Fort Drum (El Fraile Island), also known as "the concrete battleship," is a heavily fortified island situated at the mouth of Manila Bay in the Philippines, due south of Corregidor Island. The reinforced concrete fortress shaped like a battleship, was built by the United States in 1909 as one of the harbor defenses at the wider South Channel entrance to the bay during the American colonial period. It was captured and occupied by the Japanese during World War II, and was recaptured by the U.S.