Mindanao Island
by Jack McKillop

    Mindanao (07º43'N, 125º14'E), the second largest and southernmost island in the Philippines with an area of 36,547-square-miles (94,996-square-kilometers), is heavily forested and mountainous with mountains rising to 9,690-feet (2,954-meters). The Diuata Mountains bordering the eastern coast form the most prominent mountain range on the island with an average elevation of 2,638-feet (804-meters). West of this lies the fertile valley of the Agusan River, 20-to-30-miles (32-to-48-kilometers) wide followed by another range that stretches from the center of the island southward. Farther west the Butig Mountains trend northwestward from the northeastern edge of the Moro Gulf. A range also runs northwest-southeast along the southwestern coast. The country’s highest point, Mount Apo (06º59'15"N, 125º16'16"E) rises in the south near the Mindanao River basin to 9,692-feet (2,954-meters). The large Zamboanga Peninsula extends from western Mindanao, hooking southward toward the Sulu Archipelago.

History during World War II

   The first Japanese landing on Mindanao occurred on 20 December 1941 when an infantry regiment and miscellaneous troops landed at Davao City (07º04'47"N, 125º36'20"E) on the south coast. The Japanese attempted to extend their control into the interior but without success because of guerilla activity. Indeed, had the guerillas not had air and artillery support and men not been equipped with automatic weapons, it is doubtful if the Japanese could have remained on the island.
     Early on the morning of 29 April 1942, the emperor's birthday, the Japanese landed in the Moro Gulf (06º48'14"N, 123º26'15"E), midway up the west coast of Mindanao. The seizure of this area was vital to their plans because they could now advance inland to the north and east. The Filipino forces on the island were ordered to surrender on 10 May but many of the troop disobeyed and joined the guerillas in the mountains.
     By 1945, there were about 58,000 Japanese troops and 38,000 well-organized Filipino guerillas on Mindanao. On 8 March 1945, two Army companies were flown into Dipolog Airfield (08º36'02"N, 123º20'29"E) which had been captured by the guerillas. A Marine fighter squadron flew in the next day to provide close air support for the landings scheduled for 10 March.
    The American troops landed about 3-miles (4.8-kilometers) west of Zamboanga City (06º55'12"N, 122º04'44"E) on the southern tip of the Zamboanga Peninsula. The Americans moved north with assistance from guerrillas, encountering their first serious resistance on 12 March. This was overcome by 24 March and the remaining Japanese withdrew up the coast in hopes of evacuation. Flanking landings forced the Japanese into the mountains where they were contained by guerrillas for the rest of the war. Casualties were 6,400 Japanese dead and 1,100 taken prisoner, another 1,385 turning themselves in following the general surrender. the U.S. lost 220 killed and 665 wounded.
     The campaign was controversial, since the guerrillas already controlled 95% of the island and had pinned down the Japanese in the major towns. Even Samuel Eliot Morison, no MacArthur hater, wrote that "... there seems, in retrospect, to have been no sound military reason for throwing American troops into this big island. Even the official Eighth Army Report admits that Mindanao had no strategic value after Luzon and the Visayas were secured; it even indicates that this operation was undertaken for reasons of prestige, and to please our Philippine allies."


    Zamboanga, on Mindanao, was the site of a naval section base. Ten-miles (16-kilometers) across Basilan Strait, a major repair and overhaul motor torpedo (PT) base was built at Puerto Isabela on Basilan Island (06°42'15"N, 121°58'06"E). The Seabees arrived at Basilan Island on 29 March to erect facilities for repair, maintenance, and upkeep of 24 PT boats. These included a 1,450-man camp complete with mess and recreation facilities, one 370-foot (113-meter) pier for small craft, two 400-foot (122-meter) piers for mooring the large speed boats, a marine railway capable of handling three boats at a time, seven 42,000 U.S. gallon (34,972 Imperial gallon or 158,987 liter) and one 84,000 U.S. gallon (69,944 Imperial gallon or 317,975 liter) steel fuel tanks, with facilities for fueling which included a 90-foot (27-meter) fuel pier.
     While this construction was under way, a 120-man Seabee detachment was sent to Zamboanga to construct buildings and other facilities for the headquarters of the naval section base. These included communications, supply, and a 10-bed dispensary.
     San Roque Airfield (06°55'21"N, 122°03'35"E), now Zamboanga International Airport) had been built by the Japanese and was captured by U.S. Army troops in March 1945. U.S. Army engineers using considerable Filipino labor improved the existing facilities and lengthened the airstrip to 4,500-feet (1,372-meters) which was later extended to 6,000-feet (1,829-meters) to accommodate medium bombers (North American B-25/PBJ Mitchells). There were two adjacent taxiways along both sides of the runway with revetment areas. The base was renamed Moret Field in honor of USMC Lieutenant Colonel Paul Moret, who died in a plane crash off the Solomon Islands in 1943. USAAF and USMC warplanes operated out for Moret Field to attack Japanese forces still in the southern Philippines, and at its peak, around 300 aircraft were based there. The Marines were under the operational control of the USAAF’s Thirteenth Air Force. By August 1945, the Marines had three scout bomber squadrons with Douglas SBD Dauntlesses and one bombing squadron with North American PBJ Mitchells. The USAAF had a Lockheed P-38 Lightning fighter group and a detachment of Northrop P-61 Black Widow night fighters.
     A second USAAF airfield, Malabang (07º37'02"N, 124º03'32"E), a prewar airfield, was used by the Marines and by August, they had a scout bombing squadrons with Curtiss SB2C Helldivers based there.