The Japanese planned to occupy the Philippines as part of their plan for a "Greater East Asia War" in which their Southern Expeditionary Army Group seized sources of raw materials in Malaya and the Netherlands East Indies while the Combined Fleet neutralized the United States Pacific Fleet.
The Southern Expeditionary Army was created on 6 November 1941, commanded by Gen. Count Hisaichi Terauchi, who had previously been Minister of War. It was ordered to prepare for war in the event that negotiations with the United States did not succeed in peacefully meeting Japanese objectives. Under Terauchi's command were four corps-equivalent armies, comprising ten divisions and three combined arms brigades, including the 14th Army. Operations against the Philippines and Malaya were to be conducted simultaneously when Imperial General Headquarters ordered.
The invasion of the Philippines had three objectives:
- To prevent the use of the Philippines as an advance base of operations by American forces
- To acquire staging areas and supply bases to enhance operations against the Netherlands East Indies
- To secure the lines of communication between occupied areas in the south and the Japanese Home Islands.
Advance Japanese landings in the Philippines December 8–20, 1941
Terauchi assigned the Philippines invasion to the 14th Army, under the command of Lt. Gen. Masaharu Homma.:14,20 Air support of ground operations would be provided by the 5th Air Group, under Lt. Gen. Hideyoshi Obata,:21 which was transferred to Formosa from Manchuria. The amphibious invasion would be conducted by the Philippines Force under Vice Admiral Ibō Takahashi, using the Imperial Japanese Navy Third Fleet,:21 supported by the land-based aircraft of 11th Air Fleet of Vice Admiral Nishizo Tsukahara.
The 14th Army had two first-line infantry divisions, the 16th (
Susumu Morioka) and 48th Divisions (Yuitsu Tsuchihashi), to invade and conquer Luzon, and the 65th Brigade as a garrison force.:21 The Formosa-based 48th Division, although without combat experience, was considered one of the Japanese Army's best units, was specially trained in amphibious operations, and was given the assignment of the main landing in Lingayen Gulf. The 16th Division, assigned to land at Lamon Bay, was picked as one of the best divisions still available in Japan itself and staged from the Ryukyus and Palau. The 14th Army also had the 4th and 7th Tank Regiments,:24 five field artillery battalions, five anti-aircraft artillery battalions, four antitank companies, and a mortar battalion. An unusually strong group of combat engineer and bridging units was included in the 14th Army's support forces.
For the invasion, the Third Fleet was augmented by two destroyer squadrons and a cruiser division of the Second Fleet, and the aircraft carrier Ryūjō from the 1st Air Fleet. The Philippines Force consisted of an aircraft carrier, five heavy cruisers, five light cruisers, 29 destroyers, two seaplane tenders, plus minesweepers and torpedo boats.:22
Combined army and navy air strength allocated to support the landings was 541 aircraft. The 11th Kōkūkantai (Air Fleet) consisted of the 21st and 23rd Kōkūsentai (Air Flotillas), a combined strength of 156 G4M "Betty" and G3M "Nell" bombers, 107 A6M Zero fighters, plus seaplanes and reconnaissance planes.:24 Most of these were based at Takao, and approximately a third were sent to Indochina in the last week of November to support operations in Malaya. The Ryujo provided an additional 16 fighters and 18 torpedo planes, and the surface ships had 68 seaplanes for search and observation, totaling 412 naval aircraft. The army's 5th Kikōshidan (Air Group) consisted of two fighter regiments, two light bomber regiments, and a heavy bomber regiment, totaling 192 aircraft: 76 Ki-21 "Sally", Ki-48 "Lily", and Ki-30 "Ann" bombers; 36 Ki-27 "Nate" fighters, and 19 Ki-15 "Babs" and Ki-36 "Ida" observation planes.:24
Disposition of United States Army forces in the Philippines in December 1941
From mid-1941, following increased tension between Japan and several other powers, including the United States, Britain and the Netherlands, many countries in South East Asia and the Pacific began to prepare for the possibility of war.
By December 1941, the combined defense forces in the Philippines were organized into the US Army Forces in the Far East (USAFFE), which eventually included the Philippine Army's 1st Regular Division, 2nd (Constabulary) Division, and 10 mobilized reserve divisions, and the United States Army's Philippine Department. General Douglas MacArthur was recalled from retirement by the U.S. War Department and named commander of USAFFE on 26 July 1941. MacArthur had retired in 1937 after two years as Military Advisor to the Philippine Commonwealth, and accepted control of the Philippine Army, tasked by the government of the Philippines with reforming an army made up primarily of reservists lacking equipment, training and organization.
On 31 July 1941, the Philippine Department had 22,532 troops assigned, approximately half of whom were Filipino. MacArthur recommended the reassignment of the department commander, Maj. Gen. George Grunert in October 1941 and took command himself. The main component of the Department was the U.S. Army Philippine Division, a 10,500-man formation that consisted mostly of Philippine Scouts (PS) combat units. The Philippine Department had been reinforced between August and November 1941 by 8,500 troops of the U.S. Army Air Forces, and by three Army National Guard units, including its only armor, two battalions of M3 light tanks. These units, the 200th Coast Artillery Regiment (an antiaircraft unit), 192nd Tank Battalion, and 194th Tank Battalion, drew troops from New Mexico, Wisconsin, Illinois, Ohio, Kentucky, Minnesota, Missouri, and California. After reinforcement, the Department's strength as of 30 November 1941 was 31,095, including 11,988 Philippine Scouts.
MacArthur organized USAFFE into four tactical commands. The
North Luzon Force, activated 3 December 1941 under Maj. Gen. Jonathan M. Wainwright, defended the most likely sites for amphibious attacks and the central plains of Luzon. Wainwright's forces included the PA 11th, 21st and 31st Infantry Divisions, the U.S. 26th Cavalry Regiment (PS), a battalion of the 45th Infantry (PS), and the 1st Provisional Artillery Group of two batteries of 155 mm guns and one 2.95 inch (75 mm) mountain gun. The Philippine 71st Infantry Division served as a reserve and could be committed only on the authority of MacArthur.
The South Luzon Force, activated 13 December 1941 under Brig. Gen. George M. Parker Jr., controlled a zone east and south of Manila. Parker had the PA 41st and 51st Infantry Divisions and the 2nd Provisional Artillery Group of two batteries of the US 86th Field Artillery Regiment (PS).
Visayan–Mindanao Force under Brig. Gen. William F. Sharp comprised the PA 61st, 81st, and 101st Infantry Divisions, reinforced after the start of the war by the newly inducted 73rd and 93rd Infantry Regiments. The 61st Division was located on Panay, the 81st on Cebu and Negros, and the 101st on Mindanao. In January a fourth division, the 102nd, was created on Mindanao from the field artillery regiments of the 61st and 81st Divisions acting as infantry (they had no artillery pieces), and the 103rd Infantry of the 101st Division. The 2nd Infantry of the Philippine Army's 1st Regular Division and the 2nd Battalion of the U.S. 43rd Infantry (Philippine Scouts) were also made a part of the Mindanao Force.
USAFFE's Reserve Force, under MacArthur's direct control, was composed of the Philippine Division, the 91st Division (PA), and headquarters units from the PA and Philippine Department, positioned just north of Manila. The 192nd and 194th Tank Battalions formed the separate Provisional Tank Group, also under MacArthur's direct command, at Clark Field/Fort Stotsenburg, where they were positioned as a mobile defense against any attempt by airborne units to seize the field.
Four U.S. Coast Artillery Corps regiments guarded the entrance to Manila Bay, including Corregidor Island. Across a narrow 3 kilometre (2 mi) strait of water from Bataan on Corregidor was Fort Mills, defended by batteries of the 59th and 60th Coast Artillery Regiments (the latter an anti-aircraft unit), and the 91st and 92nd Coast Artillery Regiments (Philippine Scouts) of the Harbor Defenses of Manila and Subic Bays. The 59th CA acted as a supervisory unit for the batteries of all units positioned on Forts Hughes, Drum, Frank, and Wint. The majority of the forts had been built circa 1910-1915 and, except for Fort Drum and Battery Monja on Corregidor, were unprotected against air and high-angle artillery attack except by camouflage.
The USAFFE's aviation arm was the Far East Air Force (FEAF) of the U.S. Army Air Forces, commanded by Maj. Gen. Lewis H. Brereton. Previously the Philippine Department Air Force and Air Force USAFFE, the air force was activated on 16 November 1941 and was the largest USAAF combat air organization outside the United States. Its primary combat power in December 1941 consisted of 91 serviceable P-40 Warhawk fighters and 34 B-17 Flying Fortress bombers, with further modern aircraft en route. Tactically the FEAF was part of the Reserve Force, so that it fell under MacArthur's direct command.
As of 30 November 1941, the strength of US Army Troops in the Philippines, including Philippine units, was 31,095, consisting of 2,504 officers and
28,591 enlisted (16,643 Americans and 11,957 Philippine Scouts).
MacArthur's mobilization plans called for induction of the ten reserve divisions between 1 September and 15 December 1941. The timetable was met on 1 September with the induction of one regiment per division, but slowed as a lack of facilities and equipment hampered training. The second regiments of the divisions were not called up until 1 November, and the third regiments were not organized until after hostilities began. Training was also seriously inhibited by language difficulties between the American cadres and the Filipino troops, and by the many differing dialects (estimated at 70) of the numerous ethnic groups comprising the army. By the outbreak of war, only two-thirds of the army had been mobilized, but additions to the force continued with the induction of the Constabulary and a portion of the regular army, until a force of approximately 130,000 men was reached.
The most crucial equipment shortfalls were in rifles and divisional light artillery. MacArthur requested 84,500 M1 Garand rifles to replace the World War I M1917 Enfields equipping the PA, of which there were adequate numbers, but the War Department denied the request because of production difficulties. The divisions had only 20% of their artillery requirements, and while plans had been approved to significantly reduce this gap, the arrangements came too late to be implemented before war isolated the Philippines.
By contrast, the Philippine Division was adequately manned, equipped, and trained. MacArthur received immediate approval to modernize it by reorganizing it as a mobile "triangular" division. Increasing the authorized size of the Philippine Scouts was not politically viable (because of resentments within the less-well-paid Philippine Army), so MacArthur's plan also provided for freeing up Philippine Scouts to round out other units. The transfer of the American 34th Infantry from the 8th Infantry Division in the United States to the Philippine Division, accompanied by two field artillery battalions to create a pair of complete regimental combat teams, was actually underway when war broke out. The deployment ended with the troops still in the United States, where they were sent to defend Hawaii instead.
Other defense forces
The United States Asiatic Fleet and 16th Naval District, based at Manila, provided the naval defenses for the Philippines. Commanded by Admiral Thomas C. Hart, the surface combatants of the Asiatic Fleet were the heavy cruiser USS Houston, the light cruiser USS Marblehead, and 13 World War I-era destroyers. Its primary striking power lay in the 23 modern submarines assigned to the Asiatic Fleet. Submarine Squadron (SUBRON) Two consisted of 6 Salmon class submarines, and SUBRON Five of 11 Porpoise and Sargo class submarines. In September 1941, naval patrol forces in the Philippines were augmented by the arrival of the six PT boats of Motor Torpedo Boat Squadron Three. Likewise, the China Yangtze Patrol gunboats also became part of the Philippine naval defenses: USS Asheville (sunk south of Java 3 March 1942), USS Mindanao (lost 2 May 1942), USS Luzon (scuttled 6 May 1942 but salvaged by the Japanese), USS Oahu (sunk 5 May 1942), and USS Quail (scuttled 5 May 1942). In December 1941, the naval forces were augmented by the schooner USS Lanikai.
The U.S. 4th Marine Regiment, stationed in Shanghai, China, since the late 1920s, had anticipated a withdrawal from China during the summer of 1941. As personnel were routinely transferred back to the United States or separated from the service, the regimental commander, Col. Samuel L. Howard, arranged unofficially for all replacements to be placed in the 1st Special Defense Battalion, based at Cavite. When the 4th Marines arrived in the Philippines on 30 November 1941, it incorporated the Marines at Cavite and Olongapo Naval Stations into its understrength ranks. An initial plan to divide the 4th into two regiments, mixing each with a battalion of Philippine Constabulary, was discarded after Howard showed reluctance, and the 4th was stationed on Corregidor to augment the defenses there, with details detached to Bataan to protect USAFFE headquarters.
Additionally the U.S. Coast and Geodetic Survey, a paramilitary survey force, operated in Manila with the ship USC&GSS Research.