Location of IJN personnel in the Japanese Home Islands

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BobTheBarbarian
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Location of IJN personnel in the Japanese Home Islands

#1

Post by BobTheBarbarian » 11 Nov 2017, 00:09

Hello,
At the end of World War II, approximately how many Japanese naval personnel were located on each of the main islands (Kyushu, Hokkaido, Honshu, and Shikoku) together with outlying areas?

After the disarmament period, the United States kept a detailed tally, down to the last digit, of the number of army troops in each of the Area Armies and other units, as well as the total number of naval personnel in ALL of Japan (about 1,920,000 including civilian employees according to MacArthur's headquarters and 1,962,800 according to the Ministry of Health and Welfare in 1965), but neither of these figures had a subtotal for each main island or prefecture, unlike the Army.

Is there any data on this?
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Re: Location of IJN personnel in the Japanese Home Islands

#2

Post by wdgysin » 12 Nov 2017, 04:38

Here is the location of the Final Report of the Demobilization of the Japanese Armed Forces by the SCAP dated
31Dec46. part IV covers the IJN at the end of the war. The other three parts cover the IJA and forces abroad.
You can download all the parts or just the part on the Navy.
http://cgsc.contentdm.oclc.org/cdm/comp ... /351/rec/2


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Re: Location of IJN personnel in the Japanese Home Islands

#3

Post by BobTheBarbarian » 12 Nov 2017, 05:35

wdgysin wrote:Here is the location of the Final Report of the Demobilization of the Japanese Armed Forces by the SCAP dated
31Dec46. part IV covers the IJN at the end of the war. The other three parts cover the IJA and forces abroad.
You can download all the parts or just the part on the Navy.
http://cgsc.contentdm.oclc.org/cdm/comp ... /351/rec/2
Thanks, but I already indirectly referenced that data in the OP. Although there are charts detailing how many in TOTAL the Japanese Navy had and how quickly they were demobilized, there is no breakdown by region like there is for the Army.
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Re: Location of IJN personnel in the Japanese Home Islands

#4

Post by Wellgunde » 12 Nov 2017, 23:45

Unfortunately, you are not going to find a breakdown of IJN personnel totals at war's end by either prefecture and/or island in any English or Japanese language secondary source material. The Japanese 2nd Demobilization Bureau reported personnel figures to SCAP by command only, without regard to prefecture and island. The [joint] Pacific Order of Battle Conference Report dated 18 Sep 1945 lists Navy commands, units, and organizations by location and includes personnel totals. Referring each unit location to a map of Japan will allow you to keep a running total of strengths by prefecture and island. There is, however, a problem with this document. It is an intelligence work and thus subject to the inaccuracies which infect this type of document. It missed some units entirely and under reported the strengths of others. For a truly accurate picture you need to consult the Report of Occupation submitted circa October 1945 by each major occupation command (e.g. V Amphibious Corps). These include a list of each IJA and IJN unit within the occupation command's area of responsibility and includes among other items the name of the unit's commander, its strength, and its location (city or town).
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Re: Location of IJN personnel in the Japanese Home Islands

#5

Post by BobTheBarbarian » 15 Nov 2017, 05:04

Wellgunde wrote:Unfortunately, you are not going to find a breakdown of IJN personnel totals at war's end by either prefecture and/or island in any English or Japanese language secondary source material. The Japanese 2nd Demobilization Bureau reported personnel figures to SCAP by command only, without regard to prefecture and island. The [joint] Pacific Order of Battle Conference Report dated 18 Sep 1945 lists Navy commands, units, and organizations by location and includes personnel totals. Referring each unit location to a map of Japan will allow you to keep a running total of strengths by prefecture and island. There is, however, a problem with this document. It is an intelligence work and thus subject to the inaccuracies which infect this type of document. It missed some units entirely and under reported the strengths of others. For a truly accurate picture you need to consult the Report of Occupation submitted circa October 1945 by each major occupation command (e.g. V Amphibious Corps). These include a list of each IJA and IJN unit within the occupation command's area of responsibility and includes among other items the name of the unit's commander, its strength, and its location (city or town).
That's what I was afraid of.

A bit more backstory: the question in the OP came from a problem about Japanese strength on Kyushu in 1945. A number of sources, including recent works, place Japanese manpower at 900,000 or thereabouts while the Sixth Army's analysis of the their defense plan places troop levels at 735,000, of whom 25,000 were stationed on outlying islands. The most precise tally, given by D.M. Giangreco in "Hell to Pay," is 916,828, supposedly for "military personnel either in position or in various stages of deployment" at wars' end, citing this table (https://history.army.mil/books/wwii/Mac ... s/p_86.jpg) in the Reports of General MacArthur as his source. The only problem is, the section where his figures are pulled from (the values for the prefectures of Kyushu) is a list of demobilized former military members living in Japan at the end of 1948! This is a grievous error, and an especially shocking one since I consider Giangreco to be the foremost author on the subject.

Seeing this, I went to try and find any old sources that could support or refute the similar claims of other publications (Frank also gives 900,000, as does MacEachin), or the 735,000 figure given by Sixth Army G-2. I know that SCAP identified around 480,000 IJA ground troops in Kyushu after the occupation (see both the Reports and CARL link), but this alone leaves a lot to be desired since it excludes air force and naval personnel, as well as any of the over 700,000 civil employees of the IJN who might be included along with them. Thus, without definite tallies we can't know if the sizable discrepancy between the Sixth Army's figures and those of the aforementioned authors can be chalked up to simple exclusion of certain classifications of personnel, or to sloppiness as was the case with Giangreco.
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Re: Location of IJN personnel in the Japanese Home Islands

#6

Post by Wellgunde » 15 Nov 2017, 07:05

I think you may have misinterpreted the chart you referenced. Column 2 is not the number of demobilized personnel resident in Japan in 1948. It is the number of military personnel who were stationed in Japan at the time of the surrender. Do you have some page numbers for Gangreco's figures?
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Re: Location of IJN personnel in the Japanese Home Islands

#7

Post by BobTheBarbarian » 15 Nov 2017, 15:00

Wellgunde wrote:I think you may have misinterpreted the chart you referenced. Column 2 is not the number of demobilized personnel resident in Japan in 1948. It is the number of military personnel who were stationed in Japan at the time of the surrender. Do you have some page numbers for Gangreco's figures?
The claim is made on page 93, "IGHQ correctly inferred that southern Kyushu would likely be the next target and were already moving quickly and decisively to reinforce Kyushu with a massive number of troops before it could be cut off by US air and sea power, and 916,828 personnel were either in position or in various stages of deployment on the island at the time of surrender," with the citation linked to the above chart.

The context for the chart in the original source material, "Volume I supplement to the Reports of General MacArthur,
Chapter VII p. 266," (https://history.army.mil/books/wwii/Mac ... ch8.htm#s3), indeed states that it is an "Analysis of population, military and police strength by prefecture 15 December 1948," including demobilized soldiers who had since been repatriated, with more detail on the following pages.
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Re: Location of IJN personnel in the Japanese Home Islands

#8

Post by Wellgunde » 18 Nov 2017, 05:08

I have taken a look at my copies of Hell to Pay and and the Reports of General MacArthur. Now that I've seen everything in context the problem is much clearer. Giangreco has, by using the figures in the chart on page 286 of the reports, made a very large error. The chart, as you have correctly pointed out, has absolutely nothing to do with active military strength at the end of the war. SCAP was concerned with communist influence on the Japanese population (particularly among veterans) and there was a lingering fear at SCAP that the occupied might rise up against the occupiers. The chart shows the ratio between the outnumbered occupation forces and the Japanese population. When you add up the totals on column two of the chart for the seven Kyushu prefectures, you arrive at 916,828 which is what Giangreco says on page 93 of his book was the number of troops in Kyushu and available for reinforcement. What was he thinking?

Since you asked specifically about Naval forces in Kyushu, here is some more information:
1. Documents submitted to the Supreme Commander Allied Powers by the Japanese mission to negotiate surrender at Manila, dated 15 August 1945, gives the following strength figures for Kyushu:
Sasebo Naval District 94,755
5th Air Fleet 97,059
7th Fleet 6,571
2. Progress of Demobilization of the Japanese Armed Forces, dated 1 October 1945, gives the following strength figures for Kyushu:
Sasebo Naval District 98,590
5th Air Fleet 73,354
7th Fleet 7,251
The discrepancy between the figures given in 1 and 2 above can probably be attributed to the confusion reigning at IGHQ at the time of the surrender. The mission to Manila had only a very short time to compile the data requested by SCAP. There was much updating of the numbers by the Demobilization Bureaus in the year following the surrender as more accurate information became available.
3. Sixth Army's The Japanese Plans for the Defense of Kyushu, dated 31 December 1945, gives a very different picture )This document was included in Giangreco's book as Appendix B. This document gives the total for Japanese naval forces on Kyushu as 55,000. That figured is arrived at by subtracting the 680,000 Kyushu total given in Sixth Army's Estimate of the Enemy Situation with Respect to Operation Olympic, dated 1 August 1945 (Giangreco's Appendix A) from the 31 December 1945 Sixth Army document. The latter states that the difference between the two total strength figures for Kyushu was due to undercounting of IJN forces in the former document. It would seem that Sixth Army G2 was still behind the power curve. For example, the 5th Marine Division reported on 12 October 1945 that there were 12,000 to 15,000 men just at the Ainoura Naval Training Station. What was going on at Sixth Army? Were they not aware of the Manila conference numbers? Were they not talking to the Demobilization Bureaus? Were they not reading the mail?
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Re: Location of IJN personnel in the Japanese Home Islands

#9

Post by BobTheBarbarian » 27 Nov 2017, 03:32

OP here. Following up, the best I could come up with was this list of Naval combat personnel (but not administrative or other) in various locations within the Japanese mainland as presented on page 24 of JM-85, "Preparations for Operations in Defense of the Homeland." It gives the following figures:

Miura Peninsula - 12 battalions (approx. 20,000 personnel)
Kure Base area - 6 bns (10,000)
Sasebo Base area - 10 bns (16,000)
Maizuru base area - 6 bns (10,000)
Shimokita Peninsula - 6 bns (9,000)
Chinkai Naval Guard district - 3 bns (3,000)
Southwest District of Shikoku - 6 bns (10,000)

The list, however, seems incomplete. It does mention that all Naval ground forces were under effective operational control of the Army, so maybe more information can be found in former IJA sources.
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Re: Location of IJN personnel in the Japanese Home Islands

#10

Post by Wellgunde » 28 Nov 2017, 22:12

Thanks BtB. I think the JM-85 numbers may be a little low. It appears to me that they have included the ad hoc naval defense battalions but excluded the SNLF battalions. The Miura Peninsula is the Yokosuka area. This may also included Navy ground units across Tokyo Bay in Chiba. The Shimokita Peninsula area is in northern Honshu and was under the Ominato Guard District. The Chinkai Guard District was in Korea. Shikoku came under the jurisdiction of the Kure Naval District.

Army sources ignore the Navy and vice versa. Were the authors of JM-85 former army officers, navy officers or both? If only army, their numbers might be suspect.

Back to Giangreco, was he trying to inflate Japanese troop strength on Kyushu in order to bolster his case that higher Japanese troop strength would have meant higher U.S.casualties thus providing greater justification for the use of nuclear weapons?
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Re: Location of IJN personnel in the Japanese Home Islands

#11

Post by BobTheBarbarian » 29 Nov 2017, 08:51

Wellgunde wrote: Army sources ignore the Navy and vice versa. Were the authors of JM-85 former army officers, navy officers or both? If only army, their numbers might be suspect.
Considering that JM-85 covered the Naval aspect of the planned defense of Japan, it was almost certainly written by former IJN officers.
Back to Giangreco, was he trying to inflate Japanese troop strength on Kyushu in order to bolster his case that higher Japanese troop strength would have meant higher U.S.casualties thus providing greater justification for the use of nuclear weapons?
He very well might have been. In an article written in 1996 ("Casualty projections for the Invasion of Japan," http://theamericanpresident.us/images/projections.pdf) Giangreco notes that in 1945 US planners cautioned that the IJA might eventually attain a strength of 5 million as opposed to the 3.5 million they originally believed. Years later in chapter 9 of "Hell to Pay," however, Giangreco spins this by presenting it as the Japanese strength for the Home Islands only ("The Imperial Army, on Japan itself, was gearing up to be nearly twice as large as the estimated 3.5 million the Army's original manpower requirements were based on"). He backs this up with a footnote (number 125 in the above article) which reads "The total number of Japanese armed forces personnel demobilized by the U.S. Military Government after the surrender was 6,465,435, including 784,047 on Kyushu. MacArthur in Japan: The Occupation: Military Phase, vol. 1, supplement, p. 266, from the Reports of General MacArthur (Tokyo: SCAP, 1950)." Note that the 784,047 on Kyushu in this case is just the total for that island from the original table minus the figure for Kagoshima prefecture, 916,828 - 132,781 = 784,047. Thus, Giangreco on multiple counts attempts to present literally the entire IJA as what would have been faced by the US attackers on Japan alone had Operation Downfall proceeded. While surely both the arguments put forward in the rest of his book and by other authors such as Frank illustrate that the cost of invasion would have greatly exceeded that of the A-bombs without the need to falsify data, the pattern here is deeply disturbing and reeks of dishonesty, which is again dismaying as I regard Giangreco as the one of the premier scholars on Downfall.


I can say that the number of 900,000 for Kyushu appears in other sources as well, some of which predate "Hell to Pay," notably Richard B. Frank's "Downfall" and Douglas MacEachin's "The Final Months of the War with Japan" (https://www.cia.gov/library/center-for- ... 10001.html); in the latter the citation is given as one of Ed Drea's publications which in turn references "Boeicho, Boi kenshujo, [Japanese National Institute for Defense Studies], ed., Senshi sosho, Vol. 57: Hondo kessen jumbi: Kyushu no boei [Official Military History, Vol, 57, Preparations for the Decisive Battle of the Homeland: Defense of Kyushu] (Tokyo, 1972); and Hayashi Saburo, Taiheiyo senso rikusen gaishi [An Overview of Army Operations in the Pacific War], Tokyo, 1951)." Unfortunately this does not appear to be available in English.
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