Since the mountainous region is mostly on the jap Component of the peninsula, the principle rivers are inclined to movement westwards. Two exceptions would be the southward-flowing Nakdong River and Seomjin River.

Nevertheless the Sui army was lured right into a trap via the famed Koguryŏ commander Ŭlchi Mundŏk, and endured a calamitous defeat in the Salsu (Ch'ŏngch'ŏn) River. It is alleged that only 2,700 with the 300,000 Sui troopers who had crossed the Yalu survived to find their way again, as well as the Sui emperor now lifted the siege of Liao-tung Fortress and withdrew his 파라곤 forces to China proper. Yang Ti ongoing to send his armies from Koguryŏ but once more without accomplishment, and prior to extensive his war-weakened empire crumbled." ^