Location
Lat 14° 22' 0N Long 120° 37' 0E  Caballo Island is roughly one square mile in area, located at the entrance of Manila Bay. Named by the Spanish "Caballo" meaning Horse. The island has three knolls with an elevation between 150' to 350' with high ground on the western side of the island rising to 380'. The eastern coastline is flat, suitable for an amphibious landing. Located one mile to the north is Corregidor Island. Located four miles south is El Fraile (Fort Drum).

Construction
Caballo Island was developed by the U.S. Army Corps of Engineers into Fort Hughes as part of the Manila Bay defenses with gun batteries, mortars, anti-aircraft guns and other defenses and tunnels.

Wartime History
The U.S. Army defended Caballo Island to protect the entrance to Manila Bay. During March to April 1942 gun on Caballo fired at enemy targets on the Bataan Peninsula.

During early April 1942, a U.S. Marine Corps (USMC) detachment of 100 men was added to the garrison plus 200 U.S. Navy sailors from Corregidor for additional defense under the command of Comdr. Francis J. Bridget. Later, four gunboat crews totaling another 225 men were added to the defense. By the end of April 1942, the garrison totaled 800 including 93 Marines and 443 Navy. After capturing Corregidor, the Japanese Army 4th Division planned to invade Caballo. On May 6, 1942 when the American garrison on Corregidor surrendered, the force on Caballo also surrendered.

During the Japanese occupation of the Philippines, additional guns and defenses were added on Caballo. By 1945, a mixed force of roughly 400 Japanese Army and Navy troops defended the island. After the liberation of Corregidor, some surviving Japanese attempted to swim to Caballo. During February to March 1945, U.S. aircraft began using Caballo Island as a practice bombing range and U.S. Navy destroyers shelled the island.

American missions against Fort Hughes (Caballo Island)
February 4 - March 27, 1945

On March 18, 1945 the U.S. Army 38th Division, 151st Infantry 2nd Battalion loaded onto LCM landing craft departed Corregidor Island and made an unopposed amphibious landing on Caballo Island to conduct a reconnaissance and found three hills and the high ground at the center of the island heavily defended then withdrew.

On March 27, 1945 American aircraft and artillery on Corregidor bombarded Caballo prior to a Naval bombardment by the U.S. Navy 7th Fleet CTF 78 destroyers USS Conway DD-507 and USS Cony DD-508 plus rocket-equipped PT 128, PT 131 and PT 132. Eight LCM landing craft from 592nd Engineer Boat and Shore Regiment (EBSR) on Corregidor loaded the reinforced 2nd Battalion for an amphibious landing at Gray Beach at 9:00am.

At first, there was no opposition until the troops advanced inland to three knolls dubbed Hill 1, Hill 2 and Hill 3 in the middle of the island, each with an elevation of from 150' to 250'. Within 15 minutes of the landing, Hill 1 was captured. Hill 2 had steeper terrain and stiffer defense but was captured at the end of the next day.

On March 29, 1945 most of the island was cleared except for approximately 200 Japanese hiding in the east and west mortar pits of Battery Craighill and tunnels near the eastern slopes of Hill 2. On April 5, 1945 using a specially equipped LCM 503 carrying an oil/gas mixture beached under the mortar pits while combat engineers positioned a 4" pipe to the position and at 1:30pm 2,400 gallons of fuel were pump into the eastern mortar pit that was then ignited with a mortar grenade. The fire burned for two hours and cause secondary explosions.

On April 6, 1945 LCM 503 returned and pumped 3,000 gallons of fuel into the west pit that burned for three hours with secondary explosions but the Japanese continued to resist. On April 7, 1945 a total of 6,000 gallons were pumped into both pits and ignited by charges placed in captured ventilation shafts and entrances. This explosion destroyed the Japanese water and food supplies. Although there was no longer any enemy activity, the operation was repeated on April 8, 1945. In total, 15,000 gallons of fuel were poured into the island's defenses. Several days later, U.S. Army troops mopped up the island without opposition.

Today
Caballo Island is abandoned and generally off limits to visitors.

Tony Feredo adds:
"The fort's magazines and other concrete structures of the batteries are there. All old wooden building are already gone. The wharf is still original and a big chunk already got destroyed via a typhoon in 2002. No memorials except for a few markers where bones of Japanese soldiers were re-buried years after the war."

Fort Hughes
U.S. Army fortification including Battery Craighill, Battery Gillespie, Battery Woodruff, Battery William, Battery Hooker, Batttery Leach, Battery Fuger, Battery Idaho

Japanese 120mm Dual Purpose Gun Type 10 (1921)
Abandoned laying on its side on Caballo Island

60" Search Light No. 11
Search light base emplaced at a tunnel entrance.

Sherman M4 Tank
Disabled on the beach by Japanese land mine.

References
U.S. Army in World War II - Strategy and Command - Chaper I pages 23, 24
U.S. Army in World War II - The Fall of the Philippines - Chapter I pages 8
U.S. Army in World War II - The Fall of the Philippines - Chapter XXVII pages 471, 476
U.S. Army in World War II - The Fall of the Philippines - Chapter XXIX page 526
History of U.S. Marine Corps Operations in World War II - Chapter 1 page 169
U.S. Army in World War II - Triumph in the Philippines Chapter XVII pages 340, 348
U.S. Army in World War II - Triumph in the Philippines Chapter XIX pages 351-353, 354 (photo), 355-356, 357
The Army Air Forces in World War II - Chapter 14 page 433
7th Amphibious Force Task Organization Caballo Island Operation ("FORT HUGHES") 27 March 1945 [JPG]
The Official Chronology of US Navy in World War II - Chapter VII: 27 March 1945
U.S. Army in World War II - Chronology 1941-1945 page 443, 445, 450, 457, 471, 475, 493
Engineers of the Southwest Pacific, 1941-45, Volume 4 pages 563-564, 565, 566 (photo), 568, 559, 750 (index), 758 (index)
GMA News Online "Aquino detonates last batches of WW2 explosives from Caballo Island" March 5, 2011

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Last Updated
October 23, 2019