What Happened at the Battle of Salsu in 612? Eulji Mundeok, Goguryeo's Strategist

At the Battle of Salsu in 612, the Goguryeo general Eulji Mundeok lured a large Sui expeditionary force deep into his country, then attacked it as it retreated across the Salsu River, today's Cheongcheon River in North Korea. Traditional records say that of the roughly 300,000 men sent toward Pyongyang, only about 2,700 made it back. Those figures come from ancient chronicles and should be read as approximate, but the outcome is clear: the campaign failed, and Eulji Mundeok became one of the most celebrated commanders in Korean history.

Goguryeo and the Sui: a short background

In the early seventh century the Korean peninsula and southern Manchuria were divided among the Three Kingdoms of Korea: Goguryeo in the north, Baekje in the south-west and Silla in the south-east. Goguryeo was the largest, with its capital at Pyongyang. Across the Liao River, China had recently been reunified by the Sui dynasty, which conquered its neighbouring rivals in 589.

Relations between the two powers were tense. In 597 Goguryeo attacked a Sui frontier post, and a Sui invasion the following year failed. In 612 Emperor Yang of Sui launched a far larger campaign. The chronicles give a figure of over a million soldiers, plus many more in support; modern readers treat such numbers with caution, but there is no doubt it was an enormous undertaking.

A general we know mostly from one war

Remarkably little is known about Eulji Mundeok's life outside this campaign. His birth and death dates, his family and even his origins are uncertain. An eighteenth-century work says he came from Seokda Mountain near Pyongyang, and other theories exist, but none is certain. The twelfth-century Korean history Samguk sagi describes him as calm, resolute and gifted in both strategy and writing. That combination, a soldier who could also write, matters for his story.

Wearing the enemy down

The main Sui army became bogged down besieging Goguryeo's fortresses on the Liaodong frontier. Emperor Yang then sent a separate force of about 305,000 men, the article calls the figure nominal, to march directly on Pyongyang under the generals Yu Zhongwen and Yuwen Shu.

These soldiers had been issued supplies meant to last the whole march. Exhausted by the weight, many abandoned their load along the way, and the force ran short of food. Eulji Mundeok's strategy exploited this weakness. He avoided a decisive battle, drew the Sui troops further from their supply bases and wore them out.

A bold visit to the enemy camp

The most daring moment of the campaign came when Eulji Mundeok went to the Sui camp himself, pretending to surrender, so that he could judge the enemy's condition. Yu Zhongwen had been ordered to seize him, but another official advised letting him go to negotiate, and he returned safely. The Sui generals realised their mistake too late and set off in pursuit.

The poem to Yu Zhongwen

As the Sui army pressed on, the Goguryeo general sent Yu Zhongwen a short poem. It is counted among the earliest surviving Korean poems written in classical Chinese. Its four lines praise the Sui commander's strategy as reaching the patterns of heaven and earth, then suggest that, having won so much glory, he should be content and stop. The praise is ironic. The message underneath was an invitation to leave.

The battle at the river

By then the Sui force was close to Pyongyang, hungry and far from help. A Sui naval force carrying supplies had also been defeated near the city, and the commanders decided to retreat. As they crossed the Salsu, Goguryeo troops attacked the rear of the column. The retreat turned into a rout, and according to the records only around 2,700 men returned.

The dam story: a legend

Many popular retellings say that Eulji Mundeok dammed the river and released the water on the crossing army. It is a vivid image, but no contemporary source attests to a dam or a water attack; the idea appears in modern writing, including the historian Shin Chae-ho. It is best treated as legend.

Aftermath and legacy

Emperor Yang withdrew. Yu Zhongwen and Yuwen Shu were stripped of rank, and further Sui campaigns in 613 and 614 also failed. The cost of these wars added to the internal revolts that brought down the Sui dynasty, which was replaced by the Tang in 618. After this war, Eulji Mundeok disappears from the records.

In South Korea his name is everywhere: Euljiro, a major street in central Seoul; a high military decoration; and a navy destroyer all carry it.

Learn with Eulji Mundeok: English phrases about strategy

Phrase	Meaning	Example
to wear someone down	to make someone tired over time	He wore the enemy down before fighting.
to lure	to tempt someone into a place or trap	He lured the army deep inland.
to call someone's bluff	to test whether someone is serious	The Sui generals failed to call his bluff.
to cut your losses	to stop before things get worse	His poem urged the enemy to cut their losses.
a rout	a complete, disorderly defeat	The retreat turned into a rout.

Try this: Write three English sentences about a time you decided to cut your losses, or wished you had. Use "wear down" and "cut your losses" at least once.