A Japanese invasion of Hawaii

[Aurelian]

The PI operation was *not* going to be postponed. It was needed for, among other reasons, staging areas and supply bases for supporting the seizure of the SRA. And to secure the LOC between the SRA and Japan.

The Imperial Japanese Army wasn't going to divert *anything* so the Imperial Japanese Navy could seize some islands that were of no use towards the seizure of the SRA.

warspite1

From the way you talk, anyone would think that oil was in short supply and that Japan also needed access to natural rubber, tin, the Cinchona plant and bauxite that the NEI was rich in....

i know, right? Whispers: their navy needed those same resources....

[Curtis Lemay]

I'm going to admit that I have hit a snag. I don't have Pacific War installed on my PC anymore, but I do have the manual and it lists lots of details - especially base data. And what it says is that air bases are rated from 1 to 9 (worst to best). A 1 airfield only allows sea planes to operate from it (pby's, mavis's, etc). A 2 airfield allows fighters and such to operate from it. A 4 airfield allows tactical and heavy bombers to operate from it. I had thought that a 3 airfield allowed tactical bombers (bettys) to operate, but that was a no from Grigsby (unless it's a typo). The airfields in Kauai, Maui, and Hawaii are 3s. So, they would have to be expanded before the Bettys could fly in. That would take quite a while and makes their arrival anywhere around the raid impossible (at least, according to Gribsby).

So, when I took the islands in Pacific War it had to have been later in the year, probably after sinking the US carriers. It would have been a much bigger operation. The carriers would have to remain in the area, delivering carrier bombers to the airfields until the airfields could be expanded by engineers.

So...I'm going to withdraw the suggestion that the neighbor islands be grabbed at the same time as Pearl, unless there is some way that, perhaps, grass airfields could have been improvised on them.

That still leaves the idea of making the raid optional upon presence of the US carriers in port. That only involves aborting the strike until the carriers are confirmed as in port.

[TulliusDetritus]

Just for the sake of the argument: there is only one airfield that would allow Betties and Nells (or CVs' Vals and Kates) to fly (with penalties but they could fly). But with *only* bombs, not torpedoes. Penalty = reduced range load. If engineers manage to get one more level (= 4), no penalties.

It's level 3 Lahaina. Hilo and Lihue are level 1:
"Size 1: Airfield / Port / Naval / Ground Attack and Sweep Missions can't be flown"

7 december: one battalion is defending this island.

[Buckrock]

That still leaves the idea of making the raid optional upon presence of the US carriers in port. That only involves aborting the strike until the carriers are confirmed as in port.

Are you aware that Nagumo's force received the intel confirmation of no USN CV's at Pearl only about 6 hours before they historically launched (and already 12 hours into their fuel intensive dash to make that dawn launch point)? And that was one of the faster intel turn around times during the mission. Even immediately aborting and racing back north upon receipt of that intel would have still left them about 450nm from Pearl at first light, not an easy distance to explain away if spotted by the US.

Just some food for thought.

[RangerJoe]

I can remember the best pizza that I ever had, who made, baked, and delivered it. I also remember where that person was born and when, also the names of that person. I also remember what establishment it came from.

[Aurelian]

Please explain how the Japanese would control the skies? The US Army and the US Navy still had aircraft available. The Japanese KB aircraft needed work, the KB could not stay in the area for much longer. Any Japanese land based aircraft would have to be shipped in from somewhere. Also, who would service the aircraft and where would the fuel, ammo, and spare parts come from?

That's my new question too. If you fly air groups off the Japanese carriers onto these airfields, who is going to be doing the maintenance, arming and fueling of these planes? Are the trained mechanics and armorers that made up the deck crew for these carriers going to be clinging to the wings? Will they be ferried ashore somehow? Of what further military use are these carriers going to be to Japan for further offensives if they sail back stripped of most of their trained mechanics, aircrew and planes? Given the highly selective and elite nature of their pilot training program it's not like Japan had a huge cadre of carrier pilots just waiting back in Yokohama for an assignment.

This is out of sequence, but here we go. Japanese carriers would not send their air groups to land bases unless they were in port being fixed. Unlike American practice, a carrier's air group was married to the ship. Look at why Shokaku missed Midway. The decimated airgroup had to be rebuilt. And American carrier would of just shipped a new air group aboard from the base or a carrier out of action. But that was not Japanese doctrine. There was no thought of transferring Zuikaku's air group to her sister.

[Platoonist]

This is out of sequence, but here we go. Japanese carriers would not send their air groups to land bases unless they were in port being fixed. Unlike American practice, a carrier's air group was married to the ship. Look at why Shokaku missed Midway. The decimated airgroup had to be rebuilt. And American carrier would of just shipped a new air group aboard from the base or a carrier out of action. But that was not Japanese doctrine. There was no thought of transferring Zuikaku's air group to her sister.

Yeah, I know the Japanese tended to be very orthodox in keeping their air groups together when the war was going well. Air groups were considered organic to the carrier. Later in the war they relented on this a bit and carrier fighter and dive-bomber squadrons were detached from Japan's remaining front line carriers to Rabaul and Buin to boost naval air power for Operation I-Go. Didn't work out too well for Yamamoto or the air groups. Yamamoto got shot down while touring front lines bases to congratulate them for an illusory victory. The air groups got heavily attrited

But, then this is also a scenario where the rival Japanese Army and Navy are apparently holding hands and giggling with glee, so we are assuming a lot.

[RangerJoe]

This is out of sequence, but here we go. Japanese carriers would not send their air groups to land bases unless they were in port being fixed. Unlike American practice, a carrier's air group was married to the ship. Look at why Shokaku missed Midway. The decimated airgroup had to be rebuilt. And American carrier would of just shipped a new air group aboard from the base or a carrier out of action. But that was not Japanese doctrine. There was no thought of transferring Zuikaku's air group to her sister.

Yeah, I know the Japanese tended to be very orthodox in keeping their air groups together when the war was going well. Air groups were considered organic to the carrier. Later in the war they relented on this a bit and carrier fighter and dive-bomber squadrons were detached from Japan's remaining front line carriers to Rabaul and Buin to boost naval air power for Operation I-Go. Didn't work out too well for Yamamoto or the air groups. Yamamoto got shot down while touring front lines bases to congratulate them for an illusory victory. The air groups got heavily attrited

But, then this is also a scenario where the rival Japanese Army and Navy are apparently holding hands and giggling with glee, so we are assuming a lot.

Yes, that is true. It is also true that in this Scenario, the Japanese Navy is in charge when it was the Japanese Army in charge.

[Torplexed]

Just for the sake of the argument: there is only one airfield that would allow Betties and Nells (or CVs' Vals and Kates) to fly (with penalties but they could fly). But with *only* bombs, not torpedoes. Penalty = reduced range load. If engineers manage to get one more level (= 4), no penalties.

It's level 3 Lahaina. Hilo and Lihue are level 1:
"Size 1: Airfield / Port / Naval / Ground Attack and Sweep Missions can't be flown"

7 december: one battalion is defending this island.

Probably the best of the airfields inside the Hawaiian Islands outside of Oahu itself in 1941 would have been the airport at Hilo on the big island of Hawaii. It consisted of two coral and grass lined airstrips lined up with the prevailing winds. The runways were 2,500-3,000 feet long at the time. Unfortunately, it was on the "wet" side of the island, got rained on a lot and had drainage issues. Its proximity to the water meant it got shelled by Japanese submarines on at least one occasion.

Hilo airport 1941.jpg (180.09 KiB) Viewed 1127 times

After the US Army took it over it got a complete face lift by 1944. Extended and paved runways, aircraft aprons, radar installations, a lot more housing. It probably had a golf course too.

Hilo Field 1944.jpg (153.58 KiB) Viewed 1127 times

[Aurelian]

This is out of sequence, but here we go. Japanese carriers would not send their air groups to land bases unless they were in port being fixed. Unlike American practice, a carrier's air group was married to the ship. Look at why Shokaku missed Midway. The decimated airgroup had to be rebuilt. And American carrier would of just shipped a new air group aboard from the base or a carrier out of action. But that was not Japanese doctrine. There was no thought of transferring Zuikaku's air group to her sister.

Yeah, I know the Japanese tended to be very orthodox in keeping their air groups together when the war was going well. Air groups were considered organic to the carrier. Later in the war they relented on this a bit and carrier fighter and dive-bomber squadrons were detached from Japan's remaining front line carriers to Rabaul and Buin to boost naval air power for Operation I-Go. Didn't work out too well for Yamamoto or the air groups. Yamamoto got shot down while touring front lines bases to congratulate them for an illusory victory. The air groups got heavily attrited

But, then this is also a scenario where the rival Japanese Army and Navy are apparently holding hands and giggling with glee, so we are assuming a lot.

Can we assume that Hitler never declared war on the US, thus allowing them concentrating on the Pacific. IIRC, most Americans would of wanted to concentrate on Japan anyway

[RangerJoe]

This is out of sequence, but here we go. Japanese carriers would not send their air groups to land bases unless they were in port being fixed. Unlike American practice, a carrier's air group was married to the ship. Look at why Shokaku missed Midway. The decimated airgroup had to be rebuilt. And American carrier would of just shipped a new air group aboard from the base or a carrier out of action. But that was not Japanese doctrine. There was no thought of transferring Zuikaku's air group to her sister.

Yeah, I know the Japanese tended to be very orthodox in keeping their air groups together when the war was going well. Air groups were considered organic to the carrier. Later in the war they relented on this a bit and carrier fighter and dive-bomber squadrons were detached from Japan's remaining front line carriers to Rabaul and Buin to boost naval air power for Operation I-Go. Didn't work out too well for Yamamoto or the air groups. Yamamoto got shot down while touring front lines bases to congratulate them for an illusory victory. The air groups got heavily attrited

But, then this is also a scenario where the rival Japanese Army and Navy are apparently holding hands and giggling with glee, so we are assuming a lot.

Can we assume that Hitler never declared war on the US, thus allowing them concentrating on the Pacific. IIRC, most Americans would of wanted to concentrate on Japan anyway

Even if Hitler declared war on the US, in this situation I think that the Yorktown, Hornet, and the Wasp would immediate load any airgroups that they needed and set sail for the Panama Canal and then to the Pacific Ocean. The new Battleships as well. There would be intense training along the way.

[Curtis Lemay]

OK, I did a little research and found this on the neighbor island airfields:

https://aviation.hawaii.gov/airfields-a ... n-airport/

This describes Port Allen airfield on Kauai as having two runways of 3600 and 2600 feet. Consisting of rocky soil.

https://aviation.hawaii.gov/airfields-a ... t-puunene/

This describes Puunene airfield on Maui as being paved at 4500 feet.

https://aviation.hawaii.gov/airfields-a ... a-airport/

This describes Hoolehua airfield on Molokai as having three airfields of 1000, 2600, and 2600 feet each.

https://aviation.hawaii.gov/airfields-a ... u-airport/

This describes Upolu airfield on Hawaii as a grass field 3500 feet long.

What stands out is the 4500 paved runway on Maui. Also, it confirms that Maui and Kauai are the best targets for the Japs.

But what are the runway requirements for the Betty? Well, I couldn’t find anything on that. However, the attached chart shows the answer for the B-25 – somewhat similar. However, note that the B-25 has a max load weight of 36,000 pounds and its engines have takeoff HP of 1700. The Betty has max load weight of 28,000 pounds and its engines have takeoff HP of 1530. So, the B-25 has 36/28 = 1.2857 the weight of the Betty but only 1700/1530 = 1.11 the power. So, it should require 1.2857/1.11 = 1.1583 the runway length.

The chart shows that at sea level (which these airfields are at) on paved ground (which the Maui airfield is) the B-25 needs 4600 feet to take off under max load if there is no wind to assist. The Betty should, therefore, require 4600/1.1583 = 3971 feet. That means that Maui can be a home base for the Betty!!! Invasion is back on!

Also, note that the Betty can fly 3132 miles with max bomb load. Eniwetok is 2715 miles from Oahu. That means that the Betty can load up with bombs or torpedoes in Eniwetok and fly to Pearl on the go date and join in the fun in the first strike. That means more ships torpedoed and more aircraft caught on the ground. Knowing that these islands are going to be taken and will need to be safeguarded from naval vessels, cruisers and destroyers will have been given greater priority than in the historical strike. The Pearl raid is going to be even more destructive. After hitting Pearl, they can set down on Maui after its capture – with plenty of range in reserve.

There is one remaining issue: The Eniwetok airfield is rated a 2 by Grigsby. But Eniwetok is controlled by Japan pre-war. They will have months to build it up to Betty-capable if this plan is adopted.

[RangerJoe]

OK, I did a little research and found this on the neighbor island airfields:

https://aviation.hawaii.gov/airfields-a ... n-airport/

This describes Port Allen airfield on Kauai as having two runways of 3600 and 2600 feet. Consisting of rocky soil.

https://aviation.hawaii.gov/airfields-a ... t-puunene/

This describes Puunene airfield on Maui as being paved at 4500 feet.

https://aviation.hawaii.gov/airfields-a ... a-airport/

This describes Hoolehua airfield on Molokai as having three airfields of 1000, 2600, and 2600 feet each.

https://aviation.hawaii.gov/airfields-a ... u-airport/

This describes Upolu airfield on Hawaii as a grass field 3500 feet long.

What stands out is the 4500 paved runway on Maui. Also, it confirms that Maui and Kauai are the best targets for the Japs.

But what are the runway requirements for the Betty? Well, I couldn’t find anything on that. However, the attached chart shows the answer for the B-25 – somewhat similar. However, note that the B-25 has a max load weight of 36,000 pounds and its engines have takeoff HP of 1700. The Betty has max load weight of 28,000 pounds and its engines have takeoff HP of 1530. So, the B-25 has 36/28 = 1.2857 the weight of the Betty but only 1700/1530 = 1.11 the power. So, it should require 1.2857/1.11 = 1.1583 the runway length.

The chart shows that at sea level (which these airfields are at) on paved ground (which the Maui airfield is) the B-25 needs 4600 feet to take off under max load if there is no wind to assist. The Betty should, therefore, require 4600/1.1583 = 3971 feet. That means that Maui can be a home base for the Betty!!! Invasion is back on!

Also, note that the Betty can fly 3132 miles with max bomb load. Eniwetok is 2715 miles from Oahu. That means that the Betty can load up with bombs or torpedoes in Eniwetok and fly to Pearl on the go date and join in the fun in the first strike. That means more ships torpedoed and more aircraft caught on the ground. Knowing that these islands are going to be taken and will need to be safeguarded from naval vessels, cruisers and destroyers will have been given greater priority than in the historical strike. The Pearl raid is going to be even more destructive. After hitting Pearl, they can set down on Maui after its capture – with plenty of range in reserve.

There is one remaining issue: The Eniwetok airfield is rated a 2 by Grigsby. But Eniwetok is controlled by Japan pre-war. They will have months to build it up to Betty-capable if this plan is adopted.

Oh WOW! You will have the Japanese take off fully loaded and then fly individually to Oahu to bomb because fuel is so precious that they Japanese crews can't afford to form up and fly together. So single aircraft will fly that far across the open ocean with no modern GPS system. One lone bomber attacking first will ruin everything. So they will be greeted by aroused defenders since they can't be allowed to attack first. Especially since the time of the attack is so important so the higher level commanders will still be eating breakfast or traveling to their duty station.

No only that, they will have to fly straight through whatever weather there is. Please remember that the Enterprise was supposed to make port on the 5th of December but was delayed by a storm . . .

Then they will arrive at an airfield where the destroyers are probably just arriving at the beaches, so the airfields are not captured. There may be fuel there to be captured but anyone can open the spigot and light a match . . .

Not to mention that if there are any military personnel or even armed police officers there, the crews may be killed. Then reinforcements may be flown in from Oahu . . .

Not to mention any landing will see the US Navy coming out to play with any and all undamaged ships, even if their captain is not aboard . . .

You are also not considering the relative lift capabilities of each respective aircraft in your comparison.

But I have to go because a pretty feline wants attention and that is much more important than stating more problems . . .

[Buckrock]

The chart shows that at sea level (which these airfields are at) on paved ground (which the Maui airfield is) the B-25 needs 4600 feet to take off under max load if there is no wind to assist. The Betty should, therefore, require 4600/1.1583 = 3971 feet. That means that Maui can be a home base for the Betty!!! Invasion is back on!

Your estimate appears close enough.

According to Japanese records from their operations against the DEI, the minimum runway length to operate Bettys with normal combat load was 1200m (aprox 4000ft). To give them any real safety margin for operations though, 4200 ft of runway or more was the preferred runway length.

There is one remaining issue: The Eniwetok airfield is rated a 2 by Grigsby. But Eniwetok is controlled by Japan pre-war. They will have months to build it up to Betty-capable if this plan is adopted.

Yamamoto's plan for Pearl Harbor was only accepted by the IJN General Staff in late Oct '41. While he had the authority to order specialist training by the 1st Air Fleet, Yamamoto had no say in naval base construction. That could only begin with the authority of the General Staff. So at best your airfield at Eniwetok would only have about 6 weeks to be planned, prepared and constructed. Based on historical Japanese construction performances, I wouldn't like your chances.

For reference, the Japanese did build an airbase at Eniwetok during the war (in 1943 on Engebi). According to the official histories, it was the only one they ever built there and was described as a simple transit field to handle the shuttling of aircraft (including Bettys) to other bases. That airfield appears to have taken over 6 months to complete by the Japanese naval construction unit involved.

And just out of curiousity, is your plan really to have troop laden DD's accompany KB all the way to the PH Raid point and then break away prior to the strike launch so as to capture 1-2 of the Hawaiian Islands in time for the landing of Bettys that also participated in the KB raid after staging from Eniwetok? Or is this all just a bit of a wind up for those who may hold a more pessimistic view of Japan's wartime options against Hawaii?

[TulliusDetritus]

If I well understood, the modder's game I'm playing (LST) got it right then. re the Marshall islands, no, Eniwetok is level 0. Roi-Namur is the best place around, no penalties or level 4. PH/Lahaina distance? 52/53 hexes = within transfer range of the Betty. And the Nells could make it via let's say Maloelap, just like B-17s bombed Rabaul from Australia via (aka a little stop) Port Moresby.

[warspite1]

The Betty should, therefore, require 4600/1.1583 = 3971 feet. That means that Maui can be a home base for the Betty!!! Invasion is back on!

warspite1

Well if you ignore the other myriad existing problems and also then ignore the new ones that have arisen, then yes, it's back on.....

- How many Bettys are going to fly to Pearl, bomb the island and then land on Maui or wherever?
- At the time the Japanese decide to employ them they will not know if the Japanese troops have safely made it to Maui (or their exposed destroyers have been sunk en route)
- They won't know if any ground crew survived the journey
- They won't have any fighter cover (and they won't know how many US aircraft have survived to be able to attack them)
- They won't have any fuel
- They won't have any sensible AA weaponry
- They won't have any spare parts
- They won't have any ammunition
- They won't have much of anything.

What US troops were on Maui in December 1941? Just one act of sabotage and those surviving Bettys are toast and the pilots are PoW.

And still don't know which Bettys these are and where they were historically used in December 1941 - March 1942

[TulliusDetritus]

- How many Bettys are going to fly to Pearl, bomb the island and then land on Maui or wherever?

Bombing from the Marshalls is impossible. It has to be 1) transfer to "occupied island" and 2) arm, refuel there, fly and bomb x target and then come back.

[warspite1]

- How many Bettys are going to fly to Pearl, bomb the island and then land on Maui or wherever?

Bombing from the Marshalls is impossible. It has to be 1) transfer to "occupied island" and 2) arm, refuel there, fly and bomb x target and then come back.

Warspite1

I think you'll find your whole sentence was impossible

[Curtis Lemay]

That still leaves the idea of making the raid optional upon presence of the US carriers in port. That only involves aborting the strike until the carriers are confirmed as in port.

Are you aware that Nagumo's force received the intel confirmation of no USN CV's at Pearl only about 6 hours before they historically launched (and already 12 hours into their fuel intensive dash to make that dawn launch point)? And that was one of the faster intel turn around times during the mission. Even immediately aborting and racing back north upon receipt of that intel would have still left them about 450nm from Pearl at first light, not an easy distance to explain away if spotted by the US.

Just some food for thought.

With an abort option, this would get higher priority. And the mission would have been aborted when the first carrier left Pearl. Two carriers minimum for the green light.

[Curtis Lemay]

Yamamoto's plan for Pearl Harbor was only accepted by the IJN General Staff in late Oct '41. While he had the authority to order specialist training by the 1st Air Fleet, Yamamoto had no say in naval base construction. That could only begin with the authority of the General Staff. So at best your airfield at Eniwetok would only have about 6 weeks to be planned, prepared and constructed. Based on historical Japanese construction performances, I wouldn't like your chances.

For reference, the Japanese did build an airbase at Eniwetok during the war (in 1943 on Engebi). According to the official histories, it was the only one they ever built there and was described as a simple transit field to handle the shuttling of aircraft (including Bettys) to other bases. That airfield appears to have taken over 6 months to complete by the Japanese naval construction unit involved.

First, this is a discussion about what they COULD have done. Whether they would do it is secondary. Regardless, base construction in wartime conditions would depend upon priorities. Why would Eniwetok be high priority once the war was under way? Adopt this plan and it has lots of priority pre-war. Throw enough resources there and it could get done.

And just out of curiousity, is your plan really to have troop laden DD's accompany KB all the way to the PH Raid point and then break away prior to the strike launch so as to capture 1-2 of the Hawaiian Islands in time for the landing of Bettys that also participated in the KB raid after staging from Eniwetok? Or is this all just a bit of a wind up for those who may hold a more pessimistic view of Japan's wartime options against Hawaii?

?? You've lost me. The raid included destroyers. There will just be more of them.

I envision the destroyers with the troops to break away soon enough to land them the night before the raid - perhaps assisted by spies on the islands serving as pathfinders. They would lie low till time for the raid to begin. Then, upon word that the raid was underway, they strike - taking the port and airfield and overwhelming any military (if any) on the islands. After all, this would be Sunday in peacetime.