US divisions for Coronet 1946

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Larso
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US divisions for Coronet 1946

Post by Larso » 08 Oct 2021 08:09

The US Pacific theater divisions were all assigned to either the 6th or 8th Armies. The US 1st army was to be transferred from Europe to assist with the second phase of operation Downfall.

I was sure I once read which European based divisions were allocated to the invasion of Japan. Now I can't seem to find a list of these, apart from the 13th and 20th Armoured being assigned to the 8th Army. I know the 86th was being transferred and I'm pretty sure the 13th Airborne was also slated to participate but does anyone have a complete list?

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Kingfish
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Re: US divisions for Coronet 1946

Post by Kingfish » 08 Oct 2021 09:47

Perhaps this might help:
https://apps.dtic.mil/sti/pdfs/ADA637723.pdf

Scroll to the bottom of page 12 and proceed from there
The gods do not deduct from a man's allotted span the hours spent in fishing.
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Larso
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Re: US divisions for Coronet 1946

Post by Larso » 09 Oct 2021 13:04

Perfect - thank you very much!

The 4th would've had a very long war by the end.

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Kingfish
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Re: US divisions for Coronet 1946

Post by Kingfish » 09 Oct 2021 19:54

Larso wrote:
09 Oct 2021 13:04
The 4th would've had a very long war by the end.
To which the 1st Marine division would reply "Hold my Beer"
The gods do not deduct from a man's allotted span the hours spent in fishing.
~Babylonian Proverb

BobTheBarbarian
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Re: US divisions for Coronet 1946

Post by BobTheBarbarian » 11 Oct 2021 22:24

From "Staff Study Operations Coronet" (15 August 1945), the list of divisions for the invasion of Honshu was as follows:

Eighth Army
X Corps
24th Infantry Division
31st Infantry Division
37th Infantry Division
XIV Corps
6th Infantry Division
32nd Infantry Division
38th Infantry Division
XIII Corps
13th Armored Division
20th Armored Division
"D" Corps
4th Infantry Division
87th Infantry Division
8th Infantry Division

First Army
XXIV Corps
7th Infantry Division
27th Infantry Division
96th Infantry Division
III Amphibious Corps
1st Marine Division
4th Marine Division
6th Marine Division
"B" Corps
86th Infantry Division
44th Infantry Division
5th Infantry Division

AFPAC Reserve
97th Infantry Division
"C" Corps
2nd Infantry Division
28th Infantry Division
35th Infantry Division
11th Airborne Division
"E" Corps
95th Infantry Division
104th Infantry Division
91st Infantry Division

Strategic (US)
Divisions as required to permit a buildup of four divisions per month beginning in May 1946. Per "Operations Against Honshu (Tokyo Plain)" (11 December 1944), these forces would be as follows:
5 armored divisions
11 infantry divisions
1 mountain division

Final organization (excluding British/Commonwealth) - 1 Theater command, 2 Army Groups, 5 Armies, 15 Corps, 45 divisions (2,000,000 men, 377,500 vehicles).

Sources: Staff Study Operations "Coronet," 15 August 1945 (https://apps.dtic.mil/sti/pdfs/ADA637723.pdf)
History of Planning Division, ASF vol. 6 part 1(https://cgsc.contentdm.oclc.org/digital ... 1910/rec/2)
The Miracle of Lanciano: Jesus' Real Presence in the Holy Eucharist: https://web.archive.org/web/20060831022 ... tents.html

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Re: US divisions for Coronet 1946

Post by daveshoup2MD » 13 Jan 2022 05:52

Larso wrote:
08 Oct 2021 08:09
The US Pacific theater divisions were all assigned to either the 6th or 8th Armies. The US 1st army was to be transferred from Europe to assist with the second phase of operation Downfall.

I was sure I once read which European based divisions were allocated to the invasion of Japan. Now I can't seem to find a list of these, apart from the 13th and 20th Armoured being assigned to the 8th Army. I know the 86th was being transferred and I'm pretty sure the 13th Airborne was also slated to participate but does anyone have a complete list?
Slightly different source, but in Stanton's US Army WW II Order of Battle he lists the following Army divisions (formerly in the ETO) as already back in the US as of August, 1945 (two months after VE Day, essentially):

13th Armored, 20th Armored, 2nd, 4th, 5th, 8th, 10th Mountain, 44th, 86th, 87th, 95th, 97th, 104th, for a total of 13; with the divisions already in the Pacific (27 total, 21 Army and six Marine) that makes a total of 40, which seems sufficient for the Home Islands, given that containing the Japanese left behind could be left to various US Army and US marine garrisons, the Filipinos, and the Australians...

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Re: US divisions for Coronet 1946

Post by daveshoup2MD » 01 Feb 2022 05:57

daveshoup2MD wrote:
13 Jan 2022 05:52
Larso wrote:
08 Oct 2021 08:09
The US Pacific theater divisions were all assigned to either the 6th or 8th Armies. The US 1st army was to be transferred from Europe to assist with the second phase of operation Downfall.

I was sure I once read which European based divisions were allocated to the invasion of Japan. Now I can't seem to find a list of these, apart from the 13th and 20th Armoured being assigned to the 8th Army. I know the 86th was being transferred and I'm pretty sure the 13th Airborne was also slated to participate but does anyone have a complete list?
Slightly different source, but in Stanton's US Army WW II Order of Battle he lists the following Army divisions (formerly in the ETO) as already back in the US as of August, 1945 (two months after VE Day, essentially):

13th Armored, 20th Armored, 2nd, 4th, 5th, 8th, 10th Mountain, 44th, 86th, 87th, 95th, 97th, 104th, for a total of 13; with the divisions already in the Pacific (27 total, 21 Army and six Marine) that makes a total of 40, which seems sufficient for the Home Islands, given that containing the Japanese left behind could be left to various US Army and US marine garrisons, the Filipinos, and the Australians...
Just to expand on this, the 40 divisions (in total) referenced above breaks down into 29 "standard" infantry (including the 93rd, which due to a lot of reasons beyond the control of its personnel, was a special case), six Marine, two armored, the 1st Cavalry Division (Dismounted), 10th Mountain, and 11th Airborne.

That would give a pretty straightforward organization of 11 "infantry" corps equivalents (nine Army, 27 divisions total, and two Marine 'Phib corps, six divisions total), each with three divisions. Presume the 93rd gets stuck with the various rear area assignments it got historically (presumably in the Philippines, by this point), so that leaves two armored, 1st Cavalry, 10th Mtn. 11th Abn., and the last infantry division, so (on paper) two more corps equivalents.

Seems like 3-4 army level equivalents, even without the planned Commonwealth Corps' deployment...

Seems like the 1st, 6th, 8th, and 10th army headquarters would all be likely to be committed, so all things being equal, that's Hodges, Kruger, Eichelberger, and Stilwell, presumably.

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Pips
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Re: US divisions for Coronet 1946

Post by Pips » 01 Feb 2022 23:50

I'm really surprised that only two Armoured Divisions (13th and 20th) were earmarked for the Invasion. Surely any invasion force would want triple that number.

Was there any reason for such a low allocation? Or were more armoured divisions planned for follow-up landings?

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Kingfish
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Re: US divisions for Coronet 1946

Post by Kingfish » 02 Feb 2022 00:40

Pips wrote:
01 Feb 2022 23:50
I'm really surprised that only two Armoured Divisions (13th and 20th) were earmarked for the Invasion. Surely any invasion force would want triple that number.

Was there any reason for such a low allocation? Or were more armoured divisions planned for follow-up landings?
A couple of guesses on my part:
-The infantry divisions would be packed to the gills with attached armor, and given that US forces were already heavily motorized the real difference would have been negligible.

-The planners saw the terrain and concluded there was little opportunity to employ mass armor formations.

-The same planners saw the opposition and concluded the campaign would be less jog and more slog.
The gods do not deduct from a man's allotted span the hours spent in fishing.
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Re: US divisions for Coronet 1946

Post by daveshoup2MD » 02 Feb 2022 05:12

Pips wrote:
01 Feb 2022 23:50
I'm really surprised that only two Armoured Divisions (13th and 20th) were earmarked for the Invasion. Surely any invasion force would want triple that number.

Was there any reason for such a low allocation? Or were more armoured divisions planned for follow-up landings?
The US Army and Marine divisions in the Pacific basically all had attached separate medium tank battalions; Stanton's US Army Order of Battle lists 14 in the Pacific and eight more back in the US from Europe by August, 1945, the Marines had six. There were another 18 and 7 Army amphibian tractor/tank battalions (in the Pacific or the US), and the Marines had 13 of amtracs. Including the Army's tracked tank destroyer and armored field artillery battalions, and there were probably 70 or more battalions of tracked AFVs in the US forces allocated for DOWNFALL.

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Re: US divisions for Coronet 1946

Post by daveshoup2MD » 02 Feb 2022 05:13

Kingfish wrote:
02 Feb 2022 00:40
Pips wrote:
01 Feb 2022 23:50
I'm really surprised that only two Armoured Divisions (13th and 20th) were earmarked for the Invasion. Surely any invasion force would want triple that number.

Was there any reason for such a low allocation? Or were more armoured divisions planned for follow-up landings?
A couple of guesses on my part:
-The infantry divisions would be packed to the gills with attached armor, and given that US forces were already heavily motorized the real difference would have been negligible.

-The planners saw the terrain and concluded there was little opportunity to employ mass armor formations.

-The same planners saw the opposition and concluded the campaign would be less jog and more slog.
True.

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Re: US divisions for Coronet 1946

Post by jbroshot » 17 Feb 2022 05:47

Somewhat off topic, but don't forget that CORONET was to be proceeded by OLYMPIC, scheduled for Autumn 1945, landings on Kyushu

Sixth Army
I Corps - 25th, 33rd, 41st Infantry Divisions
XI Corps - 1st Cavalry Division, Americal Division, and 43rd Infantry Division
V Amphibious Corps - 2nd, 3rd and 5th Marine Divisions
plus 40th Infantry Division and 158th Regimental Combat Team
Army reserve - 11th Airborne Division

"Sixth Army, field order no. 74: Operation Olympic" can be found here on the CARL site

https://cgsc.contentdm.oclc.org/digital ... 701/rec/14

(FWIW, my father was in the 5th Marine Division)

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Re: US divisions for Coronet 1946

Post by daveshoup2MD » 17 Feb 2022 07:17

jbroshot wrote:
17 Feb 2022 05:47
Somewhat off topic, but don't forget that CORONET was to be proceeded by OLYMPIC, scheduled for Autumn 1945, landings on Kyushu

Sixth Army
I Corps - 25th, 33rd, 41st Infantry Divisions
XI Corps - 1st Cavalry Division, Americal Division, and 43rd Infantry Division
V Amphibious Corps - 2nd, 3rd and 5th Marine Divisions
plus 40th Infantry Division and 158th Regimental Combat Team
Army reserve - 11th Airborne Division

"Sixth Army, field order no. 74: Operation Olympic" can be found here on the CARL site

https://cgsc.contentdm.oclc.org/digital ... 701/rec/14

(FWIW, my father was in the 5th Marine Division)
Thanks for the link. Presuming that Kyushu requires the 6th Army as listed, that leaves (including the other divisions historically in the Pacific, plus those noted above as having already returned from the ETO to CONUS, that total:

13th, 20th armored divisions; 2nd, 4th, 5th, 6th, 7th, 8th, 10th Mountain, 24th, 27th, 31st, 32nd, 37th, 38th, 44th, 77th, 81st, 86th, 87th, 93rd, 95th, 96th, 97th, 98th, 104th; 1st, 4th, 6th Marine divisions; 29 total. Expect the 1st, 8th, and 10th armies would all be involved.

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Re: US divisions for Coronet 1946

Post by BobTheBarbarian » 21 Feb 2022 03:44

According to "History of Planning Division, ASF", vol. 6 part 1 (linked above), 7 US Armored Divisions were to take part in "Coronet" and 45 divisions total; the 13th and 20th Divisions were merely in the first group to be deployed. Overall there would be 7 Armored Divisions, 3 Marine Divisions, 1 Airborne Division, 1 Mountain Division, and 33 Infantry Divisions.

For Olympic, although no Armored Divisions as such were to be committed there were enough tank units to make up over 2,000 if memory serves (Field Order 74 has a precise breakdown of units to be landed).
The Miracle of Lanciano: Jesus' Real Presence in the Holy Eucharist: https://web.archive.org/web/20060831022 ... tents.html

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Re: US divisions for Coronet 1946

Post by jbroshot » 21 Feb 2022 06:03

Here's the entire strategic plan for the invasion of Japan

"Downfall--strategic plan for operations in the Japanese Archipelago", dated 28 May 1945, with maps and tables

https://cgsc.contentdm.oclc.org/digital ... 3387/rec/1

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