The invasion of Oahu, December 1941.

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glenn239
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Re: The invasion of Oahu, December 1941.

#211

Post by glenn239 » 20 Sep 2014, 15:48

Eugen Pinak wrote:OK, guys - here is what I've noticed: ...
Thanks for the details.

Looks like a great summary of Zimm's pros and cons - sometimes lacking on specific technical knowledge of the IJN its equipment and operating practices, but strong on the operational analysis. Back in 2007, there was no 'Shattered Sword' level of methodology in books about the Pearl Harbor attack. I'm glad to see that this is being rectified.

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Re: The invasion of Oahu, December 1941.

#212

Post by glenn239 » 20 Sep 2014, 16:00

Eugen Pinak wrote:
Really? If "Zimm - that's the author whose never set foot in a B5N2, never participated in a single carrier mission, but still thought he knew how to introduce micro-management techniques into the Pearl Harbor attack? " is not a judgement, than I don't know, what judgement is.
And the fact, that you refuse to read Zimm's book before "real" book on P-H by Wenger will be published, is not a judgement at all ;)
I stated,

The primary reservation with Zimm's AH plan was that the focus on tactical control over the target seemed to be spending a great deal of effort on something that might have tweaked the historical results a little, but too may have degraded under combat conditions. When I wrote this, I had felt the primary issues that the historical raid failed to properly address were that of a search, maintaining a strike reserve in case of trouble, keeping strike losses to a minimum, and preparing follow-up waves as soon as possible

The word "Reservation" does not mean the same thing a the word "judgement", and reservations "with Zimms' AH plan" does not mean "with Zimm's book" in general. Actually, I'm quite interested in reading Zimm's book to see what sort of fresh insights it brings to the topic.


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Re: The invasion of Oahu, December 1941.

#213

Post by glenn239 » 20 Sep 2014, 16:06

Eugen Pinak wrote:... Of course, Japanese reaction to US offensive was contrary to both logic and their doctrine, but that's another story.
What do you feel would have been the proper Japanese doctrinal response to Guadalcanal, and how did Yamamoto's differ from it?

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Re: The invasion of Oahu, December 1941.

#214

Post by OpanaPointer » 20 Sep 2014, 18:16

Eugen Pinak wrote:Nobody arguing, that Japanese haven't expected US landing on Guadalcanal.
My argument was, that Zimm's statement, that Japanese were foolish to expect US offensive before US will gather superior forces, is incorrect - US did exactly what Japanese expected. Of course, Japanese reaction to US offensive was contrary to both logic and their doctrine, but that's another story.
I'm still not getting the "what Japanese expected". Help, please?
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Re: The invasion of Oahu, December 1941.

#215

Post by Eugen Pinak » 20 Sep 2014, 19:47

From Zimm:
"Contradictory Strategies

Yamamoto’s strategy had a significant consequence that historians have not previously recognized. The attack on Pearl Harbor by its very nature made Japan’s overall concept for winning the war OBE. For Zengen Sakusen to succeed, the American fleet had to thrust west early in the war, before it was reinforced to overwhelming strength. And yet, the Pearl Harbor attack was to immobilize the American fleet for six months. These goals contradict.
With a six-month delay imposed upon the Americans, there was nothing to prevent them from waiting an additional six months when the arrival of newly constructed ships would give them the means to establish absolute material superiority."

And yet US went for an offensive without waiting for the absolute material superiority - which means Japanese strategical assumptions were essentially correct.

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Re: The invasion of Oahu, December 1941.

#216

Post by OpanaPointer » 20 Sep 2014, 21:36

Eugen Pinak wrote:From Zimm:
"Contradictory Strategies

Yamamoto’s strategy had a significant consequence that historians have not previously recognized. The attack on Pearl Harbor by its very nature made Japan’s overall concept for winning the war OBE. For Zengen Sakusen to succeed, the American fleet had to thrust west early in the war, before it was reinforced to overwhelming strength. And yet, the Pearl Harbor attack was to immobilize the American fleet for six months. These goals contradict.
With a six-month delay imposed upon the Americans, there was nothing to prevent them from waiting an additional six months when the arrival of newly constructed ships would give them the means to establish absolute material superiority."

And yet US went for an offensive without waiting for the absolute material superiority - which means Japanese strategical assumptions were essentially correct.
No, the Japanese were hoping to lure the entire USN main force into a battle near the Home Islands. Kaigun is a good source for this. The One Decisive Battle plan was their strategy. The offensive on Guadacanaru considered by them to be a local issue against relatively small forces. It was this mistaken assumption that lead them to underestimate the number of troops needed to repel the invaders.
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Re: The invasion of Oahu, December 1941.

#217

Post by Eugen Pinak » 22 Sep 2014, 11:29

OpanaPointer wrote:No, the Japanese were hoping to lure the entire USN main force into a battle near the Home Islands.
Wrong. Read the "Kaigun".
OpanaPointer wrote: The offensive on Guadacanaru considered by them to be a local issue against relatively small forces. It was this mistaken assumption that lead them to underestimate the number of troops needed to repel the invaders.
And how this statement is relatet to my point?

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Re: The invasion of Oahu, December 1941.

#218

Post by OpanaPointer » 22 Sep 2014, 11:37

You have a nice life, you hear.
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Re: The invasion of Oahu, December 1941.

#219

Post by glenn239 » 23 Sep 2014, 18:39

Eugen Pinak wrote:
And how this statement is relatet to my point?
Your point looks broadly correct - the USN offered battle with its main forces (carriers) prior to establishing superiority. The main difference to IJN doctrine prewar is that this didn't assume there had been a prior heavy battle (ie, Midway) in which the IJN carrier force had been savaged before the USN offered decisive battle.

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Re: The invasion of Oahu, December 1941.

#220

Post by Eugen Pinak » 29 Sep 2014, 12:53

glenn239 wrote:
Eugen Pinak wrote:
And how this statement is related to my point?
Your point looks broadly correct - the USN offered battle with its main forces (carriers) prior to establishing superiority. The main difference to IJN doctrine prewar is that this didn't assume there had been a prior heavy battle (ie, Midway) in which the IJN carrier force had been savaged before the USN offered decisive battle.
I still don't get, how this statement related to my point :\ Both Zimm and I were talking about PRE-war Japanese plans. Do you have ANY sources mentioning, that Midway and Guadalcanal were considered by IJN leaders before the war?

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Re: The invasion of Oahu, December 1941.

#221

Post by OpanaPointer » 29 Sep 2014, 14:50

One more point, that may have been brought up before. Territory of Hawaii residents were supported by about 600 shiploads of supplies from the US every month. To simply maintain the population, without considering occupation troops, would have been beyond the capacity of Japan. As nothing of any major value was produced in T.H. an occupation would effectively reduce the Japanese merchant fleet available for other operations by 1200, as each ship would return to the Home Islands or other destination in ballast. I imagine the US Submarine Service would have been happy to help them find their way "home".
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Re: The invasion of Oahu, December 1941.

#222

Post by glenn239 » 29 Sep 2014, 18:42

One more point, that may have been brought up before. Territory of Hawaii residents were supported by about 600 shiploads of supplies from the US every month. To simply maintain the population, without considering occupation troops, would have been beyond the capacity of Japan. As nothing of any major value was produced in T.H. an occupation would effectively reduce the Japanese merchant fleet available for other operations by 1200, as each ship would return to the Home Islands or other
destination in ballast. I imagine the US Submarine Service would have been happy to help them find their way "home".
It’s a good point – I recall that back in 2007 this was one of the things that was looked at, and came up as a debating point in the internal Japanese deliberations.

First, the peacetime US supply to Hawaii I recall being 60 ships per month, not 600, or something about .7 tons per person, assuming 6,000 tons per ship and 500,000 people in Hawaii. That’s about 45lbs per person per day. Secondly, the IJN never supplied a single captured population to its peacetime level, and would not have done so for Hawaii either. Historically through the war, the Japanese supplied about 2lbs per soldier per day. Assuming 2lbs per person per day at Hawaii, the supply is 15,000 tons per month – 2.5 supply ships. The supply ships returning to Japan would presumably be used to evacuate the surplus population so that in time no supply would be required.

In terms of the US submarine service, I see no reason why it would be more effective off Hawaii than off any of the other islands it would be plying, so that risk would be a wash.

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Re: The invasion of Oahu, December 1941.

#223

Post by glenn239 » 29 Sep 2014, 18:52

Eugen Pinak wrote:
I still don't get, how this statement related to my point :\ Both Zimm and I were talking about PRE-war Japanese plans. Do you have ANY sources mentioning, that Midway and Guadalcanal were considered by IJN leaders before the war?
I responded to,

And yet US went for an offensive without waiting for the absolute material superiority - which means Japanese strategical assumptions were essentially correct

Broadly and unfocused, I think you have a point - Nimitz did risk a counterattack without absolute superiority. Narrowly, I think you do not, as you must have known even as you typed it that the USN counterattack at Guadalcanal occurred only because the results of the Battle of Midway, and to argue, as you now seem to doing, that Nimitz would have recklessly counterattacked at Guadalcanal anyways, even with KB intact, or even his own USN carrier force shattered at an AH Midway, would be beyond the pale.

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Re: The invasion of Oahu, December 1941.

#224

Post by Wellgunde » 30 Sep 2014, 17:04

OpanaPointer wrote:One more point, that may have been brought up before. Territory of Hawaii residents were supported by about 600 shiploads of supplies from the US every month. To simply maintain the population, without considering occupation troops, would have been beyond the capacity of Japan. As nothing of any major value was produced in T.H. an occupation would effectively reduce the Japanese merchant fleet available for other operations by 1200, as each ship would return to the Home Islands or other destination in ballast. I imagine the US Submarine Service would have been happy to help them find their way "home".
The population of Hawaii in 1941 was roughly 425,000 persons. If you subtract the Hawai'ian Nisei who probably would have been allowed to stay, that’s still a lot of people to move and I don’t think the Japanese had the maritime capability to move even a fraction of that number. Besides, where would this “excess” population have been moved to? I can see the need for putting the captured male population to work in Japan, but what would they have done with the women and children and the elderly?

If the Japanese had occupied Hawaii, the submarine force would have been pushed back to the west coast of the U.S. The transit time for a Gato class submarine (based on personal experience) from San Diego to Yokosuka, Japan was around three weeks. A six week round trip would have used up most of the boat’s fuel and would not have allowed for much time on station. In other words, with Hawaii occupied, submarine patrols in Empire waters from the west coast would not have been particularly effective from a cost-benefit standpoint. The transit time from San Diego to Hawaii, however, is only eight days. That shortened distance with the resultant increase in the possible number of patrols with more time on station, would I think, have permitted the U.S. Navy to enforce a very, very effective blockade of Hawai'i.

You might argue that shore based Japanese aircraft could have unsealed such a blockade. It is very difficult to find a submarine with aircraft. Our own postwar ASW exercises proved that. Twenty years after the end of World War II, even with the latest technological advances (e.g. sonobuoys), more often than not, the only way for the aircraft to “win” an exercise (even against a diesel boat) was for the submarine to “pop smoke” and reveal its position.

Also, with regard to a Japanese occupation of Hawaii, how many troops could they have allotted to occupation duties? How many troops would they have needed to maintain an effective defense? Remember, there are eight major Hawai’ian islands with 750 miles of coastline. Once the U.S. had had time to rebuild it's carrier force, command of the air space over Hawai'i would have passed back to the U.S. leaving the Japanese occupation forces very exposed at the end of a long and tenuous supply line. Occupying Hawai'i would have been a big gamble for the Japanese. Would they have recognized it as such and still proceeded? Perhaps it's a question for which there is no answer.
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Re: The invasion of Oahu, December 1941.

#225

Post by Rob Stuart » 30 Sep 2014, 18:20

Territory of Hawaii residents were supported by about 600 shiploads of supplies from the US every month.
Can this figure be correct? 20 shiploads a day to support 425,000 people? The UK had a population of about 45 million, which is more than 100 times greater, but it certainly did not get 2000 shiploads a day. Something does not compute here.

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