1941 - invading Hawaii, possible?

[Athelstane]

This list doesn't include the rather substantial Marine Defense Battalion (actually this was a formation the size of Regimental Combat Team, not a classic battalion) anti-ship/boat gun enplacements on Oahu. If you look at the map you posted as part of post #93 you will see a number of emplacements labeled "navy guns", there were the heavy guns of the Defense Battalions (7"/45 taken from the old Mississippi (B-23) pre-dred and 5"/51 from battleships and cruisers that had been refit with either the 5"/25 or 5"/38, these 5" guns were the ones that the defenders used to count coup against the flailed first landing attempt on Wake, and some 155mm rifles). The large number of lighter guns including 90mm DP guns and roughly 60 machine guns (usually an even split between .30 cal and .50 cal on DP mounts) per battalion (there were two battalions assigned to Oahu, but 1 section of Battalion 1 was forward deployed to Wake).

I mentioned it only briefly in the previous post: "Including district, ship's detachment, and aviation marines, there were 4,500 Marines on Oahu at the time of the attack." They would have been tough. Wake showed us that.

But otherwise, I just wanted to drill in on the US Army emplacements, just to give some flavor.

The more you look at it, the sicker it gets for Yamamoto.

Basically, the Japanese Empire would have to use up almost all of its Navy, almost all of its naval aviation, almost all of its merchant marine, most of the available IJA ground forces and marines, and most of its oil reserves...and maybe, if it rolls all sixes on every move, the HYPO staff comes down with narcolepsy, and the U.S. garrison has a collapse in will to resist (the Japanese make a flukey breakthrough somewhere) before the campaign gets too old . . . it might have sort of a shot at taking Oahu.

Of course, it will have utterly wrecked itself in the process, all of its machinery will be running on fumes, and the U.S. can just retake it by the end of 1942. It could be the best gift Japan could give Hitler (TORCH would be nuked), but only through an act of sudden national suicide.

 

[Athelstane]

And remember this is a side show, The whole point in the war in the first place is the OIL. And even if the US surrendered if the fleet is badly hit then the war is still lost as they MUST invade the DEI and fight Great Britain as the have to have the oil. So if the US does enough damage to the Fleet and its support ships and freighters then it is going to be harder to take the main goal of the oil producing areas. And you are giving everyone a HUGE advanced warning notice.

That, and there is no way in a million years the Army leadership would agree to it. Not without Jedi mind tricks.

 

[wcv215]

41k would maybe be *all* of the islands and some of those were raw troops...this is from jstor but is open access from the 50th anniversary of Pearl Harbor

The United States Army in Hawaii Outpost Reinforcement in 1941 on JSTOR

Charles R. Anderson, The United States Army in Hawaii Outpost Reinforcement in 1941, Army History, No. 20 (Fall 1991), pp. 1-8

www.jstor.org

There were 43,000 combat personnel in the Hawaiian Department as of December 1941. Of these just over 2000 were on the other islands. The 41,000 is just Oahu. Also it should be noted that there were an additional 14,000 other personnel who aren't counted in those figures.

 

[TimTurner]

Seems like the logistics for this are worse than the logistics for a hypothetical Japanese invasion of Siberia in the late 1930s.

 

[Athelstane]

Seems like the logistics for this are worse than the logistics for a hypothetical Japanese invasion of Siberia in the late 1930s.

Fewer bears, though!

 

[CalBear]

Fewer bears, though!

You don’t need all that many bears. A few can go a long way! 🤠

 

[Jellico]

how long does it take for 90% of the Atlantic fleet to get withing striking range of the KB off the coast of Hawaii and how much damage did the US subs do to the KB and its support ships in the mean time?

Remember the combined US fleet is larger then the IJN. It just had commitments in the Atlantic on Dec 9th because of Europe first. But this won’t be Europe First it will be Hawaii First sorry GB but you are on your own. Lets face it GB had been fighting on its own for a while it didn’t NEED the US to instantly come to its aid so in this case the vast majority of the US military is heading West not east until Hawaii is liberated.
Remember from 41-44 the US basically fought Japan and was winning with the stuff it could spare from its real fight with Germany. In this case until the Japanese are not a threat the US will send them their very best.
And while 4 engined bombers were not that good against ships I have to wonder what a 1000 bomber raid would do…?

No I am sorry as much as the idea of Japan invading Hawaii would make a good story or movie it is just not going to happen. I mean they could invade and probably take a large chunk of Oahu but then what? A few months later once the US gets organized they are getting kicked out. And they will have accomplished just a bit more then they did on Dec 7th but lost a large part of the KB a large number of pilots and aircraft and a Huge chunk of the better faster longer ranged support ships and freighters not to mention 30-40 thousand troops. So they may do say twice as much damage to the US as in OTL but they are going to get a huge amount of damage done to them that in OTL they did not get. And the US can make good the damage while Japan can’t, This extra damage inflicted on the US is not worth the damage they will take.

Why bother sending them to Hawaii? Go round, and move to Luzon and Singapore. If Japan is hemorrhaging oil trying to resupply Hawaii, just imagine how much fun it will be to slit their throats in the South China Sea. They won't be hemorrhaging oil because they won't be getting any. Or tin, or rubber...

 

[M79]

You don’t need all that many bears. A few can go a long way! 🤠

Especially in Chicago - Da Bears can be formidable

 

[kmmontandon]

Seems like the logistics for this are worse than the logistics for a hypothetical Japanese invasion of Siberia in the late 1930s.

The biggest advantage to a hypothetical Japanese invasion of Siberia in the late 1930s is that the supply lines wouldn't be very long.

The biggest disadvantage to a hypothetical Japanese invasion of Siberia in the late 1930s is also that the supply lines wouldn't be very long.

 

[wcv215]

Seems like the logistics for this are worse than the logistics for a hypothetical Japanese invasion of Siberia in the late 1930s.

Trans-oceanic invasions are really hard even with most things in your favor. See Overlord.

 

[Look More Closely Later]

Trans-oceanic invasions are really hard even with most things in your favor. See Overlord.

Weren't the Allies outnumbered in the trans-oceanic invasion which was Operation Torch in 1942 in the original timeline?
Okay, that was mostly against the Vichy French who may have been low down the priority military supplies list for the Axis, and the Allies had one base close to some of the landings in the shape of Gibraltar, but still...

 

[Grand Admiral Thrawn]

I have to ask this question, sir. Why?

Do the Japanese have NO tankers? Do the Japanese have NO oilers? I was under the impression from reading up on the Battle for the Coral Sea, that not only did the Japanese have Oilers, but that they were better than the US Oilers? Or at least better deployed?

Even if the carriers have bunker fuel, they will run out of munitions and avgas within the week if they are supporting the invasion/suppressing Oahu. Unless the carriers do shore bombardment? And USN and destroyers can sortie at night, wreaking more havoc.

 

[DougM]

Yes ideally the US darts around the IJN and cuts them off from behind. But remember Hawaii is part of the US and those are US citizens sitting under the polite control of those very nice IJN/IJA folks with their wonderful reputation for treating foreign nationals so well. So the US will want to liberate them and the main pacific base ASAP.

As for torch. That will be delayed until 43. I expect by mid 42 Hawaii is completely liberated (assuming it was ever taken which is a long shot) The Japanese cant supply the troops. And trying to keep the fleet near Hawaii is impossible as they have to take the oil fields. So any supply ships trying yo get to Hawaii after about Feb are doing a long trip through unfriendly waters and a huge percentage will be sunk. So whatever troops are on Hawaii are going to be on there own very early on. This is not going to be that hard for the US to toss them out.

So i expect by 43 the majority of the US war effort will be heading to the Atlantic as by that point Hawaii will be liberated. The Japanese support fleet will have been heavily damaged. The IJA will have lost 30-40 thousand troops on Hawaii. They will also have done worse in against the DEI/GB/Australia and the Philippines Islands simply becuse they delayed the attack and had less rescources because of what they used at Hawaii. So the domino effect will result in at least a bit harder fight. So by early 43 Japan is over all in a much worse position.

 

[Johnrankins]

Yes ideally the US darts around the IJN and cuts them off from behind. But remember Hawaii is part of the US and those are US citizens sitting under the polite control of those very nice IJN/IJA folks with their wonderful reputation for treating foreign nationals so well. So the US will want to liberate them and the main pacific base ASAP.

As for torch. That will be delayed until 43. I expect by mid 42 Hawaii is completely liberated (assuming it was ever taken which is a long shot) The Japanese cant supply the troops. And trying to keep the fleet near Hawaii is impossible as they have to take the oil fields. So any supply ships trying yo get to Hawaii after about Feb are doing a long trip through unfriendly waters and a huge percentage will be sunk. So whatever troops are on Hawaii are going to be on there own very early on. This is not going to be that hard for the US to toss them out.

So i expect by 43 the majority of the US war effort will be heading to the Atlantic as by that point Hawaii will be liberated. The Japanese support fleet will have been heavily damaged. The IJA will have lost 30-40 thousand troops on Hawaii. They will also have done worse in against the DEI/GB/Australia and the Philippines Islands simply becuse they delayed the attack and had less rescources because of what they used at Hawaii. So the domino effect will result in at least a bit harder fight. So by early 43 Japan is over all in a much worse position.

Torch might be delayed a month or two. I doubt much more because I don't see the invasion lasting long. It is likely to be such a debacle that the US won't send Hawaii much more than it did OTL.

 

[Athelstane]

A minor aside: Drachinifel had Shattered Sword's Jon Parshall back on yesterday for an extended stream, and the question of IJN refueling of carriers at sea came up. He notes that more recent research has suggested to him that he seems to have understimated Japanese capabilities in this regard - that they had even undertaken side by side refueling by the time war broke out.

I've cued it up to the timestamp. Otherwise there's also three hours of Midway talk, for those keen on that sort of thing.

 

[Athelstane]

Torch might be delayed a month or two. I doubt much more because I don't see the invasion lasting long. It is likely to be such a debacle that the US won't send Hawaii much more than it did OTL.

Hmmmmm . . . I wouldn't be so sure.

The more I read about TORCH, the more I am struck by how vexed its genesis was. Churchill favored it; but the U.S. chiefs were opposed, viscerally, in fact. In the end, it took FDR's personal intervention to force it through. And it came very late.

In a timeline where the Japanese have (somehow) taken Hawaii, it's going to be much harder for Roosevelt to override his chiefs. Public sentiment will be overwhelmingly for dealing with Hawaii first. Roosevelt was a political creature. The result was almost sure to be a modification of strategy: "Germany First, but only after we deal witth Oahu."

And taking back Oahu was not so simple. Even if the Japanese had wrecked themselves taking it, and even if the USN had managed to isolate it from most re-supply or reinforcement, the islands are a hell of a long way from anything else. Any air support you need, you have to bring with you, on carrier decks. Which the USN had little enough of in 1942. You can't shuttle in aircraft, save for heavy bombers. All the escort carriers that went to TORCH would get commandeered, I'm afraid. It probably would start with a liberation of the big island and maybe Kauai, etc. and a build up of air power there, and you would need the escort carriers to build most of that up. It would take time; Roosevelt will not want any risk of anything short of a quick victory taking it back. And redeploying all that for TORCH (or whatever) after it's done would not be easy or fast. And that doesn't include all the amphibious ships that Nimitz would need and insist on . . . and of which, the United States had a very limited supply in 1942. TORCH was possible in OTL because WATCHTOWER could be done on such a shoestring basis.

Some of this would also depend on how many losses the USN takes in the loss of Oahu in the first place - especially of carrier decks.

So I really think any major amphibious assault in the ETO gets pushed back well into 1943 (spring/summer, I am guessing), no matter how loudly Stalin screams. This might affect the Russian front at the margins, since there was a lot of hardware hurled into Tunisia in November 1942-March 1943 that wouldn't be getting hurled. At a guess, it would butterfly away the entire Italian campaign, though this could actually be beneficial to the Allies . . .

This doesn't win the war for the Axis, of course. If anything, it would hasten Japan's defeat.

But it's moot, because it basically had zero chance of ever happening.

 

[kmmontandon]

A minor aside: Drachinifel had Shattered Sword's Jon Parshall back on yesterday for an extended stream, and the question of IJN refueling of carriers at sea came up. He notes that more recent research has suggested to him that he seems to have understimated Japanese capabilities in this regard - that they had even undertaken side by side refueling by the time war broke out.

Do they mention avgas reloading, and transferring munitions?

The biggest limiting factor to the Japanese carriers is running out of fuel and ammo for their planes, not for their ships. I believe they had enough for about 2, maybe 3 days of high-tempo operations, to begin with. And they used a lot of that up in the initial two-wave strike.

My best back-of-the-napkin calculation is that the Kido Butai, after the Pearl Harbor strike, could only support one day's worth of combat ops (either ground support or naval, but not both). I only know the fuel capacity for Akagi was around 150,000 gallons, which very roughly averages out to about ten combat sorties per aircraft. Post-strike, seven or eight sorties per aircraft of fuel is left, no idea about munitions. That's ... not much.

 

[Johnrankins]

Hmmmmm . . . I wouldn't be so sure.

The more I read about TORCH, the more I am struck by how vexed its genesis was. Churchill favored it; but the U.S. chiefs were opposed, viscerally, in fact. In the end, it took FDR's personal intervention to force it through. And it came very late.

In a timeline where the Japanese have (somehow) taken Hawaii, it's going to be much harder for Roosevelt to override his chiefs. Public sentiment will be overwhelmingly for dealing with Hawaii first. Roosevelt was a political creature. The result was almost sure to be a modification of strategy: "Germany First, but only after we deal witth Oahu."

And taking back Oahu was not so simple. Even if the Japanese had wrecked themselves taking it, and even if the USN had managed to isolate it from most re-supply or reinforcement, the islands are a hell of a long way from anything else. Any air support you need, you have to bring with you, on carrier decks. Which the USN had little enough of in 1942. You can't shuttle in aircraft, save for heavy bombers. All the escort carriers that went to TORCH would get commandeered, I'm afraid. It probably would start with a liberation of the big island and maybe Kauai, etc. and a build up of air power there, and you would need the escort carriers to build most of that up. It would take time; Roosevelt will not want any risk of anything short of a quick victory taking it back. And redeploying all that for TORCH (or whatever) after it's done would not be easy or fast. And that doesn't include all the amphibious ships that Nimitz would need and insist on . . . and of which, the United States had a very limited supply in 1942. TORCH was possible in OTL because WATCHTOWER could be done on such a shoestring basis.

Some of this would also depend on how many losses the USN takes in the loss of Oahu in the first place - especially of carrier decks.

So I really think any major amphibious assault in the ETO gets pushed back well into 1943 (spring/summer, I am guessing), no matter how loudly Stalin screams. This might affect the Russian front at the margins, since there was a lot of hardware hurled into Tunisia in November 1942-March 1943 that wouldn't be getting hurled. At a guess, it would butterfly away the entire Italian campaign, though this could actually be beneficial to the Allies . . .

This doesn't win the war for the Axis, of course. If anything, it would hasten Japan's defeat.

But it's moot, because it basically had zero chance of ever happening.

That they actually take Hawaii is a hell of assumption. My assumption is that thousands of Japanese troops will first drown in the ocean when their transport sinks, thousands more get cut down by machine gun and artillery fire between the time the get off the boat and the time they establish something resembling a beachhead. Thousands more die trying to break out of the beachhead and either fail or barely break out and few hundred to a couple thousand go a few miles inland before being totally cut off and destroyed. That seems far more likely.

 

[Athelstane]

That they actually take Hawaii is a hell of assumption.

Oh, absolutely. I hope that was clear!

I think if the Japanese actually tried Glenn's plan, on most rolls of the dice, they'd probably get ashore but just get cut to pieces, and the whole thing is over in 2-3 weeks.

But like I said, entertaining this whole schema . . . even a gutted Japanese force structure on land and sea could have significant powers of resistance. . . you still can't take something with nothing. And there's also the uncertainty about just what the Japanese would have left. I could easily see the U.S. overestimating remaining Japanese capability, and planning their force structure accordingly.

 

[Johnrankins]

Oh, absolutely. I hope that was clear!

I think if the Japanese actually tried Glenn's plan, on most rolls of the dice, they'd probably get ashore but just get cut to pieces, and the whole thing is over in 2-3 weeks.

But like I said, entertaining this whole schema . . . even a gutted Japanese force structure on land and sea could have significant powers of resistance. . . you still can't take something with nothing. And there's also the uncertainty about just what the Japanese would have left. I could easily see the U.S. overestimating remaining Japanese capability, and planning their force structure accordingly.

Seems reasonable to me, still that sounds more like a short delay than anything else. After a month or so there will be little for the army to do than hunt down the few remaining Japanese troops left on the island. The IJN will be significantly weaker than OTL after this debacle most likely and that should even things out a bit.