Operation Ten-Go - The bigger they come, the harder they fall

[Ming]

Like I said previously, regardless of whether or not the Japanese could have actually crossed the pacific without being detected and seized Pearl Harbor with 1:1 attack odds through Surprise! And Bushido! . . . No planners were going to sign off on it.

 

[Acheron]

Let us assume the Japanese take the forces for Singapore and Philippines and throw them at Hawaii (not DEI as they were running out of oil). Let us also assume the addition of the invasion force does not cause the entire operation to be detected prematurely. The amphibious landing still must come hours after the air strike, ships are simply too slow and would need get way too close to the target, alerting the Americans and potentially blowing the whole thing.

How big will the invasion force be? At Malaysia and the Philippines, Japanese transports could feasibly bring in the ground forces in several trips. The distance to Hawaii precludes this, everything required needs to be brought in now or never.

How quickly could this force overrun all of Hawaii? The Americans would of course try to muster reinforcements. We can assume the IJN dominates the waters around Hawaii, but how long can they stick around? Were the Japanese capable of supplying their ships at sea? To my knowledge, this was no mean feat. And if so, how much freight capacity will be required for the initial air strikes against the fleet, later air strikes and naval bombardment to support the ground forces and to fight a major fleet action against whatever the USN could scramble from the west coast? All of Hawaii must be taken and fortified by the time the US Atlantic Fleet can make it to the scene, one island remaining in American hands would be unacceptable to the completely overstretched logistics.

 

[Ming]

How big will the invasion force be? At Malaysia and the Philippines, Japanese transports could feasibly bring in the ground forces in several trips. The distance to Hawaii precludes this, everything required needs to be brought in now or never.

How quickly could this force overrun all of Hawaii?

This is a pretty big wrinkle. Genda apparently planned for a two to four week conquest. Really a big gamble if you have to bring everything in one trip and Oahu doesn't fall according to schedule.

The amount of shipping and fuel required to dig out the defenders if they don't collapse would really cripple Japanese efforts elsewhere, even if the naval battle is more spectacular.

Also, I've just been reminded that Turtledove wrote something about just this scenario. He had the Americans holding out until February but the Japanese still succeeding. Obviously, his books are less rigorous academic studies than they are alt hist nerd tickle bait but at least he did do a little research.

https://turtledove.fandom.com/wiki/Days_of_Infamy_(novel)

 

[Acheron]

This is a pretty big wrinkle. Genda apparently planned for a two to four week conquest. Really a big gamble if you have to bring everything in one trip and Oahu doesn't fall according to schedule.

The amount of shipping and fuel required to dig out the defenders if they don't collapse would really cripple Japanese efforts elsewhere, even if the naval battle is more spectacular.

Also, I've just been reminded that Turtledove wrote something about just this scenario. He had the Americans holding out until February but the Japanese still succeeding. Obviously, his books are less rigorous academic studies than they are alt hist nerd tickle bait but at least he did do a little research.

https://turtledove.fandom.com/wiki/Days_of_Infamy_(novel)

I heard about the book. I think it takes the Americans two tries to retake Hawaii. Sounds sensible to me, first time a rush-job, still underestimating the Japanese combined with a desire for a quick solution leading to wishful thinking -> defeat.

Once the Americans figure out how to apply their overwhelming might correctly though, Japan is doomed. Might prolong the war, so that the US has more time to build nukes, given Japanese war crimes on a large American civilian population bound to happen, these will be used generously. Japan is unlikely to keep the emperor, if they reply that this is unacceptable and that "100 million will die for the emperor" (their actual wartime slogan), the American response will most likely be "Yes, that is the idea."

 

[Dinglehoff]

Let us assume the Japanese take the forces for Singapore and Philippines and throw them at Hawaii (not DEI as they were running out of oil). Let us also assume the addition of the invasion force does not cause the entire operation to be detected prematurely. The amphibious landing still must come hours after the air strike, ships are simply too slow and would need get way too close to the target, alerting the Americans and potentially blowing the whole thing.

How big will the invasion force be? At Malaysia and the Philippines, Japanese transports could feasibly bring in the ground forces in several trips. The distance to Hawaii precludes this, everything required needs to be brought in now or never.

How quickly could this force overrun all of Hawaii? The Americans would of course try to muster reinforcements. We can assume the IJN dominates the waters around Hawaii, but how long can they stick around? Were the Japanese capable of supplying their ships at sea? To my knowledge, this was no mean feat. And if so, how much freight capacity will be required for the initial air strikes against the fleet, later air strikes and naval bombardment to support the ground forces and to fight a major fleet action against whatever the USN could scramble from the west coast? All of Hawaii must be taken and fortified by the time the US Atlantic Fleet can make it to the scene, one island remaining in American hands would be unacceptable to the completely overstretched logistics.

I'm not sure that alerting the Americans will blow the whole thing, landing wise. If they are discovered before the declaration of war or the ships getting bombed, what actions would the US command take? A preemptive strike on the japanese fleet, sail the fleet for a later sea battle or retreat, and prepare island defenses, or do nothing because there's no war yet? Either way there'd still be the same number of troops and supplies on the island and the only question is how much notice they'd have to organize the defense and whether it's enough to defeat the 1-3 divisions they'd be fighting.

 

[hkrommel]

I'm not sure that alerting the Americans will blow the whole thing, landing wise. If they are discovered before the declaration of war or the ships getting bombed, what actions would the US command take? A preemptive strike on the japanese fleet, sail the fleet for a later sea battle or retreat, and prepare island defenses, or do nothing because there's no war yet? Either way there'd still be the same number of troops and supplies on the island and the only question is how much notice they'd have to organize the defense and whether it's enough to defeat the 1-3 divisions they'd be fighting.

How many men did the Americans have? What kinds of defenses were available? Are we assuming that the Japanese navy somehow wipes out the American naval forces even though the Americans will be fighting with land-based air cover? Where will the Japanese land? The north shore of Oahu is notorious for rough surf and riptides. Landing isn't easy when half your forces are swept out to sea where they drown.

I'm genuinely curious about this. If we're assuming the Japanese OOB and strategy we should get an idea of the American one before making huge assumptions. Personally I think the Americans recall the carriers, launch CAP, mobilize local forces, and alert CONUS forces immediately upon detecting the Japanese. If that happens I hardly see Japanese naval superiority at all, which makes a landing impossible, but I'm not as familiar with the land forces the US had available. It had to be something serious, Pearl Harbor was too important to leave sparsely defended.

 

[Ming]

How many men did the Americans have? What kinds of defenses were available? Are we assuming that the Japanese navy somehow wipes out the American naval forces even though the Americans will be fighting with land-based air cover? Where will the Japanese land? The north shore of Oahu is notorious for rough surf and riptides. Landing isn't easy when half your forces are swept out to sea where they drown.
.

About two divisions of ground forces plus odds and ends and a lot of artillery.

https://history.army.mil/books/wwii/Guard-US/ch6.htm

In the year preceding the Pearl Harbor attack, the Army's officer and enlisted strength in the Hawaiian Department grew from 28,798 to 43,177, and Hawaii remained the largest of the overseas garrisons.57 Nearly half the increase represented increments, including a good many men of Japanese descent, drawn from the local population through the induction of the National Guard and the operation of the selective service system.58 Since most of the new men received from the mainland also needed more training, the Hawaiian Department of necessity became a training establishment on a large scale during 1941, resembling in many respects the ground and air training commands then so active in the continental United States.

Until 28 May 1941 the RAINBOW plans contemplated an Army wartime garrison of 79,000 for Hawaii, substantially less than had been scheduled for it in war plans of the mid-1930's.59 On that date the War Department ordered a further reduction of 21,000 and lessened the decrease only slightly to accommodate General Short's plan for additional units to guard the Navy's new air station at Kaneohe Bay on the northeast coast of Oahu.60 By 22 September 1941, when Secretary Stimson and General Marshall went over the strengths of all overseas garrisons with President Roosevelt, Hawaii had its full authorized peacetime strength of about 42,000. They agreed that any further reinforcement of the Hawaiian garrison could be deferred as long as the fleet remained in the Pacific, since the presence of the fleet reduced the threat of major attack.61 The revised RAINBOW 5 plan of November 1941 called for 17,300 more troops to be sent as war reinforcements as soon as possible, and an ultimate war garrison of about 68,000.62 Behind all these figures appears a confidence in Washington during 1941 that Hawaii by comparison with other overseas outposts was well manned, and that in the event of war Hawaii would not be on the front line of conflict as forecast by the larger war garrisons planned for it by the Army during the 1930's.

The air and artillery resources are listed here.

http://www.navweaps.com/index_oob/OOB_WWII_Pacific/OOB_WWII_Pearl_Harbor.php

Genda's two elite division plan is bold to say the least.

 

[Acheron]

About two divisions of ground forces plus odds and ends and a lot of artillery.

Americans with a lot of artillery should not be underestimated. Not to denigrate the other US army, it's just that the US king of the battlefield was a real tyrant.

 

[Dinglehoff]

How many men did the Americans have? What kinds of defenses were available? Are we assuming that the Japanese navy somehow wipes out the American naval forces even though the Americans will be fighting with land-based air cover? Where will the Japanese land? The north shore of Oahu is notorious for rough surf and riptides. Landing isn't easy when half your forces are swept out to sea where they drown.

I'm genuinely curious about this. If we're assuming the Japanese OOB and strategy we should get an idea of the American one before making huge assumptions. Personally I think the Americans recall the carriers, launch CAP, mobilize local forces, and alert CONUS forces immediately upon detecting the Japanese. If that happens I hardly see Japanese naval superiority at all, which makes a landing impossible, but I'm not as familiar with the land forces the US had available. It had to be something serious, Pearl Harbor was too important to leave sparsely defended.

If the japanese aren't discovered then the naval strike results would be the same. If they are, it's impossible to do more than speculate. The carriers were already out, and the rest of the ships would probably be sent out to sea for possible combat; unless the Roosevelt administration orders them to remain in port for political reasons. There could be great losses on either side, and the japanese might try to land without wiping out the naval forces ahead of time.

 

[hkrommel]

If the japanese aren't discovered then the naval strike results would be the same. If they are, it's impossible to do more than speculate. The carriers were already out, and the rest of the ships would probably be sent out to sea for possible combat; unless the Roosevelt administration orders them to remain in port for political reasons. There could be great losses on either side, and the japanese might try to land without wiping out the naval forces ahead of time.

You said...

I'm not sure that alerting the Americans will blow the whole thing, landing wise.

So we're assuming they're discovered. Frankly, I don't see how they could coordinate a simultaneous land and naval strike without being discovered. Too much required coordination at a low speed, they're bound to be detected.

And with that in mind, the Japanese will need to neutralize Pearl Harbor in order to accomplish anything. Otherwise they'll just be operating under American air cover and those planes will both outnumber and outgun the Japanese. Since @Ming helpfully provided some information on what forces the Americans had, the Japanese would need to slog their way against a prepared, defending enemy with artillery superiority.

So basically to succeed the Japanese need to:
1. Remain undetected (nearly impossible)
2. Neutralize the American naval forces at Pearl Harbor completely. A single destroyer or even a couple torpedo boats getting among your troop transports is enough to destroy your invasion force.
3. Neutralize the American air forces at Pearl and other bases, otherwise the land-based air can pick off the Japanese warships and transports one by one.
4. Find a landing site (still curious on where that would be)
5. Get everything in position to land
6. Land. Also to retain the element of surprise this would need to be done almost simultaneously with tasks 2 and 3, otherwise the American land forces would just get into position to give the Japanese a warm, high explosive welcome.
7. Gain a beachhead and supply it. How they supply it is a mystery to me because they need to take a port and land supplies unless they plan on using rowboats or small craft to do beach landings, which won't supply heavy weapons very well
8. Push the Americans out, across eight islands, before they get reinforced from the mainland.

I just really don't see how that is remotely plausible. Even if you hand wave 3 or 4 of those points there's still another 4 or 5.

 

[Dinglehoff]

You said...



So we're assuming they're discovered. Frankly, I don't see how they could coordinate a simultaneous land and naval strike without being discovered. Too much required coordination at a low speed, they're bound to be detected.

And with that in mind, the Japanese will need to neutralize Pearl Harbor in order to accomplish anything. Otherwise they'll just be operating under American air cover and those planes will both outnumber and outgun the Japanese. Since @Ming helpfully provided some information on what forces the Americans had, the Japanese would need to slog their way against a prepared, defending enemy with artillery superiority.

So basically to succeed the Japanese need to:
1. Remain undetected (nearly impossible)
2. Neutralize the American naval forces at Pearl Harbor completely. A single destroyer or even a couple torpedo boats getting among your troop transports is enough to destroy your invasion force.
3. Neutralize the American air forces at Pearl and other bases, otherwise the land-based air can pick off the Japanese warships and transports one by one.
4. Find a landing site (still curious on where that would be)
5. Get everything in position to land
6. Land. Also to retain the element of surprise this would need to be done almost simultaneously with tasks 2 and 3, otherwise the American land forces would just get into position to give the Japanese a warm, high explosive welcome.
7. Gain a beachhead and supply it. How they supply it is a mystery to me because they need to take a port and land supplies unless they plan on using rowboats or small craft to do beach landings, which won't supply heavy weapons very well
8. Push the Americans out, across eight islands, before they get reinforced from the mainland.

I just really don't see how that is remotely plausible. Even if you hand wave 3 or 4 of those points there's still another 4 or 5.

You're assuming much more than them just being discovered; and what's plausible isn't determined by counting off points on your list here, which I see you've padded out with superfluous points and over-confident fiction.
The historical strike force got into position without being detected. Whether they would do it with more ships is a matter of chance, as is how successful their approach to the islands would be after that point. I have no reason to believe they'd need to get landed onto an actual beach undiscovered or at the same time as the initial strike takes place, or that the japanese air forces would be completely ineffective at suppressing or destroying the land squadrons there, or that the defense forces will be particularly well prepared for your warm welcome. There's also no reason to believe reinforcements would come from the mainland, particularly if the japanese enjoy good luck and success with the naval combat, since we didn't send help to our forces that were trying to hold out in the Pacific elsewhere.

 

[Graf Zeppelin]

The Japanese force traveled with maximum stealth from the start, they pretended to be in port, sailed elsewhere and even put fake sailors of the ships in the harbors. Then proceeded with radio silence.

No way a huge and slow transport fleet escorted by half of the Japanese navy could maintain that stealth and arrive undetected.
Its extremly unlikely.

 

[Acheron]

So basically to succeed the Japanese need to:
1. Remain undetected (nearly impossible)

I agree that retaining the element of surprise is absolutely essential. And as her Erlaucht or Hochgeboren mentioned, the Japanese used extensive deception measures for the fast carrier strike force. I wonder though if it is doable. An ocean is huge, and the Japanese picked a route where they were unlikely to encounter any ships.

2. Neutralize the American naval forces at Pearl Harbor completely. A single destroyer or even a couple torpedo boats getting among your troop transports is enough to destroy your invasion force.

Well, supposedly the fleet would also have more than carriers and transports. If range permits, I would assume they would include battleships anyway, as a lot of firepower will be needed to hold Hawaii.

3. Neutralize the American air forces at Pearl and other bases, otherwise the land-based air can pick off the Japanese warships and transports one by one.

True, though didn't they accomplish this historically? It took the Americans a while to figure out how to handle the Reisen.

4. Find a landing site (still curious on where that would be)

I would assume that this would of course be done beforehand, to my knowledge, the Japanese heavily researched the Pearl Harbor naval base, surely they could also have checked for landing spots.

5. Get everything in position to land

Simple maneuvering. In Peacetime. During war, I agree, every little bit of remaining US resistance can have an effect way out of proportion.

6. Land. Also to retain the element of surprise this would need to be done almost simultaneously with tasks 2 and 3, otherwise the American land forces would just get into position to give the Japanese a warm, high explosive welcome.

If the fleet remains undetected, then of course the Japanese will have strategic surprise. Tactical surprise is another matter. Historcially, didn't the Hawaii forces quickly prepare for a landing or not? Any data on what they managed to do within the first couple of hours?

7. Gain a beachhead and supply it. How they supply it is a mystery to me because they need to take a port and land supplies unless they plan on using rowboats or small craft to do beach landings, which won't supply heavy weapons very well

True. I wonder how good a force the Japanese could land without having a harbor. And getting a harbor, what options are there, besides Pearl Harbor, which as a major military base would have considerable combat power, despite recent and effective bombing?

8. Push the Americans out, across eight islands, before they get reinforced from the mainland.

I wonder though, how many of these islands are big enough to put up a fight themselves and which must fall if the main isles fall?

I just really don't see how that is remotely plausible. Even if you hand wave 3 or 4 of those points there's still another 4 or 5.

Quite so. A heck of a gamble. Way too much would depend on US response being repeatedly and decisively inadequate.

 

[hkrommel]

I wonder though if it is doable. An ocean is huge, and the Japanese picked a route where they were unlikely to encounter any ships.

It was doable historically because the lack of radio waves emitting from the fleet. If they were a larger force that could undertake and support a landing, they would need radios, which travel a long ways and enable detection. So maybe it's possible if the US is completely asleep, but that's unlikely and that's not what happened historically. Even historically the Pearl Harbor strike was detected, but the Japanese planes happened to be in a very similar formation to a group of B-17s due to arrive that day. Sheer luck, essentially. If they're emitting radio waves though they'll need to get lucky multiple times. Just as Fortune favors the bold, it also favors those who don't rely on it.

Well, supposedly the fleet would also have more than carriers and transports. If range permits, I would assume they would include battleships anyway, as a lot of firepower will be needed to hold Hawaii.

They did have two battleships and an assortment of escorts historically, but to increase the size of that force they would be risking something like half their navy on an operation where they would be sure to suffer heavy losses even if they did win.

Aside from that, it would be extremely foolish to not fully engage the USN and risk losing the naval battle altogether, stranding your forces (assuming they even make it ashore under those circumstances) and allowing the US to sweep across the Pacific in record time.

True, though didn't they accomplish this historically? It took the Americans a while to figure out how to handle the Reisen.

It depends on what they need to accomplish. Historically the Japanese took pretty bad losses on the second wave just from AA. They would be outnumbered, outgunned, and would be reduced down to nothing in a about a week if they suffer the losses they did historically during the Pearl Harbor attack. They could of course hold back and not undertake the types of strikes that Pearl Harbor was, but that means they don't hurt the Americans and the Americans have the ability to launch strikes of their own from several airfields.

I would assume that this would of course be done beforehand, to my knowledge, the Japanese heavily researched the Pearl Harbor naval base, surely they could also have checked for landing spots.

Oh I never meant to imply that they wouldn't have selected a landing zone, I was just wanting the other poster to provide an option since that would give me a better idea of how well-prepared the US would be for a landing there, and how feasible that landing would be.

If the fleet remains undetected, then of course the Japanese will have strategic surprise. Tactical surprise is another matter. Historcially, didn't the Hawaii forces quickly prepare for a landing or not? Any data on what they managed to do within the first couple of hours?

I actually don't know for sure since I did some quick research but sources focus only on the actual air attack and submarine operations. I can't imagine they just sat around, that would be ridiculous. More likely they mobilized but waited to deploy until they knew if/where the Japanese were coming from, since that would be the best way to repel a landing.

True. I wonder how good a force the Japanese could land without having a harbor. And getting a harbor, what options are there, besides Pearl Harbor, which as a major military base would have considerable combat power, despite recent and effective bombing?

I don't know what was available at the time. Today, Honolulu has its own sizeable harbor, and there are a couple medium ones. The thing is they're all on the south side of Oahu and rather close to Pearl Harbor. As for the other islands today Maui appears to have a decent sized harbor as does Kauai, and Hawaii itself has some smaller ones. Nothing else seems capable of handling much tonnage though. As for what those looked like back in 1941, your guess is as good as mine.

I wonder though, how many of these islands are big enough to put up a fight themselves and which must fall if the main isles fall?

In terms of size I'd say the most likely places for resistance would be Maui and Hawaii, since they're big, have varied terrain including forests, mountains, and rivers, and have enough domestic agriculture and such that they can support a large force. Kauai may also be an option but since that's north of Oahu it may not be a good idea to split forces that way.

 

[Ming]

I
I would assume that this would of course be done beforehand, to my knowledge, the Japanese heavily researched the Pearl Harbor naval base, surely they could also have checked for landing spots.

Oh I never meant to imply that they wouldn't have selected a landing zone, I was just wanting the other poster to provide an option since that would give me a better idea of how well-prepared the US would be for a landing there, and how feasible that landing would be.

According to the information in pithorr's post
The plan Genda and co came up with was a diversionary landing on North Oahu and the main landing at Kaneohe bay near the naval air station. I think Turtledove just had them landing on the North shore.
Pithor's also got a good map here.

Watanabe laid out two landing sites: one on the northwest coast on both sides
of Haleiwa, the other in the area of Kaneohe Bay. The southern coast was best
suited to an invasion, but it was also the most heavily defended area of Oahu. The
west coast was eliminated, because the U.S. Navy had held invasion maneuvers
off the west coast a year before, and the Americans were likely well prepared to
defend that part of the island.57
The two landings would happen simultaneously at midnight of 7/8 December.
Half a division would land at Haleiwa, to take Schofield Barracks. The objectives
of this attack were not only to take the barracks but to draw American forces
northward, by giving the impression that it was the main effort. The actual main
attack, however, was planned for the east coast, at Kaneohe Bay, with one and a
half divisions. Two-thirds of this force would occupy that, the remainder the region
below Laie. The objective was to cross the Koolau Range, using horses, and
then descend on Pearl Harbor, cutting off any retreat to the mountains of Oahu.
The Japanese knew from intelligence that the Koolau mountains were not fortified
and in fact were open to the public. Given complete air superiority, Watanabe
estimated, it would take from two to four weeks to capture the island.

Gutsy. With total surprise and all Japanese forces getting safely ashore. . . it could maybe work. A lot of things have to roll the Japanese way though. More than happened in Singapore in my estimation.

They did have two battleships and an assortment of escorts historically, but to increase the size of that force they would be risking something like half their navy on an operation where they would be sure to suffer heavy losses even if they did win.

Genda apparently figured it would be worth it to gamble everything on seizing Hawaii like a decisive medieval battle. Again, from the book Pithorr dug up:

Transporting them,with their equipment and supplies, would require eighty transports and escort
vessels, including thirty-two destroyers, eight cruisers, four battleships, two aircraft
carriers, six to eight submarines for reconnaissance, and ten tankers. These
would be in addition to the carrier strike force.56
Assuming that the initial air strikes were successful and that the Japanese had
air superiority and given intelligence estimates of approximately two American
divisions on Oahu, Genda believed ten to fifteen thousand well equipped troops
would suffice for its capture.54 Genda realized the risks involved in moving a large
task force across the North Pacific to attack Oahu, but he felt that even if (as the
Japanese expected) a portion of the force was destroyed, the loss of shipping and
troops would not materially impact operations in the south.

Genda believed that without seizing and holding Oahu, Japan could
not hope to win the war. Oahu had to be taken at the outset of the conflict, while
surprise and initiative still worked in Japan’s favor. Once it had been occupied,
conditions would be favorable for subsequent operations in the south, and Japan
would have time to figure out how to maintain and resupply the islands. Genda
believed that Hawaii, not the Philippines, should have been Japan’s major military
objective at the outset. Where Yamamoto saw a delaying action, Genda saw
a knockout punch—the annihilation of the enemy’s operational center of gravity
with one decisive, joint operation.53

https://forum.paradoxplaza.com/foru...harder-they-fall.1354523/page-5#post-26523637

I can see the logic in retrospect (and I guess this whole thread is about others seeing it too) but as I said earlier, the high command wouldn't sign off on such an operation.

It has massive upside but It's incredibly risky and depends on slim margins. Even with perfect surprise success is not guaranteed. Too many things can go fatally wrong.

I also am not convinced that a Japanese victory here would have brought the US to the table even if it wasn't part of the world war. But I suppose I have come around to thinking if you just gotta go to war with the US in 1941 instead of backing down it was probably the optimal move. Fail fast and all that.

 

[hkrommel]

According to the information in pithorr's post
The plan Genda and co came up with was a diversionary landing on North Oahu and the main landing at Kaneohe bay near the naval air station. I think Turtledove just had them landing on the North shore.
Pithor's also got a good map here.

The problem is there are no ports there at all. Capturing the nearest port facilities would require fighting through Honolulu itself to reach its port. There are also problems in that area with rough surf and riptides, which, combined with a midnight landing, would probably lead to lots of drowning deaths and disarray.

Gutsy. With total surprise and all Japanese forces getting safely ashore. . . it could maybe work. A lot of things have to roll the Japanese way though. More than happened in Singapore in my estimation.

I guess I would have to hear more about how the plan would allow the Japanese forces to get ashore and advance 8-10 miles on foot through rough terrain with enough firepower to defeat American forces in either an urban battle (if they go for Honolulu Port) or a fight for an entrenched naval base (if they go for Pearl). Even if the Japanese somehow get ashore without raising the alarm in spite of the RADAR and defensive positions on the north coast, surely they will alert someone?

Edit: I also know you share to some extent my skepticism of this plan, I'm just genuinely curious as to how this would all work out.

 

[Ming]

The problem is there are no ports there at all. Capturing the nearest port facilities would require fighting through Honolulu itself to reach its port. There are also problems in that area with rough surf and riptides, which, combined with a midnight landing, would probably lead to lots of drowning deaths and disarray.

Considering how the Japanese handled early war landings, there are *definitely* going to be mistakes made here, possibly fatal.

I guess I would have to hear more about how the plan would allow the Japanese forces to get ashore and advance 8-10 miles on foot through rough terrain with enough firepower to defeat American forces in either an urban battle (if they go for Honolulu Port) or a fight for an entrenched naval base (if they go for Pearl). Even if the Japanese somehow get ashore without raising the alarm in spite of the RADAR and defensive positions on the north coast, surely they will alert someone?

Edit: I also know you share to some extent my skepticism of this plan, I'm just genuinely curious as to how this would all work out.

It's all there in Pithorr's book, they're going to transport cavalry across the pacific, disembark safely, quickly, quietly and then Hoofs-krieg across the Hawaiian mountains.

In the dark.

I can't imagine any reason why this plan didn't survive contact with the Imperial planning staff.

 

[Dinglehoff]

Yes, I'm assuming the Americans don't roll over and die and have their historical capabilities. I know, crazy right?

Nah, you're assuming your loose fan-fiction plays out IRL.

It's a matter of chance as much as anything is a matter of chance. Historically the Japanese were able to make their surprise attack because they were a cohesive IJN force that was able to all stay within sight of one another, which was crucial because they literally took apart their radios to avoid detection by a stray signal. What you're asking for is to have a mixed IJN/IJA force, including a massive train of cargo ships tagging along (enough to transport the Japanese land forces, transport their equipment, transport enough to keep them fed on the journey, and transport enough supplies to supply them after they land for long enough to secure a port). It's unlikely these would all leave from the same location, so they're going to be sailing around far from their own bases and near American bases trying to find each other via radio. That's a great way to get detected. But even if they all leave from the same location it would be impossible to all stay within eyesight, and they wouldn't be nearly as coordinated a force. That means they don't dismantle the radios, which means there are signals that the Americans detect long before they reach Pearl Harbor.

Ah yes; the horrors and difficulties of sailing ships within eyesight of each other, and getting apparently incompetent and dishonorable japanese army forces to navigate within eyesight of other ships and not reassemble their radios and then use them.

The Americans would be content to let them come I'm sure. All the better to fight when they're at the end of their logistical capabilities, you're ready for them, and you have the advantage in air forces.

Very big brained to let the invasion force land. Couldn't possibly go wrong, especially with their guaranteed air force advantage.

They most likely would. See, all it takes to sink a troop transport is a stern glare from a destroyer. That means the USN needs to be (1) destroyed in total or (2) fully occupied by the IJN.

The problem with the first option is that it takes time. In the time it takes for the IJN to wipe the USN out (assuming that's even possible, they didn't come close historically) the US ground forces would have ample time to anticipate and prepare for the landing, which means the landing itself might be successful but the campaign would be a failure. Barring a miracle (which you seem all too ready to assume for the Japanese) there's no way they take port facilities before they run out of food or, more likely, ammunition for heavy weapons. That means the American advantage in artillery will pound the landing forces into dust long before Japanese reinforcements arrive.

The second option is more plausible. In the event of a surprise attack, it doesn't allow American forces much time to prepare to meet the assault. But, the problem again is that the USN needs to be fully occupied simultaneously with the landing, which requires coordination and perfect timing.

1. No that's not the problem. The problem is the risk in accepting the battle necessary for the longer term invasion campaign, where the Japanese forces may be crippled or destroyed instead of winning and supporting the landings.

2. No, that's less plausible. The landing ships would have to cover the distance to the landing site undiscovered, where the air raid was able to get there much faster. Alerted or not; the defense forces will not know where the landing will take place until very late, so their preparations will not be directly tailored to the landing.

If the Americans are alerted the Japanese are toast. Even in the historical, complete surprise situation, where AA guns were unmanned and lacked ammo, there was no CAP, planes were parked wingtip to wingtip, and the entire first wave was unopposed, 29 Japanese aircraft were destroyed and over 70 were damaged. The Americans have aircraft repair facilities on the islands, while the Japanese have to rely on carrier facilities which are unable to repair certain amounts of damage.

So no, they wouldn't be "completely ineffective" but they would almost certainly lose. Even if the first wave somehow has a similar effect to the historical situation, the Americans are in a much better position to sustain losses and have a hell of a lot more AA at their disposal.

Wrong. US forces there lost like 85% of their aircraft during the historical strike and continued air attacks would not have produced the overwhelming air victory you are envisioning.

Well they had plans to defend against a landing, they weren't just sitting around doing...whatever you seem to think the US was doing at this time. Artillery was pre-sited for likely landing grounds as was AA. As soon as they get word of an invasion force those guns are in place with ammunition and crews, while infantry prepares fortifications.

On sunday during peacetime they would have been enjoying leave time, disorganized and out of defensive positions, which may not even exist beyond pre-war gun forts.

This is just ridiculous. The fact that you're equating the Philippines/Guam/Wake to the Hawaiian Islands is showcasing your ignorance of the subject. These bases were at the end of our logistical capabilities and near the beginning of the Japanese logistical capabilities. The Hawaiian Islands are just the opposite. The Japanese had bases from which they could strike reinforcements heading to these places (for example the reinforcements en route to Wake were forced to turn back by a larger IJN force). They did not have such bases on the route to Hawaii. Hawaii was also of much greater strategic importance.

Seriously, why is it that some people are so interested in hand waving any and all Axis deficiencies and treat the Allies as a bunch of bumbling fools straight out of an Axis propaganda film? On this account of American capabilities I'm at a loss as to how they won the war, since the IJN could have sailed straight into Los Angeles unopposed using nothing but Bushido powers!

Cry about it into your pillow if you like. The fact remains that those forces were not reinforced historically, and US command is likely to do the same with Hawaii if events turn out badly for them.

 

[Victor1234]

Not to wade too deeply into the feasability of invasion success once they get there, but I do think people are being very unfair to this hypothetical Japanese invasion fleet. I'm surprised everyone is prepared to treat this fleet so differently from say, Allied convoys in the Atlantic (Operation Torch anyone?) or the actual Japanese invasion fleets to Malaysia/French Indochina. The Germans spent a lot of time patrolling to try and find much larger bunches of ships they knew were coming, knowing broadly what their route was and in a much smaller ocean, but they still didn't find/intercept every single convoy. Did the Allies use radio to coordinate their convoys like idiots to give their positions away? Of course not, and neither do the Japanese need to do so. Why shouldn't they sneak through a much larger ocean where more importantly, nobody knows where they are going. Aside from forming up in a convoy and maintaining their position/heading simply by keeping specific ships on their port and starboard to avoid the need to communicate, allowing the lead ship to effectively navigate for the convoy, there are 3 generally accepted means of communications for ships of the period that don't involve radios at all (the movie Tora Tora Tora rather effectively shows at least two of these in use by the carrier strike force on the way to PH btw). These being flags, lights and signal rockets. Why do the Japanese need radio for pre-invasion coordination on the way there just for the transports?

 

[Ming]

No one is saying it would be totally impossible. However the difficulty of adding so many ships (some of which will be commandeered civilians) will increase the complexity of the operation by an order of magnitude and decrease the convoy's speed to such a degree that the chance of something going off will be incalculably higher, especially if they take the snaking approach route they historically took. (A more direct route will go right past some American bases)

Just marshaling all those vessels off the kuriles will be significant challenge and they'll be at sea much longer. . . giving intelligence assets more opportunities to catch on.

Aside from that, the Malaysia landing force *was* sighted before war broke out and was the reason Repulse was recalled to Singapore. You are quite right that the invasion was successful but the japanese did lose men due to rough sea conditions and the RAAF with much fewer air resources than would be available on Pearl did significant damage to the transports.