The invasion of Oahu, December 1941.

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Re: The invasion of Oahu, December 1941.

#226

Post by OpanaPointer » 30 Sep 2014, 18:23

"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. "

The Issei and Nisei weren't removed from Hawaii. The Governor pitched a fit when this was suggested, saying the economy would collapse if they were removed.
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Re: The invasion of Oahu, December 1941.

#227

Post by OpanaPointer » 30 Sep 2014, 18:33

Posting from Dulles right now on phone. I'll look up the shipping reference when I escape from these clowns and get home.
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Wellgunde
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Re: The invasion of Oahu, December 1941.

#228

Post by Wellgunde » 30 Sep 2014, 18:59

OpanaPointer wrote:"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. "

The Issei and Nisei weren't removed from Hawaii. The Governor pitched a fit when this was suggested, saying the economy would collapse if they were removed.
I was referring to the possibility of the Japanese forces moving the population out of the islands after a successful invasion as mentioned by a previous poster. The initial panicky knee jerk reaction of the U.S. Government immediately after Pearl Harbor is a whole different story.
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Re: The invasion of Oahu, December 1941.

#229

Post by Wellgunde » 30 Sep 2014, 19:42

Rob Stuart wrote:
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.
I agree. Judging from current Port of Honolulu shipping information the average number of merchant ships in port on any given day (subtracting the inter-island trade) averages around five. Allowing for three days in port for each ship that would mean around fifty shiploads per month. That's supporting a population of 1.4 million persons. This is a only a guestimate. Keep in mind that ships today are larger, containers make more efficient use of space, and turnaround times vary considerably. When I last lived in Hawai'i (1990's) I always thought that the port looked kind of empty.
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Re: The invasion of Oahu, December 1941.

#230

Post by OpanaPointer » 30 Sep 2014, 20:45

Remember that all the islands had to be supplied by ship.

And now back to the five-sided puzzle box.
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Re: The invasion of Oahu, December 1941.

#231

Post by glenn239 » 30 Sep 2014, 20:59

Wellgunde wrote: 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.
The census information and food resources of Hawaii is found on page one of this thread, the aspects to caring for the civilian population, in concluding section (20). With 20 supply ships per month arriving at Hawaii, that would provide room for about 30,000 civilians per month evacuated on the return trip, which means within about 6 months the food supplies might be approaching harmony.
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.
Assuming the loss of Hawaii, the US submarine fleet would concentrate at an alternative suitable base in range of the Japanese homeland. Australia has any number of suitable locations, for example.
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.
The USN was unable to perform the blockade function you outline against other IJN bases such as Truk or Rabaul circa 1942/1943, and this was from support bases far closer. Additionally, submarines are best employed in heavy volume traffic areas - diverting them to areas with less traffic would dilute their overall impact.
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?
The US garrison was 110,000 at its peak. The IJA would no doubt have skimped with respect to that total.
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.
Right.
Occupying Hawai'i would have been a big gamble for the Japanese.
The Japanese decision for war with the United States represented one of the most reckless gambles ever willingly undertaken by a power in the modern era. Operational risk should reflect directly reflect this - the more reckless the grand strategy, the more acceptable extreme risk becomes in operational patterns.
Last edited by glenn239 on 30 Sep 2014, 21:07, edited 1 time in total.

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Re: The invasion of Oahu, December 1941.

#232

Post by glenn239 » 30 Sep 2014, 21:06

OpanaPointer wrote:Remember that all the islands had to be supplied by ship.
IIRC, supply tended to come in at Honolulu then be dispersed from there to the outer islands by local steamers.

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Re: The invasion of Oahu, December 1941.

#233

Post by Wellgunde » 01 Oct 2014, 02:45

OpanaPointer wrote:Remember that all the islands had to be supplied by ship.

And now back to the five-sided puzzle box.
Then as now, the majority of shipping terminates in Honolulu with Hilo a distant second. Cargo off loaded in Honolulu is transshipped to the other islands.
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Re: The invasion of Oahu, December 1941.

#234

Post by Wellgunde » 01 Oct 2014, 05:40

glenn239 wrote: The census information and food resources of Hawaii is found on page one of this thread...

My figure is based on the 1940 United States Census. In any case, I don't think the difference between your number and my number is enough to quibble about.

glenn239 wrote: Assuming the loss of Hawaii, the US submarine fleet would concentrate at an alternative suitable base in range of the Japanese homeland. Australia has any number of suitable locations, for example.

During the war, U.S. submarines operated out of Darwin, Fremantle, and Brisbane. Patrols to Empire waters from Australia were technically feasible, however, none were ever carried out. This was due to the way the Pacific was divided up between Nimitz and MacArthur. Would the loss of Hawaii have caused a change in the boundaries between SWAPA and CINCPAC-CINCPOA? Hard to say given Army/Navy rivalry and the personalities involved: MacArthur, Nimitz, King, and Marshall. We operated two independent submarine forces in the Pacific for the duration of the war.

glenn239 wrote: The USN was unable to perform the blockade function you outline against other IJN bases such as Truk or Rabaul circa 1942/1943, and this was from support bases far closer. Additionally, submarines are best employed in heavy volume traffic areas - diverting them to areas with less traffic would dilute their overall impact.

The U.S. only seriously attempted a submarine blockade of Truk in July, August, and September of 1942. It produced poor results for a number of reasons: 1. The boats operated independently; 2. They operated too close to Truk placing them at a disadvantage vis-à-vis IJN ASW forces; 3. Not enough boats were tasked for the mission; and 4. Torpedo problems. Fortunately for us, the Pacific submarine force was willing to learn from its mistakes and make changes when necessary. With regard to a blockade of Hawai'i, how important would it have been? Sometimes political decisions and matters of national will and morale are more important than the practical or common sense approach, i.e. diversion of assets to what might be referred to as a "low traffic area." I think strangling the Japanese occupation forces would have justified any effort.
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Re: The invasion of Oahu, December 1941.

#235

Post by glenn239 » 01 Oct 2014, 20:08

Wellgunde wrote: During the war, U.S. submarines operated out of Darwin, Fremantle, and Brisbane. Patrols to Empire waters from Australia were technically feasible, however, none were ever carried out. This was due to the way the Pacific was divided up between Nimitz and MacArthur. Would the loss of Hawaii have caused a change in the boundaries between SWAPA and CINCPAC-CINCPOA? Hard to say given Army/Navy rivalry and the personalities involved
Well, let's put it this way. If FDR allowed an inter-service squabble to permit the Japanese to move their merchant traffic in home waters unmolested by Allied forces, it would represent a failure in leadership of the largest dimensions.
The U.S. only seriously attempted a submarine blockade of Truk in July, August, and September of 1942. It produced poor results for a number of reasons: 1. The boats operated independently; 2. They operated too close to Truk placing them at a disadvantage vis-à-vis IJN ASW forces; 3. Not enough boats were tasked for the mission; and 4. Torpedo problems. Fortunately for us, the Pacific submarine force was willing to learn from its mistakes and make changes when necessary. With regard to a blockade of Hawai'i, how important would it have been? Sometimes political decisions and matters of national will and morale are more important than the practical or common sense approach, i.e. diversion of assets to what might be referred to as a "low traffic area." I think strangling the Japanese occupation forces would have justified any effort.
The diversion of large numbers of submarines to an area of the Pacific with comparatively little traffic would represent a severe impairment of the undersea weapon, given that submarines perform best in target rich environments, which meant the waters near Japan and the NEI. That is to say, I think the Japanese would take the bulk of Allied submarines at Hawaii and few elsewhere any month of the war.

In terms of what Japanese planners thought of the threat, I have no idea. When I wrote this I figured that if the USN submarines were truly capable of doing this, they could have done it at Truk, or Rabaul, or anywhere at all, not just Hawaii, so the point was still moot - if the IJN could not hold communications open to its major bases then the total collapse of its position was inevitable, Hawaii or no Hawaii.

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Re: The invasion of Oahu, December 1941.

#236

Post by Wellgunde » 01 Oct 2014, 20:50

Thank you Glenn for an interesting discussion. You have certainly done a lot of excellent research.

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Re: The invasion of Oahu, December 1941.

#237

Post by Rob Stuart » 02 Oct 2014, 01:12

glenn239 wrote:

Assuming the loss of Hawaii, the US submarine fleet would concentrate at an alternative suitable base in range of the Japanese homeland. Australia has any number of suitable locations, for example.

The USN was unable to perform the blockade function you outline against other IJN bases such as Truk or Rabaul circa 1942/1943, and this was from support bases far closer. Additionally, submarines are best employed in heavy volume traffic areas - diverting them to areas with less traffic would dilute their overall impact.

The diversion of large numbers of submarines to an area of the Pacific with comparatively little traffic would represent a severe impairment of the undersea weapon, given that submarines perform best in target rich environments, which meant the waters near Japan and the NEI. That is to say, I think the Japanese would take the bulk of Allied submarines at Hawaii and few elsewhere any month of the war.



Glenn, I’d suggest that you read Clay Blair’s Silent Victory, pp. 178-180. He agrees with your point that “submarines are best employed in heavy volume traffic areas” and notes that to interdict Japanese shipping sailing between the homeland and the Indies the best place to operate was the Luzon Strait, between Luzon and Formosa. However, he points out that reaching this area from Australia was much more difficult and took longer than reaching it from Pearl Harbor. This being the case, using US submarines to support the liberation of Hawaii would not be a diversion from the submarine war against Japan. On the contrary, it would be necessary to recover Hawaii for the submarine war against Japan to prosper. The recovery of Hawaii was also necessary to secure communications with Australia (without which any submarines based there could not be supplied with torpedos or anything else they needed) and for taking the offensive across the Central Pacific. If overall tonnage sunk by US subs dropped for a few months but Hawaii were recovered, that would be a very small price to pay.

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Re: The invasion of Oahu, December 1941.

#238

Post by OpanaPointer » 02 Oct 2014, 12:14

Bad news: I was wrong about the shipping numbers.

Good news: I was only off by a factor of ten. :lol:

Anywho, Parshall and Tully, page 29, says 60 ships a month. That's at least 6,000 km one way to maintain the Nov. 1941 population. And they'd return deadheading. Of course if they abandoned the population to their own devices they'd need less.
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Re: The invasion of Oahu, December 1941.

#239

Post by glenn239 » 02 Oct 2014, 14:52

OpanaPointer wrote:Bad news: I was wrong about the shipping numbers.

Good news: I was only off by a factor of ten. :lol:

Anywho, Parshall and Tully, page 29, says 60 ships a month. That's at least 6,000 km one way to maintain the Nov. 1941 population. And they'd return deadheading. Of course if they abandoned the population to their own devices they'd need less.
Shattered Sword is referencing Hawaii Under the Rising Sun, which in turn looked at a planning debate within the IJN leadership in 1942. There was a sharp divide on Hawaii, and the anti-Hawaii faction produced a logistic study that examined Hawaiian peacetime traffic and added them a wartime requirement to transform Oahu into a major base, to get 60 ships (about 720,000 tons in the supply line). The 30 ships per month allocated to civilian supply in the study corresponded to about 25lbs per civilian per day, an absurd total which I took to indicate the planner's political focuse was seeking the highest estimate possible. In fact, 2lbs per civilian per day is probably more realistic, which is about 3 supply ships, not 30, or about 30,000 tons of shipping dedicated.

This thread did not envision Oahu as a major fleet base, so considered only 20 supply ships per month, which at 1,500 civilians per ship on the return trip, would reduce the population in Hawaii by 30,000 per month.

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Re: The invasion of Oahu, December 1941.

#240

Post by OpanaPointer » 02 Oct 2014, 14:57

And those ships would not be carrying war materials to the Home Islands, representing a net lose in resources available for the war effort.
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