This was the US and Filipino reconquest of the eastern part of Mindanao island in the southern part of the Philippine islands group by Lieutenant General Robert L. Eichelberger’s 8th Army (10 March/15 August 1945).
Mindanao is the most southerly and second largest of the major islands of the Philippines group, approximately 300 miles (480 km) across with an area of 40,360 sq miles (104530 km²). Most of the island is mountainous, but there are two marshy valleys, namely those of the Mindanao river on the south-western half of the main body of the island, and the Agusan river in the eastern half inland of the Diuata mountains. Both rivers are navigable.
The Zamboanga peninsula forms a long and notably rugged western extension of the island’s main body, whose tallest peak is Mt Apo at 10,315 ft (3144 m).
In 1941 Mindanao was not as well developed as Luzon. Its most important port and city is Davao, located on Davao Bay on the south-eastern coast and dominated by Mt Apo to the south-west. Most of the rest of the population lived along the north and east coasts. The road network was sparse, but there were two major roads, though both were of poor quality unsuitable for heavy vehicle traffic. The island’s major products were hardwood timber and Manila hemp, which was produced mostly by Japanese living in the Davao area. The indigenous population are the Moro, an Moslem ethnic group with a warrior heritage who were among the last to continue resisting Spanish and US rule.
US pre-war contingency plans for the recapture of the Philippine islands group from what was seen as an inevitable Japan conquest included the establishment of a fleet anchorage at Dumanquilas Bay on the south coast of the Zamboanga peninsula.
When war broke out, there was a heavy bomber airfield complex at Del Monte, and this was home to the bombers of the 14th and 93rd Squadrons. The remaining heavy bombers in the Philippine islands group were to have joined them there, but the move was delayed, apparently by Major General Lewis H. Brereton, commander of the Far East Air Force, so that the crews could attend a party in Manila on 7 December.
Mindanao was attacked from the opening day of the war, and on 16 December 1941 Major General Shisuo Sakaguchi’s ‘Sakaguchi’ Detachment of the 56th Division from the Palau islands group, with the headquarters of Sakaguchi’s 56th Mixed Infantry Group, the 146th Regiment and elements of some special naval landing forces, had landed at Davao on the south coast of eastern Mindanao. This force was detached from Lieutenant General Hitoshi Imamura’s 16th Army otherwise concerned with the seizure of Borneo and Java. Landing with the ‘Sakaguchi’ Detachment was Lieutenant Colonel Toshio Miura’s ‘Miura’ Detachment comprising the 1/33rd Regiment of Lieutenant General Susumi Morioka’s 16th Division.
Davao was defended by 2,000 Filipino troops, who were soon forced to withdraw.
The ‘Miura’ Detachment then established a seaplane base and brought the airfield outside Davao into operation. Davao was one of the two main staging points for the ‘B’ operation to take Borneo. The Japanese made no effort to secure the entire island of Mindanao during the first months of 1942. The ‘Miura’ Detachment was contained at Davao and Digos, and the Philippine army units, assigned to a number of defence sectors through the island, continued to train. General Douglas MacArthur, the Allied commander-in-chief in the Philippine islands group, hoped that the US and Filipino forces would hold out on Mindanao until he was able to mount an offensive from Australia to retake the island as a forward base of operations to reconquer the rest of the Philippine islands group.
After securing Cebu island, on 29 April Major General Kiyotake Kawaguchi’s ‘Kawaguchi’ Detachment (based on the 124th Regiment) landed in the Moro Gulf on the central portion of Mindanao island’s west coast and advanced to the north as well as east, and the ‘Miura’ Detachment moved to the west from Digos to meet it. After taking Panay island, the ‘Kawamura’ Detachment (based on the 41st Regiment) landed at Cagayan in Macajalar Bay near the point at which Routes 1 and 3 joined on the central portion of the north coast. When he surrendered his headquarters on Corregidor island, Lieutenant General Jonathan M. Wainwright, currently commanding all the Allied forces in the Philippine islands group by this time, released Major General William F. Sharp, commanding the Visayan-Mindanao Force, to the command of MacArthur, now based in Australia, but on the night of 7 May attempted to reassume command to order the Visayan-Mindanao force to surrender, for Wainwright feared that the 11,000 surrendered troops on the fortified islands might be massacred if the southern forces did not meet Japanese demands. MacArthur ordered Sharp to ignore Wainwright. A truce was arranged and meetings were held between Sharp and the Japanese. Once he had learned of the situation in the north from a staff officer sent by Wainwright, Sharp surrendered his forces on 10 May.
Many of the more distant units were without communications, however, and some were already executing raids and harassing attacks on the occupying Japanese troops.
By a time early in 1945, the Japanese forces on Mindanao and the islands of the Sulu archipelago had come under the control of Lieutenant General Sosaku Suzuki’s 35th Army, which had its headquarters on Cebu island. The forces on Mindanao were divided into two separate commands because of the island’s size and shape, the boundary between the two sectors lying just to the east of Lake Lanao near the isthmus connecting the Zamboanga peninsula with the rest of Mindanao. The Japanese forces on the main part of Mindanao, to the east of the dividing line near Lake Lanao, were commanded by Lieutenant General Gyosaku Morozumi with 58,000 army and navy personnel. Morozumi later assumed nominal command of the 35th Army when Sosaku Suzuki was killed on 14 June. There were 17,000 Japanese civilians (including 5,000 conscripted labourers) in the area of Davao. Morozumi exercised direct control over his own Korean-manned 30th Division (40th Field Artillery Regiment, 74th Regiment, and battalions of the 41st Regiment and 77th Regiment). Service and airfield units plus the headquarters of Lieutenant General Seiichi Terada’s 2nd Air Division were also attached to the 30th Division. These units were responsible for the defence of western and northern Mindanao. Southern and eastern Mindanao were the responsibility of Lieutenant General Jiro Harada’s 100th Division (75th Brigade and 76th Brigade), which was left largely to its own devices. Also under Harada’s command were air service and airfield units as well as Rear Admiral Naoji Doi’s 32nd Special Base Force. Most of the service units attached to both divisions had been reorganised into combat units. The Japanese airfields in the area included six in the north-west at Patag, Lumbia, Del Monte, Malaybalay, Valencia and Dansalan; three around Davao at Licanan, Sasa and Matina; two on the tip of the Zamboanga peninsula; and Bongao on the south-western end of Tawi-Tawi island near the south-western part of the Sulu archipelago.
Already in action against these Japanese forces on Mindanao were large numbers of Filipino guerrillas, who were well organised under the 10th Military District headquartered at La Paz in the north-east and under the command of Colonel Wendell W. Fertig. The 38,000 guerrillas were well armed and organised into the 105th Division (6,600 men), 106th Division (3,900 men), 107th Division (2,500 men), 108th Division (15,000 men), 109th Division (4,300 men) and 110th Division (5,400 men).
As the second largest of the Philippine islands, Mindanao had been the first objective proposed in MacArthur’s South-West Pacific Area plan for the reconquest of the Philippine islands group, but on 8 September 1944 the Joint Chiefs-of-Staff had ordered MacArthur to bypass Mindanao entirely and launch his operation to begin the recapture of the Philippine islands group with the invasion and then seizure of Leyte island. So instead of being the first US objective in the Philippine islands group, Mindanao was now the last and potentially one of the most difficult targets for reconquest as it was defended by the 35th Army of about 43,000 men. Major General Takichi Hojo’s 54th Independent Mixed Brigade was already contained by Major General Jens A. Doe’s 41st Division on the Zamboanga peninsula in ‘Victor IV’, but on the rest of Mindanao island the Japanese had Harada’s 100th Division and Rear Admiral Naoji Doi’s 32nd Special Naval Base Unit in the south and east, the remnants of Major General Seiichi Terada’s 2nd Air Division in the west and north, the 74th Regiment at Malaybay in the north centre of the island, and the depleted 30th Division at Cagayan on the northern side of the island. There were also garrisons in the other major towns, but the Japanese strength was somewhat illusory as most of the island’s interior apart from the main roads was controlled by Fertig’s Filipino guerrillas.
The campaign for Mindanao was a huge challenge for the US forces for three primary reasons: the island’s terrain and climate are generally inhospitable, the Japanese defences were extensive, and the Japanese forces were both strong (comprising as they did the most effective concentration of Japanese combat troops in the Philippine islands group) and in good fighting condition.
Like most of the Philippine islands group and the other island groups in which US Army formations found themselves committed during the Pacific campaigns, Mindanao was notably daunting in terms of its terrain and climate. The coast is long and notably irregular, the terrain is generally rugged and mountainous. Rain forest and crocodile-infested rivers are prevalent, and where these do not exist there are lakes, swamps and grasslands. These last were littered with dense groves of abacá trees (the source of hemp fibre) which proved especially problematical as they limited men’s fields of vision and sapped the endurance of men having to force their way through the groves.
The geographical and vegetative problems of Mindanao were exacerbated by the fact that there were few roads, and the overall result was an acute problem of movement. The two most important of the roads, optimistically designated as highways, were Highway 1 and the Sayre Highway. The former extended across the southern portion of the island from a point just to the south of Parang on Illana Bay in the west to Digos on the Gulf of Davao in the east and then to the north toward Davao, and the latter was the main north/south road, starting at Kabacan, mid-way between Illana Bay and the Gulf of Davao and then extending to the north through the mountains to Cagayan and Macajalar Bay on the north coast.
The Japanese concentrated their main strength around the Gulf of Davao, which was heavily mined against the possibility of an US amphibious assault, and round Davao itself, which was the island’s most populous and economically most important city. The coastal defences were strongly ringed by artillery and anti-aircraft batteries. Believing that the US forces would attack from the Gulf of Davao, and also anticipating the fact that they would eventually have to fall back from Davao, the Japanese also created a system of inland defensive bunkers behind whose perimeter they could retire and regroup to prolong the campaign as long as possible and inflict as many casualties on the US forces as they could.
It was on 10 March that the US 8th Army was ordered by MacArthur to clear the rest of Mindanao in ‘Victor V’, a campaign which was expected to last four months. Eichelberger had misgivings about the timetable attached to the operation, but his 8th Army staff produced an effective plan. Instead of a wholly foreseeable frontal descent on the strongest Japanese defences, the definitive ‘Victor V’ plan was posited on the establishment of a secure beach-head at Illana Bay in the undefended west, and then an advance to the east, through jungles and over mountains, of more than 100 miles (160 km) to fall on the Japanese from the rear. This scheme demanded that the US invasion forces achieve initial surprise and then advance both quickly and aggressively, and Eichelberger believed that this could succeed in effecting a major physical and morale blow on the Japanese defenders. The obvious keys to the success of the operation were therefore the ability of the assault forces to land quickly and secure an effective beach-head, and then the capability of the relevant forces in maintaining the speed of the eastward advance to ensure that the Japanese had no time for the creation of a westward-facing defence round and, it was hoped, allow the completion of ‘Victor V’ before the onset of the rainy season and the problems of movement that would then inevitably occur.
The ground operation was allocated to Major General Franklin C. Sibert’s X Corps, with Major General Roscoe B. Woodruff’s 24th Division (19th, 21st and 34th Infantry) from Mindoro island and Major General Clarence A. Martin’s 31st Division (124th, 155th and 167th Infantry) from Morotai island as its primary combat formations. The task of delivering the 24th Division and the headquarters of the X Corps to the assault beaches near Malabang was the responsibility of Rear Admiral Albert G. Noble’s 8th Amphibious Group of Task Group 78.2 (Mindoro Attack Force with the headquarters ship Wasatch). TG78.2 had two elements, namely Transport Group ‘Green’ with three troop-carrying destroyer conversions, 51 tank landing ships, 13 medium landing ships, seven tank landing craft, 22 infantry landing craft, eight Liberty ships, 16 support infantry landing craft and two patrol craft, a minesweeping group comprising five motor minesweepers, and an escort group comprising the destroyers Charles Ausburne, Braine, Robinson and Aulick (Destroyer Squadron 23) and Flusser and Conyngham (Destroyer Squadron 5), and destroyer escorts Jobb and Albert T. Harris; and Transport Group ‘Red’ (commanded by Captain Zurmuehlen on the US Coast Guard cutter Spencer) comprising 20 tank landing ships, three medium landing ships, two troop-carrying destroyer conversions, five infantry landing craft and seven support infantry landing craft, as well as two submarine chasers and two yard minesweepers, an escort group comprising the destroyers Dyson and McCalla.
Fire support was the responsibility of Rear Admiral Ralph S. Riggs’s TG74.2 comprising the light cruisers Cleveland, Denver and Montpelier, and destroyers Conway, Eaton, Stevens, Young, Cony and Sigourney (Destroyer Squadron 22).
The plan called the assault to be launched by 17 April so that the US formation could swiftly secure a forward airfield. Five days later, the 31st Division was to be landed at Parang, some 20 miles (32 km) farther to the south, near Highway 1, the route to Davao. As TG78.2 moved toward Illana Bay for the landings at Parang, Fertig reported that his Filipino forces had taken Malabang and its airstrip, but also that a battalion-sized Japanese force was still trapped within Malabang and Fertig’s men were unable to evict it. Starting on 3 April, Colonel Clayton C. Jerome’s Marine Aircraft Group, Zamboanga, moved from Dipolog to the Malabang airstrip, and on the basis of target information from the guerrillas proceeded to bomb the Japanese positions. By 14 April, the remaining Japanese had fled through the guerrilla lines, ending the stalemate.
With Malabang under Allied control, Sibert, Woodruff and Noble appreciated that there was now a chance to speed the initial penetration of central Mindanao, and quickly changed their plans to take advantage of developments through the landing of the 24th Division at Parang, much closer to Highway 1. While the Parang landings was completed on 17 April without a problem allowing the 24th Division to head quickly inland, the 8th Army planners assumed correctly that the Japanese might destroy the bridges along Highway 1, and therefore decided to use the 533rd Engineer Boat and Shore Regiment of Brigadier General David A. P. Ogden’s 3rd Engineer Special Brigade to exploit the possibilities offered by the Mindanao river, was runs basically parallel with Highway 1 and is navigable for some 35 miles (56 km) at a location about 10 miles (16 km) to the west of Kabacan and the Sayre Highway.
On 21 April, a small fleet of craft commanded by Lieutenant Colonel Robert Amory headed upriver and seized Kabacan and the junction of Highway 1 and Sayre Highway on the following day. This so shook the local Japanese garrisons that they pulled out to the north and west. The Mindanao river was thus turned into the principal line of communications for troops, rations and other equipment, which were disgorged far upriver.
Only one day later, on 22 April, the 31st Division waded ashore, and Marine Air Group 24 arrived at Malabang to provide air support for the ground operations on Mindanao. With both divisions now ashore and well ahead of schedule, Sibert ordered the 24th Division to continue its advance up Highway 1 to Digos, and then to seize Davao. The 31st Division would follow to Kabacan and then attack to the north up Sayre Highway toward Macajalar Bay.
The Japanese had suffered a major tactical reverse in allowing the US forces to take the key road junction of Kabacan so easily. The 30th Division and 100th Division were now completely separated by the US advance, and the X Corps could accelerate its progress. Given the speed with which it advanced, the 24th Division was virtually on top of the Japanese around Davao before Morozumi appreciated, too late, that the western landing was not a diversion but the primary US assault.
Arriving outside Digos on 27 April, the 24th Division overwhelmed the Japanese defenders, who were prepared to repel an assault from the sea but not from inland, without undue difficulty. The bulk of the 24th Division then turned to the north toward Davao without delay. On 3 May, the first combat elements of the 24th Division entered Davao in the face of a Japanese opposition considerably less formidable than had been expected, for the Japanese had destroyed the city as best they could and pulled back into the hinterland.
In 15 days of heat, humidity and tropical rain, the 24th Division had moved 115 miles (185 km) to take the last major Filipino city still held by the Japanese, but the real battle for Mindanao was now only just starting.
The X Corps had, up to this time, sought to bypass the Japanese forces’ primary defensive positions, but now started to tackle and destroy them in a two-month effort in the thickly planted abacá groves. These provided truly grim fighting conditions, and battle casualties were swelled considerably by exhaustion and disease as the US infantrymen fought their way slowly and grimly forward against the Japanese in multi-man bunkers and one/two-man foxholes. The front line advanced only slowly, but steadily.
Though exhausted and suffering from the loss of so many men, the 24th Division was able to renew its offensive by 17 May. Supported by Fertig’s guerrillas, Colonel Thomas Clifford’s 19th Infantry broke though the eastern flank of the Japanese defences and took Mandong on 29 May, so precipitating the collapse of the 100th Division, whose remnants fell back in some disorder. The US offensive began to take on aspects of pursuit and mopping up operations against bypassed Japanese pockets.
In overall terms the fighting around Davao had been costly, the 24th Division losing some 350 dead and 1,615 wounded, while the 100th Division suffered about 4,500 casualties.
The 31st Division had meanwhile driven forward on a north-easterly axis to Kibawe on Highway 1, a distance of about 40 miles (65 km), since 27 April with Colonel Edward M. Starr’s 124th Infantry in the van. At this point, though, the rainy season started and the US advance was thrown into major disarray. It was on 3 May that the 31st Division reached Kibawe in the face of stiffening Japanese resistance. The town was the starting point of a tortuous Japanese supply trail to Talomo on the island’s coast. In the ‘Battle of the Talomo Trail’, which began on 11 May, the terrain was as much of an opponent as the men of the other side. Some 1,000 Japanese held the trail, but the terrain, tropical rain forest, monsoon rain and hordes of voracious insects were the primary foes. The trail was impassable to motor transport, so the men of the 31st Division were reliant of paradropped supplies. By 30 June, the 167th Infantry had progressed a mere 5 miles (8 km) past the Pulangi river, even with the assistance of Filipino guerrillas. It lost 80 men killed and other 180 wounded, while the Japanese had suffered about 400 men killed.
On 6 May, the 124th Infantry continued to move up Sayre Highway without the reconnaissance information which a speedier advance along the Talomo trail could have provided, and thus became embroiled in the severest fighting of ‘Victor V’ campaign, and possibly of the whole Pacific war. Instructed by Morozumi to check the 124th Infantry at Maramag, some 30 miles (48 km) to the south, in order to provide time for the 30th Division to regroup, one Japanese battalion fought with such ferocity that the US regiment required six days to reach Maramag. Located in dug-out positions, foxholes with connecting tunnels, and virtually invisible pillboxes, the Japanese of this battalion chose to die rather than retreat, and banzai charges struck the 124th Infantry, which had no artillery support, on 7 May and during the night of 14/15 May. The latter ended in a Japanese rout as the automatic weapons of the US infantrymen halted the attackers, killing 73 of them. In this stage of the fighting the 124th Infantry lost 69 men killed and another 177 wounded.
The final stages of the battle for Mindanao ended with the seizure of Malaybalay by Colonel Walter J. Hann’s 155th Infantry on 21 May, and the domination of the Sayre Highway by this regiment in combination with Colonel Maurice D. Stratta’s 108th Infantry following another bloody encounter with the Japanese.
Morozumi and the surviving elements of the 30th Division fell farther back up the Agusan river valley after a vicious engagement with the pursuing 31st Division on 5 June, and eventually faded back into the jungle. Farther to the south, some of the the X Corps' smaller units seized Sarangani and Balut islands, situated off Mindanao’s southern tip, and on 12 July a battalion of the 24th Division reached the south-eastern side of Sarangani Bay by sea to reinforce a reconnaissance patrol which had located a strong Japanese force in the interior, and drive forward through the jungle.
The 31st Division had meanwhile been advancing to the north-east round the coast toward Cagayan, but on 5 May was halted by strong resistance in the area to the south-west of Cagayan. Accordingly a regimental combat team of Major General Rapp Brush’s 40th Division was landed in Macajalar Bay, to the east of Cagayan, on 10 May and this US pincer undertaking forced the 30th Division back from Cagayan toward Malaybay when the 31st Division and 40th Division met on 23 May. Further landings were made round the coast of Mindanao (at Luayin on 1 June, on Balut and Sarangani islands on 3 June, at Cabo San Agustin on 5 June, in Butuan Bay on 23 June and in Sarangani Bay on 12 July) so that the US forces could move inland from a variety of points to split the surviving Japanese defenders into small pockets, and by the end of June the mass of the 35th Army’s remnants had been forced into a 20,500-man pocket to the east of Malaybay, where it remained essentially inactive for the rest of the war.
Another pocket of 2,000 Japanese was contained in the south-eastern corner of the island by the landing in Sarangani Bay, where MacArthur had originally intended that the US forces should make their first landing in the Philippine islands group. Limited containing operations in these areas continued until the middle of August, when news of the Japanese surrender arrived. There were also smaller pockets of Japanese resistance in other parts of Mindanao, and these pockets survived in increasingly desperate straits until the end of the war, when some 22,000 men finally surrendered. Some 10,000 Japanese had been killed, some 7,000 had been wounded, and 8,000 had died of starvation, malnutrition and disease.
Supported excellently by the local Filipino guerrillas, who grew in capability as the campaign progressed and constantly supplied accurate intelligence on Japanese strengths and dispositions, the US forces lost just 820 men killed and 2,880 wounded during the whole of ‘Victor V’. In the fighting for eastern Mindanao, the Japanese lost some 21,100 men killed and 2,996 men eventually taken prisoner.
During the entirety of the five ‘Victor’ operations, the 8th Army lost 2,556 men killed and 9,412 wounded, and Japanese losses are estimated at about 50,000.
The whole of the 'Victor V' campaign was controversial as Fertig’s guerrilla forces already controlled 95% of the island of Mindanao, and had pinned down the Japanese in the major towns. After the US seizure of Luzon and the Visayan islands group had been secured in the 'Mike' and earlier 'Victor' campaigns, there was thus neither strategic nor operational value in the 'Victor V' campaign, which seems to have been undertaken largely for reasons of prestige and to please the Filipinos.