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U.S. Order of Battle

Note: The order of battle pages in the Pacific War Online Encyclopedia are still under construction. At present, we have an accurate initial order of battle and complete information on reinforcing warships, Marine units, Army units, and Army Air Force squadrons. We lack information on reinforcing Navy air squadrons other than fighter squadrons and Navy engineer shore units other than Seabees.

We present here the U.S. order of battle from 7 December 1941 on. Units that deployed as part of a higher echelon (such as regiments assigned to divisions) are not listed separately. Also, units redesignated from other units are not listed separately. The intent is to give a reasonable reinforcement schedule for war games.

Of those units that either fought in the war against Japan or were stationed on the West Coast under circumstances where they might conceivably have helped repel a Japanese incursion on the West Coast, we include all individually named warships of the U.S. Navy, all individual ground combat units to battalion size, all engineering units to regiment size, and all air squadrons.

Tabulated information

Unit. This is the name of the unit.

Commander. This is the commander of the unit at the time of its activation. For units already active when war broke out, it is the commander of the unit on 7 December 1941. In general, we do not display commanders below flag or general rank. Ships showing a commander are the flagship of that commander.

Start. This gives the date and location of the unit's activation. For units already active when war broke out, only the location is given (at 8:00 AM on 7 December 1941, Hawaii time). If no locationis given, a unit should be assumed to be at the same location as its operational headquarters (or administrative headquarters if no operational assignment is given.) Naval headquarters are located on the flagship of their commander unless otherwise specified.

Administrative Assignment. The administrative assignments in this table represent the formal organizational structure. The initial order of battle is sorted by adminstrative assignment, such that every unit appears after the unit to which it is administratively assigned.

Operational Assignment. The operational assignment, if one is given, represents temporary attachment to another unit for a single operation. For example, an aircraft carrier might be administratively assigned to a carrier division, but be operationally assigned to a task force for a particular mission.

Notes. Miscellaneous information about a unit, such as its manpower and equipment, its composition, where it was raised, what its initial orders were, and how well it performed in battle.

Organization of the tables

The order of battle tables are laid out for maximum readability by software tools while retaining some semblance of human readability. Because the complete orders of battle for the major powers are many megabytes in length, we have broken the tables up into individual sections of less than 400K to avoid difficulties with older Web browsers.

In addition to the displayed text and associated links, each unit has an HTML anchor with a unique identifier based on the unit name. For example, the entry for Pacific Fleet includes the anchor Pacific_Fleet, which appears immediately before the unit name in the table. These anchors are used to cross-reference the tables but may also be of use to software tools scanning the tables.

We are considering offering the complete orders of battle as SQL files or as C++ code. Users of the Encyclopedia who desire these or other formats may write to trollingshallows@msn.com and make their preferences know.

The order of battle

Initial U.S. order of battle

Reinforcements, 1941-1942

Reinforcements, 1943

Reinforcements, 1944-1 to 1944-7

Reinforcements, 1944-8 to 1944-12

Reinforcements, 1945

Replacements

U.S. Army deployment of manpower to the Pacific and Far East was as follows:

Month

Alaska

Central Pacific

South Pacific

Southwest Pacific

CBI

Dec 1941

2,068

15,084

0

0

0







Jan 1942

4,114

3,082

3,850

34,182

0

Feb 1942

3,605

1,363

0

20,133

0

Mar 1942

4,400

16,354

182

32,374

4,138

Apr 1942

8,967

10,085

10,986

23,100

3

May 1942

8,438

14,609

14,496

7,982

7,545

June 1942

17,066

16,362

1,899

5,582

25

Jul 1942

8,228

8,573

3,415

6,653

9

Aug 1942

6,028

10,595

2,043

31

34

Sep 1942

4,805

10,145

7,262

5,105

17

Oct 1942

4,372

4,524

22,628

2,411

10

Nov 1942

6,634

10,774

6,121

783

5

Dec 1942

5,397

2.834

5,054

11,158

2,065







Jan 1943

3,197

1,869

10,586

6,348

6,810

Feb 1943

6,185

2,482

3,671

13,258

2,815

Mar 1943

6,749

6,081

6,741

3,847

393

Apr 1943

17,811

7,042

9,410

5,100

92

May 1943

4,300

11,168

12,279

27,664

5,993

Jun 1943

9,377

10,927

12,591

16,193

74

Jul-Sep 1943
44,482
34,595
21,657
53,766
39,295
Oct-Dec 1943
8,234
40,970
40,153
68,110
38,170






Jan-Mar 1944
13,017
54,676
48,251
106,664
32,410
Apr-Jun 1944
10,915
79,777
31,630
89,177
23,494
Jul-Sep 1944
12,150
106,944

66,318
20,095
Oct-Dec 1944
10,749
77.097

79,407
30,037






Jan-Mar 1945
5,093
81,009

89,068
23,656
Apr-Jun 1945
4184
118,907

129,941
13,212
Jul-Aug 1945
5180
64,645

169,318
3,095






Total
246,105
822,573
274,905
1,073,673
253,492

By subtracting out the manpower of formations specified in the order of battle tables, multiplied by a suitable factor to represent the division slice, one can estimate the number of Army ground replacements deployed to the Pacific. One may also estimate the replacement rate from casualty figures.

The replacement model for the influential Pacific War (Victory Games 1985) called for an accumulation of 5 replacement battalions per month through November 1943; 8 per month through December 1944, and 10 per month thereafter. These replacements could be applied to any land unit of any service, and there were rules for using cadre and replacements to create new regiments. This was obviously a crude model, but it is hard to know how one could do better.

The Pacific War model for air reinforcements and replacements did not distinguish the two, nor did it distinguish services or aircraft type. A single pool of air replacement/reinforcement squadrons for all Allied nations was built up, starting in January 1941, at the rates shown in the table below.  A training model was implemented by having these replacement squadrons enter the pool initially untrained. Replacement squadrons with over two years' training were considered fully trained; those with over a year's training were considered moderately well-trained; and those with over three month's training were considered poorly trained. The impact of second-generation Allied aircraft designs was represented by reducing the experience level cutoffs by six months after  February 1943 (e.g. a squadron was fully trained in 18 months.) Replacement squadrons could not be deployed to combat with less than three months' training. Training ceased when a squadron was deployed for combat, but there were mechanisms for improving the training level of deployed squadrons if they performed well in combat. There was a very simple model of air-sea rescue. While crude, this air replacement/reinforcement model captured the growing skill of Allied airmen as the war progressed.

Note that this air replacement/reinforcement schedule assumes that availability of pilots is more crucial than availability of aircraft. This was largely the case during the war.

Allied air squadron reinforcement/replacement schedule

Months    
Squadrons entering training
1941-1 to 1941-11
10 per month
1941-12 to 1942-12
20 per month
1943-1 to 1943-12
35 per month
1944-1 to 1944-12
50 per month
1945-1 to 1945-7
70 per month

Further information on training rates for Navy, Marine, and Coast Guard pilot training rates can be gleaned from the following tables of pilots on active duty and pilots completing training.

U.S. Navy pilots on active duty

1 July
Navy officer
Navy enlisted
Marine officer
Marine enlisted
1941
3,483
629
453
52
1942
9,059
732
1,284
85
1943
20,847
774
4,898
132
1944
37,367
475
10,416
41
1945
49,380
439
10,229
47

Naval aviators (Navy, Marine, Coast Guard) completing training

Year
Pilots completing training
1941
3,112
1942
10,859
1943
20,842
1944
21,067
1945
8,880


The U.S. Army trained 193,400 pilots, including 35,000 Army fighter pilots, during the war. This is the total for all theaters. Most Navy and almost all Marine pilots went to the Pacific, but the Army sent an almost mathematically precise 30% of its squadrons to the Pacific, in accordance with the "Germany First" policy. This fraction would have begun increasing in 1945 as victory loomed in Europe. Pilot training was strongly peaked around December 1943, when 74,000 students were in the training pipeline, dropping to 8000 students in training by the time the war ended.


References

"93rd Seabee Battalion" (accessed 2010-10-11)

Bradley et al. (1992)

DANFS

Grossnick and Armstrong (1997)

Morison (1948, 1949)

Maurer (1982)
Molesworth (2008)

Morton (1953)

Roberts (2000; accessed 2010-1-11)

Rottman (2002)

Stanton (2006)

Tillman (1997a, 1997b)

Victory Games (1985)

Willmott (1982)



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