A Japanese invasion of Hawaii

[Orm]

I find the notion that the Japanese could spend unlimited amounts of oil, and energy, to send their fleets back and forth absurd.

However, I do find the thought that Japanese could have some flexibility on when to strike intriguing. Not sure how long that timespan would have been. A couple of days? A week? And what information would they have tried to get? And would they have trusted it as accurate if they got it from agents? How long time delay would information from a spy to getting to the fleet have?

Anyway. If the Japanese had some flexibility, or even unlimited, unreasonable, flexibility, would they really have waited for a better target profile before attacking? Not even considering the risk they were taking by delaying? I am stating that if the Japanese had that flex, and had that certain information that the BBs were in port, but the CVs missing, they would have launched.

So, back to my original question. If the Japanese wait for the carriers to be in Hawaii, then what if the battleships left before the carriers arrive? How would the Japanese strike force react then?

[Platoonist]

I find this discussion interesting. As I did with previous discussions. What if there was 2 carries in harbour, but a majority of the battleships had left. Would even the Japanese Admiralty, back then. have thought that was a better target?

Yamamoto definitely wanted to sink battleships at PH and made sure the Kido Butai carried the weapons to do it. Lauded as he is as the "Father of Japanese Naval Aviation" and a believer that battleships were white elephants, he also firmly believed that they were fixed in the minds of the American public as the sine qua non of sea power. Should the Japanese succeed in sinking one or more of these behemoths, Yamamoto expected that their will to continue the war would sink along the shattered battlewagon. His utterances about sinking carriers were largely an afterthought. That is why he was so insistent on developing a torpedo that could function in the shallow water of Pearl Harbor as well as using modified 16" battleship shells dropped from level bombers. Simply dive bombing with the 250kg bombs that the Aichi Val carried wasn't going to penetrate the armored deck of a BB although they could do serious harm through the wooden deck of a carrier.

[Aurelian]

Yamamoto also thought battleships were far more important than carriers. (Note the flagships he picked.) He was also willng to trade his carriers for sunk American BBs. (The Attack on Pearl Harbor. Strategy, Combat, Myths, Deceptions by Alan D. Zimm)

[Platoonist]

Yamamoto also thought battleships were far more important than carriers. (Note the flagships he picked.) He was also willng to trade his carriers for sunk American BBs. (The Attack on Pearl Harbor. Strategy, Combat, Myths, Deceptions by Alan D. Zimm)

In the book, Zimm mentions at one point Japanese planners seriously considered sending the carriers on a one-way mission. Since all of Japan's big fleet carriers lacked the range to get to Oahu and back, the planners considered sailing the carriers there, launching the strike, and then after recovering the planes, they would shift the pilots and carrier crews to escorting vessels and then scuttle the carriers before heading home. This bizarre proposal was dropped when other means were found to refuel the carriers.

Sinking US carriers was all to the good, but Yamamoto wanted US battleships dead as a demoralization tool even if it meant sacrificing flattops.

[RangerJoe]

I find this discussion interesting. As I did with previous discussions. What if there was 2 carries in harbour, but a majority of the battleships had left. Would even the Japanese Admiralty, back then. have thought that was a better target?

warspite1

I am assuming this question has nothing to do with the notion that the KB could sail up and down the North Atlantic for weeks or months on end in order to determine when the Japanese Empire go to war with the USA, the Dutch and the British Empire. But is instead a thought provoking question on whether the Japanese had really understood that the carrier was the key combat vessel in the Pacific and the day of the battlewagon - as the primary capital ship - was over.

If the Japanese had the choice, I think they were still wedded to the battleship as the key weapon. Yes, they understood the value of the carrier in the expanse of the Pacific, but actions later in the war perhaps suggested they still had the idea that the decisive battle would be fought between battleships.

But on the other hand, the lack of use of the battleships later on could be because of the lack of oil - Midway took a heavy toll on oil stocks.

An interesting question indeed.

If the KB could sail up and down the North Atlantic I am sure that it would have been noticed. I do believe that the Royal Navy would have been scared . . .

[warspite1]

Yamamoto also thought battleships were far more important than carriers. (Note the flagships he picked.) He was also willng to trade his carriers for sunk American BBs. (The Attack on Pearl Harbor. Strategy, Combat, Myths, Deceptions by Alan D. Zimm)

warspite1

So if this is all true - and all the evidence I’ve seen points to that being true (and most others here believe that to be the case) - then what makes Yamamoto suddenly believe that an attack on Pearl Harbour HAS to include the US carriers? And that no carriers = no attack?

The notion that Yamamoto believed the destruction of the carriers was the most important element of any attack on PH is central to this ‘plan’ but doesn’t appear to borne out in his thinking. So the central premise for this totally unworkable plan does not stack up and is giving Yamamoto ideas with hindsight.

[Platoonist]

Apparently, there were different target priority orders to placate different audiences. Typical, perhaps of the Japanese tendency to try and keep harmony in the group and let everybody save face. The Naval General Staff, anxious to preserve their carriers, were told that land-based air was first on the strike list. Yamamoto was told that battleships would have top priority. The aviators actual executing the attack had the final say, and were hoping the carriers would be there as that would be their first priority regardless of orders. This caused a muck-up in the actual attack as Genda and Fuchida directed directed roughly 40% of the torpedo bombers to go after the carrier moorings even though a float plane recon fight that morning radioed that there were no US carriers in port. They could have been more profitably used on battleships and heavy cruisers. They sank the old target ship Utah instead and put a torpedo in the light cruiser Raleigh.

Yamamoto's controversial decision to include midget submarines in the attack may have been indicative of his lack of faith in air power alone to deliver the decision. Especially when it came to sinking battleships. The airmen didn't want them included, fearing that might jump the gun and ruin the surprise element of the attack. If not for US bureaucratic bungling after the USS Ward fired on one, they might have succeeded in doing just that.

[warspite1]

Apparently, there were different target priority orders to placate different audiences. Typical, perhaps of the Japanese tendency to try and keep harmony in the group and let everybody save face. The Naval General Staff, anxious to preserve their carriers, were told that land-based air was first on the strike list. Yamamoto was told that battleships would have top priority. The aviators actual executing the attack had the final say, and were hoping the carriers would be there as that would be their first priority regardless of orders. This caused a muck-up in the actual attack as Genda and Fuchida directed directed roughly 40% of the torpedo bombers to go after the carrier moorings even though a float plane recon fight that morning radioed that there were no US carriers in port. They could have been more profitably used on battleships and heavy cruisers. They sank the old target ship Utah instead and put a torpedo in the light cruiser Raleigh.

Yamamoto's controversial decision to include midget submarines in the attack may have been indicative of his lack of faith in air power alone to deliver the decision. Especially when it came to sinking battleships. The airmen didn't want them included, fearing that might jump the gun and ruin the surprise element of the attack. If not for US bureaucratic bungling after the USS Ward fired on one, they might have succeeded in doing just that.

warspite1

Thanks Platoonist. Nice post. Can I ask where that information came from? Is it Zimm?

[Platoonist]

Yes. The information is from his 2011 US Naval Insitute publication; Pearl Harbor Combat Strategy, Myths and Deceptions. Very analytical and eye opening work.

[TulliusDetritus]

Interesting all of this. So Yamamoto was not a true revolutionary. No big difference with the Taranto attack then. If true, he was merely an unconscious agent of history.

[Platoonist]

Interesting all of this. So Yamamoto was not a true revolutionary. No big difference with the Taranto attack then. If true, he was merely an unconscious agent of history.

There are certainly a lot of shades of grey with Yamamoto. He often bristled at the arrogance and contempt toward the enemy becoming prevalent in the IJN after early victories and he loathed the bone headed-nature of the IJA officer corps. But he seems to have succumbed to hubris himself on occasion. His rather slip-shod planning at Midway, and the way his underlings rammed the faulty table top exercises and war games through, over-turning results they didn't like is indicative of that.

Then there the whole sorry story of the attritional fighting around Guadalcanal where he could never quite seal the deal, but that is another topic.

[Aurelian]

Yamamoto also thought battleships were far more important than carriers. (Note the flagships he picked.) He was also willng to trade his carriers for sunk American BBs. (The Attack on Pearl Harbor. Strategy, Combat, Myths, Deceptions by Alan D. Zimm)

warspite1

So if this is all true - and all the evidence I’ve seen points to that being true (and most others here believe that to be the case) - then what makes Yamamoto suddenly believe that an attack on Pearl Harbour HAS to include the US carriers? And that no carriers = no attack?

The notion that Yamamoto believed the destruction of the carriers was the most important element of any attack on PH is central to this ‘plan’ but doesn’t appear to borne out in his thinking. So the central premise for this totally unworkable plan does not stack up and is giving Yamamoto ideas with hindsight.

Yamamoto's planners at one time considered a one way mission. Why? No Japanese carrier had the range to sail from Japan to Pearl and back. They would scuttle any carrier that couldn't return due to fuel. Remember what the land based bombers did to Force Z? They projected that same ability on American bombers, so they expected to lose one, likely more than one. (They did fix the range problem (overloading them with fuel so they could replenish. And adding tankers.) But that would of not helped fending off the expected bomber attacks.

Any crippled CV would of been scuttled as towing them back to Japan was out of the question. Distance, winter weather, lack of fuel, to say nothing of continues land based bomber attack, would of seen to that. Japanese intel reported 550 aircraft on Oahu.

His plan was that even if they were detected 24 hours before the attack, they were to attack. I don't see anyone thinking they would be American coming back to port. like how they thought the incoming raid were B-17s due from the mainland.

[Aurelian]

Yes. The information is from his 2011 US Naval Insitute publication; Pearl Harbor Combat Strategy, Myths and Deceptions. Very analytical and eye opening work.

I bought it based on the recommendation from someone here. It is a very good book.

[Curtis Lemay]

I'll just repeat that the invasion force to Malaya WAS detected. No effective action was taken. And IF the carrier strike force was detected it would probably be by a civilian ship. No guarantee that the details registered would have much relation to reality or that they would have been taken seriously (especially if nothing happened when the carriers were aborted).

For sure, two carriers were worth (in real terms) much more than eight BBs. And it would be better to abort the mission than strike with no carriers in Pearl.

After the strike, landing some battalions on the neighbor islands, then flying in some Zeros and Bettys to torch Pearl risks very little for putting Pearl out of action for a long time.

[warspite1]

For sure, two carriers were worth (in real terms) much more than eight BBs. And it would be better to abort the mission than strike with no carriers in Pearl.

warspite1

Okay so can we break this down into bitesize chunks? As you say, you've wargamed this scenario using detailed sims so can you let me know how you've played this out?

So for the purposes of this discussion we are to accept that Yamamoto had more foresight than historically and told his superiors that at least two carriers must be in Pearl and taken out - or the whole operation is pointless. It is also agreed that all operations (except the PI) are to take place (and need to be co-ordinated), and there will be landings by troops in the HI (but not Oahu) together with airbases established at some point. But we will come to all this later. The first point to understand is the attack on Pearl itself.

So firstly:

1941
- The KB sail on the 26 November. They know that there are two carriers at Pearl at this time.
- 3 December. The KB refuel.
- I am not sure on real life comms security but for the purposes of this scenario let's assume that the KB can receive secure messages (but can't transmit).
- By this time (3 December) the KB are made aware that Enterprise has left Pearl.
- On the 5 December they get the unwelcome news that Lexington has left Pearl and there is still no sign of Enterprise. Saratoga appears to the Japanese to be a long term absentee.

So how have you played this out initially?
- Have the KB returned to port?
- Do they wait around for a few days? If so, how much endurance (fuel and food) does the KB have if they wait?
- When do they have to turn back?

We know that Enterprise returns to Pearl only on the 7th and Lexington a few days after (10th? exact date unknown as she was diverted to look for the KB and actually returned on the 13th).

So in this phase, how have you wargamed this opening phase?

[Curtis Lemay]

Okay so can we break this down into bitesize chunks? As you say, you've wargamed this scenario using detailed sims so can you let me know how you've played this out?

Only the invasion. No existing wargame allows the raid the option to abort everything.

1941
- The KB sail on the 26 November. They know that there are two carriers at Pearl at this time.
- 3 December. The KB refuel.
- I am not sure on real life comms security but for the purposes of this scenario let's assume that the KB can receive secure messages (but can't transmit).
- By this time (3 December) the KB are made aware that Enterprise has left Pearl.
- On the 5 December they get the unwelcome news that Lexington has left Pearl and there is still no sign of Enterprise. Saratoga appears to the Japanese to be a long term absentee.

So how have you played this out initially?
- Have the KB returned to port?
- Do they wait around for a few days? If so, how much endurance (fuel and food) does the KB have if they wait?
- When do they have to turn back?

We know that Enterprise returns to Pearl only on the 7th and Lexington a few days after (10th? exact date unknown as she was diverted to look for the KB and actually returned on the 13th).

So in this phase, how have you wargamed this opening phase?

It would abort and fall back to a refueling/resupply point. Wait for a try occurring the following Sunday.

Just want to re-emphasize the level of inert obliviousness the Allied forces were in:

1. The Malaya invasion forces were detected well in advance. No effective action was taken.
2. The Pearl aircraft were detected by radar. Ignored.
3. A mini-sub was detected at the harbor entrance and probably sunk. Ignored.
4. The Japanese ultimatum was decoded a day before Pearl - except for one part which was held for the morning. No action taken.
5. When the final part of the ultimatum was received on the day of the attack - clearly a war warning - the opportunity to telephone Kimmel was aborted. A message via telegraph was bungled and didn't arrive till after the attack.
6. When the attack occurred, news of it was disbelieved. It couldn't have been Pearl!
7. Land AAA guns in Pearl didn't have ammo initially.
8. Aircraft on Oahu were deployed to prevent sabotage - a disaster for the air raid.
9. The day of the attack - after news of Pearl has spread - the air forces on Luzon were caught on the ground and destroyed.

The North Pacific in December has very bad weather and high seas. Detection of the carriers would have been unlikely and even if it occured, the report would have been unlikely to have much accuracy or be interpreted to be what it actually was. This would be made worse if the Japs aborted and nothing happened. Having cried wolf once and been wrong, how would any intel officer ever be listened to again?

[Platoonist]

Another factor that Zimm brings up in his book, is that Japan had no reserve A6M Zeros in late 1941. Production was anemic and not keeping up with demand. One major bottleneck was the limited availability of the 20mm cannon. In order to fill out the air groups on the new carriers Shokaku and Zuikaku, the Japanese had to pull them from the active light carriers Ryujo and Hosho and the escort carrier Taiyo. They then replaced their Zeroes with the obsolescence open cockpit A5M Claude. Most of the IJN's land-based squadrons were in the same boat, so to speak.

There were some land-based Zero squadrons based in Formosa. The Tainan Air Group. But they were committed to covering the Betty's that were to bomb Clark and Nichols Field in Luzon and to help keep the PI isolated and the southern advance covered. The Claude didn't have the range and would have been far inferior to the P-40 Warhawks based there even if it did.

[Aurelian]

And the B-17s there could of bombed Formosa. But, but, this wasn't supposed to happen as the Japanese were to ignore the PI to take some islands in Hawaii....

[warspite1]

We will need to cover the Zero (and other aircraft) situation in due course, but for now, I want to focus on how the PH attack gets underway.

1941

Okay so the KB receive the news of Lexington's departure on the 5 December. At this point they return to the tankers to top up once more in the hope that the carriers will return shortly (I assume food supplies are not an issue). The KB get the news that Enterprise is back in Pearl on the 7 December and heads east once more to await news on Lexington. If they get the good news she too has returned in the next few days, then the Japanese will look to strike Pearl on Sunday 14 December. I think we can assume Lexington would have returned around the 10th? Then, having got to Pearl, unless anyone knows anything different in terms of USN plans for Enterprise and Lexington, we shall assume they were not due to sail from Pearl again until after 14 December.

So next question:

Communications are not my thing. So if anyone knows about this stuff can they comment on what was possible in December 1941 please.

Potential problem facing the Japanese

The KB, approximately just over half way between Japan and Hawaii, are under strict radio silence and are reliant upon comms from Pearl to tell them whether the carriers are in port. How would spies in Pearl let Nagumo know of the carrier situation? And just as important, would any communication be safe from prying US or British ears?

This plan has to ensure that operations in the South China Sea and the Western Pacific remain co-ordinated so as not to give the Allies advance warning. How do Japanese spies in Pearl let Tokyo know the situation so that this information can be disseminated to the various commands either to cease operations or to begin them? Again, I am thinking about this from a security perspective.

[Buckrock]

Good to see you're still relentlessly at it Warspite1. No rest for the wicked.

I have to say in this case, Curtis Lemay's theoretical dog just wouldn't have hunted in reality, no matter what a commercial wargame might allow the wartime Japanese to do.

Anyway, the intel concerning the comings and goings at PH was being sent to Tokyo through the Japanese Consulate in Honolulu using diplomatic comms. Tokyo would then pass this on to Nagumo at sea. This process normally added at least a day's delay for the PH info to reach Nagumo.