeo was only a small kingdom, it was still able to defeat the million-strong armies of All Under Heaven on two occasions.’”

— Choe Bu (崔溥), Pyohaerok (漂海錄, Record of a Castaway’s Journey), 1488, 19th Year of King Seongjong of Joseon