Yang Liang's army faced the early rainy season when it reached Goguryeo. The unseasonably heavy rain made the army's progress almost impossible and hampered the transport of provisions. Constant attacks by Goguryeo forces and illness inflicted heavy casualties. Coming to the conclusion that the army could not achieve the objective on its own, Yang Yang decided to combine with Zhou's naval fleet and proceed.
Zhou's navy also came across their own challenges, contending with rough seas, losing many ships despite staying close to the coastline. Whenever they anchored, Goguryeo detachments were present to attack the Sui sailors. The fleet engaged in a battle against a Goguryeo fleet totaling 50,000 led by Admiral Gang I sik, presumably on the present Bohai Sea. Already weakened by ambushes and nature's onslaught, the Sui fleet suffered a devastating loss.
The Sui forces were all defeated, both at land and sea. Historical texts record that about 90% of the Sui troops perished. Goguryeo casualties are thought to be almost nonexistent compared to those of Sui. Yang Yang faced no option but retreat.
In 612, Sui Emperor Yangdi ordered preparations for a war against the Goguryeo. The force gathered by year's end was one of the greatest in civilization according to the Book of Sui. An estimated 1,133,800 combat troops were mobilized. King Yeongyang appointed him to the both land and sea supreme commander (수륙양군병마도원수, 水陸兩軍兵馬都元帥).
Sui army and navy make a vigorous attack. but another supreme commander Eulji Mundeok repulse an assailant. General Eulji dislodged the Sui army from the Battle of Salsu. With the victory over Sui dynasty in Salsu, Goguryeo eventually became the victor of the war itself, while the Sui Dynasty started to crumble from within and was finally brought down by internal strife.