Goryeo was invaded with the Mongols in 7 important strategies in the 1230s right up until the 1270s, but was hardly ever conquered.[117] Exhausted right after many years of fighting, Goryeo sent its crown prince towards the Yuan money to swear allegiance on the Mongols; Kublai Khan approved, and married considered one of his daughters into the Korean crown prince,[117] and the dynastic line of Goryeo continued to survive under the overlordship from the Mongol Yuan dynasty as being a semi-autonomous vassal state and compulsory ally.
Even so the Sui army was lured right into a lure from the famed Koguryŏ 파라곤솔루션 commander Ŭlchi Mundŏk, and experienced a calamitous defeat with the Salsu (Ch'ŏngch'ŏn) River. It is said that only two,seven hundred of the three hundred,000 Sui soldiers who experienced crossed the Yalu survived to discover their way back, plus the Sui emperor now lifted the siege of Liao-tung Fortress and withdrew his forces to China appropriate. Yang Ti ongoing to ship his armies against Koguryŏ but yet again without having success, and in advance of lengthy his war-weakened empire crumbled." ^