The conflict began in 598 AD when Emperor Wen of Sui launched a massive land and sea invasion after King Yeongyang's preemptive strike. However, the first campaign ended in disaster for Sui as torrential rains and storms destroyed their fleets and supply lines, forcing a retreat after losing most of their forces to disease and hunger. Due to a lack of historical records, the exact details of any battles fought during this campaign remain largely unknown.
In 612 AD, the second and largest invasion was led by Emperor Yang. He mobilized a staggering 1.13 million regular troops, a force that stretched for hundreds of miles. When their siege of the Liao fortresses stalled, Emperor Yang detached a specialized strike force of 305,000 men to march directly toward the Goguryeo capital, Pyongyang.
General Eulji Mundeok of Goguryeo met this challenge with a brilliant and multi-stage strategy. He personally visited the Sui camp under the guise of surrender to discover their severe lack of provisions. Then, his forces feigned defeat seven times in a single day, luring the overconfident and starving Sui troops deep into Goguryeo territory near Pyongyang. After sending a mocking poem to the Sui commander suggesting they turn back, Eulji Mundeok waited until the exhausted Sui forces were halfway across the Salsu (Chongchon River) while retreating, and then struck in full force. Only 2,700 out of the 305,000 Sui soldiers survived the retreat in what became known as the legendary Battle of Salsu.
Stubbornly, Emperor Yang attempted two more invasions in 613 and 614. However, the 613 campaign was cut short by the rebellion of Yang Xuangan within China, and the 614 campaign ended in a hollow peace treaty after both sides were exhausted. The massive war debt and loss of life triggered a chain of peasant uprisings across China, leading to the murder of Emperor Yang and the total collapse of the Sui Dynasty in 618 AD.