Battle of Salsu (612): Eulji Mundeok Defeats the Sui Army

The Battle of Salsu was a decisive victory of the Korean kingdom of Goguryeo over an invading army of the Chinese Sui dynasty in 612. Led by the general Eulji Mundeok, Goguryeo forces lured a large Sui expeditionary force deep into their territory near Pyongyang, then attacked it as it retreated across the Salsu River, usually identified with today’s Chongchon River. According to the Book of Sui, only 2,700 out of 305,000 men returned, making the battle one of the most famous defeats in Chinese and Korean history.

Background: Sui and Goguryeo

After the Sui reunification of China in 589, the Sui emperors expected neighbouring states to accept a subordinate position. Goguryeo, the largest of the Three Kingdoms of Korea, controlled a broad territory from the Liaodong peninsula in modern China to the Han River region, with its capital at Pyongyang.

Relations were tense. In 598 Goguryeo raided across the Liao River frontier, and Emperor Wen of Sui sent a large army in retaliation, but it was defeated by bad weather, disease and supply shortages before achieving much. When Emperor Yang came to the throne in 604, he grew suspicious after discovering in 607 that Goguryeo had been in contact with the Eastern Turks, and demanded that King Yeongyang come to his court. The king refused.

The great invasion of 612

Emperor Yang prepared a vast campaign. The Grand Canal, extended north to Zhuojun near modern Beijing in 608, carried supplies to the assembly area. According to the Book of Sui, the army that marched out in early 612 numbered 1,133,800 combat troops, organised in 24 divisions, with twice as many supply workers. Modern historians consider these figures exaggerated, but the force was certainly one of the largest of the medieval world.

The Sui crossed the Liao River on pontoon bridges after heavy fighting and besieged Liaodong fortress (near modern Liaoyang). Goguryeo’s stone fortresses proved hard to take. Commanders were under orders to refer any offer of surrender to the emperor, and Goguryeo defenders used this repeatedly to gain time, so the siege dragged on for months.

Goguryeo’s defence relied on a network of mountain and plain fortresses with thick stone walls, many built on hills with their own water sources. When an enemy approached, farmers moved into the fortresses with their grain and livestock, leaving little in the countryside for invaders to seize. This strategy forced a large army to besiege strongholds one by one while its own supplies, carried over hundreds of kilometres, steadily ran down.

A Sui fleet under Lai Hu’er sailed to the Taedong River and landed near Pyongyang. After plundering the outer city, his troops were ambushed and driven back to their ships with heavy losses.

The march on Pyongyang

Frustrated by the delays, Emperor Yang sent a separate force of nine armies, given in the Book of Sui as 305,000 men, under the generals Yu Zhongwen and Yuwen Shu, to march directly on Pyongyang. Each soldier was issued about 100 days’ rations, as well as weapons and equipment. Many found the load too heavy and secretly buried their food, so the army began to run short of supplies by the time it reached the Yalu River.

Eulji Mundeok visited the Sui camp, pretending to negotiate a surrender, and used the chance to observe the soldiers’ condition. He then left before he could be detained. As the Sui advanced, he fought a series of small actions and deliberately retreated, drawing them further south. The Sui histories say that Yu Zhongwen won seven engagements in a single day, but every victory pulled his hungry troops deeper into hostile country.

The Sui army crossed the Salsu and halted about 30 li (roughly 15 km) from Pyongyang, whose walls were too strong to storm without supplies. According to both Chinese and Korean sources, Eulji Mundeok sent Yu Zhongwen a short poem mockingly praising his brilliant strategy and suggesting that, having won so much, he should be content and go home. He also offered a sham surrender, promising that the king would visit the emperor if the Sui withdrew.

The battle at the river

With no realistic way to take Pyongyang, the Sui generals ordered a retreat. Goguryeo forces harried them on all sides. When the Sui army reached the Salsu and about half of it had crossed, Eulji Mundeok’s troops attacked the rearguard. The general Xin Shixiong was killed, and the army collapsed into flight.

According to the Book of Sui, the survivors fled about 450 li to the Yalu River in a single day and night. Of the 305,000 men who had set out, only 2,700 returned to the Sui lines. These numbers may include stragglers and should be read with caution, but there is no doubt that the expeditionary force was destroyed. Emperor Yang abandoned the campaign and withdrew in the autumn of 612.

Key people

• Eulji Mundeok: Goguryeo general and minister who planned the campaign of retreat and counterattack.
• King Yeongyang (r. 590–618): king of Goguryeo during the wars with Sui.
• Emperor Yang of Sui (r. 604–618): who led the invasion in person.
• Yu Zhongwen and Yuwen Shu: Sui commanders of the expedition against Pyongyang, both dismissed after the defeat.

Myths and facts

A widely told Korean story says that Goguryeo dammed the Salsu River and released the water as the Sui army crossed, drowning thousands. This dramatic episode does not appear in the Book of Sui or in the Korean Samguk Sagi of 1145, which describe a surprise attack on the rearguard during the crossing. It is best regarded as later folklore.

The poem sent to Yu Zhongwen, by contrast, is recorded in early sources and is often described as one of the oldest surviving poems by a Korean author.

Consequences

Emperor Yang invaded Goguryeo again in 613, but abandoned the campaign when the official Yang Xuangan rebelled in China. A third invasion in 614 ended with a token Goguryeo submission. The human and financial cost of these wars, on top of the canal and palace projects, fuelled rebellions across China, and in 618 the Sui dynasty fell and the Tang dynasty took power.

Goguryeo survived further Tang attacks, including Emperor Taizong’s campaign of 645, but it was finally conquered in 668 by an alliance of the Tang and the Korean kingdom of Silla.

Legacy

In Korea, Eulji Mundeok is honoured as a national hero. Euljiro, a major street in central Seoul, is named after him, as are a South Korean destroyer and an annual military exercise. The battle is remembered as a symbol of successful resistance by a smaller state against a far larger empire.

Timeline

• 598: Emperor Wen’s first expedition against Goguryeo fails.
• 607: Emperor Yang demands that the king of Goguryeo come to his court.
• 612, early in the year: The Sui army sets out from Zhuojun and crosses the Liao River.
• 612, spring and summer: Sui forces besiege Liaodong fortress; Lai Hu’er’s fleet is defeated near Pyongyang.
• 612, summer: Yu Zhongwen and Yuwen Shu march on Pyongyang.
• 612, seventh lunar month: The Sui army is destroyed at the Salsu River.
• 613 and 614: Two further Sui invasions fail.
• 618: The Sui dynasty falls.

Why it matters

The Battle of Salsu stopped the largest Sui invasion of Korea and preserved Goguryeo’s independence. Its staggering cost helped destroy the Sui dynasty, changing the course of Chinese history.