Planning of Invasion Operations

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:

First Period: Invasion of the Philippines, Malaya, Borneo, Celebes, Timor, northern Sumatra, and key points in southern Sumatra (Palembang) and the Bismarck Archipelago.

Second Period : Invasion of Java and occupation, at the opportune time, of airfields in southern Burma.

Third Period : Pacification of occupied areas and, depending on the situation, completion of operations in Burma.3

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:

1. Whether Japanese Army and Navy air strength, operating from 300-mile distant bases in southern French Indo-China at the extreme limit of land-based fighter plane radius, would be able to provide effective cover for the landing forces against relatively superior British air power.

2. Whether air bases acquired through the occupation of Borneo and Malaya could be immediately and effectively exploited in the ensuing operations against Sumatra and Java.

3.  Whether the vital oil-producing areas could be taken before the wells and installations had been seriously damaged.

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

Operational Strength

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

Southern Army: General Headquarters in Saigon, French Indochina:

14th Army:
Philippines Attack Force
Army Headquarters (in Formosa)
Army Troops (65th Brig. & other elements)(in Formosa)
48th Division (main elements) (in Formosa)
16th Division in Amami-Oshima
Remaining elements in Pescadores and Palau

15th Army:
Burma Attack Force

Army Headquarters (in S. Indochina)
Elements 55th Division (in S. Indochina)
Army troops 55th Division (less elements) (in N. Indochina)
33d Division in Central China

16th Army:
East Indies Attack Force

Army Headquarters (in Japan Proper)
2d Division (in Japan Proper)
Elements 56th Division (56th Mixed Inf Group) in Palau

25th Army:
Malaya Attack Force

Army Headquarters (on Hainan Island)
5th Division (on Hainan Island)
Imperial Guards Division in S. Indo-China17
18th Division in Canton
Army troops in Formosa
Army Reserves
21st Division in North China
56th Division (main elements) in Japan Proper
3d Air Group:
Malaya Attack Force
5 fighter groups (in South China and N. Indochina)
4 light bomber groups (in South China and N. Indochina)
2 reconnaissance groups (in South China and N. Indochina)


5th Air Group:
Philippines Attack Force
2 fighter groups (in S. Formosa)
2 light bomber groups (in S. Formosa)
1 heavy bomber group (in S. Formosa)
1 reconnaissance (in S. Formosa)

China Expeditionary Forces: General Headquarters in Nanking
23d Army:
Hongkong Attack Force
Army Headquarters (in Canton)
38th Division (in Canton)

Guam Occupation Force: Directly under Imperial General Headquarters
South Seas Detachment
Detachment Headquarters (in Bonin Islands)
144th Inf Regt (in Bonin Islands)
1 artillery battalion (in Bonin Islands)
Other elements

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

Combined Fleet

Main Body:  Under direct command C-in-C, Combined Fleet.
Mission: To support overall operations.
6 battleships, 2 aircraft carriers, 2 light cruisers, 1 destroyer.
Task Force: Under C-in-C, 1st Air Fleet.
Mission: To attack the American Fleet in the Hawaii area and subsequently support operations of the South Seas and Southern Forces.
6 aircraft carriers, 2 battleships, 2 heavy cruisers, 1 light cruiser, 11 destroyers, 3 submarines.
Advance (Submarine) Force: Under C-in-C, 6th Fleet.
Mission: To reconnoiter Hawaiian waters in advance of Pearl Harbor attack, cooperate with Task Force in execution of attack, and attack enemy naval forces along west coast of the United States.
27 submarines, 1 submarine tender, 1 coastal defense ship.
South Seas Force: Under C-in-C, 4th Fleet.
Missions:  To occupy Wake; defend and patrol inner South Seas area and protect surface traffic; cooperate with the Army in the successive occupation of Guam and Rabaul.
Southern Forces: Under over-all command of C­in-C, 2d Fleet.
Missions: To destroy enemy fleet and air strength in the Philippines, Malaya, and Dutch East Indies areas; act as surface escort and support landings of Army forces in Philippines, Malaya, Borneo, and Thailand; prepare for invasion operations in the Dutch East Indies, Timor, and Burma.
Main Body: Under direct command C-in-C, 2d Fleet.
2 battleships, 2 heavy cruisers, 10 destroyers.
Philippines Force: Under C-in-C, 3d Fleet.
1 aircraft carrier, 5 heavy cruisers, 5 light cruisers, 29 destroyers, 4 torpedo boats, 4 minesweepers, 3 base forces.
Malaya Force: Under C-in-C, Southern Expeditionary Fleet.


Plate No. 12: Map, Disposition of Japan's Military Forces Prior to Outbreak of War

Disposition of Japan's Military Forces Prior to Outbreak of War


Malaya Force: (continued) 5 heavy cruisers, 3 light cruisers, 15 destroyers, 16 submarines, 1 minelayer, 1 coastal defense ship, 1 naval air flotilla, 2 base forces.
Air Force: Under C-in-C, 11th Air Fleet.
2 naval air flotillas (shore­based), 2 destroyers.
Submarine Force: Under Commander, 5th Submarine Flotilla.
2 submarines, 1 submarine tender.
Northern Force: Under C-in-C, 5th Fleet.
Missions: To patrol and defend waters east of Japan Proper; defend the Bonin Islands; guard the route of the Task Force; protect surface traffic.
2 light cruisers, 1 destroyer, 2 torpedo boats, 1 shore-based air group, 1 base force.
China Seas Fleet: Under C-in-C, China Seas Fleet.
Missions: To continue operations in China and destroy local enemy forces; cooperate with the Army in taking Hongkong; protect surface traffic in Chinese coastal waters; cooperate with ground forces.
2 coastal defense ships (old-type heavy cruisers), 1 light cruiser, 3 destroyers, 6 torpedo boats, 13 gunboats, 5 base forces, 4 Special Naval Landing Parties.

Operations Orders

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

1.   Preparations for War

a.  The Empire anticipates the outbreak of war with the United States, Great Britain, and the Netherlands. When it has been decided to complete over-all operational preparations, an order will be issued setting the approximate date (Y-Day) for the commencement of operations and announcing "First Preparations for War." The various forces will, upon receipt of this order, act as follows:


(1) All fleets and naval units, without special orders, will be organized according to the allocation of forces for the First Period Operations of First Phase Operations, and will complete battle preparations. At the appropriate time, as directed by their commanders, they will proceed to alert areas prior to the start of operations.

(2) All units will be sharply on the alert for possible attacks by American, British and Dutch forces.

b. When the necessary advance forces for the execution of operations are dispatched to the areas of operations, "Second Preparations for War" will be ordered. The various forces will, upon receipt of this order, act as follows:

(1) Submarine forces attached to the Advance Force, Task Force, Commerce Destruction Force,23 Southern Force, and South Seas Force will, at the appropriate time as directed by their commanders, leave for their respective areas of operations.

(2) The remainder of these Forces will, as directed by their commanders, proceed so as to be in designated positions for the start of hostilities.

* * * * *

2. Start of hostilities

a. The date for the start of hostilities (X-Day) will be fixed by Imperial Order (to be issued several days in advance). After 0000 hours on X-Day, a state of war will exist. 24 All forces will commence operations according to plan.

* * * * *

First Phase Operations

1. Operational Plan

a. The Advance Force, Task Force, South Seas Force, Northern Force, and Main Body will operate against the American Fleet.

The Advance Force [will scout and carry out surprise attacks on enemy naval forces in the Hawaii area and on the west coast of the United States.]

The Task Force [will attack and destroy enemy naval forces at Hawaii at the start of hostilities.]25

The South Seas Force will occupy or destroy enemy key points in the vicinity of its operational area26 and prepare to meet enemy naval forces in the Australian area.

The Northern Force will be charged with patrolling against the Soviet Union.

b. The Southern Forces, while holding local superiority, will annihilate enemy naval forces in the Philippines, British Malaya, and Netherlands Indies areas, and will carry out the following operations in cooperation with the Army.

(1) Operations against British Malaya and the Philippines will be launched simultaneously. The initiative will be taken in launching a sustained air offensive against enemy air and naval forces in these areas, and Army advance expeditionary groups will be landed as quickly


as possible in strategic areas of Malaya, the Philippines and British Borneo. Air forces will be moved forward and air operations intensified.

(2) Following the successful completion of these operations, the main bodies of the Army invasion groups will be landed in the Philippines and Malaya and will quickly occupy these areas.

(3) During the first period of operations, strategic points in the Celebes, Dutch Borneo, and southern Sumatra will be occupied. If favorable opportunity arises, strategic points in the Moluccas and Timor will also be taken, and necessary air bases established in these areas.

(4) As these air bases are completed, Air forces will gradually be moved forward, and enemy air strength in the Java area will be destroyed. When this has been accomplished, the main body of the Army invasion group will be landed and will occupy Java.

(5) After the capture of Singapore, strategic points in northern Sumatra will be taken, and operations will be carried out at the appropriate time against Burma to cut the enemy supply route to China.27

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:

The Task Force will move out of Tankan Bay on 26 November and, taking every precaution to conceal its movements, will advance by late evening of 3 December to a rendezvous point at 42 degrees N. 170 degrees W., where refueling will be speedily carried out.31

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:

1.  The Empire of Japan has decided to open hostilities against the United States, Great Britain, and the Netherlands during the first part of December.

2The Combined Fleet will destroy enemy naval and air forces in the Far East and will repulse and destroy any enemy naval forces which may come to the attack.

3The Commander-in-Chief, Combined Fleet, will cooperate with the Commander-in-Chief, Southern Army, in executing swift attacks on American, British, and Dutch strategic bases in East Asia and in oc­


Map, Track of Carrier Task Force for Pearl Harbor Attack, Plate No. 13: Pearl Harbor Attack, 8 December 1941

Map, Air Attack of Oahu, Plate No. 13: Pearl Harbor Attack, 8 December 1941

Pearl Harbor Attack, 8 December 1941


cupying and securing vital areas in the South.32

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:

1. Imperial General Headquarters has prepared for the invasion of strategic areas in the South.

2. The Commander-in-Chief, Southern Army, shall, in cooperation with the Navy, concentrate his main forces in Indochina, South China, Formosa, and the Ryukyu Islands and shall carry out preparations for the invasion of the strategic southern areas. The start of the invasion operations will be by separate order.

3. In the event of attack by American, British and Dutch forces, either together or singly, the Commander-in-Chief, Southern Army, is authorized to counterattack with the forces at his disposal in self­defense.35

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:

1. Strategic areas to be occupied are the Philippines, British Malaya, the Netherlands Indies, and a part of southern Burma.

2In executing these operations, effort will be made to preserve order and stability in Thailand and Indochina; and from these areas the blockade of China will be reinforced.

3. Military government will be established in occupied territories in order to assure the restoration of order, the acquisition of vital resources for national defense, and the self-sufficiency of the occupying forces.38

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:

1. The Empire of Japan has resolved to wage war against the United States, Great Britain and the Netherlands.

2. The Commander-in-Chief, Southern Army, will begin invasion operations on 8 December. However, if a Japanese-American agreement should be reached before that date, the operations will be cancelled.

3. Prior to 8 December, the Commander-in­Chief, Southern Army, is authorized:

a.  In the event the enemy takes the initiative in launching a serious attack, to begin invasion operations at an opportune moment, in cooperation with the Navy.

b. In the event of a British invasion of Thailand, to occupy that area at an opportune moment in cooperation with the Navy.

c. In the event enemy aircraft repeatedly reconnoiter our strategic bases or troop convoys, to order that they be shot down.40

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.

Pearl Harbor Operation

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: Sunk–four battleships, one cruiser, two tankers; heavily damaged–four battleships; lightly damaged–one 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


Plate No. 14: Pearl Harbor on 8 December 1941 (Tokyo Time), Original Painting by Tsuguji Fujita

Pearl Harbor on 8 December 1941 (Tokyo Time)


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


Plate No. 15: Map, Southern Operations, December 1941-May 1942

Southern Operations, December 1941-May 1942


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


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