PC: Attack on Pearl Harbor as an invasion of Hawaii?

[FillyofDelphi]

I don't think Japan had any allies in the summer of 1945, unless someone wants view the relationship between the USSR and Japan with particularly rose colored glasses.

They still had some puppets floating around I think, but "allies" isen't a term Japan could apply to any sovereign nation. And besides: does anybody REALLY think the Soviets would have offered surrender terms that were any more lenient than the Americans? Stalin is going to insist on a Red Tokyo, and will get it at bayonet point on the Home Isles if he has to.

 

[Lost Freeway]

Given that the Soviets were literally preparing for an invasion all summer those must be really, really rose tinted.

Of course.

 

[Grognard49]

Just out of curiosity, how ready were the US combat brigades to defend Oahu within ~12 hour notice that would be the case in this scenario? Did they train for this possibility? They appear to be close to full strenght, but was that the case for supporting elements also, e.g. artillery and tanks (if the had any at that point)? And was there enough ammunition for ~week of intensive combat in the island?

The Hawaiian Department of the U.S. Army had practiced raid/assault responses for Oahu for over 10 years. Assigned units practiced deployments to their field locations frequently. According to "Guarding the United States and Its Outposts" by the United States Army Center of Military History:

"Within minutes after the first torpedoes and bombs struck at Pearl Harbor, General Short issued orders that put the Hawaiian Department on a full war footing. By 8:45 a.m. his headquarters had begun to operate a forward command post located in tunnels at the Aliamanu Crater, three miles west of Fort Shafter. Between 8:20 and 9:00 a.m. the major ground commands-the Hawaiian Coast Artillery Command and the 24th and 25th Infantry Divisions-received word to deploy and take the actions required under a No. 3 Alert. Actually, all three had begun so to act before they got the formal word. The 24th Division had a battalion of infantry on the road from Schofield Barracks to its assigned battle position by 9:00 a.m., and thereafter other divisional units left Schofield as soon as they had drawn and loaded their ammunition and otherwise prepared for action. By late afternoon, all divisional elements were digging in at their assigned field positions, with all weapons except heavy howitzers at hand and ready to fire. As General Short put it, in the deployment "everything clicked," one of his junior officers explaining: "We had gone so many times to our war positions that it just seemed like drill when they were firing at us." The deployment showed clearly enough that the Hawaiian Department was thoroughly prepared to resist invasion, however unready it was against the peril of surprise air attack."

The entire publication can be found at http://www.army.mil/cmh-pg/books/wwii/Guard-US/index.htm

 

[galveston bay]

The Hawaiian Department of the U.S. Army had practiced raid/assault responses for Oahu for over 10 years. Assigned units practiced deployments to their field locations frequently. According to "Guarding the United States and Its Outposts" by the United States Army Center of Military History:

"Within minutes after the first torpedoes and bombs struck at Pearl Harbor, General Short issued orders that put the Hawaiian Department on a full war footing. By 8:45 a.m. his headquarters had begun to operate a forward command post located in tunnels at the Aliamanu Crater, three miles west of Fort Shafter. Between 8:20 and 9:00 a.m. the major ground commands-the Hawaiian Coast Artillery Command and the 24th and 25th Infantry Divisions-received word to deploy and take the actions required under a No. 3 Alert. Actually, all three had begun so to act before they got the formal word. The 24th Division had a battalion of infantry on the road from Schofield Barracks to its assigned battle position by 9:00 a.m., and thereafter other divisional units left Schofield as soon as they had drawn and loaded their ammunition and otherwise prepared for action. By late afternoon, all divisional elements were digging in at their assigned field positions, with all weapons except heavy howitzers at hand and ready to fire. As General Short put it, in the deployment "everything clicked," one of his junior officers explaining: "We had gone so many times to our war positions that it just seemed like drill when they were firing at us." The deployment showed clearly enough that the Hawaiian Department was thoroughly prepared to resist invasion, however unready it was against the peril of surprise air attack."

The entire publication can be found at http://www.army.mil/cmh-pg/books/wwii/Guard-US/index.htm

This book is excellent on the subject as well.... warplans and exercises had been underway from almost the beginning of the US deployment of troops to the island

https://www.amazon.com/Guardians-Empire-U-S-Pacific-1902-1940/dp/0807848158

 

[sloreck]

The US forces on Oahu were fully motorized, and could move guns, ammo, and supplies as well as men around quickly. Civilian trucks were there to be requisitioned as well. Until the Japanese get some sort of port they will have very little motor transport, and even at best they would not have a lot. US forces will do their best to make sure little useful is left for the Japanese in any territory they occupy, and you can be sure the civilians will get in their vehicles to flee. Sure they'll try to take vehicles, and use whatever gas they can, but I doubt the US forces will leave many vehicles or much gas behind - they are too professional for that.

 

[Shadow Master]

The problem I have with Conroy and Turtledove in their books is that they ignore this major issue.

I have to agree, it won't be easy, but it will make for a short campaign, one way or the other. Either the Japanese take Oahu in short order, after garrisoning all the other main islands and bringing in all the land based airpower needed to fend off the USN, and freeing the KB for other missions, or they fail to do so, and loose fairly quickly.

 

[Glenn239]

... except there's a very good chance the IJN lost/spent plenty of ships, carrier aircraft, skilled pilots, vital stocks of war material, professional amphibious specialists, ect. that it otherwise had IRL.

Underlined. Japanese industry couldn't deliver a follow-up to the Zero. The F6F was dominant, meaning that in any battle from 1943 onwards IJN losses were going to be large, and USN losses small. And that wasn't even considering USN AA improvements. Egusa - one of the elite dive bomber pilots in the world - fought at the Marianas in 1944 and he was shot down short of the US fleet just like all the green crews. Japanese carrier pilot training didn't matter against F6F.

Again. Smart risks vs. dumb risks.

Sure thing The IJN should wait until 1944, because 'smart risk' theory says those titantic battles are going to go so well for the Japanese! Three dozen US carriers (CV to CVE) with 2,000 aircraft coming at you? Anyone who knows anything about Pacific carrier warfare knows that a couple hundred F4F and P40 were far better in combat against IJN aircraft than tangling with three or five hundred F6F Hellcats! If you're flying a B5N2, you're much better off being bounced by 200 F6F's than 20 F4F's. That's just common sense.

Pearl Harbor IRL was a smart risk.

In the Apollo program, before the launch of a Saturn V was authorized there was a pre-launch check sequence to determine the risk. Once in Earth orbit, another check sequence occurred to determine the risk for leaving orbit. Once in orbit around the Moon, another check sequence was made to determine the risk of a landing. At each stage, the amount of risk that was acceptable while proceeding increased. The reason was because of the risk that had already been taken to reach that point - if the mission aborted, those risks would have to be taken again to reach the same point.

That concept applied to Hawaii. The Pearl Harbor Raid as executed was not a smart risk because Nagumo failed to account for what NASA engineers understood - the risk getting into the dominant position by 12 noon justified the risk of continuing with the attack. If Nagumo were a NASA flight controller, he'd have aborted the Moon landing in orbit around the Moon with all lights green, then, blown up on the launch pad at Midway on his next attempt.

Not attacking the Soviets from behind and risking having them come back to bite you in the butt later was... well, as smart a risk as they could take with the U.S.S.R. Better than having to fight it out with them for the whole course of the war.

The Japanese needed to fight the Soviets in 1942. Win or lose, it was better than waiting until 1945.

 

[Glenn239]

I don't think Japan had any allies in the summer of 1945, unless someone wants view the relationship between the USSR and Japan with particularly rose colored glasses.

"Now without allies" for Japan in August 1945 refers to the unconditional surrender of Germany, not the Soviet Union.

 

[Glenn239]

Japan cannot take Hawaii and the Southern Resource Area simultaneously. Wash, rinse, and repeat.

Strategically the Japanese had to take Hawaii, the Southern Resource Area, and be in a position to attack the Soviet Union by the summer of 1942. And all of that was just on the chance the US might talk. But take the NEI and then just sit there? That strategy leads straight to unconditional surrender, 100% of the time, guaranteed.

This is not even considering how taking Hawaii starting 12/8 affects taking Rabaul and other islands in that area as well as Wake or the PI campaigns.

Rabaul, the Solomons, Truk - these were all irrelevant. The only thing that mattered was whether the US would decide that their interests were better served talking or not talking. Nothing except Hawaii and war with the Soviet Union could possibly impact that US calculation. If Japan goes for Hawaii and gets spanked, it can take the NEI after that. If it fails to take the NEI after that then it can surrender. Guess what? Japan is way ahead of itself historically.

If they try and take Hawaii 2-3 months after PH they will be smeared.

Actually, I just read that in January 1942 Oahu's aerial defenses were surprisingly weak still. About 110 army aircraft and 90 navy, (including PBY's).

If they try to take the Southern Resource Area 2-3 months after PH it becomes very iffy, and expect greater destruction of the oil fields if they are going to be overrun - a bad thing for the Japanese.

If the IJN has overrun Hawaii what is going to protect the NEI? Australia? Even if Australia stays in, with IJN naval supremacy after Hawaii, every last single plane and soldier will be for home defense. Britain? They'll be protecting India.

 

[Glenn239]

nation. And besides: does anybody REALLY think the Soviets would have offered surrender terms that were any more lenient than the Americans? Stalin is going to insist on a Red Tokyo, and will get it at bayonet point on the Home Isles if he has to.

Sure, Stalin just marches his army across the Sea of Japan.

 

[Glenn239]

I have to agree, it won't be easy, but it will make for a short campaign, one way or the other. Either the Japanese take Oahu in short order, after garrisoning all the other main islands and bringing in all the land based airpower needed to fend off the USN, and freeing the KB for other missions, or they fail to do so, and loose fairly quickly.

If the USN carriers can be sunk while the IJN carriers remain sufficiently battle worthy themselves, and if from the loss of the US carriers a blockade can be effected, then Oahu, more than likely, falls. If the USN carriers exchange evenly or better, then the IJN will lose.

 

[FillyofDelphi]

If the USN carriers can be sunk while the IJN carriers remain sufficiently battle worthy themselves, and if from the loss of the US carriers a blockade can be effected, then Oahu, more than likely, falls. If the USN carriers exchange evenly or better, then the IJN will lose.

I'll get to your response to my stuff later, but as I can answer this quickly...

If Japan can enforce a blockade of Hawaii, the land invasion becomes unnecessary. They can just starve Oahu out; unlike in a normal siege situation, the Americans aren't in a position to evacuate or kick out the civilians to save food (Being a small island chain in the middle of an ocean of deadly nothingness). Its, strangely enough, very similar to the whole Operation Aquatic Large Feline problem.

 

[Shadow Master]

(SNIP)
The entire publication can be found at http://www.army.mil/cmh-pg/books/wwii/Guard-US/index.htm

Another very nice link sir, thank you! Sorry that I missed this post from last week, but I have not been home since Aug 31st till today except for a few hours monday/tuesday, and then just after midnight, as I was helping a friend clean up his father's estate labor day weekend, and then got a call tuesday that sent me down to southern Florida to evac a family member out of the path of Irma, so please forgive me for not responding sooner to this post or this thread.

There seems to be quite a bit of discussion of Japan winning the war, or loosing the war, based upon how quickly they take the NEI, or perhaps, more accurately, that their inevitable defeat can be better staved off, for a limited time, by capturing the NEI sooner rather than later. While taking the NEI can give them some oil production (which they may or may not be able to get home, regardless of enemy action), it cannot win them the war, nor postpone their defeat all that long. OTOH, taking the Hawaiian islands (which cannot win them their war, either), can make it far harder for the USA to interfere with their oil supplies until the USA manages to either retake Oahu, or build up the capacity to project power into the western Pacific ocean. As I see it, there can be only one of three ways for the US to do this, one is around Africa, two is through the Aleutian islands in the far north Pacific, and three is swinging far south and coming through Australia/NZ. All of these alternatives are far inferior to just retaking the Hawaiian islands, but hey. If the USA didn't see themselves going that route, might we see B-36's operating out of Attu/Kiska?

Basically, I see this concept as a very interesting WI scenario, not a way for Japan to win a war they cannot win, and if such a hobby-for-entertainment-purposes-only discussion is offensive to some, I can only apologise to them, and continue with the idea for others that share my interest in this concept of a Japanese alternate WWII war.

 

[Glenn239]

If Japan can enforce a blockade of Hawaii, the land invasion becomes unnecessary. They can just starve Oahu out; unlike in a normal siege situation, the Americans aren't in a position to evacuate or kick out the civilians to save food (Being a small island chain in the middle of an ocean of deadly nothingness). Its, strangely enough, very similar to the whole Operation Aquatic Large Feline problem.

Siege can work but requires the IJN carriers to be sufficiently intact and sufficient land based air forces in the outer islands. (When I say carriers I mean carrier borne air forces as much as the ships - the IJN didn't have frontline aircraft in reserve, but did have several hundred obsolescent carrier types available). The US carriers can break a siege even by exchanging themselves 1:1 with IJN carriers - I doubt IJN land power could maintain a blockade alone.

 

[Glenn239]

There seems to be quite a bit of discussion of Japan winning the war, or loosing the war, based upon how quickly they take the NEI, or perhaps, more accurately, that their inevitable defeat can be better staved off, for a limited time, by capturing the NEI sooner rather than later. While taking the NEI can give them some oil production (which they may or may not be able to get home, regardless of enemy action), it cannot win them the war, nor postpone their defeat all that long.

The NEI is a straw man, intended not as a serious proposal for how Japan could succeed in the war. Saying NEI "must" be first, and in maximum strength, is just trying to suck up all the shipping resources so there's not enough left for Hawaii too. It's a way to avoid even discussing the premise of a maximum strength eastern offensive at start.

OTOH, taking the Hawaiian islands (which cannot win them their war, either), can make it far harder for the USA to interfere with their oil supplies until the USA manages to either retake Oahu, or build up the capacity to project power into the western Pacific ocean.

Biggest effect with the fall of Hawaii would be a naval vacuum in the Pacific and Indian Ocean in the 2nd half of 1942. It's even possible the Australians would make a separate peace. Eventually land based air fills in the gaps.

After that, the IJN from 1943 to the end of the war consumed millions of tons of oil for next to no measurable gain. In that the IJN failed to win a single battle, and its warships failed to sink a single major warship. It literally didn't matter whether the IJN had to idle its fleet on January 1st 1943 due to oil shortages or not, the combat effect of the Japanese navy after the first year was negligible. The F6F Hellcat decided the matter. For Japan, Hawaii at least gives the illusion of a formidable position, that might make the Americans consider talking. (Probably not, but you never know). The Japanese can bluff their oil reserves to an extent. They can't bluff ownership of Hawaii and Sumatra.

As I see it, there can be only one of three ways for the US to do this, one is around Africa, two is through the Aleutian islands in the far north Pacific, and three is swinging far south and coming through Australia/NZ. All of these alternatives are far inferior to just retaking the Hawaiian islands, but hey. If the USA didn't see themselves going that route, might we see B-36's operating out of Attu/Kiska?

Historically the USN came storming west out of Oahu when ready. That's because it was the most direct, logistically feasible, route. I would assume that if Oahu fell in 1942, in 1944 the USN would retake it. It might take the Marshalls first to better isolate it. Either way, any possible political gain for Japan comes in 1942 or 1943 at the latest.

Basically, I see this concept as a very interesting WI scenario, not a way for Japan to win a war they cannot win....

To even have a chance at negotiated peace the Japanese needed to take Hawaii (50/50), then the NEI (90/10) then the SU and cut the TSRR (50/50) then have the US offer terms (30/70). That's an 8% chance, of not even victory, just less defeat. What that says is Japan should have taken Hull's offer in November 1941. But militarists only see military solutions - any concession or diplomatic wrangling is "weakness".

 

[Finbarr the Fair]

Interesting, if sometimes heated, concept and discussion.

Is there a consensus first on what the IJA and IJN would have to commit to having even a 50:50 chance of taking Oahu and neutralizing teh US presence in the Hawaian chain? Then what impact would committing these forces to Hawai have on the sequencing of their attacks on Borneo and the DEI. (I'm assuming that the attacks on the Philippines and Malaya/Singapore can still go ahead simultaneously with Pearl Harbour and the invasion. IF these conquests are delayed the whole strategy becomes even more problematic.)

Success in taking Oahu etc. does give the Japanese at least a chance of making the US an offer it has to consider. "let us have the Southern Resource Area and we'll return it to you". Of course, there had better be no atrocities during the Occupation for that to stand any chance of not provoking a new war pdq. I'll let American posters decide whether the offer stands any chance of being successful if suggested during the lull in the conflict the Japanese envisaged after they achieved their objectives.

However, losses taken at PH etc. plus the delay in launching phase two attacks on the DEI, Borneo and Burman mean these objectives could take longer to fall and there could be more damage to the installations. Meaning Japan will not be able to fight the war beyond 1943, just when the USN is ready to retake PH and advance across the central Pacific. In 1943 expect action on the SW front to get bases for submarines and aircraft to interdict Japanese SLOC.

Wider issues - seizing Hawai makes 'Germany First' hard to sustain so expect some impact on the War in the Atlantic, N. Africa and Ostfront - longer second happy time, no Torch and less lend lease to the Soviets. So it might do the German war effort some good for a while. Until August 1945 I suppose.

So, interesting option but it seems too risky even for the Japanese. Especially if it does reduce the prospects for a quick capture of its key resource targets.

 

[Shadow Master]

I have been away from this for awhile, both from helping friends and family, and from dealing with the sicknesses shared with me by my fellow travelers on the flight home from Irma. Still haven't licked the coughing, but the fever and sneezing is over.

I like this concept enough to look into it for at least an outline of an ATL, but I'm not doing anything more till I recover my health, unfortunately.

 

[sloreck]

Let's just assume that the Japanese scrape together the transport to get enough troops and supplies to the Hawaii to take Oahu, and that furthermore they manage to conceal this massive movement as well as they did the KB movement. Even those who propose this as a good idea will agree this means the taking of Borneo, DEi, and Malaya is significantly delayed (4-6 months) IF they can do it at all given the Allies will have a better chance to get things sorted out to defend. Just keeping the force in Hawaii supplied with food, fuel, and ammunition will eat up a lot of Japanese merchant shipping, before the USN with submarines and/or surface ships sink any of these. Furthermore escorting these convoys over this vast distance will require significant naval forces. What this means is, even more than OTL, the Japanese will stake EVERYTHING on the Hawaii attack and the USA getting weak in the knees and folding.

Will the Japanese treat any captured US military personnel any better than they treated Allied POWs elsewhere? NO, so that will be an "issue". Will the Japanese get first call on any food from Hawaii produced/caught there? YES, and as the supplies from Japan get scantier civilian rations WILL drop to starvation levels and if the USA sends food for civilians via neutrals, that will also be taken by the Japanese (like red cross parcels OTL), so another "issue". Will the Japanese occupation authorities be less than civil to the "white" population and the Chinese, like in other areas where such civilians were in occupied areas? YES, even if they don't go all Nanking or "volunteer" women to provide staffing for soldiers brothels so yet more "issue". Finally, if the US attempts to recover Oahu militarily will the Japanese use the civilian population of Hawaii as shields similar to what happened in manila OTL? YES, no question about, an "issue".

IMHO even if the USA says "OK take what you want in the "southern resource area" just give us Hawaii back", which would require not just one but a whole battalion of ASBs to make happen, when the Japanese leave Hawaii the residua of the occupation will so piss off the USA that a resumption of the war is inevitable.

OTL the Japanese plan was basically kick the USA so hard initially and occupy everything they need/want so quickly that the morally corrupt Americans would accede to their demands. The fallback was that in doing this, they would establish defensive lines strong enough so that these morally weak Americans would give up and not be willing to spend blood and treasure to break through. As crazy as this strategy was, there was a fallback at least in theory, and while things were being sorted out the Japanese would have access to the raw materials they needed for their economy and the ongoing war in China. With the "Hawaii" plan, the Japanese DO NOT get access to the raw materials and food they need to continue the war in China and sustain and build military forces defending the island chains, and they don't have enough resources to grab all the islands they did OTL.

If the Japanese attempt to take Hawaii and fail, they have pretty much lost the war right then and there - certainly in less than 12 months. If they do take Hawaii, it will most assuredly cost them significant losses in ships, and aircraft as well as expendables. Keeping Hawaii supplied will be a huge drain on Japan and the IJN and long term they simply cannot hold it if the USA wants it back. It is inevitable that a Japanese occupation of Hawaii will generate an incredible amount of resentment and hatred on the part of Americans, and the terms imposed on Japan will reflect this (compared to OTL).

Japan takes Hawaii makes an interesting OTL and some interesting although ASB books, but is probably not possible and if Japan tries for this with resources adequate to the task maximally gains them Hawii but loses much else of value.

 

[trurle]

OTL the Japanese plan was basically kick the USA so hard initially and occupy everything they need/want so quickly that the morally corrupt Americans would accede to their demands. The fallback was that in doing this, they would establish defensive lines strong enough so that these morally weak Americans would give up and not be willing to spend blood and treasure to break through. As crazy as this strategy was, there was a fallback at least in theory, and while things were being sorted out the Japanese would have access to the raw materials they needed for their economy and the ongoing war in China. With the "Hawaii" plan, the Japanese DO NOT get access to the raw materials and food they need to continue the war in China and sustain and build military forces defending the island chains, and they don't have enough resources to grab all the islands they did OTL.

If the Japanese attempt to take Hawaii and fail, they have pretty much lost the war right then and there - certainly in less than 12 months. If they do take Hawaii, it will most assuredly cost them significant losses in ships, and aircraft as well as expendables. Keeping Hawaii supplied will be a huge drain on Japan and the IJN and long term they simply cannot hold it if the USA wants it back. It is inevitable that a Japanese occupation of Hawaii will generate an incredible amount of resentment and hatred on the part of Americans, and the terms imposed on Japan will reflect this (compared to OTL).

Japan takes Hawaii makes an interesting OTL and some interesting although ASB books, but is probably not possible and if Japan tries for this with resources adequate to the task maximally gains them Hawii but loses much else of value.

Yes, the all-out invasion to Hawaii need Japanese motives to be completely different from OTL. Forget about resources. To make invasion to Hawaii plausible, it can be motivated only by fear.
Well, i can imagine (just in theory) the different lead-up to the conflict, with some skirmishes against US in 1937-1941 period, and much better relations with British, Soviets and Dutch. Therefore, fear of the powerful and aggressive US instead of fear of maritime blockade may motivate Japanese to attack Hawaii in the manner Shadow Master promotes. May be the POD must be back to the non-adoption of the "Good Neighbour Policy" by US back in 1933.

 

[Shadow Master]

Let's just assume that the Japanese scrape together the transport to get enough troops and supplies to the Hawaii to take Oahu, and that furthermore they manage to conceal this massive movement as well as they did the KB movement. Even those who propose this as a good idea will agree this means the taking of Borneo, DEi, and Malaya is significantly delayed (4-6 months) IF they can do it at all given the Allies will have a better chance to get things sorted out to defend. What this means is, even more than OTL, the Japanese will stake EVERYTHING on the Hawaii attack and the USA getting weak in the knees and folding.

I feel that this is pretty accurate overall, and does indeed cover the situation clearly. Taking Oahu, after taking the outer islands and bringing in land based airpower to augment/replace the KB, is indeed a huge gamble. Once I get over the last of the illnesses that I am suffering from ATM, I want to take a good long look at the tonnage requirements that would be needed for the Hawaiian theater.

Just keeping the force in Hawaii supplied with food, fuel, and ammunition will eat up a lot of Japanese merchant shipping, before the USN with submarines and/or surface ships sink any of these. Furthermore escorting these convoys over this vast distance will require significant naval forces.

This is of course one of the things I am going to want to research. Looking at the OTL "Defensive Perimeter", I have to wonder what securing Oahu does to the need for all those small, far flung garrisons? Will the Japanese just flat out abandon in mass many of these islands, I think not, but can they strip them down a great deal with Oahu in Japanese hands, I think so. So I'll have some good deal of work to do, once I am feeling up to the task.

IMHO even if the USA says "OK take what you want in the "southern resource area" just give us Hawaii back", which would require not just one but a whole battalion of ASBs to make happen, when the Japanese leave Hawaii the residua of the occupation will so piss off the USA that a resumption of the war is inevitable.

I cannot even picture this happening, but hey. Not the part about the renewed war over Japanese mistreatment of POW's and civilians, but the part where the USA even agrees to anything short of total victory in the first place.

OTL the Japanese plan was basically kick the USA so hard initially and occupy everything they need/want so quickly that the morally corrupt Americans would accede to their demands. The fallback was that in doing this, they would establish defensive lines strong enough so that these morally weak Americans would give up and not be willing to spend blood and treasure to break through. As crazy as this strategy was, there was a fallback at least in theory, and while things were being sorted out the Japanese would have access to the raw materials they needed for their economy and the ongoing war in China. With the "Hawaii" plan, the Japanese DO NOT get access to the raw materials and food they need to continue the war in China and sustain and build military forces defending the island chains, and they don't have enough resources to grab all the islands they did OTL.

Another of the things on my agenda is going to be the costs of a consolidated DP, with a Japanese Oahu/Hawaiian islands, vs the OTL DP. And yet another will have to be the OTL USN submarine war, and where the US subs were based out of historically, and where they are going to be forced to be based out of in this ATL. So many research tasks will have to be done, over the coming months, but, looking at the level of participation and interest in this thread, I think that this will be a journey well worth taking. At a minimum, I would consider dispelling & disproving several pre-conceived ideas about this "Invasion Hawaii" concept a victory for myself, and the forum community as a whole. Even if the total success I am projecting for this operation turns out to be flat out impossible, I will have learned that through first hand R&D, and will be able to share this information with anyone that cares to read up on the "Sea lion of the Pacific", as one fellow put it.

If the Japanese attempt to take Hawaii and fail, they have pretty much lost the war right then and there - certainly in less than 12 months. If they do take Hawaii, it will most assuredly cost them significant losses in ships, and aircraft as well as expendables. Keeping Hawaii supplied will be a huge drain on Japan and the IJN and long term they simply cannot hold it if the USA wants it back. It is inevitable that a Japanese occupation of Hawaii will generate an incredible amount of resentment and hatred on the part of Americans, and the terms imposed on Japan will reflect this (compared to OTL).

I have to agree there, no doubts about it. Failure in an ATL, where the Japanese go down this path, costs them the war, and sooner rather than later. And who knows, my efforts to prove that this could have been done, may indeed turn out to prove that the costs in the Eastern Pacific, in terms of men, material, losses, and just flat out tying up of resources desperately needed elsewhere, might cause the intended seizure of the SRA to be impossible to execute, or so costly due to delays, that the Japanese loose their war and Empire a couple years sooner than OTL.