The Harbor Defenses of Manila and Subic Bays (formerly "Coast Defenses of Manila and Subic Bays") were part of the Philippine Department of the United States Army, prior to, and during, World War II.
In July 1941, these units were commanded by Major General George F. Moore, whose Philippine Coast Artillery Command was headquartered at Fort Mills, on Corregidor. This command included Fort Hughes (Caballo Island), Fort Drum (El Fraile Island), and Fort Frank (Carabao Island) at the entrance to Manila Bay, as well as Fort Wint (Grande Island) at the entrance to Subic Bay. At this time, there were 4,967 troops assigned to the Harbor Defenses.
Manila and Subic Bays were mined by the Asiatic Fleet, stationed in Manila Bay. These minefields were designed to stop all vessels, except for submarines and shallow-draft surface craft.
With the exception of those areas covered by the 60th and 200th Coast Artillery (AA) Regiment, the Philippine islands were virtually defenseless against air attack.
Chief of Coast Artillery Major General Joseph A. Green had recommended reassigning elements of the Harbor Defenses to anti-aircraft duty, but this proposal was rejected. The War Department had been intending to send three additional AA regiments and two brigade headquarters, however this was not accomplished before the Japanese invasion in December of 1941.