Philippines campaign (1944–1945)

By mid-1944, American forces were only southeast of Mindanao, the largest island in the southern Philippines – and able to bomb Japanese positions there using long-range bombers. American forces under Fleet Admiral Chester W. Nimitz had advanced across the Central Pacific Ocean, capturing the Gilbert Islands, some of the Marshall Islands, and most of the Marianas Islands, bypassing many Japanese Army garrisons and leaving them without hope of resupply or reinforcement. American carrier aircraft were already conducting air strikes and fighter sweeps against the Japanese in the Philippines, especially focusing on IJA and IJN airfields. U.S. Army and Australian Army troops under the American General Douglas MacArthur, the Supreme Commander of the Southwest Pacific Theater of Operations, had either overrun, or else isolated and bypassed, all remaining Japanese Army units on New Guinea and the Admiralty Islands. Before the invasion of the Philippines, MacArthur's northernmost conquest had been at Morotai in the Dutch East Indies on 15–16 September 1944. This was MacArthur's only base within bomber range of the southern Philippines. U.S. Navy, Marine Corps, and Army as well as Australian and New Zealand forces under the commands of General MacArthur and Admiral William F. Halsey Jr. had previously isolated the large Japanese South Pacific base at Rabaul, New Britain, during Operation Cartwheel. Allied forces had captured more lightly defended islands surrounding Rabaul, and then constructed air bases on them from which to bomb and blockade the Japanese forces at Rabaul into combat ineffectiveness, while avoiding a costly battle against the large IJA garrison there. Following victories in the Marianas campaign (on Saipan, on Guam, and on Tinian, from June–August 1944), American forces were drawing close to Japan itself. From the Marianas, long-range B-29 Superfortress heavy bombers of the U.S. Army Air Forces (USAAF) could bomb the Japanese home islands from well-supplied air bases that enjoyed direct access to supplies via cargo ships and tankers. The earlier phase of long-range B-29 raids against Japan had been carried out from the end of a circuitous supply line via British India and British Burma, which proved to be inadequate in sustaining an effective bombing campaign. All B-29s were transferred to the Marianas during the fall of 1944. Although Japanese decisionmakers recognized that Japan was losing the war at this stage, the Japanese Government, as well as the Imperial Japanese Army and Navy, refused to entertain the prospect of surrender. There had been a close relationship between the people of the Philippines and the United States since 1898, with the Philippines becoming the Commonwealth of the Philippines in 1935, and promised independence in mid-1946. Furthermore, an extensive series of air attacks by the American Fast Carrier Task Force under Admiral William F. Halsey against Japanese airfields and other bases on the Philippines had encountered little opposition from land-based Japanese aircraft. Upon Admiral Halsey's recommendation, the Combined Chiefs of Staff, meeting in Canada, approved a decision not only to move up the date for the first amphibious landing in the Philippines, but also to move this landing north from the southernmost island of Mindanao to the central island of Leyte. The new date set for the landing on Leyte, 20 October 1944, was two months before the previous target date to land on Mindanao. By late 1944 the Filipino people were anticipating an American invasion. After the defeat of American forces on the islands in April 1942, the Japanese had occupied the entirety of the island chain. The Japanese occupation was harsh, accompanied by atrocities and with large numbers of Filipinos pressed into slave labor. From mid-1942 through mid-1944, MacArthur and Nimitz supported the Filipino guerrilla resistance via U.S. Navy submarines supply runs and a few parachute drops, so that the guerrillas could harass the Japanese Army and take control of the rural jungle and mountainous areas, which amounted to about half of the archipelago. While remaining loyal to the United States, many Filipinos hoped and believed that liberation from the Japanese would bring them freedom and their already-promised independence. The Australian government offered General MacArthur the First Corps of the Australian Army to support the liberation of the Philippines. MacArthur suggested that two Australian infantry divisions be employed, each of them attached to a different U.S. Army Corps, but this idea was not acceptable to the Australian Cabinet, which wanted to have significant operational control within a certain area of the Philippines, rather than simply being part of a U.S. Army Corps. No agreement was ever reached between the Australian Cabinet and MacArthur – who might have wanted it that way. However, units from the Royal Australian Air Force and the Royal Australian Navy, such as the heavy cruiser , were involved. In addition to rejecting Australian ground troops, MacArthur also rejected the use of Marines for major ground combat operations during all 10 months of the Philippines campaign. The only contributions by the U.S. Marine Corps in this campaign were USMC aircraft and aviators, who provided air cover for U.S. Army ground units and assisted U.S. Army Air Forces aircraft, as well as one small USMC artillery unit, V Amphibious Corps (VAC) Artillery, commanded by Brigadier General Thomas E. Bourke. These 1,500 USMC artillerymen only fought in the Philippines during the Battle of Leyte from 21 October to 13 December. This small artillery contingent was the only USMC ground combat unit that served in the Philippines in 1944-45. During the Allied re-conquest of the Philippines, Filipino guerrillas began to strike openly against Japanese forces, carried out reconnaissance activities ahead of the advancing regular troops, and fought alongside advancing American divisions. ==Leyte==

On 20 October 1944, the U.S. Sixth Army, supported by naval and air bombardment, landed on the favorable eastern shore of Leyte, one of the islands of the Visayas island group, northeast of Mindanao. The Japanese miscalculated the relative strength of the American naval and air forces, and attempted to destroy the landing forces using most of the remaining surface strength of the IJN. This resulted in a sequence of naval engagements collectively known as the Battle of Leyte Gulf, fought from 23 October to 26 October. This decisive victory by the U.S. Navy, its Fast Carrier Task Force, its surface fleet, and its submarines effectively destroyed the remainder of the Imperial Japanese Navy (IJN), which had already lost all of its effective aircraft carrier forces. The IJN had four of its carriers sunk (which were albeit equipped with depleted air squadrons, and used only as decoys), numerous battleships and heavy cruisers, and a large number of light cruisers and destroyers. The IJN was effectively crippled after the battle, and was unable to fight another fleet action for the rest of the war. The U.S. Sixth Army continued its advance from the east, as the Japanese rushed reinforcements to the Ormoc Bay area on the western side of the island. While the Sixth Army was continually reinforced, the U.S. Fifth Air Force and the U.S. 3rd Fleet's Task Force 38 were able to devastate the Japanese attempts at air attacks and at landing new reinforcements and supplies, and also provide much support to the Army's ground troops during the Battle of Ormoc Bay from 11 November to 21 December 1944. Filipino guerrilla forces also performed valuable service in maintaining public order and in keeping the roads and highways free of congestion. After the American beachheads were established, the Leyte guerrilla groups were attached directly to the Sixth Army at the corps and division level in order to assist in scouting, intelligence, and combat operations. With the initial U.S. Sixth Army landings on the beaches at Tacloban and Dulag, Colonel Ruperto Kangleon's units went into action. They dynamited key bridges to block Japanese displacement toward the target area; they harassed enemy patrols; and they sabotaged supply and ammunition depots. Information on enemy troop movements and dispositions sent from guerrilla outposts to Kangleon's Headquarters was dispatched immediately to Sixth Army. During frequent torrential rainfall and over difficult terrain, the American advance continued across Leyte and onto the major island of Samar, just north of Leyte. On 7 December 1944, the U.S. Army units made another amphibious landing at Ormoc Bay and, after a major land and air battle, the landing force cut off all Japanese ability to reinforce and resupply their troops on Leyte. Although combat continued on Leyte until the end of the war, most major fighting had subsided by early 1945. ==Mindoro==

The U.S. Sixth Army's second major target to attack was Mindoro. This large island sits directly south of Luzon and Manila Bay, and MacArthur's main goal in seizing it was to construct airfields that could extend American air superiority over the major seaport and capital city of Manila on Luzon. The Seventh Fleet's large invasion convoy from Leyte to Mindoro came under sustained attack by kamikaze aircraft, but Japanese air units were unable to delay the American invasion of Mindoro. Mindoro was only lightly occupied by the Japanese Army, and much of it was held by Filipino guerrillas, so Mindoro was quickly overrun. U.S. Army engineers rapidly constructed a major air base at San Jose. Besides its proximity to Luzon, Mindoro possessed another advantage for American forces: frequent good flying weather given its dry climate. This is in sharp contrast to Leyte, which receives torrential rains most of the year, not only giving it poor flying weather, but making it very muddy and difficult to construct airfields. Mindoro was also the location of another breakthrough: the first appearance during the War in the Pacific of USAAF squadrons flying the fast, long-range P-51B Mustang fighters. Mindoro was a major victory for the 6th Army and the USAAF, and it also provided the major base for the next move of MacArthur's 6th Army: the invasion of Luzon, especially at Lingayen Gulf on its western coast. ==Luzon==

, 40th Div., take cover behind advancing tanks while moving up on Japanese positions on Panay Island. On 15 December 1944, landings against minimal resistance were made on the southern beaches of the island of Mindoro, a key location in the planned Lingayen Gulf operations, in support of major landings scheduled on Luzon. On 9 January 1945, on the south shore of Lingayen Gulf on the western coast of Luzon, General Krueger's Sixth Army landed its first units. Almost 175,000 men came ashore along a twenty-mile (32 km) beachhead within a few days. With heavy air support, Army units pushed inland, taking Clark Field, northwest of Manila, in the last week of January. Two more major landings followed, the first to cut off the Bataan Peninsula, and the second to isolate Manila from the south, which included a parachute drop. On 3 February 1945, elements of the U.S. 1st Cavalry Division pushed into the northern outskirts of Manila, and the 8th Cavalry Regiment (organized as infantry) passed through the northern suburbs and into the city itself. As the advance on Manila continued from the north and the south, the Bataan Peninsula was rapidly secured. On February 16, paratroopers and amphibious units simultaneously assaulted the island of Corregidor. Taking this stronghold was necessary because Japanese troops there could block the entrance of Manila Bay. The Americans needed to establish a major harbor base at Manila Bay to support the expected invasion of Japan, which was planned to begin on 1 November 1945. Japanese resistance on Corregidor ended on 27 February, and then all resistance by the Japanese Empire ceased on 15 August 1945, obviating the need for an invasion of the Japanese Home Islands. Despite initial American optimism for a quick victory, fighting in Manila was protracted and intense. It took until 3 March to clear the city of all Japanese troops, included Japanese naval infantry who fought tenaciously and refused to either surrender or to evacuate as the Japanese Army had previously done. Fort Drum, a fortified island in Manila Bay near Corregidor, held out until 13 April, when a team of Army troops went ashore and pumped 3,000 gallons of diesel fuel into the fort, then set off incendiary charges. No Japanese soldiers in Fort Drum survived the subsequent blast and fire. As the fighting in Manila was coming to a close, the other challenge faced by the newly liberated city was its available water supply. The Shimbu Group under Gen. Shizuo Yokoyama had fortified positions east of Manila in the Sierra Madre mountain range - practically controlling Ipo Dam, Wawa Dam, and its surrounding areas. Without the control of the Ipo Dam, only a third of the necessary amount of water could be supplied to the city. Facing a humanitarian crisis, the XI Corps decided to retake the Ipo Dam and the Wawa Dam. The result was a seesaw battle, and the longest continuous combat engagement in the Southwest Pacific Theater from 28 February to 30 May 1945. Facing the Shimbu Group during the Battle of Wawa Dam and Battle of Ipo Dam was initially the 6th Army's XIV Corps, which would later be replaced by XI Corps. While the fighting took three months, the American forces supported by Filipino guerillas led by Marcos "Marking" Agustin decimated the Shimbu Group, forcing Gen. Yokoyama to withdraw his forces further east deeper into the Sierra Madre Mountains. Soon afterwards, US troops landed at Infanta, cutting off the Shimbu Group from the last settlement of sizable development that they controlled. Up until the end of the war, the guerrillas scoured the Sierra Madre Mountains, hunting down the remnants of the Shimbu Group, who were either hiding out, or trying to make their way north. . Overall, ten U.S. divisions and five independent regiments battled on Luzon, making it the largest American campaign of the Pacific war, involving more troops than the United States had used in North Africa, Italy, or southern France. ==Finishing up the campaign==

. Palawan Island, between Borneo and Mindoro, the fifth largest and westernmost island of the Philippines, was invaded on February 28, with landings of the Eighth United States Army at Puerto Princesa. The Japanese put up little direct defense of Palawan, but cleaning up pockets of Japanese resistance lasted until late April, with the Japanese withdrawing into the mountains and jungles, dispersed as small units. Throughout the Philippines, U.S. forces were aided by Filipino guerrillas in finding and dispatching Japanese holdouts, the last of whom, Hiroo Onoda, surrendered in 1974, in the mountains of Lubang Island near Mindoro. The U.S. Eighth Army then moved on to its first landing on Mindanao (17 April), the last of the major islands of the Philippines to be retaken. Mindanao was followed by the invasion and occupation of Panay, Cebu, Negros, and several islands in the Sulu Archipelago. These islands provided bases for the U.S. Fifth and Thirteenth Air Forces to attack targets throughout the Philippines and the South China Sea. Following additional landings on Mindanao, U.S. Eighth Army troops continued their steady advance against stubborn Japanese resistance. By the end of June, remaining Japanese units were compressed into isolated pockets on Mindanao and Luzon, where fighting continued until the Japanese surrender on 15 August 1945. ==Aftermath==

Lieutenant Hiroo Onoda surrenders to Philippine President Ferdinand Marcos, 11 March 1974 Upon the surrender of Japan, some 45,000 Japanese prisoners of war were taken into custody by American authorities in the Philippines. These POWs were held in a number of camps around the country, and were used as labor for war reparations. Gen. MacArthur formed the Philippine War Crimes Commission, while Pres. Sergio Osmeña formed the National War Crimes Office. Both offices supported each other in the pursuit of war crimes trial in Tokyo, and later on the Philippine War Crimes Trial. Some units of the Japanese Army were out of radio contact with Tokyo at the time of Japan's surrender, and it was difficult to convince some of them that the war had ended. As a result, several Japanese troops held out for months and even years after the end of hostilities. As at many Pacific Islands with Japanese holdouts, major Japanese officials, including members of the Imperial Family, visited in person to convince the soldiers that they must surrender by order of the Emperor. The final Japanese holdout in the Philippines surrendered in 1974. ==Casualties==

;U.S. Army and Army Air Forces ;Japanese In addition it is estimated that a million Filipino civilians were killed in the Philippines campaign. ==See also==