Top Photo: H-Hour of "R" Day for the landing of the 24th Division, at Parang, Green Beach, Mindanao. The pre-naval bombardments had completely destroyed all the houses on the beach. April 17 1945. Mindanao, Philippine Islands. National Archives NAID: 204950572

After the capture of Iwo Jima and the battle for Manila in the Philippines in February 1945, major combat operations in the Pacific shifted to Okinawa in April and the months-long battle to wrest control of that island from the Japanese. But large portions of the Philippines were still under Japanese occupation, and General Douglas MacArthur felt an obligation to liberate all of the islands in order to fulfill his promise to “return.” He assigned General Robert Eichelberger’s newly formed Eighth US Army to embark on a series of operations, codenamed Victor I through Victor V, to liberate the remaining islands south of Luzon. 

The smaller islands, including Mindoro, Panay, and Cebu, were not strongly garrisoned and fell fairly quickly to the overwhelming American forces who by now had perfected the art of amphibious combat. But the larger island of Mindanao, at the extreme southern end of the chain, still held an estimated two Japanese divisions, as well as a large prewar Japanese civilian population of up to 10,000, mostly in the city of Davao, that might also assist in the defense. While Filipino guerillas controlled most of the island’s rugged interior, the Japanese garrison still held the large cities on Mindanao. Accordingly, Eichelberger assigned Major General Franklin Sibert’s X Corps, consisting of the 24th and 31st Infantry Divisions, to liberate all of the island and restore control to Filipino authorities.

Mindanao, the second-largest island in the Philippines, was incredibly diverse, geographically and demographically. The island’s mountainous interior contained rich mineral resources, while its valleys had been widely cultivated, especially by American agricultural firms like Del Monte, which established extensive pineapple and banana plantations along the northern coast. Larger cities, including the capital of Davao, were connected to the rest of Asia, but remote areas of the interior still held indigenous peoples with little contact with the outside world. The island also held the Philippines’ largest Islamic population, the Moros, who lived primarily in the northwest and had fiercely resisted American colonization 40 years earlier during the Philippine–American War. The Japanese had extracted mineral and food resources for their home islands, leaving Mindanao impoverished and subject to brutal rule, with frequent atrocities committed against Filipino civilians. This treatment led to a robust resistance movement, which grew in strength during the war as refugees and escaped prisoners from the Davao Penal Colony contacted American authorities and received clandestine resupply from submarines and airdrops. MacArthur’s landing on the nearby island of Leyte in October 1944 drew Japanese forces into that battle, and by the time the Americans arrived in April 1945, guerrillas controlled around 95 percent of the island. Both Japanese divisions garrisoning the island—the 100th in the south near Davao and the 30th in the interior and northern coast—lost two-thirds of their strength to fighting on Leyte. But the 40,000 who remained were skilled at ambush and delay tactics and could not be isolated from the many sources of food, including the omnipresent rice paddies, that dotted the island.

Aware that the Japanese had prepared strong defenses in and around the port of Davao, American planners characteristically looked for a place to make an unopposed landing. They found it on the island’s west coast, near the city of Cotabato, where a broad plain would deny the defenders any significant geographical obstacles and the wide Mindanao River remained navigable to small craft well into the island’s interior. The west coast was also within range of newly liberated airfields on the Zamboanga Peninsula, an appendage extending from Mindanao’s northwest tip and curving southwest toward Borneo. Guerrillas and units of the 41st Division liberated the peninsula in Operation Victor IV before proceeding down the Sulu Archipelago. When X Corps planners learned that guerrillas controlled the coast above Cotabato and an airstrip near Malabang, they switched the 24th Division’s planned assault to an unopposed landing and ordered the division to race swiftly inland and seize the formidable defenses around Davao, on the island’s southeast coast, from the rear. To alleviate congestion on the unimproved beachheads, the 31st Division was to land five days later, after the 24th had cleared the area, and follow it inland as far as the road junction at Kabacan. From there, the 24th would continue east to Davao, while the 31st would move north along the misnamed Sayre “Highway” to the northern coast. X Corps planners hoped this unexpected and rapid assault would isolate the defenders, preventing the two Japanese divisions from linking up in some inaccessible part of the island’s interior, facilitating the ultimate liberation. The operation unfolded almost exactly as planned, with the 24th liberating Davao on May 3 and the 31st reaching Kabacan ahead of disorganized elements of the Japanese 30th Division, pushing them back north up the highway. But the Japanese could still put up a strong defense if they chose to, and they proved it to the lead elements of the 31st Division in a May 6–12 clash that became known as the Battle of Colgan’s Woods.

Remains of Davao City, Mindanao, after Allied bombings over this area. National Archives NAID: 204952384

The 31st had moved inland so quickly, and both the Filipino guerrillas and the retreating Japanese had done such a good job wrecking the many bridges on the Sayre Highway, that the division outran its motorized support, including supply trucks and artillery pieces. Destroyed bridges over deep defiles meant that soldiers had to continue mostly on foot, with the few vehicles that could be winched across the chasms on wire cables. But the supply trucks and heavier artillery pieces had to wait until engineers could fill gaps and construct bridges that would allow them to keep up with the rapidly advancing infantry. Logistical difficulties were ameliorated with frequent airdrops by C-47s operating from airfields near the coast, though a shortage of parachutes meant rations sometimes had to be dropped directly at a low altitude, with the result, as one chaplain pointed out, that “the cheese gets thoroughly mixed up with the tobacco,” as each ration also contained a pack of cigarettes. Fire support was a more difficult challenge, with Marine SBD Dauntless dive bombers operating from the coast providing what support they could. To slow the American advance, a Japanese battalion put up fierce resistance at an extensively fortified and dense stand of timber near Lake Pinamaloy, with spider holes and underground tunnels connecting well-concealed firing positions constructed among the tall roots of the banyan trees. 

Vultee L-5 "Guinea Short Lines" being refueled at Valencia Airstrip, Mindanao, Philippine Islands. Due to road conditions trucks could not bring fuel this far into the forward area, therefore fuel was flown by C-47 "Skytrains," in five gallon cans. National Archives NAID: 204991683

When the 124th Infantry Regiment’s 2nd Battalion hit the woods, it had only moved a short distance before the defenders popped up and attacked them from behind. In a desperate effort to rescue wounded men, Catholic chaplain Captain Aquinas Colgan crawled forward but was killed by a machine gun burst while dragging a man to safety, earning him the Distinguished Service Cross. The surviving soldiers were so affected by the loss of their beloved chaplain that they named the engagement the Battle of Colgan’s Woods. Each day, entire companies moved into the killing zone, only to be driven to ground and cut apart before they could withdraw. For a week the 124th futilely attempted to push through the roadblock, though one battalion did succeed in outflanking the obstacle and isolating the defenders. After a week, the supporting artillery finally arrived and, along with the Marine dive bombers now armed with napalm, burned the woods into what one soldier described as charred matchsticks. Cut off, running out of ammunition, and subject to an unrelenting barrage, the surviving Japanese attempted a futile banzai charge but were cut down to a man. The brutal combat in the woods, which cost the 124th Infantry hundreds of casualties, demonstrated that the Japanese were still capable of mounting a formidable defense if conditions were favorable. 

Evacuation of patients by air from Valencia airstrip in C-47's which flew them to base hospital at Malabang. The C-47's flew rations in and patients out. National Archives NAID: 204950734

Fortunately, the battle proved to be the last major engagement for the 31st Division. By the end of May, they linked up with a regiment of the 40th Division sent to secure a foothold on the northern coast and were pushing the Japanese deeper into Mindanao’s inaccessible interior. The campaign officially ended when Japan announced its surrender on August 15, 1945, with the 31st Division’s 167th Infantry still fighting on the Kibawe-Talomo Trail when word of the war’s end arrived. Within weeks, Japanese and American soldiers who had once hunted each other with no quarter in the jungles were playing volleyball together near the prisoner-of-war camps, presaging the rapid reconciliation between the two countries in the postwar years. On September 2, the division accepted the formal surrender of the surviving Japanese troops on the island, though some holdouts remained in the interior for years afterward. When the 24th Division left to serve as occupation troops in Japan, the Army replaced them with the 93rd Infantry Division, a segregated unit of Black soldiers that had initially served in combat in the Soloman Islands but had gradually been relegated to service as manual laborers and occupation troops as the campaign progressed. The 31st, made up largely of soldiers from the American South, and the 93rd clashed over a number of issues, including the 93rd being camped downstream of the 31st (and subjected to whatever flowed downstream in the river) and competition for the affections of Filipinas in the nearby towns. The many clashes between Black and white troops in the Philippines illustrated the discrimination African Americans still faced. Although the war effort had saved the world for democracy, there was still work to be done at home to ensure that all Americans enjoyed its benefits, and Black WWII veterans would be major catalysts in the growing Civil Rights Movement.

The liberation of Mindanao was, in some respects, an unnecessary campaign militarily, but it had important political implications, as it enabled the United States to fulfill its promise of independence to the Philippines, which finally came the following year. The campaign also highlighted the weakened but still dangerous state of the Japanese military in 1945 and provides insights into the combat capabilities of units that would have made the planned invasion of the home islands of Japan. While the campaign was not the costliest or longest of the Pacific theater, it still illustrates the nature of combat in the Southwest Pacific and the importance of allies, regular or irregular, in conducting military operations in that corner of the globe. The soldiers who survived the campaign greeted the end of the war with relief and took their many experiences home with them in a sustained effort to build an even more perfect union.