This little bitty waterside fort at the mouth of the narrow Yeomha Strait which guards the entry to the Han River and thus to Seoul, had the good fortune to be attacked not just by the French Navy in 1866 and the American Navy in 1871, but also by the Japanese in 1876 [EXPIRED LINK REMOVED: https://www.koreanhistoryproject.org/Ket/C23/E2303.htm]. The last incident led to the Ganghwa Treaty, the first step in the collapse of the 600-year Chosun Dynasty at the end of the 19th century, and the colonization of Korea by Japan for 35 years in the first part of the 20th century.
Marks from the cannonballs can still be seen on the tree and the wall below.