The Battle of Mindanao (Filipino: Labanan sa Mindanaw; Cebuano: Panagsangka sa Mindanaw; Japanese: ミンダナオの戦い) was fought by the Americans and allied Filipino guerrillas against the Japanese forces on the island of Mindanao in the Philippines as part of Operation VICTOR V. It was part of the campaign to liberate the Philippines during World War II. The battle was waged to complete the recapture of the southernmost portions of the archipelago from the Imperial Japanese Army.
Background
The campaign for Mindanao posed the greatest challenge for the liberating Allied forces, primarily for three reasons: the island's inhospitable geography; the extended Japanese defenses; and the strength and condition of the Japanese forces, which contained the significantly remaining concentration of combat troops in the Philippines.
Like most of the Philippine Islands and other similar places the U.S. Army operated elsewhere in the Pacific, the geographical conditions of Mindanao, the second largest island in the Philippines, offered very little inspiration for soldiers who would have to fight there. It boasted a long and irregular coastline, and the topography was generally characterized as rugged and mountainous. Rain forests and numerous crocodile-infested rivers covered the terrain, the rest by either lake, swamp or grassland. These grassland regions—along with dense groves of abacá trees, a source of hemp fiber—offer the worst obstacles, limiting vision and sapping the strength of soldiers.
The few roads in Mindanao further complicated the problem of movement. The generously named Highway 1 cut across the southern portion of the island, from just south of Parang on Illana Bay in the west to Digos on Davao Gulf in the east and then north to Davao. The other, Sayre Highway the main north-south road, started at Kabacan, midway between Illana Bay and Davao Gulf, then ran north through the mountains of Bukidnon and Macajalar Bay (off Misamis Oriental Province) on the northern coast.
The strongest of the Japanese defenses were concentrated around the Davao Gulf area, which was heavily mined to counter an amphibious landing, and in Davao City, the island's largest and most important city. Artillery and anti-aircraft batteries extensively ringed the coastal shoreline defenses. Believing that the Americans would ultimately attack from Davao Gulf and also anticipating that they would be eventually driven from the city, the Japanese also prepared defensive bunkers inland behind its perimeter where they could retire and regroup, with the intention of prolonging the campaign as long as possible.
Operation VICTOR V
On 10 March 1945, the U.S. Eighth Army—under Lieutenant General Robert L. Eichelberger—was formally ordered by General Douglas MacArthur to clear the rest of Mindanao, with the start of Operation VICTOR V, with expectations that the campaign would take four months. Eichelberger had misgivings about the projected timetable. His Eighth Army staff came up with a more effective plan.
Instead of the expected headlong frontal assault on the Japanese defenses, the plan called for securing a beachhead at Illana Bay in the undefended west, then driving eastward more than 100 miles (160 km) through jungles and mountains to strike from the rear. The objective, which called for achieving surprise and pressing forward quickly and aggressively by the invading forces, Eichelberger deemed, could unhinge the Japanese both physically and psychologically. The key to success involved the beachhead performance of the landing force and the ability of units to maintain the momentum of their attack, preempting Japanese reactions, and hopefully before the rainy season started, which would impede movement.
Ground operations were assigned to X Corps, under Major General Franklin C. Sibert, with Major General Roscoe B. Woodruff's 24th Infantry Division and Major General Clarence A. Martin's 31st Infantry Division as the principal combat units. Amphibious Task Group 78.2 (TG 78.2), under Rear Admiral Albert G. Noble, was tasked to carry the 24th Division and X Corps headquarters to the assault beaches near Malabang by 17 April to secure a forward airfield. Five days later, the 31st Division was expected to be in Parang, 20 miles (32 km) south, located near Highway 1, the route to Davao.
Battle
Capture of Zamboanga and Sulu
On the same day Eichelberger's forces were ordered to invade Mindanao, remnants of Major General Jens A. Doe's 41st Infantry Division carried out Operation VICTOR IV, the seizure of Zamboanga, the large peninsula that extended to the southwest, concurrent with the recapture of Palawan, dubbed Operation VICTOR III. A sizable force—numbering about 8,900 men of Lt. Gen. Tokichi Hojo's 54th Japanese Independent Mixed Brigade (IMB)—had established strong defensive positions around Zamboanga City at the southern tip of the peninsula.
The slow construction of the airfield at Palawan posed a problem for tactical air support augmenting the Zamboanga operation. With the seizure of a makeshift airstrip at Dipolog, about 145 miles (233 km) to the northeast of Zamboanga City, the Americans rapidly exploited the opportunity, airlifting two reinforced companies from the 21st Infantry Regiment, 24th Division to ensure control of the airstrip. Soon thereafter, Marine Aircraft Groups Zamboanga (MAGSZAM) under Col. Clayton C. Jerome was flying sorties off the airstrip to cover naval bombardment and landing preparations off Zamboanga City.
After the bombing of the landing areas by the 13th Air Force and a three-day bombardment by the U.S. Navy, the 162nd and 163rd Infantry Regiments landed 3 miles (4.8 km) west of Zamboanga City at San Mateo. Japanese opposition to the landings were minimal, and the 41st Division troops quickly captured the city, which was decimated by the pre-invasion bombardments. The next day, 11 March, the Americans encountered strong resistance when they attacked Japanese positions in the hills overlooking the coastal plain. For two weeks, American infantry—ably supported by Marine aviation and naval gunfire—fought the Japanese along a 5 miles (8.0 km) front, in terrain so rugged that tanks could not be used, and in positions heavily fortified with deep earthen emplacements, barbed wire, minefields, and booby traps.
On 23 March, after heavy fighting, the center of the Japanese line finally broke, and in the next three days, the 162nd Infantry continued eliminating resistance in the central sector. The 186th Infantry replaced the 163rd and continued the attack. The 54th Japanese IMB was forced to pull out a week later, harried by guerrilla units, retreating through the peninsula and into the jungle. After some time, mopping-up operations resulted in 220 Americans killed, compared to 6,400 Japanese dead.
Alongside the Zamboanga operation, smaller units of the 41st Division invaded the Sulu Archipelago, a long stretch of islands reaching from the Zamboanga Peninsula to north Borneo. Rapidly taken in succession were Basilan, Malamaui, Tawi-Tawi, Sanga Sanga and Bangao. On 15 April, strong resistance at Jolo was encountered. Anchoring their stubborn defense around Mount Daho, some 3,750 Japanese troops held off the 163rd Infantry, supported by Filipino guerrillas. By 22 April, the Allies took the position after hard fighting and the rest of the Japanese troops fled and held out in the west for another two months. The 163rd suffered 35 dead and 125 wounded by mid-June 1945, while some 2,000 Japanese perished.
Senshi Sōsho in its Operation to conquer the Philippines (比島攻略作戦) and Navy Invasion Operations in the Philippines and Malaya Area (比島・マレー方面海軍進攻作戦) as part of its invasion series does not mention the Battle of Tamparan. In the Battle of Tamparan, Muslim Moros massacred 85 Japanese out of a 90 strong unit using mainly swords against Japanese armed with rifles, which is testified to by Japanese survivors. The memoirs written by the Japanese survivors in the Tanaka battalion of the battle accuse the Muslims of being "unmanageble", violent, ferocious and fanatic and a Japanese officer Lt. Col. Tanaka Yoshinari said that they were "local natives yet uncivilized in the ways of the Empire" and the Japanese viewed the Muslims as "inferior" and "savages".
Senshi Sōsho's Shō-gō rikugun-sakusen (2), published by Japan's Defence Ministry Bōeichō senshishitsu, is contradicted by Japan's own Ministry of Health and Welfare (社会・援護局) on the number of Japanese dead on the island of Jolo during the Battle of Sulu (スールー諸島の戦い). The Japanese Ministry of Health and Welfare says 6,030 Japanese were in Jolo and most of them were killed, in contrast to Senshi Sōsho which claims there were only 3,425 Japanese of the Independent Combined (Mixed) 55th Brigade (独立混成第55旅団 (日本軍)) on the island. Senshi Sōsho says 135 Japanese survived out of the 3,425 in total on Jolo, and that the casualty rate was 96%, and only mentions the battle on Jolo starting after the American landing on 9 April in 1945 and attributes most Japanese casualties to American actions. barely mentioning local Muslim Moro guerillas.
Japan Center for Asian Historical Records (JACAR) gives yet a totally different number from both Senshi Sōsho and the Japanese Ministry of Health and Welfare, saying there were 3,875 Japanese soldiers in Jolo.
Japanese veterans who actually survived the Battle of Sulu on Jolo, endorsed the number by the Japanese Ministry of Health and Welfare that said 6,030 Japanese were there and most of them were killed except 88 survivors, with the Japanese veterans saying one third were killed by local Muslim guerillas right after the 55th mixed brigade landed on Jolo on 4 October 1944 a year before the Americans landed, one third killed by Americans after they landed in Jolo in April 1945, and one third dead of disease.
Japanese survivors reported being slaughtered, beheaded, and barely putting up a fight with "pathetic" deaths by the Moro counter-insurgents. Worsening the issue was the lack of supplies or support from the Japanese military. Japanese survivors, armed with mountain artillery, reported being "overwhelmed like children" by Moro weaponry, which included rifles, kris daggers, tabar axes, bolo and barong knives, campilan swords, spears, and bows. Japanese were regularly beheaded in ambushes by Muslim guerillas with swords.
American military sources also contradict Senshi Sōsho on Jolo, the Americans said 3,900 Japanese were still lodged on Jolo's Mount Daho after the Americans landed in April in 1945, not counting Japanese already killed by local Muslim guerillas in the year before that, and then the Americans and guerillas both attacked Mount Daho to kill the remaining Japanese. The American 41st infantry took a picture and met with local guerillas in Indanan village on Jolo, from the guerilla Company C, 1st Bn, 125th Infantry.
15 and 16 year old Japanese conscripts were sent with just bamboo spears and no guns to reinforce Japanese soldiers in Zamboanga in the Battle of Mindanao, who were fighting "ferocious head hunters" Muslim Moros, who the Japanese deeply hated and feared. The Japanese medic who witnessed this then realised Japan lost. He also said that Japanese university graduates were automatically given officer positions even though they had no knowledge about warfare. The Japanese medic was forced to lick leaves for water and eat lizards, snakes and cats due to a lack of food supplies in the jungle. The Japanese military did not send any medical packages, orders or military supplies to his garrison. They were ordered to perform vivisections on children.
The remaining 100 Japanese surviviors of the brigade were starving to death and forced to scavenge for water and food around the mountains as the Muslim guerillas steadily killed their remaining officers. The Japanese 363rd battalion were starving and struck with malnutrition due to lack of food after reaching Mount Tumantangas. Japanese infected with malafria were just left to die by other Japanese. Japanese soldiers stole food supplies from dead and still living but sick Japanese and fought each other for food. At Tumantangas mountain, Japanese wounded and ill were left to die by fellow Japanese who stole their rucksacks and food as Japanese units fought each other for the remaining food, one of the Japanese officers who was left to die was regarded as a tyrant by his men.