Japanese Monograph No. 149

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part II

PREPARED BY MILITARY HISTORY SECTION HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY OFFICE OF THE CHIEF OF MILITARY HISTORY DEPARTMENT OF THE ARMY

FOREWORD

This is the second of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

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Preface

Through Instructions No. 126 to the Japanese Government, 12 October 19subject: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilisation Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult) particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators and Interpreters Service, G2, General Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in

English by the Japanese Research Division, Military History Section, General Headquarters, Far East Command and is based on the translation of the Japanese original. Editorial corrections were limited to those necessary for coherence and accuracy.

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TABLE OF CONTENTS

Page

Chapter I

The Third Replenishment Plan

1

The Plan and Subsidiary Means Used to Replenish Naval Surface Strength

2

Air Strength Plan

7

Chapter II

Acceleration of War Preparations and Supplementary Armament Plans Caused by Outbreak of China Incident

11

Acceleration of War Preparations

11

Supplementary Armament Plan

14

Extraordinary Military Expenditure

16

The Fourth Replenishment Plan

17

Appendix I

Third Replenishment Plan

25

Ship Construction

25

Aircraft Preparation - Land-based

27

Aircraft Preparation - Land-based Air Group

27

Appendix II

Expected Air Strength at the Time of the Completion of the Third Replenishment Plan

29

Appendix III

Outline of the First War Preparations Analysis Conference

31

Appendix IV

Fourth Replenishment Plan of the Naval

34

Aircraft Preparation - Land-based Air Group

34

Shipboard Air Strength

35

Ship Construction

37

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TABLE OF CONTENTS (CONT'D)

Page

Chart No. 1

Approved Budget (Fiscal year 1937)

3

Chart No. 2

Ship Construction Progress of Third

6

Chart No. 3

Budget (Fiscal year 1939)

20

Chart No. 4

Ship Construction Progress of the Fourth

21

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Chapter I The Third Replenishment Plan

In December 1934, Japan submitted notification of the abrogation of the Washington Treaty. At the same time, after intensive research for the coming disarmament conference, it was found that Japan did not have the facilities, material or money to compete with the western powers in naval armament. It was planned, therefore, that in order to safeguard herself, Japan would stress the point of finding the common upper limit of naval strength and of reducing or entirely abolishing offensive vessels, such as battleships and aircraft carriers. It was felt that the naval ratio that had been adopted both in the Washington and London Treaties was unreasonable and would not guarantee the security of Japan.

The Naval Disarmament Conference of the five powers, Japan, Great Britain, United States, France and Italy was held in London in December 1935. Since Great Britain and the United States not only disagreed in principle with Japan's contention that the naval treaty was unreasonable, but ignored it, Japan withdrew from the conference in January 1936. Thus, with the expiration of both the Washington and First London Naval treaties, Japan was no longer committed to any treaty obligations with Britain and the United States.

These events combined to make Japan feel herself in an isolated position in regard to the Occidental powers. In addition, from the time of the establishment of Manchukuo the Chinese people had openly

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shown their resentment against Japan, and, especially in North China, armed clashes were frequent. With the marked increase of clashes in Asia between Japan and China and between Japan and the Soviet Union, Japan began to feel pressure from all sides, which she believed would have to be overcome at any cost.

In March 1936, Great Britain requested the Japanese Government to take part in the limitation of guns on capital ships provided in the Second London Naval Treaty (British-American-French Naval Qualitative Limitations Treaty) but Japan declined the invitation. Since the end of 1935, in view of the unexpected delay in carrying out the Second Naval Replenishment Plan, Japanese naval authorities had been preparing for the next armament replenishment plan. As a result, the Third Replenishment Plan, extending over five years (four years in the case of aircraft) beginning in the 1937 fiscal year, was formulated. This plan called for a total of 66 ships (including two battleships) amounting to approximately 270,000 tons; also included in the plan were 14 new air units, bringing Japan's total air strength to 53 units. (See Appendix I) The approved budget for shipbuilding was approximately 800,000,000 yen. (3 1/2 yen = $1.00) (See Chart I) The progress of ship construction is shown in Chart 2.

The Plan and Subsidiary Means Used to Replenish Naval Surface Strength

This was the first plan made and put into effect by the Japanese Navy after it had been freed from obligations of international dis-

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Chart 1 Approved Budget (Fiscal year 1937)

Type of Ship

Tonnage

Number of Ships

Cost (in 1,000 yen)

Total (in 1,000 yen)

Battleships

35,000

2

98,000

196,000

Aircraft Carriers

24,500

2

80,850

161,700

Minelayer (Class A)

11,600

1

24,940

24,940

Minelayer

(Class B)

5,400

1

9,750

9,750

Emergency Net Layers

2,000

2

4,500

9,000

Escort Ships

1,200

4

3,060

12,240

Gunboats

(Class A)

1,000

2

3,300

6,600

Gunboats

(Class B)

270

2

1,174.5

2,349

Destroyers

2,000

18

9,000

162,000

Submarines

(Class A)

2,600

2

14,560

29,120

Submarines

(Class B)

2,100

12

12,180

146,160

Minesweepers

600

6

2,130

12,780

Naval Transport

10,000

1

4,400

4,400

Survey Ship

1,600

1

3,760

3,760

Light

Minelayers

700

5

2,450

12,250

Subchasers

300

9

2,450

13,500

Total

70

806,549

Budget Appropriation for Each Fiscal Year (in 1,000 yen)

Total

1937

1938

1939

1940

1941

806,549

48,007

206,342

232,392

229,057

90,751

In addition, on account of a rise in prices, a 57,669,038 yen increase was authorized for the fiscal year 1941.

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armament treaties. Every effort was to be made to compensate for

lack of quantity in naval strength by the improvement of quality. To do this, lt was necessary to re-equip vessels in order to make each ship as effective as possible.

Battleships

Due to lack of facilities, materials and the time necessary for construction. and from the viewpoint of expense, it was realised that lt would be impossible to raise the ratio of battleships. Therefore, as the Japanese Navy could not compete with the United States Navy in regard to the number of battleships, it was decided to construct the two largest and most effective battleships in the world, the Yamato and Musashi.

Since 1931, with each armament plan, the modernisation of capital ships had been carried out. The conversion of the nominal training ship Hiei back to a battleship was begun in 1937, when the ship was freed from treaty limitations.

Aircraft Carriers

In view of the vulnerability of aircraft carriers, quantity rather than quality of carriers was given first consideration, and a policy was adopted whereby the ratio of Japanese aircraft carriers would be kept equal to, if not greater than, that of the United States.

It was considered that the two aircraft carriers of the Shokaku class, which had been included in the Third Replenishment Plan (See

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Chart 2) would easily be able to balance the United States Navy in the number of carriers completed in accordance with the First Vinson Plan. However, since 1937 the United States had been planning an increase in aircraft carriers. It was also reported that the number of carriers to be constructed according to the Second and Third Vinson Plans would total between 8 and 10. It seemed therefore that, in spite of the Japanese plan to maintain parity with the United States, this would not be realised. Under the circumstances the Japanese Navy decided to conduct intensive research and investigation into the progress of the United States naval armament, and, if necessary, in order to obtain parity, to requisition and convert first-class merchant ships into aircraft carriers.

Cruisers

The Japanese Navy's most favorable ratio with the United States Navy, under treaty restrictions, was cruisers. Generally speaking, however, the number of Japanese cruisers could not exceed 70 percent of the United States cruisers. The Japanese Navy, therefore, adopted a policy of equipping each cruiser with as many guns and torpedoes as possible. Furthermore, with the removal of treaty restrictions, it was able by the end of the 1938 fiscal year to complete the Conversion of the light cruisers Mogami and Mikuma into heavy cruisers, by replacing l55mm guns with 200mm guns.

The light cruisers Kumamo and Suzuya, which were of the same type as the Mogami, and the Tone and Chikuma, which were based on the

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Chart-2 Ship Construction Progress of Third Naval Replenishment Plan

Type

Period of Construction

Ships

Battleships

Nov 37 to Aug 42

Yamato Musashi

Carriers

Dec 37 to Sep 41

Shokaku Zuikaku

Seaplane tender

Nov 38 to Jan 42

Nisshin

Minelayer

Jul 39 to Oct 41

Tsugaru

Emergency Netlayer

Apr 38 to Jun 40

Hatsutake Aotaka

Escort Ships

Hot 38 to Mar 40

4 - Shimsihu Class

Gunboats (Class A)

Fab 39 to Apr 41

Hashidate Uji

Gunboats (Class B)

Aug 38 to May 40

Fushimi Sumida

Destroyers

Sap 37 to Jun 41

15 - Kagero Class

Submarines (Class A)

Jan 38 to Oct 41

1 - I-9 Class 1 - I-10 Class

Submarines (Class B)

Jan 38 to Oct 41

6 - I-15 Class

Submarines (Class C)

Aug 37 to Oct 41

5 - I-16 Class

Subchasers

Oct 37 to Aug 39

6 - No. 7 Class

Naval transports

Jul 39 to Jul 40

Kashino

Survey ship

Jan 40 to Jan 42

Tsukushi

Light Minelayer

Jun 37 to Oct 40

5 - Sokuten Class

Minesweepers

Oct 37 to Jun 39

9 - No. 4 Class

TOTAL: 66 ships, approximately 277,000 toss.

(Note) Construction of three destroyers and one submarine was

cancelled in order to divert the funds to the construction of the two super-battleships, Musashi and Yamato

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Second Replenishment Plan, were in the process of construction, so that they could be completed as heavy cruisers, without going through the process of conversion.

Thus, when the Second Replenishment Plan was fully carried out, the number of heavy cruisers in the Japanese Navy totalled eighteen. In spite of the fact that the Third Replenishment Plan did not include the construction of cruisers, it appeared that, as far as cruisers were concerned, the Japanese Navy would be able to maintain an almost equal strength with the United States Navy.

Air Strength Plan

Although the budget appropriation approved for the preparation of air strength of approximately 140,000,000 yen, reaching a total of about 200,000,000 yen by the addition of various other subsidiary expenditures, may appear small when compared with the 800,000,000 yen for shipbuilding scheduled in the Third Replenishment Plan, this was actually not so. The expenditure for the maintenance and replacement of 53 land-based air units and about 600 shipboard aircraft, when this plan was carried into effect, totalled an extraordinarily large amount. Moreover, with the rapid increase in air strength, airfields had to be constructed and expanded. Factories also were established under the administration of the Naval Aeronautical Department for the manufacture, maintenance and repair of aircraft equipment.

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With the commencement of the Third Replenishment Plan, not only did the Naval Aeronautical Department become more and more important as a training control unit, but its duties as a repair and construction control organ brought it more closely in line with the Naval Technical Department. This situation resulted in subsequent approved budgets being almost equal for both organs.

Soon after the commencement of the Third Replenishment Plan, the China Incident broke out, so that the operational loss of naval aircraft showed a rapid increase, with the resultant difficulties in executing armament plans and activating forces. Measures were taken at this time to obtain unanimous approval of the Extraordinary Military Expenditure (See p. 16). Increase of industrial production was intensified with the expansion of the war front, and, in spite of the fact that it became necessary to increase various emergency armament and war preparations for the China Incident, their completion was successfully expedited. The bulk of the land-based air force (totalling 12 units excluding one unit of medium attack planes and one unit of medium flying boats) was completed by the end of the fiscal year 1938; the uncompleted unit of medium attack planes was completed within the fiscal year 1939 and the medium flying boats within the fiscal year 1940. The completion of shipboard strength was realised between 1938 and 1941 (except for aircraft for the Musashi which was completed in 1942) according to the time of completion of shipbuilding.

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The grand total of air strength at the time of the completion of this plan was roughly estimated as shown in "Expected Air Strength at the Time of Completion of the Third Replenishment Plan" (See Appendix II) though it was subject to many additions and changes with the development of the China Incident.

The preparation of land air bases steadily progressed with the preparation of aircraft. Land-based air groups which were activated by the end of 1940 were as follows:

Name of Air Group

Date of Activation

Note

1

YOKOSUKA

1 Apr 1916

According to the Second Replenishment Plan

2

SASEBO

1 Apr 1918

3

KASUMIGAURA

1 Nov 1922

4

OMURA

1 Nov 1922

5

TATEYAMA

1 Jun 1930

6

KURE

1 Jun 1931

7

OMINATO

1 Nov 1933

8

SAEKI

5 Feb 1934

According to the Second Replenishment Plan

9

MAIZURU

1 Oct 1935

10

KISARAZU

1 Apr 1936

11

KANOYA

1 Apr 1936

12

CHINKAI

1 Oct 1936

13

YOKOHAMA

1 Oct 1936

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14

TAKAO

1 Apr 1938

According to the Third Replenishment Plan

15

SUZUKA

1 Apr 1938

16

OITA

5 Dec 1938

17

TSUKUBA

5 Dec 1938

18

KASHIMA

5 Dec 1938

19

CHICHI JIMA

1 Apr 1939

20

USA

1 Oct 1939

21

CHITOSE

1 Oct 1939

22

YATABE

1 Deo 1939

23

HYAKURIHARA

1 Dec 1939

24

IWAKUNI

1 Dec 1939

25

TSUCHIURA

5 Nov 1940

26

MIHORO

1 Oct 1940

According to the

Fourth Replenishment Plan

27

GENZAN

1 Oct 1940

28

TOKO

1 Oct 1940

29

HAKATA

5 Not 1940

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CHAPTER II

Acceleration of War Preparations and Supplementary Armament Plans Caused by Outbreak of China Incident

Acceleration of War Preparations At the time of the outbreak of the China Incident in July 1937, the Third Replenishment Plan was already under way, and the subsidiary preparations to modernise existing ships and reorganize air groups were making steady progress. In order to prevent obstructing the execution of the armament program, the Japanese Government and the Navy desired to localise the Incident. However, the Incident spread to Central and South China, causing a general clash between Japan and China.

In early and middle July the Navy made preparations to cope with the situation (See Monograph No. 144; "Political Strategy prior to Outbreak of War," Part I, 1931-1939, Chapter II.) These preparations included:

a. Reorganisation of units and deployment of necessary strength for emergency to include the activation, preparations for deployment and alerting of two Special Combined Air Groups and a Special Naval Landing Force.

b. Drafting of necessary personnel.

c. Acceleration of manufacturing and stockpiling of equipment, war materials (especially materials impossible to import in wartime), bombs and machine gun ammunition.

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d. Preparation for requisitioning necessary ships and complete equipment of navy vessels.

e. Establishment of necessary facilities for defense of key

positions.

By the middle of August, the main results obtained from the above preparations were:

a. The Aoba and Kinugasa, having been repaired, were engaged in army transportation as guard ships.

b. The Belfast Maru, Kinugasa Maru and Choko Maru had been requisitioned.

c. The Asahi Maru had been requisitioned and converted into

a hospital ship, while a special sick bay had been organized aboard the hospital ship Muroto.

d. The First Naval Harbor Master's Department had been established aboard the naval auxiliary ship Asahi, and this ship attached to the Third Fleet and used for salvage and repair.

e. The necessary facilities for the transportation of a Special Naval Landing Force to the Tsingtao area had been installed on the Settsu and Yakaze.

On 13 August 1937, the Chinese Army made an attack on a Japanese naval land combat unit at Shanghai, which precipitated the two armies into a full-scale war.

Believing that the Incident would continue to expand for a considerable time, and that friction with the Three Powers would necessarily increase during that period, the Navy determined to

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accelerate war preparations immediately to cope with the situation. On 23 August, in order that the Chief of Navy General Staff might present his views to the Navy Minister, the First War Preparations Analysis Conference was held. (See Appendix III)

In spite of the capture of Nanking in November 1937, the China Incident dragged on, and cases of protest and interference by the Three Powers occurred so frequently that the execution of war preparations based on the conferences held on all such occasions between the Navy Ministry and the Navy General Staff became standard procedure. Moreover, preparations covering a long period were to be given priorities by weighing their importance with the existing and next armament plans, and by advancing their completion dates in the form of additional armament. Special emphasis was placed on:

Replenishment of aircraft lost in operations

Obtaining and training aircraft personnel

Completion of operational air bases and strengthening of their defenses

Gradual overhaul or modernization of all existing navy vessels

Gradual requisitioning and conversion of ships and construction of miscellaneous small ships

Procurement, increased production, storage and supply of required war materials

Strengthening of various land and sea facilities along with the completion of the above strength and equipment.

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Supplementary Armament Plan

In order to achieve the objectives agreed upon by the Navy Ministry and the Navy General Staff, it became obvious that it would be necessary to execute an additional armament plan for the period between the Third and Fourth Replenishment Plans.

Ship Strength

In the fiscal year 1938, a budget appropriation of 17,200,000 yen for the construction of three ships two training ships (three requested) and one storeship (two requested) was approved as an expenditure extending to 1941. The construction of these ships was to be carried cut together with the Third Replenishment Plan.

The obsolete ships used for training had always been regarded as a disgrace and, with the sharp increase in the number of cadets, and the tremendous development in ships' equipment and tactics, it became absolutely necessary to replace them. The Katori and Kashima (displacement tonnage per ship 5,800 tons) were completed and commissioned as training ships in April and May 1940 respectively.

One storeship, the Irako (displacement tonnage, 9,570 tons) was completed and commissioned in December 1941. However, with the expansion of the area of fleet training and the extension of the training period, this one storeship was considered completely inadequate to cope with the situation.

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Air Strength

The Navy General Staff requested 75 additional medium attack planes for the war with China within the fiscal year 1937. This meant almost doubling the existing strength of medium attack planes within half a year. Every effort was made to accelerate production by advancing to the utmost the date of completion of two and a half units of medium attack planes in accordance with the Third Replenishment Plan, completing three units of medium attack planes as an additional armament plan in 1938, and reinforcing the Kanoya and Takao Air Groups with the above units, thus expediting the replenishment of loss by the operational forces.

It required great effort to replenish and maintain air strength even in peacetime. It was, therefore, found extremely difficult to maintain combat strength by the prompt replenishment of losses in the China operations, and, at the same time, to plan the increase in strength demanded by the armament plan, For instance, the number of aircraft which was scheduled to be completed by the third year of the China Incident as a replenishment, or strengthening, of war preparations for the Incident, in addition to aircraft scheduled in the existing armament plan (excluding the above mentioned additional armament of three units of medium attack planes) was estimated as shown below:

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Carrier Fighters

131

Carrier Bombers

57

Carrier Attack Planes

71

Reconnaissance Seaplanes

59

Medium Attack Planes

72

Heavy Attack Planes

0

Transports

0

Total

390

Needless to say, these figures indicated the budgetary strength which was estimated after considering the Extraordinary Military Expenditure appropriation, not the actual strength which was assigned and committed to the China operations. It is interesting to note that the actual number of aircraft completed in a year was much the same as the total number of aircraft scheduled in past armament plans covering several years.

Extraordinary Military Expenditure

With the outbreak of the China Incident, measures were taken to obtain unanimous approval of the Extraordinary Military Expenditure. This was done not only from the standpoint of urgency of operations and preservation of secrets, but it was also a very effective means of accelerating armament and war preparations.

In the past the expenditure of the budget had been restricted within narrow limits. The Extraordinary Military Expenditure made lt possible to divert money from one item or expenditure to

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another or to expend it for a new item in accordance with changes in plans.

The Fourth Replenishment Plan

Soon after the outbreak of the China Incident, the Chinese Government submitted a protest to the League of Nations. The United States Government in October 1937, as though in concert with this action accused Japan of violating the Kellogg Pact. Anti-Japanese feeling in both Great Britain and the United States was aggravated at this time by the Panay and Lady Bird Incidents, caused in connection with the capture of Nanking. Although these incidents, themselves, were settled by diplomatic measures, with the expansion of operations in Central and South China, cases of violations of rights and interests, particularly of Great Britain and the United States, occurred so frequently that anti-Japanese feeling became increasingly evident. This, together with the acute situation in Europe, caused both Great Britain and the United States to greatly accelerate the strengthening of armament and war preparations.

The German-Austrian Anschluss and the German invasion and annexation of the Sudeten area, which were carried out in the spring and fall of 1938, seemed to be drawing Europe closer to a great cataclysm. World conditions caused Great Britain and France to place themselves on a quasi-wartime footing, and the United States to further step up armament and war preparations against the Axis Powers.

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The armament of the United States Navy, according to the First Vinson Plan for the fiscal year 1934, was to be expanded to the limit permitted by the treaty. Moreover, a budget for an increase of 2 battleships, 20 destroyers, 6 submarines and 333 aircraft was approved in 1936. In addition, a plan for a huge amount of armament, totalling 81 vessels, was announced for the fiscal year 1937: 2 battleships, 3 aircraft carriers, 11 cruisers, 16 submarines, 48 destroyers and 1 gunboat. Besides this, a budget for the construction of two replacement battleships from the fiscal year 1939 onward was requested. Furthermore, in May 1938, the Second Vinson Plan, requiring 46 combat ships (including three battleships and two aircraft carriers), 26 auxiliary ships, 950 aircraft and one airship was signed by the President. The Second Vinson Plan was a ten-year plan. At the same time, a budget for about 1,100,000,000 dollars was passed for land and sea facilities.

In view of the United States increase in strength according to the plan for the fiscal year 1937, and the Second Vinson Plan, which was approximately four times that of the Third Replenishment Plan for the Japanese Navy, Japan, in spite of her difficulties in China, felt forced to cope with the situation at any cost by means of another armament plan.

The Japanese Navy was confronted with the absolute necessity of completing its armament, while on the other hand, operations on

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the Chine mainland necessarily required priority of Army armament. This gave rise to a number of problems in regard to the financial and material limits of the country. In the meantime, the Navy Ministry and the Navy General Staff, upon investigating the contents of the two huge armament plans of the United States Navy, advanced the next armament plan, aiming at Japan's ship strength to at least equal one of the American plans, and her air strength to be on parity. They continued negotiations with the ministries concerned until at last in 1939 the budget passed the Diet. This was known as the Fourth Replenishment Plan of the Naval Armament Completion Plan for the fiscal year 1939. (See Appendix IV) An approved budget of approximately 1,200,000,000 yen was appropriated for the construction of 83 vessels (including two battleships). (See Chart 3) The progress of construction of these vessels is shown in Chart 4. In air strength, this plan called for 75 units as a nucleus comprising 34 1/2 operational units and 40 1/2 training units, both of which belonged to land-based air forces. About 300,000,000 yen was appropriated solely for the construction of aircraft. This plan was intended to cover six years (five years in the case of air strength) from the fiscal year 1939 to 1944.

The Third Naval Replenishment Plan aimed to double the naval air strength in five years, in spite of the fact that it had taken over 20 years to build it to its present strength. The Navy did

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Chart 3 Budget (Fiscal year 1939)

Type

Tonnage

Number

Cost (in 1,000 yen)

Total Cost (in 1,000 yen)

Battleships

40,000

2

130,000

260,000

Carrier

28,500

1

101,175

101,175

Cruisers (Class B)

6,600

4

26,400

105,600

Cruisers (Class C)

8,200

2

31,160

62,320

Destroyers (Class A)

2,100

18

10,605

190,890

Destroyers (Class B)

2,600

6

12,090

72,540

Cruising Submarines (Class A)

2,600

1

16,640

16,640

Cruising Submarines (Class B)

2,200

15

14,190

212,850

Submarines (Navy Large Type)

1,600

10

10,480

104,800

Training Ship

6,000

1

7,200

7,200

Seaplane tender

5,500

1

11,825

11,825

Light Minelayers

700

10

2,660

26,600

Mine sweepers

700

6

2,660

15,960

Subchasers

300

4

1,620

6,480

Emergency net layer

2,000

1

4,900

4,900

Oil tanker

5,000

1

6,000

6,000

Total

83

1,205,780

Annual Budgets (in 1,000 yen)

1939

1940

1941

1942

1943

1944

Total

60,150

119,250

289,785

384,184

290,080

62,330

1,205,780

These budgets were approved as general accounts. However, they were included in the extraordinary military expenditure after the fiscal year 1942.

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Battleship 110

Apr 40 to Dec 40

Construction in progress

Dec 40 to Jun 42

Construction suspended

Jun 42 to Nov 44

Converted to carrier Shinano

Battleship 111

Nov 40 to Dec 40

Construction in progress

Dec 40 to Mar 43

Construction suspended

Mar 43

Dismantled

Carrier

Jul 41 to Mar 44

Taiho

Cruiser (Class B)

Jun 40 to Nov 44

4 Agano Class cruisers

Cruisers (Class C)

1939

1 ship - construction suspended.

Feb 41 to Feb 43

Oyodo

Destroyers (Class A)

May 39 to Jul 43

3 Kagero Class

12 Yugumo Class

1 Shimakaze

Destroyers (Class B)

Jul 40 to May 43

6 Akitsuki Class

Submarine (Class A)

Apr 40 to May 42

I-11 Class Submarine

Submarine (Class B)

Jun 39 to Apr 43

I-14 I-15 Class Submarines

Submarine (Navy Large Type)

Jun 40 to Aug 43

10 I-176 Class submarines

Training ship

Oct 39 to Jul 41

Kashii

Seaplane tender

Nov 40 to Apr 42

Akitsushima

Light Minelayer

Sep 39 to Jul 43

1 ship - construction suspended

9 Improved Sokuten Class

Subchaser

Jul 39 to Mar 41

4 No. 13 Class Subchasers

Minesweeper

Sep 40 to Mar 43

6 No. 19 Class Minesweepers

Emergency Netlayer

Dec 40 to Not 41

Wakataka

Tanker

Mar 42 to May 43

Sunosaki

Note: Although the budget approved by Diet showed a total of 83 ships to be constructed, the Navy decided to build only 80 ships and to use the extra appropriations to construct two super battleships. Later, it was found that this plan

not practical and Battleship 110 was converted into the Carrier Shinano, while, after suspending construction on Battleship 111 in December 1940, lt was finally dismantled in March1943.

--21--

not have complete faith in this ambitious program, however, it was felt necessary to attempt this goal in order to instill the "air strength first" idea into the naval armament plan. About this time aircraft production had made unexpected progress as a result of the China Incident. Taking advantage of this momentum, this plan aimed at developing the low aircraft production capacity of Japan at any cost to carry out the Fourth Replenishment Plan. Therefore, subsequent to the commencement of this plan, it was made a rule to give priority to the naval air armament plan within the limits of scheduled manpower, materials and facilities. Accordingly, from that time forward, naval air armament was not restricted for financial reasons. The building up of air power, however, was retarded by the fact that, in spite of the vision of the few who could see the tremendous importance of air power, with many the basic idea of huge warships and big guns as a nucleus of sea power, with air power as auxiliary strength, still predominated.

With the Third Replenishment Plan almost completed, but before the Fourth Replenishment Plan was completely drafted, in October 1938, naval air armament under the Fourth Replenishment Plan was begun. The plan made unexpectedly good progress due to strong advocacy of "air strength first" in naval armament. Production facilities were expanded and aircraft production techniques were much improved.

--22--

When the situation became critical in August 1941, the order was given to advance the plan by one year, changing it to a four-year plan to be completed in the fiscal year 1942. Not only was this plan completed as revised, but, during this time, a large amount of the strength lost due to the China Incident was replaced. From 1941 onward, although each supplementary armament plan and each new armament plan was put into effect in advance, they were rarely completed in the specified time.

The number of aircraft completed in the fiscal years 1940 and 1941 to replace the expended aircraft was estimated to be:

Carrier fighters

75

Carrier bombers

37

Carrier attack planes

36

Reconnaissance seaplanes

43

Medium attack planes

102

Total

293

Thus, from a practical angle, the air strength of the Japanese Navy at the time of the outbreak of the Pacific War was almost equal to the expected strength at the time of the completion of the Fourth Replenishment Plan. Details of the plan in connection with other war preparations and armament plans will be mentioned in monograph No 160.

Compared with the preparation and replenishment of the above air groups, the expansion of aircraft production and the training of air personnel lagged far behind. The greatest difficulties encountered in air preparation and armament throughout the Pacific war, and even in pre-war days, were the poor aircraft equipment and the shortage of well-trained air personnel.

--23--

Appendix I

Third Replacement Plan

Ship Construction

Tonnage per Ship (Standard Displacement)

Number of

ships

Total Tonnage

Speed

(knots)

Cruising

Range

Principal Armament

Remarks

Battleships

64,000

2

120,000

27

16 knots

7,200 nautical miles

460mm guns

9

155mm guns

12

127mm Dual Purpose guns

12

Aircraft

6

Aircraft Carriers

20,000

2

60,000

34

18 knots

9,700 nautical miles

12.7mm Dual Purpose guns

16

Aircraft-96/Fighter/Primary

18

Fighter/Secondary

8

Bomber/Primary

54

Bomber/Secondary

18

Seaplane

Tender

9,500

1

9,500

22

16 knots

8,000 nautical miles

140mm guns

6

Originally planned for minelayers

Reconnaissance Seaplane Primary

20

Reconnaissance Seaplane Secondary

5

Facilities for boarding Type A

Midget Submarines

Minelayer

4,000

1

4,000

21

14 knots

6,400 nautical miles

127mm guns

4

Depth Charge Thrower

1

Mines

600

Minelayer (Emergency Net Layers)

1,600

2

3,200

20

14 knots

4,100 nautical miles

40mm Machine guns

2

Depth Charge Thrower

1

Antisubmarine Nets

24

Escort Ships

860

4

3,440

20

14 knots

8,000 nautical miles

120mm guns

3

Depth Charge Thrower

1

Gunboats (Class A)

990

2

1,980

19.5

14 knots

2,500 nautical miles

120mm Dual Purpose guns

3

Gunboats (Class B)

320

2

640

17

14 knots

1,400 nautical miles

Torpedo Tube

1

Destroyers

2,000

15

30,000

35

18 knots

5,000 nautical miles

120mm guns

6

The approved budget was for 18 vessels. The budget for three of them was diverted to battleship construction.

Torpedo Tubes

8

Submarines

(Class A)

2,200

2

4,400

Surface 23.5

16 knots

16,000 nautical miles

140mm gun

1

Torpedo Tubes

6

Aircraft

1

Submarines

(Class B)

1,950

6

11,700

Surface

23.6

16 knots

14,000 nautical miles

140mm gun

1

The approved budget was for 12 vessels. The budget for one of them was diverted to battleship construction.

Torpedo Tubes

6

Aircraft

1

Submarines

(Class c)

2,100

5

10,900

Surface

23.4

16 knots

,000 nautical miles

140mm gun

1

Torpedo Tubes

8

Minesweepers

630

6

3,700

20

14 knots

2,000 nautical miles

120mm guns

2

Depth Charge Throwers

2

Naval

Transport

10,360

1

10,360

14

14 knots

8,000 nautical miles

120mm Dual Purpose guns

(Equipped with facilities for the transportation of 460mm gun)

2

Survey ship

1,400

1

1,400

20

16 knots

8,000 nautical miles

120mm guns

4

Light

Minelayers

720

5

3,600

20

14 knots

2,000 nautical miles

80mm Dual Purpose guns

1

Depth Charge Throwers

2

Subchasers

290

9

2,610

20

14 knots

2,000 nautical miles

40mm Machine guns

TOTAL

66

269,510

--25--

Aircraft Preparation - Land-based Air Croup

Classification

Number of Units

Number of Aircraft

Total Namber of Aircraft

Per Unit

Scheduled

Primary

Secondary

Primary

Secondary

Operational Air Group

Carrier Combers

1

12

4

12

4

16

Land Attack Planes

2.5

12

4

30

10

40

Reconnaissance Seaplanes

1.5

8

4

12

6

18

Medium Flying Boats

1

4

2

4

2

6

Total

6

58

22

80

Training Air Group

Primary

1

12

18

12

18

30

Intermediate

5

12

12

60

60

120

Combat Trainers

2

12

4

24

8

32

Total

8

96

86

182

GRAND TOTAL

14

154

108

262

NOTE: The total of 14 units in the above chart is some times regarded as included in the Third Replenishment Plan, because the completion of shipboard air groups mas delayed along with the progress of ship construction.

Shipboard Air Strength

Classification

Number of Aircraft

Total Number of Aircraft

Primary

Secondary

Carrier Fighters

48

12

60

Carrier Bombers

144

48

190

Reconnaissance Seaplanes (Ship board)

38

4

42

Total

230

64

294

NOTE: There was a budget appropriation for carrier bombers but for attack planes. This was a budget problem with the appearance of new carrier bombers.

--27--

Appendix II

Expect Air Strength at the Time of the Completion of the Third Replenishment Plan

Aircraft type

Group

Operational air group

Plan

Former Plan (after reorganization)

First Plan

Second Plan

Third Plan

Total

Former Plan

(after reorganization)

First Plan

Classification of Number

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total.

Carrier fighters

1.5

18\6

24

1.0

12\4

16

2.5

30\10

40

5.0

60\20

80

0.58

6\2

8

1.0

12\4

16

Carrier bombers

1.0

12\4

16

1.0

12\4

16

Carrier attack planes

1.0

12\4

16

3.5

42\14

56

4.5

54\18

72

0.5

6\2

8

3.0

36\12

42

Carrier Reconnaissance planes

2.0

24\8

32

Medium attack planes

1.0

9\3

12

2.5

30\10

40

2.5

30\10

40

6.0

69\23

92

Large attack planes

1.5

12\3

15

12\3

15

Reconnaissance planes

2.5

20\10

30

1.0

8\4

12

1.5

5.0

40\20

60

2.0

16\8

24

Shipboard Reconnaissance Seaplanes (other than carriers)

Small flying boats

1.5

12\6

18

1.J

12\6

18

0.5

4\2

4

Medium flying boats

3.0

........12\6

18

1.0

4\2

6

4.0

16\8

24

Large flying boats

1.0

2\0

2

1.0

2\0

2

2.0

4\0

4

Primary trainers

3.0

30\54

90

Intermediate trainers.

Combat trainers

13\4

Research planes

1.0

4

16

0.5

8\2

8

Total

7.5

71\29

100

9.5

76\28

104

7.5

74\23

97

6.0

58\22

80

30.5

279\102

381

9.0

104\80

184

4.5

54\18

72

Armament Plan

Classification\Plan

Former Plan

First Plan

Second Plan

Third Plan

Total

Land-based operational air strength

100

104

97

80

381

Land-based training air strength

184

72

8

182

446

Carrier and shipboard air strength

510

284

294

1,088

Total

970

389

556

1,915

on of the Third Replenishment Plan

Land-based air group

Shipboard air strength

Grand Total

Training air group

Total

Second Plan

Third Plan

Total

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Ships up to and in First Plan

Second Plan

Third Plan

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary

Auxiliary

Total

0.5

4\2

8

2.0

24\8

32

7.0

84\28

112

81\30

111

36\18

54

48\12

60

165\60

225

249

86

337

1.0

12\4

16

144\48

192

144\68

192

156

52

208

3.5

42\14

56

8.0

96\32

128

154\60

214

84\42

126

240\102

342

336

134

470

2.0

24\8

32

2.0

24\8

32

24

8

32

6.0

89\23

92

69

23

92

1.5

12\3

15

12

3

15

2.0

16\8

24

7.0

56\28

84

20\0

20

72\18

90

92\8

110

148

46

196

122\41

163

14\0

14

38\4

42

174\45

217

174

45

219

0.5

4\2

6

2.0

16\9

24

14

8

24

4.0

16\8

24

14

8

24

2.0

4\0

4

4

0

4

1.0

12\8

30

4.0

48\72

120

4.0

48\72

120

48

72

120

5.0

60\60

120

5.0

60\60

120

5.0

60\60

120

60

60

120

2.0

24\8

32

2.0

24\8

32

2.0

24\8

32

24

8

32

1.5

18\6

24

1 5

18\6

18

6

24

0.5

6\2

8

8.0

96\86

182

22.5

260\186

446

53.0

539\288

379\131

510

206\78

284

230\64

294

815\273

1,088

1,354

561

1,915

--29--

Appendix III

Outline of the First War Preparations Analysis Conference

23 August 1937

Matters for Consultation

Concerning War Preparations

Arrangements and Explanations

Policy

In anticipation of the China operations being protracted, war preparations which are of direct necessity will be completed. In addition, part of the war preparations required for sea operations will be accelerated in order to brush off interference, if any, of the Three Powers.

Outline

Surface Units

The completion of the following ships being re-equipped or reinforced will be accelerated. Akagi, Yamashiro, Mogami, Submarine I-71

The re-equipment of ships which are slated to be completed by the end of 1937 will bo continued as scheduled. The re-equipment of four ships mentioned in the left column is slated to be completed in the first half of 1938, and the date of completion is set as the end of January 1938 with the exception of the Akagi, which requires special preparation in order to strengthen sea-air strength.

The construction of the following ships will be accelerated: Soryu, Tsurugizaki, Takasaki. Chitose. Subchasers and other ships nearing their completion in accordance with the Naval Replenishment Plan for the fiscal year 1937.

Besides the above, the existing surface units of the strength included in the war organisation plan for the fiscal year 1937 will be equipped so as to execute operations effectively.

Emphasis will be laid on the acceleration of preparation of ships under repair or under overhaul. However, obsolescent ships such as the Hirato, Yahagi and Karazaki are excluded from such preparation.

Necessary ships will be requisitioned.

Converted seaplane tenders 4; converted combined collier and oil tanker 1; converted

--31--

Converted aircraft carriers equipment and materials required for conversion work will be prepared for three ships of Asama Maru class.

gunboats 4; converted ships Ko 12; converted subchasers 4.

Motors to be used for operating lifts, the lifts themselves, other materials and blueprints for conversion plans.

Air Strength

Medium attack planes and their equipment. Manufacturing and completion of the above a according to Navy Secretariat Secret Document No 2893, will be accelerated to the utmost.

Other aircraft and their equipment. The losses of the existing strength will be replenished. Aircraft and its equipment will be completed to achieve strength on wartime footing for the fiscal year 1937.

Besides those now being assembled, 75 aircraft will be completed in 1937.

A monthly output of 120 aircraft is scheduled. It will be increased to 350 by the end of the fiscal year 1937.

Defense

It will be completed in accordance with the Secondary and the Tertiary Defense in the Essentials of Naval Defense Program for the fiscal year 1937.

Facilities

Air bases

Effort will be made to complete immediately air bases

under construction and other necessary facilities.

Communications facilities

Communications facilities necessary for the above-mentioned defense will be completed.

The air bases mentioned on the left will be established

chiefly on South Sea Islands

and the Kuriles. Places necessary to establish new air bases

are Genzsan and Chitose (in

Hokkaido).

To be established: Second Transmitting Station of Shanghai Land Combat Unit; Harbin Radio Receiving Substation; Rashin Communications Unit; Niigata

Radio Finder Station; Mikuriya Radio Direction Finder Station. Completion of Equipment for Communications Units.

Construction and repair facilities

Efforts will be made to complete facilities required for the prepara-

--32--

tion of above strength and of the Sixth Expeditionary Preparation Materiel.

Personnel

Efforts will be made to train the personnel required for the operation and maintenance of the above strength and facilities.

Personnel on First and Second Reserve Lists to be called to active service. Aircraft personnel to be trained.

Preparation of Expeditionary Materiel

Based on the above strength, preparations will be made for the completion of materiel for the opening of hostilities in accordance with the Expeditionary Preparations Regulations for the fiscal year 1937. Every effort will be made for the procurement and preparation of fuel, raw materials, bombs and other necessary arms.

Air defense equipment: Dual purpose guns; machine guns; range finders; sound locators.

Anti-Submarine equipment:

Mines; antisubmarine nets with mines; hydrophones.

Shells, powder and other equipment.

--33--

Appendix IV

Fourth Replenishment Plan of the Naval Armament Completion Plan Aircraft Preparation - Land-based Air Group

Classification

Operational air groups

Training air groups

Transport planes

Total

Namber of Units

34.5

40.5

75

Number of aircraft

566

877

35

1,443 Plus 35

NOTE: If the strength of former plans is included, the total strength will amount to 128 units (2270 aircraft) 65 operational units (947 aircraft) and 63 training units (1323 aircraft) and 35 transports.

Details of this air strength are:

Classification

Number

of Units

Number of aircraft

Per Unit

Total

Primary

Secondary

Total

Primary

Secondary

Total

Operation air group

Carrier fighters

6.5

12

4

16

78

26

104

Carrier attack alarms

2.0

12

4

16

24

8

32

Medium attack Planes

18.5

12

4

16

222

74

296

Reconnaissance seaplanes

7.5

8

4

12

60

30

90

Medium flying boats

Reorganized Two groups reduced

8

4

12

No increase or decrease in number

Large flying boats

Reorganized Two groups increased

8

4

12

28

16

44

Total

34.5

412

154

566

Training air group

Primary trainers

7.5

12

18

30

90

135

225

Intermediate trainers

15.5

12

12

24

186

186

372

Combat trainers

17.5

12

4

16

210

70

280

Total

40.5

486

391

877

Transport planes

Large transport planes

24

Medium transport planes

11

Total

35

GRAND TOTAL

75.0

898

545

1,443 Plus 35

--34---

NOTE: Approval was obtained to include the 3.0 medium attack plane units planned in the 1938 Extraordinary Military Expenditure in the 18.5 medium attack plane units in this plan.

Subtracting 597 trainers from 1443 aircraft, there were 846 operational aircraft in all. This number corresponded to the number of navy aircraft in the Second Vinson Plan.

Shipboard Air Strength

Classification

Number of aircraft

Remarks

Primary

Secondary

Total

Carrier fighters

24

12

36

Carrier aircraft

Carrier bombers

24

12

36

"

Carrier attack planes

36

18

54

"

Reconnaissance seaplanes

48

0

48

Shipboard aircraft

Total

132

42

174

NOTE: The first completion expenditure for shipboard air strength is included in the ship budget in each armament plan.

It was planned to organise air groups at Komatsushima, Tainan, Misawa, Katori, Tokushima, Matsushima, Shinchiku, Mikawa Bay, Chitose and Genzan (as well as eight training air groups). However, the plan was to be changed as occasion demanded in accordance with the establishment of airfields, training programs or other situations that might arise.

--35--

Appendix IV(Cont'd)

Fourth Replenishment Plan of the Naval Armament Completion Plan - 1939

Ship Construction

Tonnage (Displacement

tonnage)

Number

Total Tonnage

Speed

(knots)

Cruising Range (knots-nautical miles)

Principal Armament

Note

Battleships

64,000

2

128,000

27.0

16-7,200

460mm guns

9

One ship's construction suspended and ship

dismantled.

One a ship converted to carrier.

155mm guns

12

100m dual purpose guns

12

Aircraft

6

Carrier

30,360

1

30,360

33.3

18-10,000

100m dual purpose guns

6

Aircraft

52

Cruisers (Class B)

6,500

4

26,000

35.0

18-6,000

150mm guns

6

80m dual purpose guns

4

Torpedo tube

8

Cruisers (Class C)

8,000

2

16,000

35.0

18-8,700

155mm guns

6

One ship's construction suspended

100m dual purpose guns

8

Destroyers

(Class A)

2,000

16

32,000

35.0

18-5,000

127mm guns

6

The budget for 18 destroyers was approved, but the amount for the ten destroyers was diverted to the construction of super-battleships.

Torpedo tubes

8

Destroyers

(Class B)

2,700

6

16,200

33.0

18-8,000

100m dual purpose guns

8

Torpedo tubes

4

Submarines

(Class A)

2,200

1

2,200

Surface Speed

23.5

Surface Speed 16-16,000

140mm gun

1

Torpedo tubes

6

Aircraft

1

Submarines

(Class B)

1,950

14

27,300

23.6

16-14,000

140mm gun

1

The budget for 15 submarines was approved, but the amount for one submarine was diverted to the construction of super-battleships.

Torpedo tubes

6

Aircraft

1

Submarine

(Navy Large Type)

1,500

10

15,000

23.1

16-8,000

25mm machine guns

4

Torpedo tubes

6

Training ship

5,800

1

5,800

18.1

12-10,000

140mm gun

4

127m dual purpose guns

3

Flying boat tender

4,650

1

4,650

19.1

14-8,000

127mm dual purpose guns

4

(Facilities for landing 1 large type flying boat)

Minelayer

1,600

1

1,600

20.0

14-3,000

80mm dual purpose guns

2

Depth charge throwers

1

Light

minelayers

720

10

7,200

20.0

14-2,000

80mm dual purpose guns

1

Depth charge throwers

2

Minesweepers

630

6

3,780

20.0

14-2,000

120mm gun

1

Large minesweeping equipment

Subchasers

440

4

1,760

16.0

14-2,300

80mm dual purpose guns

1

Depth charge throwers

2

Oil tanker

4,460

1

4,460

18.0

14-9,000

120mm dual purpose guns

2

Gasoline supply equipment for an aircraft carrier at sea.

Total

60

322,310

--37--