American Defenses of Corregidor and Manila Bay 1898–1945

The defense of Manila Bay was a key concern in safeguarding American interests in the Philippines and the Far East. The US Navy had been able to destroy the Spanish naval squadron and capture the city of Manila due to the lack of effective Spanish harbor defenses. The US government declared the Manila Bay islands military reservations on April 11, 1902. The Corps of Engineers surveyed these islands, and began construction of the first battery on Corregidor in September 1904. Lessons learned from the construction and use of the gun and mine defenses built a decade before in the continental United States resulted in a distinct change in the design and layout of the defenses built after 1904. The newer defenses would have a larger main caliber of gun, the 14in., and smaller numbers of secondary weapons than built into the previous defenses. The batteries themselves were built with larger and more spacious working and loading platforms. In many ways, the defenses planned for the Philippines were a transition between the older system of 10in. and 12in. guns and the newer 14in. guns.

Corregidor, the largest island in Manila Bay, received the bulk of fortification efforts. Between 1904 and 1910, the island was transformed into a fortress with nine major batteries mounting 25 modern coast artillery weapons, along with the necessary support facilities. The US Army designated this military reservation Fort Mills (after Major-General Samuel M. Mills), and this became the main post and headquarters for the Harbor Defenses of Manila Bay. Corregidor provided the infrastructure for the construction of the other island forts. Thousands of workers, both contract and convict labor, were brought to the islands to construct a vast array of concrete structures. Fortifications on Carabao Island were built from 1908 to 1913, and were designated Fort Frank (after Brigadier-General Royal T. Frank). El Fraile Island received the most unusual fortification ever built by the US Army. The island was leveled to the waterline and a massive reinforced-concrete structure was built between 1909 and 1918 to support specially designed turreted guns. While its formal name was Fort Drum (after Brigadier-General Richard C. Drum), it became known locally as the ""concrete battleship."" Caballo Island was fortified from 1911 to 1919, and was designated Fort Hughes (after Major-General Robert P. Hughes). The US Army would also name each gun battery upon completion after deceased US Army personnel in honor of their achievements. As each defense work was completed by the US Army Corps of Engineers and armed by the US Army Ordnance Department, its operation would be transferred to the US Army Coast Artillery Corps.
The US Navy did not like the shallow waters of Manila Bay - it wanted its main Far East naval station in the deeper waters of Subic Bay. To defend this potential anchorage, the Army purchased El Grande Island, located in the middle of the entrance to the bay, in 1905. The island was fortified during the years 1906-10, and was designated Fort Wint (after Brigadier-General Theodore J. Wint).