IJA Radar

[Mil-tech Bard]

This is the second picture, as the site does not seem to want put it in the same post.

[Wellgunde]

What I have found interesting is the way that the Kume Jima radar seems to have been wipped out in terms of US Navy reporting to the War Department in Washington DC. Based upon this and the OSRD Division 15 report on Radio Countermeasures, it sure looks like the Navy Department was trying to hide the existence of the IJN Kume Jima Radar and the implications of it for the post-war reputations of the USA Navy brass involved in running the Okinawa campaign.

Since the map is dated July 1945, I'm going to assume that it only documents active radar installations. According to a U.S. Seventh Air Force report, "8 P-47s from Ie Jima make bombing, strafing, and rocket attacks on radar and ground installations on Kume Jima in Amami Gunto" on May 18, 1945.


Thank you for the refs; there's a treasure trove of info there. Does report no. 11 cover installations only in Japan and adjacent areas?

[Mil-tech Bard]

>>Since the map is dated July 1945, I'm going to assume that it only documents active radar installations

No. The map includes Aguni Jima, which was taken by US Marines in June 1945.

That is in fact proof that Kume Jima information was not passed from the Navy Department to the War Department. It shows slow information flow from the Pacific to Washington DC and from the Navy's photo intelligence (USN Signals intelligence for radar was under their photographic branch at that time) to the War Deppartment's Military Intelligence Division.

By way of reference, the Kume Jima Radar emitter was spotted by USN submarine patrols prior to the Okinawa landings in Dec 1944/Jan 1945.

>>Does report no. 11 cover installations only in Japan and adjacent areas?

It covers the entire Japanese Empire as of July 1945.

[Mil-tech Bard]

>>According to a U.S. Seventh Air Force report, "8 P-47s from Ie Jima make bombing, strafing, and rocket attacks on radar
>>and ground installations on Kume Jima in Amami Gunto" on May 18, 1945.

I would appreciate it very much if you either post a copy of that report or give the document's reference so I can look it up.

However, the P-47 pilots got it wrong.

I have a US Naval radio countermeasures report (TF 31 Okinawa Report 18 May thru 21 June 1945 [special reports Sec D -- naval communication -- RCM, pg (V)-52]) that the Kume Jima Radar was emitting until 14 June 1945.

This report was among the digitized War Diaries of the US Navy that the FOLD3 service posted in 2012.

[Mil-tech Bard]

Wellgunde ,

See the following link and text regards the date of capture of the Tachi-6 on Kume Jima.


Company "A", 1st Battalion, 7th Marines,
1st Marine Division(1)
30 July, 1945

http://kumejima.warwickhi.com/Marinestakekume.html

"July 2, 1945

At approximately 0330 the 81-mm fired a harassing mission and the enemy returned the fire by spraying the bivouac area and defensive perimeter with two 13.2-mm dual-purpose MG's. The 81-mm fired two missions and neutralized the enemy machine guns. One strecher bearer was critically wounded and died as a result of wounds received from enemy fire.

A coordinated attack was launched at 0730 on the enemy position on the peak at TA 7390-0 by Company "A", Amph Recon Bn. moving south from road at TA 7391R and south. Company "A", 7th Marines, moved west along the ridge from hill at TA 7591-U. Company "B", Amph Recon Bn., was deployed with combat groups on a line generally from TA's 7290-Y-5 to 7290-N. The attack was preceded by preparatory fire from two 75-mm howitzers (LVT(A)'s) and the 60-mm and 81-mm sections. The attack progressed against inaccurate enemy rifle fire; movement was across extreemly steep and rugged terrain where thick vegetation hindered both movement and observation. By 1400 the enemy positions were completely overrun. The bulk of the ememy holding force is believed to have withdrawn and scattered in the wooded area in TA's 7489, 7589, and 7689. Two heavy MG's, caliber 13.2-mm were captured intact by Able Company, 7th Marines. The enemy is estimated to only have one MG, and it has been removed from a crashed plane, probably 7.7-mm.

Enemy radar equipment was destroyed by Able Company, 7th Marines. All troops returned to initial beachhead and occupied their original defensive positions."

[Wellgunde]

The bit about the P-47s was in U.S. Army Air Forces in World War II - Combat Chronology (1941-1945). You can download a PDF here:
http://www.afhra.af.mil/shared/media/do ... 29-036.pdf

It's hard to accept a conspiracy for the deletion of Kume Jima although such things have happened. I think bureaucratic ineptitude, wishful thinking, misfiled reports, fog of war, or a host of similar reasons might be likelier causes. MIS Colonel, "Where's the radar report?" MIS Captain, "We're waiting for confirmation on Kume Jima." MIS Colonel, "We're a week over the deadline; just leave it off and we'll figure it out later."

That's a good catch by the way.

[Mil-tech Bard]

Wellgunde,

I am not big on conspiracies, either.

However, Brass hats "covering their anatomy" when post-war budgets are afoot is a completely different matter.

I have checked against both the 10th Army invasion of Kume Jima and Summary Technical Report of Division 15, NDRC, Vol. 1, RADIO COUNTERMEASURES, Chapter 15 (Pacific radio countermeasure operations) and the Kume Jima radar was not in either.

Tenth Army's report, part 2 of Capture of Okinawa Gunto, did mention a _RADIO_ on Kume Jima...but this was after the Fleet Marine Recon Battalion; Able Company, 7th Marines July 1945 War Diary; Commander Task Group 31.24 ( ComDes Ron 63)'s
Action Report - Capture of KUME SHIMA, Okinawa Gunto, 25-27 June 1945; and the Island Command (ISCOM) Kume Jima said _RADAR_.

In fact see:

Commander Task Group 31.24 ( ComDes Ron 63)

Subject: Action Report - Capture of KUME SHIMA, Okinawa Gunto, 25-27 June 1945

>much snipped<

6. Conclusion

Destroyers who hare done Radar Picket duty around Okinawa the past
three months have long been suspicious of KUME SHIMA. Bogies seemed to appear
if by magic, from the shadows of this island; and on the few occasions they were
able to use a round trip ticket, disappear as strangely into KUME.

The landing strip, immediately behind Green Beach, contained a number
of wrecked planes. indicating it my have been used for emergency landings. The
strip itself, however, was reported to be in such poor shape that it
could hardly have been used as an operational or even staging field. It seems
probable that a radar and radio on KUME SHIMA served as a beacon to bogies
approaching the Okinawa Area from the south and west. The destroyers,
then, perhaps more so than any other units, will be
glad to see this island out of enemy hands. It should make a first
rate, unsinkable Radar Picket, and soon relieve the destroyers of
their vigil along the FORMOSA-OKINAWA Air Highway.

The one thing the release of the Nimitz War Diaries make clear is that the founding of the Defense Department was very much on the minds of Senior Naval Brass in planning and executing the Okinawa campaign.

In fact, it seems to be a large reason why the USAF's 7th Air Force was cut out of commanding land based air operations on Okinawa in favor of the USMC commanded "Tactical Air Force -- Tenth Army."

[Wellgunde]

I'll buy that. Interservice rivaly, turf battles, and budget shares have been major considerations in U.S. military planning since the founding of the republic. I must admit that it never occurred to me that anyone might have been thinking about post war military structure in the summer of 1945 and that it would have influenced operations while the war was still in progress.

[Mil-tech Bard]

I'll buy that. Interservice rivaly, turf battles, and budget shares have been major considerations in U.S. military planning since the founding of the republic. I must admit that it never occurred to me that anyone might have been thinking about post war military structure in the summer of 1945 and that it would have influenced operations while the war was still in progress.

Try the Late Fall/Early Winter of 1944. The dickering between Gen. Buckner and Adm. Turner -- Excuse me i mean planning -- for Okinawa was Oct-Nov 1944.

Tactical Air Force Tenth Army was not established until Dec 1944.

The plan to take Okinawa, which was all about establishing land based radars and fighter bases to project American air power through out the Island chains between Kyushu and Formosa, was done without an air force!

And it showed!

The lack of attention paid by Turner and Buckner had a huge and horrible influence on the logistics required to establish the American land based radar network.

Turner had to call for another Marine Air Warning Squadron and a US Army Signal Air Warning Company in April and they didn't arrive until June 1945.

And it is why only one of the five Islands originally scheduled for Okinawa Phase III Operations in Nov 1944 was actually captured by July 1945.

[Wellgunde]

That is in fact proof that Kume Jima information was not passed from the Navy Department to the War Department. It shows slow information flow from the Pacific to Washington DC and from the Navy's photo intelligence (USN Signals intelligence for radar was under their photographic branch at that time) to the War Department's Military Intelligence Division.

Not surprising.

How wide was the distribution list for the radar report and what was the time lag between the information cut off date and publication?

[Mil-tech Bard]

The Japanese Radar Report was a intended as a wide distribution working document that was to be amended monthly. It replaced Ratel #5. **

As for data cut off, I don't need to know it.

Aguni Jima was invaded 9 June 1945.

Kume Jima was reconnoitered 13-14 June by FMF Reconnaissance and invaded 26 June.

The Kume Jima radar was on the air until 14 June 1945, until the crew was certain it was going to be lost and they disabled it.


**edited to reflect reading Ratel #11

Introduction page of Ratel No 11 Dated 20 July 1945

[Mil-tech Bard]

I have run across a report called NAVAL INTELLIGENCE, Navpers 16047, copyright 1948, that explains why the US Navy had such a hard time locating Japanese Radars around Okinawa.

None of the outlying islands like Kume Jima was photographed prior to the invasion of Okinawa!

They were all photographed by Turner's CVE photo planes _after they arrived in the Ryukus_ in Late March 1945.

[Wellgunde]

I am impressed by your research on this subject. As we discussed, a lot of important factors seem to have fallen through the cracks before and during the Okinawa campaign. Who was doing the actual radar signature collection? There also seems to be a very considerable time lag between collection and promulgation of the information to the operating forces. Another question which comes to mind is exactly what were the capabilities of the primitive combat information centers on World War II USN ships?

[Mil-tech Bard]

Wellgunde,

There are a bunch of issues, but I think they are more appropriate for my "The Role of IJA/IJN Land Based Radar in the Okinawa Campaign" thread.

I'll try and drop a few of the bone headed issues of Okinawa planning mistakes there.

[Mil-tech Bard]

What was the name/rank of the Okinawa Area Base Force Commander?

It seems he was just as gifted at causing casualties to the US Navy as General Mitsuru Ushijima was to the US Army and Marines, with a lot less publicity post-war.