Japan's initial strategy, as outlined earlier, was formulated with the dual purpose of gaining swift control of the economic resources of the southern regions, essential to the prosecution of the war, and of eliminating British and American military bases which barred the way to these resources and might be used as counteroffensive springboards against Japan.1
The primary objectives of the initial Japanese operations, therefore, involved the invasion of the Philippines, Malaya, Borneo, and the Netherlands East Indies, with particular emphasis on the seizure of Manila and Singapore, the two major bases of the United States and Great Britain in the Far East. The Pearl Harbor attack, although held essential by dominant Navy opinion to assure Japanese supremacy at sea for the execution of the Southern Operations,2 was, in fact, a secondary and supporting operation.
The magnitude of these operations, unprecedented in military history, gave rise to difficult planning problems. Intensive studies were carried out by Imperial General Headquarters to determine the sequence of operations and the allocation of the limited ground, sea, and air strength available so as to ensure local superiority of forces in the areas of attack.
During the initial planning stage, two alternative sequences for the invasion operations were considered: (1) Philippines, Netherlands East Indies, Malaya; and (2) Malaya, Netherlands East Indies, Philippines. However, after full study, Imperial General Headquarters concluded that it would be most advantageous to exploit the psychological element of surprise to the utmost. The proposed sequences were therefore scrapped, and it was decided to attack the Philippines and Malaya simultaneously with the Navy's surprise blow at Pearl Harbor on the first day of war. Seizure of Borneo, the Celebes, Sumatra, and Java was to follow under a schedule which divided the "First Phase"
(Dai-ichi dan) operations into the following three periods:
Although no fixed time limits were set for the completion of operations in the various areas, Imperial General Headquarters estimated that the major part of the invasion operations could be completed in 50 days for the Philippines, 100 days for Malaya, and 150 days for the Netherlands East Indies.4
Tactical procedures varied according to the enemy situation and Japanese capabilities in the different areas of attack. In the Philippines, General MacArthur's air strength, which Japanese intelligence indicated was undergoing gradual reinforcement, was a potential threat to the Japanese invasion fleet of slow-speed transports.5 Hence it was decided to precede the landing of ground troops with intensive air attacks, executed jointly by Army and Navy air units, with the objective of paralyzing enemy air power.6 In the Malayan invasion, for which high-speed transports less vulnerable to air attack were reserved, it was planned to start landing and air operations almost simultaneously. Three particularly thorny problems presented themselves to Imperial General Headquarters in working out this plan of widely dispersed operations:
The first and second problems were the selfimposed consequence of the allocation of virtually the entire carrier strength of the Combined Fleet to the Pearl Harbor operation. To ensure minimum air cover for the Malaya landings, fighter units of the 3d Army Air Group in Indochina had to be considered wholly expendable,7 and possibly heavy damage to the escorting naval units of the Southern Expeditionary Fleet was also accepted as a calculated risk. The second problem was met by the decision to push the speedy occupation of strategically located air bases in Borneo and
Malaya, and to effect their prompt restoration to operational use by the Japanese Air forces.
To insure acquiring the needed oil resources intact, plans were laid to capture the main oilproducing centers in Dutch and British Borneo soon after the start of hostilities, and as soon as air bases had been taken in Malaya, to take Palembang by airborne assault.8
In the autumn of 1941, when preparations began for the Southern Operations, the total strength of the Japanese Army stood at 51 divisions, of which 28 were assigned to operations in China and 13 stationed in Manchuria and Korea for defense against the Soviet Union. Only ten divisions remained in the homeland, five of which were newly-formed and of questionable fighting ability. The Army Air Forces had approximately 1,500 first-line planes.
Of this total strength, owing to commitments in China and inability to risk weakening defense against the Soviet Union, Imperial General Headquarters decided that not more than 11 divisions and two air groups (approximately 700 planes) could be allotted to the Southern Operations. The Navy, for the accomplishment of its double mission of supporting the land invasions and attacking Pearl Harbor, was in a position to employ almost the entire strength of the Combined Fleet, including the bulk of the naval air force of 1,669 planes.9 The maximum transport and supply shipping tonnage which could be made available for Army and Navy use was approximately 3,900,000 tons.10
Despite the apparent weakness of these forces in relation to the vast scope of the projected operations, Imperial General Headquarters estimated that its invasion plans would succeed. The combined troop and air strength of Great Britain, the United States, and the Netherlands in the planned theater of operations was estimated at approximately 370,000 men and 720 planes,11with a naval strength of approximately 12 to 16 battleships and five or six aircraft carriers. However, this potential fleet strength was dispersed, with the main elements stationed in the Indian Ocean and at Hawaii.12
Military intelligence reports on the target areas in September 1941 indicated that the bulk of the ground strength mentioned above was composed of colonial troops of inferior quality. Taking this into consideration, Imperial General Headquarters estimated that
success could be assured by maneuvering available Japanese military strength so as to develop a three-to-one local superiority of forces in all invasion sectors.13
Achievement of this superiority required adherence to a carefully determined invasion schedule and the double use of troops and shipping in successive operations. Thus, it was decided that forces and shipping assigned to the Philippines, Hongkong, Guam and Malaya operations would be used again in succeeding operations.14 The Burma operations were to be carried out by troops diverted from other combat zones where they were no longer needed.
To provide the 11 divisions called for by the invasion plans, five divisions were diverted from the China front, and six were taken from the homeland. These were further reinforced by the addition of the bulk of the Kwantung Army's service troops, which were withdrawn from Manchuria.15 The main strength of the 3d Air Group was detached from the China Expeditionary Forces, and the main strength of the 5th Air Group was taken from Manchuria. Both were reorganized to include the best air units from China, Manchuria, and Japan Proper.
Just before the outbreak of hostilities, the tactical grouping and disposition (Plate No. 12) of Army forces allocated to the Southern Operations were as follows:16
The Imperial General Headquarters decided that virtually the whole of the Navy's "outer combat force"18 would be employed in the operations against the United States, Great Britain, and the Netherlands. The tactical grouping of this force and mission assignments in the initial operations were as follows:19
The basic orders directing the Army and Navy forces to prepare for hostilities in early December were issued by Imperial General Headquarters immediately following the 5 November Imperial conference which fixed the end of November as the final deadline for the decision on war in case of failure to achieve a diplomatic settlement.20
The Imperial General Headquarters Navy Directive No. 1, issued on 5 November, ordered the Commander-in-Chief, Combined Fleet, to prepare "for the eventuality that war with the United States, Great Britain, and the Netherlands may become unavoidable in the first part of December."21
It directed that the necessary forces be assembled "at the appropriate time at initial staging areas", and laid down the general plan of fleet operations, which was incorporated in Combined Fleet Top Secret Operations Order No. 1, issued on the same date.22 Essential portions of this order follow:
Preparations for War and Start of Hostilities
First Phase Operations
The basic Fleet order quoted above was followed on 7 November by Combined Fleet Top Secret Operations Order No. 2, which fixed Y-Day, the approximate date for the start of hostilities, as 8 December and ordered "First Preparations for War".28 A further order of the same date ordered the Task Force to assemble at Tankan Bay, in the Kuriles, and take on supplies until 22 November.29
On 21 November Imperial General Headquarters Navy Order No. 5 directed the Commander-in-Chief of the Combined Fleet to advance the necessary forces at the appropriate time to positions of readiness for the start of hostilities. At the same time Imperial General Headquarters Navy Directive No. 5 stipulated that these forces should immediately be ordered to return to home bases in the event of a Japanese-American agreement.30 A Combined Fleet operations order issued on 25 November stated:
Following the Imperial conference decision to go to war, Imperial General Headquarters Navy Section on 7 December issued an order to the Commander-in-Chief, Combined Fleet, which stated:
On 2 December Imperial General Headquarters Navy Directive No. 12 ordered the Commander-in-Chief, Combined Fleet, to launch operations on 8 December. In pursuance thereto Admiral Yamamoto issued a Combined Fleet order on the same day, designating 8 December as X-Day.33
Concurrently with these fleet orders, Imperial General Headquarters Army Section issued the basic orders and directives for Army invasion operations in the Southern area. An order issued on 6 November named General Hisaichi Treacle Commander-in-Chief of the Southern Army, fixed the order of battle,34 and directed invasion preparations as follows:
The general plan of joint Army-Navy operations and definition of respective spheres of responsibility were laid down in a ArmyNavy Central Agreement concluded in Tokyo between 8 and 10 November by General Terauchi, for the Southern Army, and Admiral Yamamoto, for the Combined Fleet.36 This was implemented by a series of detailed operational agreements concluded between the fleet and Army commanders assigned to operations in each invasion area at a joint staff conference at Iwakuni, on the Inland Sea, from 14 to 16 November.37
On 15 November a further Imperial General Headquarters Army Order to the Commanderin-Chief, Southern Army, stated:
Acting under this directive and the ArmyNavy Central Agreement, General Terauchi issued implementing orders to the forces under Southern Army command on 20 November,
allocating the Fourteenth Army (Lt. Gen. Masaharu Homma) to the invasion of the Philippines, the Twenty-fifth Army (General Tomoyuki Yamashita) to the invasion of Malaya, the Fifteenth Army (Lt. Gen. Shojiro Iida) to the occupation of Thailand and operations in Burma, and the Kawaguchi Detachment (main strength composed of one infantry regiment of the 18th Division, temporarily detached from Twenty-fifth Army, under command of Maj. Gen. Seiken Kawaguchi) to the invasion of British Borneo. The 5th Army Air Group was placed under Fourteenth Army command for the Philippines operations, and the 3d Army Air Group was assigned principally to support of the Malaya invasion.39
The date for the launching of hostilities was finally fixed by an Imperial General Headquarters Army order issued to the Commander-inChief, Southern Army, on 1 December, which stated:
General Terauchi left Tokyo by air on 25 November and reached Saigon on 5 December, three days before the scheduled start of hostilities. There he set up the General Headquarters of the Southern Army.
By 22 November the 32 warships comprising the Carrier Task Force under command of Vice Adm. Chuichi Nagumo (Commander-in-Chief First Air Fleet) had concentrated at the assembly point in Tankan Bay, where final battle preparations were completed. Task Force Top Secret Operations Order No. 1, laying down the plan of attack, was issued on 23 November.41
The eastward movement of the Task Force began at 0600 on 26 November. In order to escape detection while en route, the Force maintained strict radio silence and took a northerly course well off commercial shipping lanes and beyond the range of patrol planes from American island bases.42 A destroyer screen moved ahead of the main force in order to give advance warning if unfriendly vessels were encountered. Whenever weather conditions were favorable, refueling was carried out from supply train tankers.43
At 0400 4 December, the Task Force altered its course to the southeast and proceeded until 0700 on X-1 Day, 7 December, when it headed due south and began the final run toward Oahu at a speed of 24 knots. (Plate No. 13) At 0130 on 8 December, from a point approximately 200 nautical miles north of Oahu, the First Attack Unit of 183 planes took off from the decks of the six carriers, formed over the Task Force, and at 0145 headed for Pearl Harbor.44
Flying at 3,000 feet over dense but broken cloud formations, the first wave sighted the northern shoreline of Oahu at 0310 and immediately deployed, receiving the order to "attack" at 0319 (0749 Hawaii time). Dive bomber groups spearheaded the attack with swift strikes at Wheeler, Hickam and Ford Island airfields, crippling enemy fighter strength before it had a chance to get off the ground. Immediately thereafter torpedo plane and level bomber groups converged on the fleet anchorage at Ford Island and attacked the heavy units lying at berth.
The second wave of 167 planes took off from the carriers at 0245, reaching offshore the eastern coast of Oahu at 0424 (0854 Hawaii time), when the "attack" order was given. Dive and level bombers again swept in on the fleet anchorage, striking at ships not severely hit in the first attack. Fighter groups went in as escorts with both first and second waves, and when enemy air opposition failed to develop, they strafed ground targets. Both attacks continued from thirty minutes to one hour.
By 0830 (1300 Hawaii time) all aircraft, except nine missing from the first wave and 20 from the second, had returned to the carriers, and the Task Force began its withdrawal to the northwest at full speed. On 16 December the carriers Soryu and Hiryu (2d Carrier Division) and cruisers Tone and Chikuma (8th Squadron) broke off from the Task Force to take part in softening-up air attacks against Wake. The rest of the force continued toward home bases, arriving in the Inland Sea on 23 December.
On the basis of photographic analysis and reports by flight personnel, the Navy estimated the results of the Pearl Harbor air strike as follows: Sunkfour battleships, one cruiser, two tankers; heavily damagedfour battleships; lightly damagedone battleship. Approximately 248 planes were estimated destroyed on the ground, 17 shot down in the air, and possibly 230 destroyed in hangars.45
Coordinated with the air strike were simultaneous attacks by the Advance (Submarine) Force, under command of Vice Adm. Shimizu. This Force, consisting of 27 of the Navy's best submarines, had left its bases in Japan and Kwajalein, in the Marshalls, between 16 and 24 November, and by X-1 Day had taken up positions controlling the entrance to Pearl Harbor. Its missions were to observe enemy fleet movements prior to the Task Force attack, to, carry out torpedo attacks (with A-Target midget submarines)46 simultaneously with the
air strike, to attack any enemy ships trying to put to sea, and to watch the movements of surviving enemy war craft after the Task Force withdrawal.47
Between 2012 and 2303 on 7 December, several hours in advance of the air strike, five midget submarines were released from their "mother" submarines at positions from five to twelve nautical miles from Pearl Harbor and, aided by moonlight, gradually made their way toward the harbor entrance. Since radio communication was then discontinued, exact knowledge of their actions was lacking, but it was believed on the basis of offshore observation and later radio reports that at least three of the craft had successfully penetrated into the harbor. A heavy explosion witnessed at 1631 8 December was believed to indicate that a large warship had been sunk or severely damaged, presumably by midget submarine action.48
Although rescue submarines remained off Oahu for several days to pick up any of the midget craft which might have survived the attack, none returned.49 Until early January part of the Advance Force continued to operate in the vicinity of Hawaii, largely to observe fleet activity and interfere with the anticipated transport of reinforcements to the Far Eastern zone of operations. Most of these submarines, at different times, proceeded to the west coast of the United States to attack shipping.50
South Seas and Southern Operations51
While Vice Admiral Nagumo's Task Force temporarily crippled the United States Pacific Fleet at Pearl Harbor, Japanese forces in the South Seas area and Southeast Asia began operations in execution of other phases of the over-all war plan. (Plate No. 15)
The Navy's South Seas Force, charged with operations in the general area of the Japanese mandated islands, began air attacks on 8 December to knock out American air bases on Guam,Wake, and Howland Islands. On 10 December troops of the Army's South Seas Detachment, with the naval support of the South Seas Force, effected surprise landings on the northwestern and eastern shores of Guam before dawn and occupied the island without serious resistance.52 This eliminated the isolated enemy base in the heart of the Japanese mandated islands.
At Wake, following repeated attacks by Navy planes based in the Marshalls, 1,000 special naval landing troops attempted a dawn landing on 10 December but were forced to withdraw due to effective air attack by remaining American planes and heavy seas. Following the arrival of the aircraft carriers Soryu and Hiryu, diverted from the Task Force returning from Hawaii, and 500 additional naval landing troops, a successful landing was accomplished during the night of 22-23 December, and the
island was completely occupied the following day.53
In the Gilbert Islands, naval landing parties occupied Makin and Tarawa on 10 December and immediately constructed an advance air base on Makin. The capture of these islands and of Wake, enabling their utilization as air bases, strengthened the Navy's strategic outer defense line against American counterattack from the Central Pacific.
In the principal theater of operations in Southeast Asia, the Japanese forces struck swiftly at the strategic center of British strength in Malaya. The advance invasion units of the Twenty-fifth Army (main strength of the 5th Division and elements of the 18th Division) embarked from Hainan Island on 4 December. Early on 8 December54 these forces, supported by the main strength of the Navy's Malaya Force and under air cover provided by the 3d Army Air Group, began landing operations at Singora and Pattani, in southern Thailand, and Kota Bharu, in northern Malaya. The Kota Bharu force, severely attacked by British planes after it landed on the beach, temporarily withdrew but, with reinforced air cover, succeeded in a second landing later the same day.55
Concurrently with the landing operations, land-based bombers of the 22d Naval Air Flotilla flew from Indochina bases at 0500 on 8 December to bomb enemy military installations at Singapore. Two days later, on 10 December, Navy torpedo planes and bombers crippled the British Far Eastern Fleet by sinking the powerful battleships Prince of Wales and Repulse and a destroyer in the waters east of Malaya.56
With the occupation of Singora, Pattani and Kota Bharu, Army Air units immediately began operating from these advance bases, gained mastery of the air over Malaya and provided direct support for the ground forces advancing on Singapore. The Twenty-fifth Army's drive progressed smoothly despite sporadic enemy resistance, and by late January 1942, all units had reached the Johore Straits at the southern tip of Malaya. Singapore fell on 15 February.57
To the north, the Imperial Guards Division (temporarily attached to the Fifteenth Army moved across the Indo-Chinese border into Thailand on 8 December, while some of its elements landed by sea at points along the Kra Isthmus. These operations were accomplished without resistance. In January, the main strength of the Fifteenth Army (55th and 33d Divisions) concentrated at Rahaeng and Bangkok in preparation for the invasion of Burma.58
In the Borneo and Celebes area, Japanese operations likewise proceeded according to plan. Embarking at Camranh Bay, French IndoChina, on 13 December, the Kawaguchi Detachment (three infantry battalions plus Yoko
suka 2d Special Naval Landing Force landed near Miri, on the coast of British Borneo, on 16 December and occupied the oil fields and airfield.59 The detachment, moving by sea, took Kuching on 23 December. Brunei, Labuan Island, Jesselton, and Tawau were taken in subsequent operations.60
Strategic points in Dutch Borneo were occupied by elements of the Sakaguchi Detachment which, after taking Davao in the Southern Philippines, had hopped to Jolo Island, in the Sulu Archipelago. This force occupied Tarakan on 11 January 1942 and Balikpapan on 24 January. Simultaneously with these operations, Navy forces invaded the Celebes, taking Menado on 11 January, Kendari on 24 January and Amboina on 31 January.61 These operations gave the Japanese forces control over important oil-producing areas and at the same time provided strategic forward bases for continuation of the southward advance on Java.
In the China area, joint Army-Navy plans at the start of hostilities called for the invasion of Hongkong as soon as the Malaya landings had been accomplished. The 38th Division (Twenty-third Army) and the Second China Expeditionary Fleet were assigned to this operation.62 The 38th Division moved from Canton to the Kowloon Peninsula on 14 December, and joint Army-Navy amphibious operations against Hongkong began on 18 December. On 25 December the British forces surrendered.63 Meanwhile Japanese Army and Navy units in the Shanghai and Tientsin areas took control of the foreign concessions there.
The initial offensives of the Japanese armed forces on virtually every front thus attained a measure of success that was beyond original expectations. The United States and Great Britain were forced to assume the defensive, while the security of the Japanese homeland against Allied counterattack was greatly strengthened through the seizure of strategic areas. Acquisition of the resources of the southern regions not only cut off the flow of these resources to the United States and Great Britain, but placed Japan in a favorable economic position for the prosecution of an extended war.
Only in the Philippines, despite the early capture of Manila, did the Japanese Army fall sharply behind its invasion timetable as a result of the wholly unexpected and bitter resistance offered by General MacArthur's isolated forces on Bataan.64 The protracted American defense of Bataan, which was brought into sharp relief by the unexpectedly early conquest of Singapore, a modern fortress with facilities far in excess of the rundown, antiquated installations of Corregidor, required extraordinary measures by Imperial General Headquarters.65