Iwojima from Japanese Viewpoint

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hisashi
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Iwojima from Japanese Viewpoint

Post by hisashi » 09 Dec 2005 02:46

1.Ogasawara Group

Before 1944, only a navy airfield (without aircrafts except a few months in 1944) and small navy garrison were located in Iwojima. The army had some coastal fortification in some of Ogasawara Islands, and Chichijima fortress HQ controlled them.
In February, after the loss of Marshall Islands, Japanese army began to think seriously of defending Ogasawara Islands. In this period, however, Ogasawara was considered as rear area relative to Truk or Saipan.
Army troops in this area were under 31st army in Saipan, Army and navy agreed 31st army was under Central Pacific Theater Fleet in Saipan.
Army located some battalion-sized and company-sized fort infantry troops along with some artilleries in Iwojima and navy gradually reinforced coastal artilleries and AA guns.
The commander of Chichijima fortress HQ was concurrently appointed as the commander of Ogasawara Group. This group was in the paper, and this appoint meant that he was authorized to command army troops in Marcus Island and many small reinforcement troops in Ogasawara area.

2.Kuribayashi

The army must sort out the order of battle among many small troops but it needed a new HQ with staffs enough to manage division-sized personnels. They did so. In May 1944 they raised 109th division in Ogasawara, sending new HQ staffs, communication troops and various , balanced support troops from Tokyo divisional district. This division had special form reflecting the situation in there islands; the division had two mixed brigades, 1st in Chichijima and 2nd in Iwojima. fort infantry troops were converted to independent infantry battalions, directly attached to either mixed brigade. The army appointed Lt.Gen.Kuribayashi to the commander of 109th division and Ogasawara Group.
During the battle in Saipan, navy 27th air squadron (land-based air units) arrived to Iwojima along with some army aircrafts, but soon damaged and mostly retreated to Japan. squadron HQ remained in Iwojima.
Kuribayashi thought Iwojima was more valuable for the allied than Chichijima. Seeing the situation in recent landing and ongoing battle in Guam/Saipan, he abandoned the idea of preventing landing at seashore. He ordered to locate their fortification inland so that they resist as long as they could.

3.Loss of Saipan and reinforcements

The situation in Saipan was desperate even from the eye of Japanese GHQ. They reinforced Iwojima with troops kept for repulsive landing to Saipan; tank 26th regiment, independent mortar 20th battalion and two middle mortar battalions. They also sent 145th infantry regiment, a part of 46th division moving to the east end of Java, but stayed in Japan because of bad shipment situation. The rest of 46th division already in Indonesia eventually moved to west end of Malaysia and they were nearby Taiping at the end of war.
According to Senshi Sosho five high-velocity gun battalions were also intended for the defense of Indonesia with 46th division, but this number of 47mm guns are unusual for reinforcement to ordinal division. Perhaps they were gathered according to the request of firepower from Kuribayashi.
Moreover they newly raised independent mixed 17th regiment for Ogasawara area. Most of this regiment went to Chichijima and only 3rd battalion was placed at Iwojima.
Navy raised in June the 204th naval construction battalion, which contained 250 to 300 hired koreans and about 200 hired inhabitants (about 1600 men in the unit). Another 30 inhabitants were hired by the army as advisors of vegetable raising in this severe field. This unit took over the job of a detachment from department of facilities, Yokosuka Chinjufu. As a unit the detachment disappeared, but I have no idea how many workers continued to work in 204th.
In November 27 12 Zero fighters and 2 recce planes (Nakajima C6N Saiun 'Myrt') raided Saipan and strafed B-29 on the ground. This is perhaps the last sortie by Japanese from Iwojima.

4.The order of battle in December 1944

I found a very excellent content on this topic, so I will only comment on this TO&E.
http://militaryhistory.about.com/gi/dyn ... IJcmd.html

'Brigade Artillery Group' was a kind of battlegroup. This group was a mixed-up team of large-calibre army weapon troops in Iwojima. Roughly speaking, Kuribayashi attached infantry guns to local battle groups, kept tanks, HMG battalions and 47mm high-velocity guns as tactical reserves and controlled artilleries as divisional/brigade artilleries.
Trench Mortar 1st Company was an independent unit raised for Iwojima.
Engineer unit of 2nd mixed brigade was the third company of independent engineer 9th regiment. It had slightly more than 300 men.
2nd and 3rd trench mortar battalion is 'chu- (middle)' mortar battalion. A small difference of name reflects types of weapons they had. We will discuss it later.

5.The locality and quality of personnels

Except 145th infantry regiment, most of troops in Iwojima were raised in 1944. The personnels were often old reserve ones. Senshi Sosho refers to the conversation between Kuribayashi and staff officers who visited Iwojima. Kuribayashi said 'Batallion leaders from 19th or 24th class are no good'. The 19th class of army war school graduated in 1907. Well known officer in this class were Lt.Gen. Masaharu Homma (1887-1946) and Gen. Hitoshi Imamura (1886-1968). Kuribayashi himself was in the 26th class.

The following is a list of troops and related divisional districts.

Most of HQ troops of 109th division: Tokyo
Independent Trench Mortar 1st Company:Kyoto
145th Regiment: Kumamoto (mainly Kagoshima prefecture)
Field Hospital (109th division): Tokyo
Third Battalion,17th Independent Mixed Regiment: Hiroshima
26th Tank Regiment: Tokyo
309th Independent Infantry Battalion: Sendai and Kumamoto
310th Independent Infantry Battalion: Hiroshima
311th Independent Infantry Battalion: Kumamoto
312th Independent Infantry Battalion: Kurume
314th Independent Infantry Battalion: Kurume
Engineer Unit: Utsunomiya
Second Mixed Brigade artillery unit: unknown
Second Middle Mortar Battalion: Kurume
Third Middle Mortar Battalion: Tokyo
20th Independent Artillery Mortar Battalion: Korea
8th Independent Anti-Tank Battalion: Tokyo
9th Independent Anti-Tank Battalion: Tokyo
10th Independent Anti-Tank Battalion: Osaka
11th Independent Anti-Tank Battalion: Hiroshima
12th Independent Anti-Tank Battalion: Hiroshima
1st Independent Machine Gun Battalion: Tokyo
2nd Independent Machine Gun Battalion: Tokyo
20th Special Machine Cannon Unit: Hiroshima
21st Special Machine Cannon Unit: Hiroshima
43rd Special Machine Cannon Unit: Tokyo
44th Special Machine Cannon Unit: Tokyo
Rocket Gun Company: Unknown
Fifth Fortress Engineer Company: Kumamoto
21st Well Drilling Team: unknown
Iwo Freight Depot Team:unknown
Engineer unit, mixed 1st brigade: Zentsuji

6.Deployed Weapons

Two months after Kuribayashi came to Iwojima, the army revised the doctorine of defense against allied landing, as he intuitively noticed and ordered. Under superior bombing and naval fire for the enemy, setting firepoints close to seashore makes forts easy to destroy. Threatening the enemy as long as possible is the most desirable in this situation.
Unfortunately before Kuribayashi could think of navy men, navy guns were already located close to seashore. The army did not demand navy to relocate the pieces more inside.
Navy had in Iwojima (numbers are pieces of guns, not of fortifications);
17 12.7cm AA guns
2 fortifications with 7.7cm AA guns (# of pieces unknown)
2 fortifications with 8cm AA guns (# of pieces unknown)
4 15cm guns
4 14cm guns
3 12cm guns
and many 25mm AA machine guns.

Second mixed brigade artillery unit, artillery batallion of 145th regiment and artillery battery of tank 26th regiment had in total:
10 type-38 12cm howizer (old weapon from Russo-Japanese War)
27 75mm fild guns of various types (modified type 38, type 90)
5 75mm mountain guns

20th independent artillery mortar battalion:
12 type-98 320mm spigot mortars
24 type-94 90mm mortars.

2nd and 3rd middle mortar battalion:(each)
10 type-96 150mm mortars
6 type-94 90mm mortars

Independent Trench Mortar 1st Company:
12 navy-made type-2 81mm mortars
note: navy SNLF had been supplied small arms from the army, but it became difficult because of weapon shortage in the side of the army. From 1943 the navy began to produce type-2 81mm mortar similar to army type-97 81mm mortar, common in armies of the world, using factories in Yokosuka chinjufu. In this case navy supplied mortars for an army company. This entry is based on 'Non-Infantry Regiments of Japanese Army',edited and published by Shi-Jinbutsu Oraisha, 1994.

Infantry gun companies of eight infantry battalions had:(each)
2 type-92 70mm infantry guns
2 type-94 37mm high-velocity guns

Rocket gun company:
40 launchers, 434 rockets (perhaps 20cm and 40cm type were mixed)

20th, 21st, 43rd and 44th special machine cannon unit:
unknown, but similar unit in other theater had 10 to 12 type-98 20mm AA guns or navy-made 25mm AA guns.

1st and 2nd independent machine gun battalion:
As a standard each battalion had 24 type-92 HMGs. (3 companies*4 platoons*2 squads)

Tank 26th regiment had 11 Type-97 Medium Tanks (old and new turrets) and 12 type-95 light tanks. After the war a turret of type-89 medium tank, but it is said this was a piece carried in for fortification.

7.Order of Battle in Action

Here is an excellent collections of tactical maps.
http://militaryhistory.about.com/gi/dyn ... ojima.html

Kuribayashi formed 6 aerial battlegroups (chiku-tai) and his own battlegroup (kita-chiku kyotentai). each of them were an infantry battalion with infantry guns and similar support weapons. Navy men in seashore fortifications went under the command of these battlegroups when the allied approached. The following is the infantry battalion in each battlegroup.
North battlegroup: 3rd/17th mixed brgd.
East: 314th
West: 311th
South: 309th
Middle: 1st/145th rgt.
Suribachi Mountain: 312th
note: Middle battlegroup covered the gap of south battlegroup and Suribachi Mountain. So the first landing came to the area of South and Middle battlegroups.
In this map
http://www.rickard.karoo.net/Maps/IwoJima2m.jpg
Middle battlegroup is ignored, though 1st/145th is rightly recognized.
Some tanks were attached to south and west battlegroups, but most tanks were reserved in the southwest of 3rd airfield.
310th battalion was the first reserve deployed in February 20 to build second defense line. tank 26th regiment and 3rd/145th were put into action in the next day. 2nd/145th became Kuribayashi's last battalion, along with engineer units and navy HQ staffs. At dawn of March 26, Kuribayashi made his final assault, heading by himself with Rear Admiral Ichimaru, the commander of 27th air squadron. Kuribayashi was very rational man, but in this last moment, he did a little bit irrational; the two commanders wore white outstanding cross brace. He ordered in advance that his corpse should not be taken to the enemy. He was wounded and commited suicide when he could not command any more because of heavy bleeding. His staffs buried him somewhere.

Maj.Gen.Senda, the commander of mixed 2nd brigade, commited suicide in March 17 in a small underground fort while retreating to divisional HQ. His long-missing remnants were found in 1983.

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Peter H
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Post by Peter H » 11 Dec 2005 06:26

The 26th Tank Regiment originally lost most of its tanks,sunk at sea on a transport?

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hisashi
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Post by hisashi » 11 Dec 2005 17:07

Peter H wrote:The 26th Tank Regiment originally lost most of its tanks,sunk at sea on a transport?

Yes, once they lost 28 tanks in July 1944 in halfway to Iwojima, and rebuilt the regiment with 23 tanks.

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Re: Iwojima from Japanese Viewpoint

Post by Brady » 23 Feb 2010 07:43

Wounderfull detail.

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Re: Iwojima from Japanese Viewpoint

Post by Honza » 22 Jun 2010 21:30

I'm going to bump this up because it is relevent to my reasearch on the battle.

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Re: Iwojima from Japanese Viewpoint

Post by LWD » 23 Jun 2010 14:55

Over on the IJN board there has been a series of posts detailing the IJN losses in transit often by ship and unit. For those interested it's worth digging around over there.

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Re: Iwojima from Japanese Viewpoint

Post by Fatboy Coxy » 02 Jul 2010 06:43

Excellent Post Hisashi

I have a couple of questions though. I guess the 5 high-velocity gun battalions you mention are the 8th to 12th Anti Tank Battalions in the OOB. Do you know how many 47mm guns they had each, and would they have also been equipped with any anti-tank rifles?

hisashi wrote:They also sent 145th infantry regiment, a part of 46th division moving to the east end of Java, but stayed in Japan because of bad shipment situation. The rest of 46th division already in Indonesia eventually moved to west end of Malaysia and they were nearby Taiping at the end of war.
According to Senshi Sosho five high-velocity gun battalions were also intended for the defense of Indonesia with 46th division, but this number of 47mm guns are unusual for reinforcement to ordinal division. Perhaps they were gathered according to the request of firepower from Kuribayashi.

8th Independent Anti-Tank Battalion: Tokyo
9th Independent Anti-Tank Battalion: Tokyo
10th Independent Anti-Tank Battalion: Osaka
11th Independent Anti-Tank Battalion: Hiroshima
12th Independent Anti-Tank Battalion: Hiroshima

Second mixed brigade artillery unit, artillery batallion of 145th regiment and artillery battery of tank 26th regiment had in total:
10 type-38 12cm howizer (old weapon from Russo-Japanese War)
27 75mm fild guns of various types (modified type 38, type 90)
5 75mm mountain guns


Regarding the second mixed artillery unit, I would expect the artillery battalion from the 46th Infantry Div's Artillery Regiment (attached to 145th Infantry Regiment) to be equipped with 12 75mm Field Guns. Do you know what guns would have been assigned to the 26th Tank artillery battery. If I suggest 3-5 guns, that leaves 10 x 12cm, 10-15 x 75mm and 0-5 75mm mountain guns. So we must have had a battalion of 12cm guns, a battalion or several independant batteries of 75mm field guns and 1 battery of mountain guns (if it isn't the 26 tank battery), do you know their identity.

Lastly the OOB web link lists Engineer Battalion, Captain Kikuzo Musashino, as part of the 46th Infantry Division attachment that came. Would this have been company size (300 men) with the Japanese calling their Divisional Engineer battalions "Regiments" in the same way as the British, so a battalion from one of these "Regiments" would actually be a company.

Regards

Steve

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hisashi
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Re: Iwojima from Japanese Viewpoint

Post by hisashi » 02 Jul 2010 11:09

I don't know of the first and second question. Usually I reveal all details I have, and I don't have more.

In my impression, when IJA gave rthe name 'regiment' to battalion-sized group of men, they thought of officers' post. A regiment was led by a colonel and some (typically two) Lt.Col. in the HQ for general administration and coordinated training. A battalion had only one major or Lt.Col. so engineer regiment nust be a regiment for engineer offisers' chance of promotion.

On Iwojima the situation was totally different. 145th (infantry) regiment only had an engineer company, led by Capt.MUSASHINO.
The 109th division had in total 5 company-sized engineer units from various origin. Kuribayashi formed a temporal engineer regiment by the 5 companies, led by Major MAEKAWA Yoji. A few webpages state mostly the same information and perhaps the origin is senshi sosho.

http://officers.hp.infoseek.co.jp/22iko ... jima-1.htm

Note: the name all in capital is a family name.

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Re: Iwojima from Japanese Viewpoint

Post by Akira Takizawa » 02 Jul 2010 14:21

> Do you know how many 47mm guns they had each,

12 pieces

> and would they have also been equipped with any anti-tank rifles?

No. AT rifles were deployed at infantry.

> Do you know what guns would have been assigned to the 26th Tank artillery battery.

8 Type 90 75mm Field Guns.

Taki

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Re: Iwojima from Japanese Viewpoint

Post by Fatboy Coxy » 03 Jul 2010 07:32

hisashi wrote:I don't know of the first and second question. Usually I reveal all details I have, and I don't have more.


I'm sorry hisashi, this post wasn't meant as a critisism, your post was very informative.

And once again thank you Taki for your post.

Counting the artillery pieces up we have
12 x 75mm field guns with a battaltion of 46th Inf Div artillery regiment (attached to 145th Inf Regt)
8 x 75mm field guns with battery of 26th Tank Regt
10 x 120mm guns with ? arty battalion
7 x 75mm Field guns with ? battalion/battery
5 x 75mm Mountain guns with ? battalion/battery

dose anyone know what units these were and did they suffer losses during the transportation to the island, or were they divided between islands as a needs must?

Steve

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Re: Iwojima from Japanese Viewpoint

Post by Akira Takizawa » 03 Jul 2010 08:26


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Re: Iwojima from Japanese Viewpoint

Post by Fatboy Coxy » 03 Jul 2010 13:48

Thank you again Taki, your web site is very informative.

The allocation of guns to units looks to have been done with regard to what fire missions they would be given, unless its replacing lost guns with whats available. Normally a artillery battalion from a divisional artillery regiment would have of been issued with only one type, 75mm or possibly 105mm. 120mm guns would normally be held in independant battalions.

I can see how the Mortars and Howitzers would be most useful. The range is not important as much as the effect plunging fire has on dug in troops. And it must be easier to hide and camouflage these guns.

Steve

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Re: Iwojima from Japanese Viewpoint

Post by john whitman » 03 Jul 2010 14:16

Taki:

I agree. This is a nice site. But I have a question about the 3rd Independent Mountain Gun Regiment on Saipan. How did the 3rd Regiment acquire 150cm howitzers? Were these 150cms part of the regiment before it left Manchuria? I understand that the 3rd was sent to Saipan without horses or trucks. Is this correct?

Or did the howitzers and men join the regiment on Saipan? Were the howitzers sent to Saipan and a unit then created?

Thanks for the help.

John

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Re: Iwojima from Japanese Viewpoint

Post by john whitman » 03 Jul 2010 23:02

Ooops. I meant 150mm.

John

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Re: Iwojima from Japanese Viewpoint

Post by Akira Takizawa » 04 Jul 2010 02:09

3rd Independent Mountain Gun Regiment had two battalions. But, one battalion had been already sent to Kuril. So, when it was sent to Saipan, a battalion equipped with 15cm howitzers from 9th Field Heavy Artillery Regiment was attached to it.

It is hard to believe that it had no horse, but I cannot confirm it by my sources at hand. I will check it, when I go to the library.

Taki

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