The 'Battle of Lingayen Gulf' was the main undertaking of the Japanese 'M' (ii) conquest of th Philippine islands group (21/23 December 1941).
Next to the Greater Sunda islands group of the Netherlands East Indies, the Philippine islands group is the largest archipelago in the world, extending to a length of more than 1,150 miles (1850 km) from north to south and about 700 miles (1125 km) from east to west. The islands extend from latitude 5° to 22° N and lie between longitudes 117° and 127° E. The group’s western and eastern sides are bounded by the South China Sea and the Philippine Sea respectively, unbroken by islands for 600 miles (965 km) until reaching the Palau islands group. On the Philippine island groups' south-western side are the Sulu and Celebes Seas, which separate the group from Borneo and Celebes in the East Indies. To the north of Luzon, the northernmost of the main islands, it is only 220 miles (355 km) across the Luzon Strait to Formosa, which was at the time Japanese territory, while the Indo-Chinese mainland is 750 miles (1205 km) to the west. From Manila, the capital of the Philippine islands group, Pearl Harbor is 5,300 miles (8530 km) to the east-north-east, while Tokyo is only 1,800 miles (2895 km) to the north-north-east.
The Philippine islands group comprises 7,083 islands and islets, of which only 2,773 had received names by 1941. Only 466 of the islands are larger than 1 sq mile (0.4 km²) in area, but there is a small number of very large islands. The two largest, Luzon and Mindanao, account for over two-thirds of the entire group’s land area. The coastal length of these islands is 12,000 miles (19310 km). In the World War II period, between 600 and 700 of the islands were populated.
The continental-type islands are of volcanic origin, and eruptions, earthquakes and landslides constitute hazards. The islands are rugged and mountainous with the highest elevation being Mt Apo at 9,691 ft (2954 m) on southern Mindanao. Valleys are interspersed with rocky, terraced mountains, hills and ridges extending the length of the islands, most of which are oriented roughly north/south. Spurs and fingers run off many of the ridges. Only Luzon and Mindanao have extensive lowlands, and highly varied vegetation ranges from dense hardwood forests covering 70% of the land to scrub tree- and brush-covered areas to open grasslands. The trees include teak, ebony, ironwood and cypress plus a number of native hardwoods. About 19% of the Philippine islands' land area is considered arable with the river valleys and plains possessing extremely fertile volcanic soil. In the southern islands coral limestone composes much of the soil. The coasts are often rocky and edged with cliffs, although suitable landing beaches are found in many areas, especially within the numerous bays and gulfs. Coastal swamps with mangroves and nipa palm are found in some areas. The beaches are frequently wide with few, if any, natural obstacles. Access inland varies between some level coastal plains to gradually rising terraced slopes to hills and ridges. Water is abundant on most islands with significant rivers found on the larger ones.
The 11 largest islands constitute 95% of the land mass, and in descending order of size these are Luzon, Mindanao, Samar, Negros, Palawan, Panay, Mindoro, Leyte, Cebu, Bohol and Masbate. The Philippine islands group is divided into three main areas: Luzon in the north, the largest island; Mindanao in the south, the second largest island; and the Visayas in the central portion. The Visayas surround the Visayan and Sibuyan Seas and consist of the last nine islands listed above and some 6,000 smaller islands covering 33,000 sq miles (85470 km²).
Although the Philippine islands group is located in the tropics, the climate is mild and not oppressively hot as found on most other Pacific islands, although hot and humid periods occur in April and May. There is more variation between day and night high and low temperatures than there is with seasonal differences , however. There is only a 12° C (10° F) difference between the coolest and hottest months. Most of the islands receive more than 70 in (1780 mm) of rain per year, but some areas receive more than 200 in (5080 mm). The eastern portions of the islands receive most of their rain between October and April during the north-east monsoon. The south-west monsoon blows from June through September delivering rain in the western portion. The islands' central mountains affect the monsoons with the windward areas receiving the heaviest rain and leeward sides considerably less. Southern Luzon, part of the Visayas and most of Mindanao experience no pronounced dry season, but other islands have a dry season between March and May. The Philippines sit astride the typhoon belt and up to six a year can strike the islands.
Malaria and other tropical diseases are a problem, but plague and smallpox were under control.
The Philippine islands group was well developed in economic terms. Manila had become a regional commercial centre for the distribution of US goods and was the main port of entry. Smaller ports of entry were Cebu, Iloilo, Zamboanga, Jolo, Legazpi and Davao, all of which offered good harbour facilities. There were another 200 ports of call throughout the islands for inter-island steamers and ferries, making roads and railways of secondary importance on many islands. On Luzon there was a telephone system, and most cities and principal towns on other islands were linked by telephone, telegraph and radio. Most provincial governments operated telephone systems so that many barrios (villages) had at least one telephone linking them to the outside. Submarine cables linked Manila with Guam, Shanghai and Hong Kong and there were four trans-oceanic radio stations.
There were some 13,750 miles (22125 km) of roads throughout the islands, and more than 700 miles (1125 km) of railway on Luzon and almost 133 miles (214 km) on Panay and Cebu. All of the larger islands possessed well-developed road systems with coastal roads and one to four connecting cross-island roads depending on their size.
The Philippine islands group was basically agrarian, the principal crops being rice, coconuts, sugar cane, coffee, tobacco, maize and tropical fruits. The chief exports were hemp, coconut products, tobacco and lumber. Hemp, from the abacá tree, was an important export and the loss of the Philippine islands group to the Japanese in World War II made hemp and Manila rope scarce products, forcing navies across the world to search for alternatives. Embroidered materials were also an important export. Mining was not fully developed, but there are significant deposits of gold, silver, iron, chrome, manganese, copper and lead, some of which had been tapped. Animal life included a domesticated water buffalo, deer, wild pigs and mongoose. Cattle and pigs constituted the main livestock population.
In 1941, the Philippine islands group had a population of 16,771,900 persons. Some 6,400,000 of these lived in the Visayas, 920,000 on Leyte, and most of the rest on Luzon. The vast majority were Filipinos of Malayan stock with a mixture of Spanish and Chinese blood, and spoke more than 65 different, but related dialects. There was also a small population of an aboriginal pygmy race known as the Awtas. The Moros, a name given by the Spanish, are a Filipino Islamic warrior society who live on western Mindanao, southern Palawan, and the Sulu archipelago, and have long remained outside mainstream Filipino society. In 1937 the Tagalog dialect, the most common among the wealthy and influential of central Luzon, was adopted as the basis of the Pilipino national language. Twice as many people spoke the Visayan dialect. English was also adopted as an official language. Within the Philippine army most of the officers spoke Tagalog while many of the rank and file spoke other dialects. While there are similarities between dialects, few can understand each other.
In 1941 about 27%, mainly on Luzon, spoke English and only 3% Spanish. The majority of Filipinos were Catholic.
There were about 9,000 Americans on Luzon and small numbers on other islands. There were also 117,000 Chinese and 30,000 Japanese, most of whom (about 15,000) lived in the vicinity of Davao on Mindanao and most others in the Manila area. Most were interned at the start of hostilities.
The Philippine army, advised and supplied by the USA, included a small Philippine army air corps of some 500 men with 40 aircraft. The existing Insular Constabulary, a 5,000-man professional and national militarised police created in 1901, was included in the army as the Philippine Constabulary Division under the command of Major General Guillermo Francisco, who retained control of the constabulary under the Japanese. There was no navy, just a small Army Off Shore Patrol, which was to have received motor torpedo boats. There were also US Army and US Navy presences as well as the Philippine Scouts, a component of the US Army. The Philippine Scouts were considered a well-trained and disciplined force comprising Filipino rank and file under US Army officers with a leavening of Filipino officers.
The Philippine islands group had no conventional military tradition when authorised to create an army in 1935. The president-elect, Manuel Quezon, asked his friend, General Douglas MacArthur, a former US Army chief-of-staff, to serve as the military adviser to the commonwealth government in the establishment and development of a system of national defence. A regular force of 10,000 troops was planned, and this was to be backed by a reserve of 400,000 men, a goal to be achieved by 1946. The regular force included the 1st Regular Division and the Philippine Constabulary Division, which continued its police duties with detachments stationed throughout the islands. Conscription was introduced, but the conscripts served only a 22-week training period before transfer to the reserves. A military academy to train officers was established at on Luzon at Baguio, which was also the nation’s summer capital. The commonwealth was divided into ten military districts, each with one reserve division projected to grow to three. Divisions, regiments and many battalions were commanded by US Army officers. Defence plans for the larger islands were developed, and since these were intended for use by the commonwealth once full independence from the USA was granted, did not include US military or naval participation. Officers and non-commissioned officers were trained for cadre leadership positions and as instructors in 1936, and conscription began in 1937. Training was conducted at camps scattered throughout the Philippine islands with the US Army providing training and technical assistance.
Overall US military command was maintained by the Philippine Department, which had been established in 1913, with its headquarters in Manila. The department was commanded by a major general until 1941. MacArthur had retired from the US Army in 1940 to become the commander-in-chief of the Philippine army with the local rank of field marshal, but when war with Japan appeared likely he was recalled to active US duty as a lieutenant general and assumed command of the newly formed US Army Forces in the Far East on 27 July 1941. As such he was also the commanding general of the Philippine Department. One day earlier the Philippine army had been placed under his command. The principal formations within the new command were the Philippine Division, the Harbor Defense of Manila and Subic Bays, the Far East Air Force under Major General Lewis H. Brereton at Clark and Nichols Fields, various separate units, and the Philippine Department, which became a supply and administrative organisation for the US and Philippine armed forces. The Philippine Division (31st, 45th and 57th Infantry), which had been created in 1921, was comprised mainly of Philippine Scout units, with the 31st Infantry as the sole US-manned unit, and totalled totaling 10,500 men. The division was commanded by Major General Jonathan M. Wainwright and stationed at Fort William McKinley, to the south of Manila. The Harbor Defense of Manila and Subic Bays, headquartered at Fort Mills on Corregidor island in the mouth of Manila Bay, was commanded by Major General George F. Moore and included four US Army and Philippine Scout coast artillery and anti-aircraft regiments with 5,300 men. The Far East Air Force comprised fewer than 280 aircraft, of which only half were considered modern, and 5,600 men. These forces totalled 10,500 US Army and 12,000 Philippine Scouts personnel.
The US Navy elements in the Philippine islands were parts of the Asiatic Fleet commanded by Admiral Thomas C. Hart, and the shore establishment was commanded by Rear Admiral Francis Rockwell of the 16th Naval District. The Asiatic Fleet (Task Force 5) possessed only three cruisers, 13 destroyers of World War I vintage, 29 mostly old submarines, six gunboats, a patrol wing with 24 aircraft, and some service vessels. Under the Naval District were 1,700 men of the 4th Marines, recently evacuated from China, and the 1st Separate Marine Battalion. In all there were about 20,000 US service personnel in the Philippine islands.
The Philippine army had been fully mobilised by progressively calling up the reservists giving it a strength of 120,000 troops, but these men were under-armed, poorly equipped and only partially trained. Large unit-level training and manoeuvres had never been conducted for lack of funds. Most units were much below their establishment strengths, with few of the divisions approaching their modest 8,600-man authorisation. Many divisional sub-units were never formed and all units lacked even basic equipment and matériel. There was virtually no artillery. A total of 100 cargo ships of equipment and matériel was scheduled in the first months of 1942, along with 22,500 US troops in two infantry regiments, artillery units, support units and advisers, but time had run out.
The Philippine army units on Luzon included the 1st Regular, 11th, 21st, 31st, 41st, 51st, 71st and 91stv Divisions (the last pair in reserve) with 76,750 men. In the Visayas were the 61st Division and the 74th and 75th Regiments (Provisional). On Mindanao were the 81st, 101st and 102d Divisions plus single regiments detached from the 61st, 71st, and 91st Divisions. On 4 November 1941, The North Luzon Force and the South Luzon Force, commanded by Wainwright and Brigadier General (later Major General) George M. Parker respectively, were organised to oversee the training and tactical control of Philippine army formations and units on Luzon. The Visayan-Mindanao Force was formed for the same purpose in the central and southern Philippine islands under Colonel (later Major General) William F. Sharp with its headquarters on Cebu until the end of December, when it moved to Mindanao. The Philippine army was placed directly under MacArthur’s command at the start of the Pacific War.
Anticipating a Japanese attack, US air patrols sighted Japanese aircraft as early as 4 December 1941 within 20 miles (32 km) of Luzon. The Japanese successfully launched air attacks on the main US airfields around Manila on the morning of 8 December, destroying almost 100 aircraft on the ground. The Japanese landed a naval landing force on the small Batan island, the northernmost of the Philippine islands group, on the same day. The tiny garrison was swiftly defeated and the Japanese began work on an airfield. Most Japanese air and ground forces committed to the Philippine islands group were launched from Japanese-occupied Formosa and the Pescadores islands group to the north under the command of Lieutenant General Masaharu Homma’s 14th Army backed by the 5th Air Group with 307 aircraft under Lieutenant General Hideyoshi Obata. At this time the 14th Army comprised Lieutenant General Susumu Morioka’s 16th Division (9th, 20th and 33rd Regiments and the 22nd Field Artillery Regiment, and Lieutenant General Yuitsu Tsuchihashi’s 48th Division (1st and 2nd Formosa Regiments, 47th Regiment and 48th Mountain Artillery Regiment).
The Imperial Japanese navy forces included the 3rd Fleet, reinforced by elements of the 1st Fleet and 2nd Fleet under the command of Vice Admiral Ibo Takahashi, and the 11th Air Fleet under the command of Vice Admiral Nishizo Tsukahara with 444 aircraft.
The largest and northernmost of the main Philippine islands, Luzon is about 340 miles (545 km) long on its north/south axis and 130 miles (210 km) across at its widest. The island had an area of 40,814 sq miles (105708 km²), and its Bicol peninsula juts from the main body of the island 200 miles (320 km) to the south-east toward Samar island. This irregularly shaped peninsula varies from 10 to 40 miles (16 to 64 km) in width. Luzon’s topography varies greatly with several north/south mountain ranges with the Sierra Madre along the upper eastern coast with a maximum elevation of 6,188 ft (1886 m), the broad Cordillera mountains extending up the centre with Mt Pulog at 9,613 ft (2930 m), and the Caraballo mountains on the west-central coast with the highest elevation 6,686 ft (2038 m). In northern Luzon is the islands' largest waterway, the Cagayan river, which flows to the north between the Cordillera and Caraballo mountains in a valley some 50 miles (80 km) wide, and is the second largest food-producing area on Luzon. Numerous tributaries feed the river from the mountains. Another river valley, the Agno/Pampanga valley, is located in central Luzon, reaching from Lingayen Gulf to Manila Bay. Lingayen Gulf is 20 miles (32 km) wide and 30 miles (48 km) deep, and provided both the Japanese and Americans with their main landing site in 1939 and 1944 respectively. The adjoining river valley provides a natural corridor to Manila. Manila Bay, which is slightly larger than Lingayen Gulf, but protected by the Bataan peninsula, provides an excellent anchorage.
The city of Manila, the commonwealth capital, is located on the south-eastern coast of the bay and in 1941 possessed a population 623,400. A large lake, Laguna de Bay, lies to the south-east of Manila and a smaller lake, Lake Taal, to the south. Numerous bays and gulfs with good landing beaches are found on both the east-central and west-central coasts.
The two main bases of the Far East Air Force were Clark Field almost 50 miles (80 km) to the north-west of Manila and Nichols Field on the city’s southern edge. There were small airstrips scattered throughout the islands.
US Navy bases included Olongapo Navy Base on the northern end of Subic Bay at the upper north-west base of the Bataan peninsula, Mariveles Navy Section Base at the southern end of the Bataan peninsula, and Cavite Navy Yard on the south-eastern side of Manila Bay. Satellite facilities included a radio station and seaplane base at nearby Sangley Point.
At dawn on 10 December two landing forces, the 'Tanaka' Detachment and the 'Kanno' Detachment, comprising reinforced elements of the 2nd Formosa Regiment and totalling some 4,000 men, had landed at Aparri on the eastern end of Luzon’s northern coast and at Vigan toward the northern end of the island;s western coast respectively. These units linked on the island’s north-western corner on 12 December, but some of their elements also moved to the south. They were intended to secure local airfields and as diversions to attract US and Filipino forces, but MacArthur did not take the bait and withheld the North Luzon Force in order to attack the main Japanese force when it appeared. Also on 10 December the Batan Attack Force secured Camiguin island off the coast to the north of Aparri for its airstrip. Cavite Navy Yard was heavily bombed.
On 12 December, the 2,500-man 'Kimura' Detachment with the 33rd Regiment and the 1st Kure Special Naval Landing Force from the Palau islands group landed in the Albay Gulf on the south-eastern end of Luzon’s long tail, the Bicol peninsula. This force seized Legazpi and its airstrip, and then moved slowly up the peninsula after defeating elements of the South Luzon Force’s 41st and 51st Divisions. Heavy air attacks continued against the few remaining US aircraft and bases. US and Filipino ground forces harassed the advancing Japanese, but most were concentrated to meet the expected main landing in Lingayen Gulf, some 130 miles (210 km) to the north of Manila. By 14 December three Imperial Japanese army air force air regiments had arrived on the captured airfields, and some Imperial Japanese navy air arm elements had been landed the south. The two Japanese services had designated an operational boundary across Luzon on latitude 16° N from the southern end of Lingayen Gulf on the western coast to Casiguran Sound on the eastern coast, and the Imperial Japanese navy was initially responsible for operations in southern Luzon.
On 16 December the 'Miura' Detachment and 'Sakaguchi' Detachment from the Palau islands group landed on Mindanao.
The main Japanese landing on Luzon was the 'Battle of Lingayen Gulf', which started on 21 December. Preparatory moves toward this decisive part of the Japanese seizure of Luzon had already been made by the air attack on Clark Field and the landings of Japanese forces at five points in northern and southern Luzon and Mindanao in the early and middle parts of December, with the Imperial Japanese army air force seizing airfields and basing aircraft for ground support, and the Imperial Japanese navy air arm establishing seaplane bases at Camiguin island, Legazpi and Davao. The main landing of Japanese forces targeted Lingayen Gulf as this was sited attractively close to the Philippine capital of Manila, and Lamon Bay on the opposite coast to the south.
The Japanese invasion force of 43,110 men was under the overall command of Homma’s 14th Army, and comprised Tsuchihashi’s 48th Division less the 'Tanaka' Detachment and 'Kanno' Detachment which had already landed in the 'Battle of Aparri' and 'Battle of Vigan' respectively. A newly formed division raised in Formosa, it lacked combat experience, but it was nonetheless the best equipped and motorised division in the Japanese army. It also contained elements of the 16th Division including the 4th and 7th Tank Regiments with a total of between 80 and 100 tanks respectively, and three field artillery regiments.
The invasion force sailed in three convoys, each of which constituted a separate task force with a separate landing point and objective. The Japanese maintained strict secrecy and only senior commanders were aware of the targets. The first task force, known as the 'Kamijima' Detachment, comprised the 9th Regiment in 21 transport vessels, and departed Keelung in northern Formosa during the morning of 17 December escorted by the same naval force used in the Japanese invasion of Batan island. The second task force comprised the 1st Formosa Regiment of the 48th Division and the 7th Tank Regiment, and was carried in 28 transport vessels which departed at 12.00 on 18 December from Mako in the Japanese-occupied Pescadores islands group between Formosa and mainland China under escort of the same ships that had previously escorted by the Vigan invasion force. The third task force comprised the 47th Regiment of the 48th Division and 4th Tank Regiment, and departed Takao on Formosa during the evening of 18 December under escort of the same ships that had previously escorted the Aparri invasion force. Distant cover was provided by Vice Admiral Ibo Takahashi’s 3rd Fleet and ships of Vice Admiral Nobutake Kondo’s 2nd Fleet.
All three convoys arrived together at Lingayen Gulf on the night of 21 December.
The convoy from Takao was scheduled to land its embarked troops at Agoo, a small village in La Union province on the eastern shore of Lingayen Gulf, beginning at 05.00 on 22 December. The convoy from Mako was intended to start landing it embarked troops at 05.50 at Caba, 7 miles (11.25 km) to the north of Agoo. The 'Kamijima' Detachment was to land at Bauang, 7 miles (11.25 km) to the north of Caba from 07.30. This was intended to provide the 14th Army a landing zone 15 miles (24 km) wide along the narrow coastal plain just to the north of the Luzon’s central plains and protected from flanking counterattack from the east by the Cordillera mountains. Once ashore, the troops were to move inland without consolidating the landing zone. The 'Kamijima' Detachment in particular was to strike to the north to occupy San Fernando and Baguio, and to link with the Vigan invasion that was moving south along the coast. The other two forces were to press to the south past Rosario to secure the bank of the Agno river, the first major terrain obstacle on the road to Manila.
The landing operations did not proceed as smoothly as planned, however. Hampered by bad weather and heavy seas, the convoy overshot its target and anchored 4 miles (6.4 km) farther to the south than intended. Powerful surf made landing difficult and a number of landing craft were destroyed. Rather than the pinpoint landings which had been envisaged, therefore, the Japanese forces found themselves spread apart over a wide area of the landing zone and unable to land their tanks and heavy equipment as planned.
Despite considerable advance warning of the impending invasion, the US-led forces in the Philippine islands group were ill-prepared. Lingayen Gulf was the most logical area in which to land a large invasion, but the entire 120-mile (195-km) coast was protected by only two Philippine army divisions, of which only one had any artillery. The US leadership had anticipated that a landing would occur at the southern end of the gulf, which is where the Philippine 21st Division placed its artillery batteries. The northern sector was held by the Philippine 11th Division, supplemented by the 71st Division, a newly raised formation with only 10 weeks of training, and the 26th Cavalry (Philippine Scouts), which was stationed on Route 3 some 12 miles (19 km) to the south of Rosario.
Aside from the poor weather conditions, resistance to the Japanese landing was minimal. The US submarine S-38 managed to sink the army transport Hayo Maru during the morning of 22 December, and Seal sank Hayataka Maru on the following day. Coastal artillery slightly damaged the auxiliary seaplane tender Sanuki Maru. Despite the fighter cover provided by the 24th and 50th Sentais, four Boeing B-17 Flying Fortress four-engined heavy bombers managed to inflict some strafing damage. The only location at which the Japanese faced ground opposition was at Bauang, where an element of the Philippine 12th Regiment’s headquarters opened fire with its single 0.5-in (12.7-mm) heavy machine gun on the 'Kamijima' Detachment as it landed.
After coming ashore, the 'Kamijima' Detachment immediately moved to the north along Route 3 and by 17.00 had secured the town of Bauang, with its 3/9th Regiment continuing on the road toward Baguio to secure the airfield at Naguilian. It was opposed by the Philippine 71st Division under the command of Lieutenant Colonel Donald Van N. Bonnett, who had orders to stop the Japanese advance at San Fernando. Bonnett positioned one of his battalions with a battery of 75-mm (2.95-in) guns on the coastal road, and sent a second battalion on a flanking manoeuvre along a secondary road to the east. The rate of the Japanese advance was too rapid for the inexperienced and poorly trained Philippine troops to get into position, and Bonnett subsequently gave orders for the division to withdraw to beyond Baguio by 00.00.
In the southern sector, the 1st Formosa Regiment and part of the 48th Mountain Artillery Regiment under the command of Colonel Hifumi Imai had landed at Aringay by 10.30 and advanced to the south in the direction of Rosario along the coastal road. They had been joined by 16.00 by the 48th Reconnaissance Regiment and the 4th Tank Regiment, which had landed at 07.30 just to the north of Damortis. Also in the southern sector, the 47th Regiment and one battalion of the 48th Mountain Artillery Regiment, under the command of Colonel Isamu Yanagi, was also advancing toward Rosario. Their movement was opposed by one infantry battalion of the Philippine 11th Division under the command of Brigadier General William E Brougher, but after a minor skirmish, the Philippine forces were routed. At this point, Homma was still unable to land his artillery and heavy equipment because of the surf, and therefore decided to shift his anchorage and landing points farther to the south. The 48th Division was ordered to take San Fabian, which had two 155-mm (6.1-in) coastal artillery guns, and the Japanese drive along the shore of Lingayen Gulf was accordingly extended farther to the south than had originally been intended.
To oppose the Japanese advance on Manila, Wainwright stationed the Philippine 26th Cavalry along the coastal road to the north of Rosario at the village of Damortis. Receiving reports that the Japanese were advancing on bicycles and in light motor vehicles, Wainwright also dispatched a platoon of five tanks. When the 26th Cavalry encountered forward elements of the 48th Reconnaissance Regiment and 4th Tank Regiment, it fell back to Damortis, where defensive positions had been created. However, with its command tank destroyed and the remaining four damaged by Japanese 47-mm anti-tank guns, the outnumbered and outgunned 26th Cavalry withdrew, leaving Damortis under complete control of the Japanese by 19.00.
Rosario then became the centre of American resistance. Earlier in the afternoon, Wainwright had ordered Brigadier General Clyde A Selleck to take the Philippine 71st Division to Damortis to hold the junction of the road linking Rosario and Baguio to the east of Rosario. However, by the time his force reached Rosario, Selleck learned that the Japanese were advancing from both Damortis and Agoo. By the evening, the survivors of the 26th Cavalry reached Rosario with the Japanese in close pursuit. At 20.00, the Japanese tanks penetrated the 26th Cavalry’s rearguard, in the process inflicting considerable casualties, and it was only by blocking a bridge a few miles to the west of Rosario with a burning tank that the Americans managed to slow the Japanese attack and prevent a panic-struck rout. The centre of Rosario was the scene of a pitched battle between troops of the Philippine 71st Division and a part of Colonel Yanagi’s 47th Regiment. Fortunately for the Americans, however, much of Yanagi’s force had been ordered back for the capture of San Fabian, enabling the Philippine forces to escape.
Within one day of their landing, therefore, the Japanese had secured a large section of Lingayen Gulf’s coast and advanced to the north, south and east. To the north, they had joined with Tanaka’s force from northern Luzon and to the south had occupied Rosario. The only opposition had come from the Philippine 26th Cavalry, whose poorly equipped and outnumbered men were unable to slow the Japanese advance.
On the morning of 23 December, the Philippine 71st Division set up defensive positions along Route 3 to the south of Sison, with the remnants of the 26th Cavalry falling back to Pozorrubio to regroup. The advance of the 47th Regiment was slowed until 12.00 by the Philippine artillery, by which time the 47th Regiment had been joined by the 48th Reconnaissance Regiment and 4th Tank Regiments. Supported by aircraft, the Japanese now launched a concerted attack, and the Philippine 71st Division broke and fled, abandoning its artillery. At 19.00, the Japanese entered Sison, with the US and Filipino line moved back to a position just to the north of Pozorrubio, and the 26th Cavalry continuing its retreat to Binalonan. The Japanese continued their attack into the night, driving the Philippine 91st Division from Pozorrubio and ending US hopes of making a stand there.
Even before the fall of Sison, Wainwright had received MacArthur’s permission to withdraw behind the Agno river as the senior general believed that further defence of the Lingayen Gulf area was impossible. Wainwright hoped to launch a counterattack with the Philippine Division and other units being held in reserve.
In the early morning of 24 December, the 4th Tank Regiment encountered the Philippine 26th Cavalry to the north-west of Binalonan. Although lacking anti-tank guns, the 26th Cavalry made a strong stand, inflicting considerable casualties on the Japanese, but with the arrival of the 2nd Formosa Regiment later in that same morning, the 26th Cavalry found itself outnumbered and almost encircled. For more than four hours, the 26th Cavalry held its ground, until the remaining 450 men began to withdraw at 15.30. By dusk, the survivors had reached Tayung on the far side of the Agno river, and the Japanese had entered Binalonan. At this point, the Japanese were in position to enter the central plain of Luzon for the final drive to Manila.
Despite adverse weather, Homma had been able to land the bulk of his 14th Army at Lingayen Gulf without encountering significant opposition, and in a matter of a few days had secured the northern approaches to the Philippine capital.
The subsequent Japanese occupation of the Philippine islands group was repressive, but many areas on larger islands and hundreds of remote inhabited islands remained unoccupied: the Japanese in fact controlled only 12 of the Philippine Republic’s 48 provinces. A combination of rugged terrain, the occupation force’s self-confinement to the cities and larger towns, the resentment of the Filipino people, and their faith in the return of US forces led to the creation of a very substantial resistance movement. Guerrilla units were raised independently in mid-1942 and were gradually unified throughout the Visayan islands group and on Mindanao by MacArthur’s headquarters in Australia. As a consequence of the extent of Japanese occupation on Luzon, guerrillas kept a low profile until a time late 1944, when they emerged in large numbers to support of the US 'Mike' invasion. In the central part of Luzon, the 30,000-person People’s Anti-Japanese Army (Hukbo ng Bayan Laban sa Hapon or Hukbalahap) rose independently of US support. The Huk resistance was strongly nationalist and would continue its own guerrilla war after the liberation of the Philippine islands group. Guerrilla leadership was provided by hundreds of US and Filipino servicemen from all branches and organisations who had refused to surrender.
In October 1943, most Filipino prisoners of war were released by the Japanese after a puppet Philippine government was formed, and some of these released men joined the guerrillas. Supplies and arms were delivered from Allied-held areas by submarine and flying boat. Until the 'Mike' invasion, guerrilla activities throughout the islands were generally low-keyed and avoided large-scale operations. Some units suffered when they attempted overly ambitious operations. While they harassed the Japanese, the guerrillas concentrated their efforts in building their strength to support the forthcoming series of US invasions. Even so, the guerrillas were credited with killing between 8,000 and 10,000 Japanese during the occupation, and proved extremely valuable in providing intelligence information, aiding reconnaissance teams, and recovering downed airmen and escaped prisoners of war. The guerrilla movement was not without its internal problems, however. There were conflicts between the different groups as many had their own political agendas, or vied for power or recognition, or simply exploited local civilians. Animosities between groups were common, even after the US invasion, with some units openly fighting each other. Once the invasion came, the guerrillas' real value was realised as they continued to provide timely intelligence, served as scouts and guides, secured roads and village in advance of the US forces, and harassed the Japanese rear areas. The guerrilla units were of varied organisation, but in the Visayan islands and Mindanao area were subdivided into the old 4th to 10th Military Districts, with many units picking up the designations of former Philippine army units. Some units were sufficiently well supplied, organised and trained to conduct low-level conventional operations alongside US units, and it is estimated that 260,000 Filipinos served in guerrilla organisations in both combat and support roles. Even more were in the underground and auxiliary organisations.
After the surrenders of the various elements of the Philippine islands group, the Japanese ordered remaining Philippine government officials to return to work. In an effort to lighten the occupation’s harsh nature, most did. Philippine government officials soon proposed a provisional executive under the authority of the commonwealth, but the Japanese refused the proposal as some Philippine officials sought trade agreements with Japan. Fearing accusations of sedition should the USA return, many were reluctant to follow this path. Jorge Vargas, a former mayor of Manila, formed a provisional council of state unrelated to the commonwealth. In late 1942 all political parties were abolished and the Kapisanan Sa Paglilingkod Sa Bagong Philipinas, or Kalibapi (Association for Service in the New Philippines) was formed under Vargas. Youth and women’s auxiliaries were formed and the Supra party boasted some 1.5 million members in 1944.
In the meantime Japan attempted to convert Philippine production to its own military needs. Much of the harvest went to feed the occupation troops. The average citizen did what was necessary to survive the occupation confused by the choices of resistance and collaboration. It was soon realised that Japan’s promise of 'Asia for the Asians' did not translate as any form of equality, as often demonstrated by the heavy-handed military government and frequent outright brutality. Food, medicine and consumer products were in very short supply, and inflation soared. Refusal to deliver food quotas, sabotage and passive resistance increased. As a result of the Japanese export of food and materials from the Philippine islands group and the massive influx of troops, rice and other essential foodstuffs had to be imported from Thailand and Indo-China.
Early in 1943, Japan offered the Philippines the opportunity for self-government under a new constitution supporting their 'Greater East Asia Co-Prosperity Sphere' if the new country would declare war on the USA. Believing that the USA would forgive collaboration under the circumstances and that Japan would retaliate if the offer was rejected, the offer was reluctantly accepted. The puppet Republic of the Philippines, given token independence in October 1943 under President Jose P. Laurel, a former secretary of the interior, declared war on the USA in September 1944. No active effort was undertaken by the new republic, and the following month US forces landed on Leyte island in 'King II'.
Some effort was made by the Japanese military administration to raise pro-Japanese armed forces, mainly to combat the various guerrilla groupings, but gained little success in this area because of the widespread hatred of the Japanese, the faith that the USA would return, and the general sympathy for the guerrillas. The Philippine Constabulary was retained for police duties and former Philippine army officers were given constabulary commissions. The Japanese pressured the government to increase the constabulary’s size and level of training to combat the growing guerrilla threat, but at the same time were no prepared to arm it, fearing the weapons would end in guerrilla hands. For the most part, the constabulary performed only as a police force, although some anti-guerrilla actions were undertaken by a few units.
In December 1944, the Japanese combined several local efforts to raise armed units to form the Kalipunang Makabayan, ng mga Pilipino, or Makapili (Patriotic League of Filipinos) as a resurrection of a Spanish-era guard originally comprised of Indians imported from Mexico. The recruitment goal of 20,000 men, but fewer than 5,000 men, mainly from central and southern Luzon, volunteered for service. Under the command of General Artermio Ricarte, the Makapili dug fortifications, served as guides and gathered intelligence for the Japanese.
Elements also undertook anti-guerrilla operations with the 8th Division. In October 1944 Ricarte also formed the Hoan Giyugun, or Giyugun (Security Force), but little came of it. Many of the Makapili and Giyugan were tried for treason after the war, but few of the constabulary were.
Lieutenant General Shigenori Kuroda assumed command of the 14th Army and the military government in May 1943, and in August 1944 the army was upgraded to the 14th Area Army to provide a single headquarters responsible for the defence of the Philippine islands group. Kuroda considered the Philippines islands groupo be indefensible because of its size and the limited forces available to him, and took no action to improve the situation, and the islands' roads and railways fell into disrepair. Regardless, the Philippine islands group became the key supply distribution centre for the occupied Netherlands East Indies, Malaya, Burma and New Guinea as well as a vital link between those distant forces with the home islands. Kuroda’s protector, Premier Hideki Tojo, was dismissed after the fall of Saipan, and Kuroda was replaced by General Tomoyuki Yamashita on 26 September 1944. At this time the 14th Area Army comprised the 16th Division and 30th Division, and the 30th, 31st, 32nd and 33rd Independent Mixed Brigades. The fall of the Marshall island and Mariana island groups in early and mid-1944, combined with the loss of eastern New Guinea, led the Japanese high command to the ineluctable conclusion that the Philippine islands group would soon become an Allied objective. To the Japanese the Philippine islands group was the 'east wing of the Southern Sphere', and the campaign for these islands would be the decisive battle of the war and the last line of Japanese defence in the south. Their loss would isolate Japan from its extensive forces and resources in the Netherlands East Indies. The Japanese high command felt that 15 divisions, eight brigades and significant air units were now essential for the retention of the Philippines, but only half that number was available. By this time, the Japanese had developed 68 airfields scattered throughout the Philippine islands group.
Preparations for the forthcoming and indeed fairly imminent US invasion began in the middle of May 1944 after the success of the Allied 'Reckless' in April at Hollandia on the eastern part of New Guinea. Men, equipment and aircraft flowed into the Philippine islands group, new units arrived, and existing units were upgraded: for example, the four brigades were enlarged to divisions. This effort lasted through the summer of 1944 into September, the month before the 'King II' landings on Leyte island. The headquarters of the Southern Expeditionary Army Group, controlling all the Japanese forces in South-East Asia and the South Pacific, moved from Saigon in Indo-China to Manila in the middle of May. In September 1944, the 14th Area Army was directly responsible for Luzon with four divisions and three brigades, with the 2nd Tank Division on its way. Its subordinate 35th Army, under the command of Lieutenant General Sosaku Susuki, defended the Visayan islands group and Mindanao with four divisions and a brigade. The 14th Area Army had under its overall command 224,000 men as well as air service personnel, labourers and civilian employees.