Kanmon Undersea Railway Tunnel & the Invasion of Japan

Discussions on all aspects of the Japanese Empire, from the capture of Taiwan until the end of the Second World War.
Mil-tech Bard
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by Mil-tech Bard » 26 Aug 2019 01:15

smallag,

These are the platforms and associated "Stinger" remote control program decodes as of 8 Nov 1944:

Type .............Code Name.........Status
AK Program......Stinger Charlie....Experimental
DE Program......Stinger George....Experimental
LVT Program.....Stinger Able.......Operational
LCVP Program...Stinger Dog........Operational
PT Program......Stinger Baker......Experimental
“X” Craft.........“X” Craft"..........Experimental


Look here for them:

RG 38
Entry A1 329
New Development Subj File 1942-46
Boxes 1 to 15

smallag
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by smallag » 27 Aug 2019 13:47

Awesome! Thanks! :thumbsup:

smallag
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by smallag » 10 Oct 2019 21:38

:D Confirmation that "Special Hull" C-36204 was ordered by BuShips (CAPT Hyman G. Rickover) for test by BuOrd in association with Project Stinger. Hull was to used for live scuttling/detonation tests, but looks like the project was halted before this ordnance test took place. PT "Drones" were to carry 17 tons of TNT within the Steel cribbing. A group of twelve PT "Drone" boats were to be used to lay both bouy markers and to clear a channel through harbor defensive mine fields (first scuttled then charge detonation). They would then be followed by three DEs "Drones" with 1200 tons of TNT to widen the channel for the follow on AK (ammo ship) "Drone" loaded with 8000 tons of TNT. The AK would destroy the harbor, much like in Bergen and Bombay and Halifax. Then a DE with Napalm and other pyrotechnics ordnance would be sent in and detonated to set the remaining Harbor defenses on fire. Pretty vicious way to neutralize a harbor.

By the end of the project in December 44, only 10 PT Boat kits were ordered (photos of C-36204, Elco hull 3683 were used for the instruction manuals). PT-140 was the "Drone" test PT Boat used during the Summer and Fall of 44, and the 70' experimental Higgins "Hellcat", PT-564 was used as a control boat. This accounts for the "2" PTs mentioned as part of the project. A PV-1 Ventura was also tested as a control aircraft. There was a request for two of the Hacker boats from Campbell. Not sure of how they were used, but there is definitely a pretty good tie-in with the OSS project (several of the same officers).

From the RG-38 records at NARA. Thank you Mil-tech Bard!

von Shapp
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by von Shapp » 13 Jan 2020 02:35

smallag wrote:
10 Oct 2019 21:38
PT "Drones" were to carry 17 tons of TNT within the Steel cribbing. A group of twelve PT "Drone" boats were to be used to lay both bouy markers and to clear a channel through harbor defensive mine fields (first scuttled then charge detonation). They would then be followed by three DEs "Drones" with 1200 tons of TNT to widen the channel for the follow on AK (ammo ship) "Drone" loaded with 8000 tons of TNT. The AK would destroy the harbor, much like in Bergen and Bombay and Halifax. Then a DE with Napalm and other pyrotechnics ordnance would be sent in and detonated to set the remaining Harbor defenses on fire. Pretty vicious way to neutralize a harbor.
That's a pretty good summation of the USN's drone program and how it was to be used. Also, good job spotting the Rickover connection. :D

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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by von Shapp » 13 Jan 2020 13:55

smallag wrote:
18 Feb 2019 17:04
Sorry for restarting this thread so many years afterwards. I do PT Boat research
Maybe you can help me a bit.

I've found slim information on PT Boats in OLYMPIC -- this is pretty much what I've got:

Regarding future operations, ComMTBRonsPac had prepared an estimate of MTB's potentialities around Kyushu for CinCPac in early June, and shortly thereafter he directed ComMTBRons7thFlt to evaluate the materiel and personnel of the SEVENTH Fleet squadrons with any eye to their use in OPERATION OLYMPIC. CinCPac was then considering decommissioning the older SEVENTH fleet squadrons; Com7thFlt recommended against this until all need for them was clearly over.

No MTB's had been included in the first disseminated plans for OPERATION OLYMPIC. However, in early August, subordinate commanders of ComPhibsPc indicated possible uses for up to 200 MTB's in the invasion of southern Japan. ComMTBRonsPac was drawing up plans for such operations when the war ended.

....

No higher echelon officially communicated with ComMTBRons Pac regarding participation in OPERATION OLYMPIC and he received no plans for this operation. He had, however, as noted above, drafted for CinCPac an estimate of motor torpedo boat potentialities around Kyushu, and, In conferences on and after 7 August in Manila, ComPhibsPac asked him to submit a plan for the use of motor torpedo boats off Japan. In this connection, subordinate commanders of ComPhibsPac asked ComMTB-RonsPac to provide upwards of 200 motor torpedo boats. Hostilities ended before the plan could be submitted.

Mil-tech Bard
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by Mil-tech Bard » 24 Jan 2020 13:32

The photo below is as photo shop I put together from the OSS briefing package for Campbell from the winter of 1944

Javaman -- Campbell_a_joint_AAF_and_OSS_project - 8.jpg
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Mil-tech Bard
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by Mil-tech Bard » 25 Jan 2020 13:30

Adm Turner had a real hate on for PT-Boats and this showed at Okinawa, much to the detriment to forces there.

See:
The Amphibians
Came to Conquer
THE STORY OF
ADMIRAL
RICHMOND KELLY TURNER


"Planning for Use of PT Boats at Okinawa
Before relating the story of the Okinawa assault, the reason for the absence of PT boats in the
assault forces will be mentioned.

Vice Admiral Turner, and many other naval officers who had witnessed the PT boat operations in the
Guadalcanal and New Georgia operations, thought that the PT boats were anywhere from somewhat to
vastly overrated by the public and the press.

Admiral Hall tells the story that prior to the Okinawa operation the overall commander of the PT
boats, who had participated in the South Pacific operations, reported to him in Leyte for duty in
connection with training for the upcoming Okinawa landings. Admiral Hall asked Admiral Turner by
dispatch what part the PT boats would play in the operations so he could arrange appropriate
training for them. Vice Admiral Turner informed Admiral Hall that the PT boats would not even be
allowed to enter the Okinawa area until D plus 4 or later. Admiral Hall explained:

He evidently had no use for them, and I had no use for them. When I was doing my part of the
Normandy landing, (OMAHA Beach) they were of no use whatsoever.32"

Mil-tech Bard
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by Mil-tech Bard » 25 Jan 2020 13:57

The use of PT-Boats in Olympic is mentioned in At Close Quarters:
http://www.ibiblio.org/hyperwar/USN/Clo ... /PT-8.html

At Close Quarters
PT Boats in the United States Navy
by
Captain Robert J. Bukley, Jr.
USNR (Retired)
with a Foreword by
President John F. Kennedy


page --441--

"The original plans for Operation Olympic, the projected invasion of
the Japanese home islands, made no provision for PT operations.
Subsequent to the drafting of the operation plan, however, the
Commander Amphibious Force Pacific Fleet asked Commodore Bates to
submit a plan for use of PT's off Japan, and subordinate commanders of
the Amphibious Force made requests on him to provide more than 200
PT's for use in connection with the invasion. Hostilities ended before
the plan could be submitted."

and

Page 445

"26. THE END AND THE BEGINNING

In mid- August 1945, 30 squadrons of PT's were in commission. Nineteen
were in the Seventh Fleet, six in the Pacific Fleet, three were being
reconditioned in the United States for Pacific duty after combat in
the European theater, one was shaking down in Miami, and one was the
training squadron at Melville. By the end of the year all had been
decommissioned except Squadron 4, the training squadron, and the brand
new Squadron 41. In addition there was Squadron 42, which had been
fitting out in New York in August, and which was the only PT unit
placed in commission after the end of hostilities."


And is also in the Administrative History of ComMTBRonsPac on Fold3:
""No higher echelon officially communicated with ComMTBRonsPac
regarding participation in OPERATION OLYMPIC, and he received no plans
for this operation. He had, however, as noted above, drafted for
CinCPac an estimate of motor torpedo boat potentialities around
Kyushu, and, in conferences on and after 7 August in Manilia,
ComPhibsPac asked him to submit a plan for the use of motor torpedo
boats off Japan. In this connection, subordinate commanders of
ComPhibsPac asked ComMTBRonsPac to provide upwards of 200 motor
torpedo boats. Hostilities ended before the plan could be submitted."
From what I can gather, 7th Fleet went around Adm Turner and his staff to Adm Nimitz with the proposal during the planning process for Operation Olympic, as they were the ones with the PT-boat tenders needed to execute the proposed plan.

Evidently the destroyermen on Nimitz' staff jumped on the proposal like a bass for a well thrown fishing lure.

None of them wanting to take their Fletcher's or Sumners into shallow waters at five knots to hunt for suicide boats after what happened to the LCI gunboats off Mariveles, Corregidor Channel, Luzon in Feb 1945 plus the damaging of USS Charles J. Badger (DD-657) and USS Hutchins (DD-476) off Okinawa in April 1945

smallag
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by smallag » 10 Feb 2020 01:51

From June thru September 1945, MTB Ron 4 was conducting a large number of shallow water torpedo training and tests in Rhode Island. I found this during my research into the little known Huckins PTs. Huckins PT-100 shot over 100 torpedoes during this time which seems to be a record for a single PT Boat. She also was the last operations Huckins PT after the war. Unfortunately I have yet to find any specific on tactics used/develped or intended target, although other PTs were employed as the target boats. This could imply that these Mk13 torpedoes were going to play some intended role during the invasion.

The final version of the Elco PTs, PT761 class was to include the new SO-5 radar and associated torpedo fire control system, in addition to a redesigned superstructure providing greater visibility and height. This could support the hypothesis that again, torpedoes were going to be employed extensively by the invasion forces for defense. I derive this since attacking PTs want a very low silhouette and stealth, whereas in defense mode, being large is not as important a factor and provides better SA for the crew. The Elco Turret ("Thunderbolt") Quad 20mm was in full albeit reduced production, but it looked like most were going to continue to be mounted on capital ships such as BBs, with no plans to install them on invasion bound PTs. This is all info I gathered from NARA and the Naval War College Archives.

I'll continue to look for info.

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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by daveshoup2MD » 10 Feb 2020 03:17

Seems like if the goal was to let the Japanese deploy as many troops as possible on Kyushu and then invade conduct CORONET absent OLYMPIC, this strategy would have worked well! ;)

I've read there was some consideration when it became (somewhat) more clear close to the end of the war that Kyushu was heavily defended to mount a smaller operation for airbases on Shikoku in the autumn of 1945 and then go for CORONET in the spring of 1946 ... doesn't seem to have gone very far, and after H & N and the Soviet entry, the entire plan for an invasion of Japan was moot, but OLYMPIC/MAJESTIC at almost army group strength in the fourth quarter of 1945 seems less than optimal for the side with complete maritime and air dominance - sort of the opposite of island hopping.

smallag
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Re: Kanmon Undersea Railway Tunnel & the Invasion of Japan

Post by smallag » 10 Feb 2020 15:15

From a posting on another forum in response to my request for related PT Boat information:

Nimitz himself planned to build a number of naval installations in the southern portion of Kyushu. The largest was planned for Takasu on the eastern side of Kagoshima Bay, near Kanoya Airfield. At Takasu, the Navy would build an artificial harbour, with piers to handle ten attack transports and a tanker simultaneously. The base would also be capable of repairing small craft, patrol boats and landing craft as well as having storage facilities of commonly used supplies such as ammunition and fuel. Covered storage of 1 million sq ft would hold supplies for servicing the fleet. Nearby, the Navy would adapt one of the airfields at Kanoya to accept planes from the Naval Air Transport Service. Smaller and more specialised facilities were planned for Uchinoura, a small bay on the southern side of Ariake Wan, at the mouth of Manose Gawa near the southern end of Fukiagehama as well as at Yamagawa ear the mouth of Kagoshima Bay. Uchinoura would serve naval forces operating near Ariake Wan, Manose Gawa would allow tankers to unload their fuel to the nearby marine air bases and Yamagawa would become a PT-boat base. All these facilities were to be operational by X-Day+120. (CINCPAC Operations Plan, OLYMPIC, USMC Geographic File, Japan, Box 50, Folder B1-1, WNRC)

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