Battle of Salsu River
Goguryeo forces under Eulji Mundeok routed a Sui strike force at the Salsu (Cheongcheon) River.

Yan Liben · Public domain · Source
Emperor Yang invaded with 1.13 million men. When Liaodong Fortress held, a strike force of some 300,000 under Yu Zhongwen and Yuwen Shu marched on Pyongyang. Eulji Mundeok drew it in with feigned defeats and sent Yu a poem: "Your merit is already great; be content and stop." As the exhausted army crossed the Salsu in retreat, Goguryeo struck; only 2,700 men are said to have returned.