In 612, Emperor Yang of Sui invaded Goguryeo with well over one million men. Unable to overcome the stalwart Goguryeo defense at Liaoyang/Yoyang, he dispatched 300,000 troops to Pyongyang, the capital of Goguryeo.

The Sui forces were unable to advance further due to the internal discord within the Sui Dynasty command, and the lack of supplies due to the secret disposal of the soldiers' personal equipment and munitions in the middle. Goguryeo General Eulji Mundeok , who had been blocking the Sui forces for several months, noticed this. He prepared to attack the Salsu River (Cheongcheon River) and caused damage while pretending to retreat deep into Goguryeo territory. Eulji Mundeok had cut off the flow of water with a dam in advance, and when the Sui troops reached the river, the water level was shallow. When the unsuspecting Sui troops were halfway across the river, Eulji Mundeok opened the dam, causing the onslaught of water to drown thousands of enemy soldiers. The Goguryeo cavalry then charged the remaining Sui forces, inflicting enormous casualties.

The surviving Sui troops were forced to retreat at a breakneck pace to the Liaodong Peninsula to avoid being killed or captured. Many retreating soldiers died of disease or starvation as their army had exhausted their food supplies. This led to an overall campaign loss of all but 2,700 Sui troops out of 300,000 men. The Battle of Salsu is listed among the most lethal "classical formation" battles in world history.

With a victory over Sui China at the Salsu River, Goguryeo eventually won the Goguryeo–Sui War, while the Sui dynasty, crippled by the enormous loss of manpower and resources as a result of its Korean campaigns, started to crumble from within and was finally brought down by internal strife, to be replaced soon thereafter by the Tang.