Sueojangdae (守禦將臺 Defense Commander's Post) is a two-story military facility used for observation as well as for directing battles. This structure was built on the western side of Namhansanseong Fortress as one of four command posts. During the Manchu Invasion of 1636, King Injo himself helped to direct and encourage the troops from here. They held out for 45 days against a Qing force of 120,000.
At Samjeondo, King Injo of Joseon had to surrender and was forced to accept vassal status to the Manchu Empire. It marked Joseon Korea's humiliating submission to Manchu Qing Dynasty.