Japan loses heavily at Pearl Harbor, what impact on rest of Pacific War?

Re -5th CAR DIV.

I checked sources. We're both right. From "Beyond Pearl Harbor" one of the leaders of Zuikaku's Kate group states that most (24 of 27) of the air group was green and spent its intensive training period doing basic combat stuff.

But for the Vals, different story. Aichi Kanbaku Val Units pg 22-23 states that the dive bomber pilots came mostly from the land based air units of 12th and 14th Ku (China), which were disbanded and transferred in bulk to the 5th CAR DIV. In checking pg 386 of Japanese Naval Fighter Aces, 12th and 14th Ku had fighter establishments. This means in all probability the fighter pilots for 5th division came in part from these sources too. These pilots had not worked together as naval carrier units, but from China, they were vets, not green.
 
But the IJN didn't go through the expense of building the 1st Air Fleet because they thought it was a bunch of 2nd-rate powder puffs that would go down to US pixie cannons at first blush.

Yet before the attack, Genda and Fuchida expect very high losses to the attacking force. They also expected higher hit ratios than were delivered by the dive bombers and torpedo planes
 
25 (Yorktown) + 27 (Enterprise) + 27 (Hornet) + 28 (Midway) = 107 fighters. Using your methodology, if Midway were a 'what if' you would claim these should shoot down 60+ IJN planes. But they actually shot down about 34. How do you double the theoretical effectiveness over actual results? First, you list the total establishment at Oahu (about 90 fighters nominal operational). Then, you ignore the total establishment at Midway, and instead list only the planes for each engagement. But that ain't how it worked - in all air battles not all planes got into perfect position for firing passes. It took until 1944 with a vastly superior fighter and years of training for the USN to optimize intercept numbers. That is, if 50 fighters are on CAP, getting ALL 50 into the intercept. That ain't an easy thing to do. Planes are fast and hard to see, even in large groups. It took years.
5,



On May 8th the US task force defended itself with 40 planes on CAP. 17 fighters assigned plus 3 escorts returned early and joining in the CAP, plus 23 SBD dive bombers. These 40 aircraft shot down about 10 IJN aircraft, (4 dive bombers and 6 torpedo bombers), for a kill rate of 25%.



Here's the actual numbers for various engagements up to Santa Cruz, (fighter on defense vs. kills made)

Pearl 14/9
Wake 2/3
Darwin 10/1
Ceylon 65/11
Coral 40/10
Midway 27/11
Yorktown 31/14 (12 Yorktown plus 19 TF-16)
Yorktown 22/6 (6 Yorktown plus 8 taking off, plus 8 from TF-16. You listed '7' shot down by fighters in this attack, but one Kate blew up near Yorktown so was probably AA)
Ryujo vs Guadalcanal 16/7
Eastern Solomons 53/12 (24 IJN aircraft shot down, but probably half to AA)
Santa Cruz (raids 1 and 2) 68/24 (62 IJN aircraft shot down, but most to anti-aircraft, which now had 40mm and 20mm in abundance).

That's 348 fighters shooting down 108 IJN planes, or a 31% kill rate.




The Val of the first wave lost was due to navigational error returning to the fleet, not to American defenses. This is known because the plane radioed the fleet after 1pm it was ditching.



9 kills to shipborne AA is probably about right for the 2nd wave. Of these, most were Vals at low level trying to exit the harbor against 50-cal, or hit in the later stages of their dives.



Correct, on average. But about 50% of the time it's fewer losses and 50% of the time it's heavier losses. The 50% heavier tended to be weighted towards fewer Zero escorts.



To get above 30 you have to start playing games between establishment numbers and engagement numbers, ignoring bad cases (like Darwin) and focusing on good cases. This would be classic 'victory disease' thinking patterns, which are where defeats happen because all variables are imagined as best case.



The US fleet was fully manned and firing for the second wave. It shot down 9 planes, by your own numbers. You have Zimm. On page 272 it gives rounds expended as between 3,188-4,929 x 5" and 2,801 x 3", (367 guns) plus 5,770 x 1.1" (64 guns) and 275,000 x 50-cal, (397 guns).

7,730 rounds of 3-5" appear to have shot down nothing. The others got about 17 planes, (8 first wave, 9 second wave). Per barrel expenditure was -

3-5" = 21 rounds each.
1.1" = 120 rounds each.
50 cal = 692 rounds each.

The big stuff maybe might double their fire, but what's 2 x 0?
The 1.1 was notoriously unreliable, which is why the 20mm was being rushed in to replace it.
The 50 cals shot about as much as can be imagined.

Sure, more planes might be shot down. But alot more?



That's what I'm sensing. You want crippling losses. Anything to get to that. But the IJN didn't go through the expense of building the 1st Air Fleet because they thought it was a bunch of 2nd-rate powder puffs that would go down to US pixie cannons at first blush. They built something that could fight. So where's your crippling losses from that? Sitting in the future, at Santa Cruz, with 20mm and 40mm mounts, that's where. But the USN had no 20mm and 40mm mounts at Hawaii.

actually with the awesome firepower, excellent fighters and airmen, and inferior Japanese crews and airframes (for the most part) the best the US ever did was 90% against the Kamikazes.

But why in your estimation was Coral Sea cancelled and the Japanese carrier fleet inactive after Santa Cruz? Historians say it was because of crippling aircrew losses.

29 lost historically at Pearl Harbor, many of whom are from the best trained and most experienced air groups (Akagi, Kaga, Soryu and Hiryu) because they had the most dangerous missions (attacking the fleet). The Shokaku and Zuikaku airgroups were assigned airfield suppression because they were considered less trained and experienced. Anything that increases the losses to the experienced 4 carrier airgroups is going to have long term effects.

Even if the numbers are just increased to 30 aircraft shot down by fighters (from 10 historically) which we seem to agree is not an unreasonable assumption if the fighters are actually in the air at the start of the battle makes that 49 aircraft lost. If we double or triple the torpedo planes shot down (also not unreasonable as only the last of the attackers were engaged ... the 5 shot down were at the tail end of the torpedo attack) that makes it 59 aircraft lost. The fleet guns manned with sufficient ammunition flow (remember they only had their ready boxes initially and exhausted them before a steady flow of ammunition could get going) is bound to get at least 5 or so of the level bombers (of 50). That makes 64 shot down.

Even if only a couple of dozen fighters survive Raid 1 to fight Raid 2 (and there was a 30 minute lull to rearm and refuel) they will likely add at least 3 or 4 more (probably more as these are likely the most adept of the American pilots and also the most aggressive) that makes it 68.

The entire attack force was only around 360 aircraft (as fighters were kept back for CAP over the fleet). That is an 18% loss rate even in your most pessimistic view point. Generally speaking anything over 5-7% was considered a severe loss in the ETO Bomber Offensive.

If torpedo aircraft losses are higher, and flak is more effective against the level bombers, the flak available to meet the Second Wave is less suppressed thus the fleet is more likely to achieve more against that wave as fewer ships are hit or suffering catastrophic damage.

This all adds up. It doesn't require many changes to get to 25%. If better command decisions had been made by the US Army (specifically), then more fighters would have been available, the flak guns would have been at their assigned defense areas instead of parked. More losses in the airfield suppression attacks result. If the fighters had been in their hardened shelters instead of parked on the ramp fewer of them are lost, and more are available for the Second Wave.

You are asserting that nothing the US could have done would have inflicting crippling damage to the Japanese. The goal of this OP is to determine what would have happened if those losses had been inflicted, which requires determining how those losses could have been inflicted.

A number of books, including General Kenny's memoirs, and this outstanding work "Fire in the Sky" as well as "Guadalcanal:Starvation Island" look at South Pacific Campaign and its daily attrition which exceed the rate of Japanese ability to replace losses as the key to the air war in the Pacific. But you knock out 18-30% of the principal Japanese strike force (its aircrews and aircraft) on the first day of the war and that attrition already starts to become a serious problem.

Coral Sea and Midway demonstrate very strongly that far higher losses could have been inflicted, with the equipment and weapons available at the time of Pearl Harbor.

That doesn't require pixie cannons or magic.

also your numbers for Wake Island seem very low.. is that from the first day or for the duration of the campaign?

In my timeline I gave the American fighters about a 30% effectiveness against fighters, while giving the Japanese about a 50% effectiveness (on average as some where fighting P36s). I gave the US fighters a higher effectiveness (about 40%) against bombers, while giving the Japanese about 60% based on what I know of the combat histories of both through Guadalcanal. (That effectiveness is hits scored as a percentage of the attacking force, not as a percentage of the force being attacked

I gave US fleet and Army flak variable effectiveness ratings depending on whether it was engaging low flying torpedo bombers, level bombers flying at 10,000 feet in a predictable flight path and a much lower effectiveness against dive bombers (assuming that those destroyed mostly would be splashed as they pulled out and a small percentage lost vs damaged by ground fire).

One other important thing about Pearl Harbor... it doesn't really matter what the US losses in pilots are (well except obviously to the men involved). They can be replaced very readily, as were their aircraft losses. The Japanese do not have that luxury or ability, particularly in terms of carrier aviators.

Even if both US CV are lost engaging the Japanese, if they manage to knock 2 of the Japanese out of the war for several months through damage or casualties to their airgroups, they are inflicting crippling losses.

There are lots of variables that make this OP possible.
 
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Yet before the attack, Genda and Fuchida expect very high losses to the attacking force. They also expected higher hit ratios than were delivered by the dive bombers and torpedo planes

From Zimm apparently they got about as good as they could expect from the Level Bombers. He criticized strongly the diversion of dive bombers against the Nevada (which even with 5 bomb hits did not suffer catastrophic damage... the torpedo it took was what lead to her being beached). He also criticizes the torpedo attack plan (too many allocated to carrier row). To be fair, the technical challenges of dodging all kinds of obstacles while launching a torpedo attack in a rather confined space (not even considering what the defensive fire should have been) make the results (if I recall correctly about 18 torpedoes hit out of 40) pretty good I think.

The dive bombers should have concentrated on the stationary ships in the destroyer nests (where up to 5 were tied up together), the fleet docks (where cruisers were tied up to the docks) and they should have ignored the Shaw (and the floating drydock) and allocated more on the main drydock (and the Pennsylvania). The US Army lacked the capability to inflict serious damage on the 1st Air Fleet and the PBYs at Kanoehe could find the Japanese.. maybe. Allocating the dive bombers sent to those airfields would have provided more to hit the American fleet, particularly the vulnerable ships that were concentrated and grouped together. The Zeros could have strafed after the level bombing attack at Hickam and left the base entirely alone in the 2nd Wave without serious consequences to the Japanese

Of course no one knew just how ineffectual level bombers were going to be against moving targets so that is of course hindsight. But the attack could have done a lot more damage to the primary objective.. the US fleet.

The Japanese expected to lose 2 CV, and thus about a third of their airgroups. They got away basically unscathed.


Anything that starts that attrition early that eventually destroyed the 1st Air Fleet (first reducing it to 4 CV, and then sinking that core element) is going to have massive butterflies...such as (as I said earlier) likely no Ceylon Raid, a reduced Darwin Raid, and probably (as it was outside of the range of land based air support) a much delayed invasion of Rabual that set into motion the New Guinea and Solomons Campaigns. Knock out anywhere from a quarter to a third of the Japanese aircrews, and you basically take out of the war for several months at least 2 CV, possibly even 3.

They only operated 81 (Kaga), 72 (Akagi, Shokaku, Zuikaku), and 54 (Hiryu and Soryu) aircraft each, and it took months to fully replace losses. Reduce that number by a quarter from 414 aircraft to 300 and basically that is both of the CVL out of action to train new airgroups. Knock a third (to 250) and now the Japanese are down to 3 CV. Knock out 50%, and at roughly 200 aircraft the Japanese can only operate 2 CV and 1 CVL

Those numbers become crippling very quickly
 
Yet before the attack, Genda and Fuchida expect very high losses to the attacking force. They also expected higher hit ratios than were delivered by the dive bombers and torpedo planes

Right, but Genda and Fuchida also didn't think it would be a one-off attack. They thought it would be an extended battle over the course of days.
 
actually with the awesome firepower, excellent fighters and airmen, and inferior Japanese crews and airframes (for the most part) the best the US ever did was 90% against the Kamikazes.

Pretty sure the kamikaze loss rate was 100% in strikes making contact with the US fleet, if I understand the term correctly.

But why in your estimation was Coral Sea cancelled and the Japanese carrier fleet inactive after Santa Cruz? Historians say it was because of crippling aircrew losses.

Actually, Zuikaku searched for Yorktown after the battle, on the 9th or 10th (forget which), the intention being to sink it. But Fletcher had already departed the scene. Why Hara retreated initially on the 8th I personally think is because Shokaku got pasted and he didn't want to risk his division by losing his last operational deck.

Zuikaku's trom is here. You can go through the various carriers to get an idea of what went on after Santa Cruz., Zuikaku was operational again it looks like at the end of December 1942, Shokaku about May 1943.

http://www.combinedfleet.com/Zuikak.htm

Santa Cruz was the first battle in which IJN strike losses approach the levels you're projecting for Pearl Harbor. The problem? This was because of 40mm and 20mm AA, (and maybe some 5" proximity). None of which were at Pearl Harbor.

The Shokaku and Zuikaku airgroups were assigned airfield suppression because they were considered less trained and experienced.

When I said Aichi 99 Kanbaku says 5th CAR DIV's Val pilots came from 12th and 14th Ku in China, that ends the discussion on these units - they were composed in large part from combat vets. The fighter pilots probably came from the same source.

Even if the numbers are just increased to 30 aircraft shot down by fighters (from 10 historically) which we seem to agree is not an unreasonable assumption if the fighters are actually in the air at the start of the battle makes that 49 aircraft lost. If we double or triple the torpedo planes shot down (also not unreasonable as only the last of the attackers were engaged ... the 5 shot down were at the tail end of the torpedo attack) that makes it 59 aircraft lost. The fleet guns manned with sufficient ammunition flow (remember they only had their ready boxes initially and exhausted them before a steady flow of ammunition could get going) is bound to get at least 5 or so of the level bombers (of 50). That makes 64 shot down.

65 shot down in the two raids (combined) against fully alerted defenses is a defendable opinion, provided the defending fighters manage a mass interception. Not 100s shot down. Not 200. (Zimm goes full jingo on his hypothetical kill estimates, IMO).

The entire attack force was only around 360 aircraft (as fighters were kept back for CAP over the fleet). That is an 18% loss rate even in your most pessimistic view point. Generally speaking anything over 5-7% was considered a severe loss in the ETO Bomber Offensive.

65 would send Nagumo on his way. The raid would be a strategic failure, but from a tactical perspective, indecisive for either side.

If torpedo aircraft losses are higher, and flak is more effective against the level bombers, the flak available to meet the Second Wave is less suppressed thus the fleet is more likely to achieve more against that wave as fewer ships are hit or suffering catastrophic damage.

The second wave flak was about as active as can be imagined, so call it 9 kills and leave it at that.

This all adds up. It doesn't require many changes to get to 25%. If better command decisions had been made by the US Army (specifically), then more fighters would have been available, the flak guns would have been at their assigned defense areas instead of parked. More losses in the airfield suppression attacks result. If the fighters had been in their hardened shelters instead of parked on the ramp fewer of them are lost, and more are available for the Second Wave.

The USAAF didn't put around 130 fighters on Oahu because flak was effective. It had them there because AA was garbage. In terms of USAAF fighters, we're assuming these scrambled to meet the first wave, so revetments are only used for non-operational fighters.

You are asserting that nothing the US could have done would have inflicting crippling damage to the Japanese.

No, what I said is that it took about 350 fighter sorties to shoot down 100 IJN planes in 1942. So, if you're projecting 100 or 150 lost, if I were writing it, I'd have it the USAAF prepositioned 350 fighters on Oahu for an ambush. If you want 200 shot down, maybe pre-position 900 fighters on Oahu.

A number of books, including General Kenny's memoirs, and this outstanding work "Fire in the Sky" as well as "Guadalcanal:Starvation Island" look at South Pacific Campaign and its daily attrition which exceed the rate of Japanese ability to replace losses as the key to the air war in the Pacific. But you knock out 18-30% of the principal Japanese strike force (its aircrews and aircraft) on the first day of the war and that attrition already starts to become a serious problem.

So, if the Japanese lost 8,000 planes and pilots in the Solomons, those 100 lost at an AH Pearl Harbor (1/80th of that total) mean what?

Coral Sea and Midway demonstrate very strongly that far higher losses could have been inflicted, with the equipment and weapons available at the time of Pearl Harbor. That doesn't require pixie cannons or magic.

Not pixie cannons specifically, but either them or 40mm and 20mm cannons; between Coral Sea and Midway, 122 US fighters shot down 41 aircraft against about 63 escorts. At Oahu they've got 90 and there are around 80 escorts.

also your numbers for Wake Island seem very low.. is that from the first day or for the duration of the campaign?

At Wake there was 1 air battle where IJN carrier aircraft tangled with defending fighters. Two IJN Kates were shot down, two F4F's were shot down, one Kate pancaked back at the fleet, (crew recovered).

In my timeline I gave the American fighters about a 30% effectiveness against fighters, while giving the Japanese about a 50% effectiveness (on average as some where fighting P36s).

I'd recommend something like 10% effectiveness against the Zero, 25% against escorted strikes, 50% against unescorted strikes. Doing a quick estimate, those 350 fighters shot down about 22 Zeros. In the raids, when looking at escort strength, when this was 20 or fewer Zeros they lost about 87 planes shot down on 259 defending fighters (vs 89 escorts, or 3:1). When it was 36 or more escorts, they lost 21 planes shot down, (91 fighters vs 144 escorts, or about 1.6 to 1 in favor of the Zeros.

I gave US fleet and Army flak variable effectiveness ratings depending on whether it was engaging low flying torpedo bombers, level bombers flying at 10,000 feet in a predictable flight path and a much lower effectiveness against dive bombers (assuming that those destroyed mostly would be splashed as they pulled out and a small percentage lost vs damaged by ground fire).

Call it maybe 25 to AA against alerted defense, both waves, total. More torpedo bombers shot up and ditched back at the fleet.

One other important thing about Pearl Harbor... it doesn't really matter what the US losses in pilots are (well except obviously to the men involved). They can be replaced very readily, as were their aircraft losses. The Japanese do not have that luxury or ability, particularly in terms of carrier aviators.

Santa Cruz says that once the 20mm and 40mm were in numbers in the US fleet, IJN pre-war aviator doctrine was useless. Therefore, that the time to use these units was in the first six months of the war.

Even if both US CV are lost engaging the Japanese, if they manage to knock 2 of the Japanese out of the war for several months through damage or casualties to their airgroups, they are inflicting crippling losses.

When this combined wave of defending fighters rips into the attack and shoots down 30 aircraft, then 25 more fall to AA and 10 more to damage later, there isn't going to be a carrier battle. Nagumo will scoot.
 
IMO it's much harder to give the Japanese crippling losses than it is to reduce the American losses.
 
From Zimm apparently they got about as good as they could expect from the Level Bombers. He criticized strongly the diversion of dive bombers against the Nevada (which even with 5 bomb hits did not suffer catastrophic damage... the torpedo it took was what lead to her being beached). He also criticizes the torpedo attack plan (too many allocated to carrier row). To be fair, the technical challenges of dodging all kinds of obstacles while launching a torpedo attack in a rather confined space (not even considering what the defensive fire should have been) make the results (if I recall correctly about 18 torpedoes hit out of 40) pretty good I think.

Nevada was heading for open sea after taking a torpedo hit, then did beach patrol after being dive bombed. Zimm suggests the DB attack was a mistake, but it was this attack that created complications with the torpedo hit and led to uncontrolled flooding. If the Kaga leader made any serious mistake in the decision, it was attempting to sink the ship in the narrow channel rather than allowing her to move to sea, then trying to sink her there instead.

The dive bombers should have concentrated on the stationary ships in the destroyer nests (where up to 5 were tied up together), the fleet docks (where cruisers were tied up to the docks) and they should have ignored the Shaw (and the floating drydock) and allocated more on the main drydock (and the Pennsylvania). The US Army lacked the capability to inflict serious damage on the 1st Air Fleet and the PBYs at Kanoehe could find the Japanese.. maybe. Allocating the dive bombers sent to those airfields would have provided more to hit the American fleet, particularly the vulnerable ships that were concentrated and grouped together. The Zeros could have strafed after the level bombing attack at Hickam and left the base entirely alone in the 2nd Wave without serious consequences to the Japanese

One serious error I think was in training - 1/3rd (18 aircraft) of the 5th division Kate squadron should have received specialist training in recce and not committed at all to the attack once at least one carrier was known to be at sea. Another error was in planning - they decided to go with two waves. They should have combined deck loads and done one wave, even if the second deck launch was understrength, (ie, 18 aircraft not 27).

The Japanese expected to lose 2 CV, and thus about a third of their airgroups. They got away basically unscathed.

Yamamoto was prepared to lose 2 CV's and 1/3rd of his air groups if the primary mission was achieved, which was securing the eastern sea front during the period of the southern operations.

Anything that starts that attrition early that eventually destroyed the 1st Air Fleet (first reducing it to 4 CV, and then sinking that core element) is going to have massive butterflies...such as (as I said earlier) likely no Ceylon Raid, a reduced Darwin Raid, and probably (as it was outside of the range of land based air support) a much delayed invasion of Rabual that set into motion the New Guinea and Solomons Campaigns. Knock out anywhere from a quarter to a third of the Japanese aircrews, and you basically take out of the war for several months at least 2 CV, possibly even 3.

None of what you list was particularly significant. I notice also that you didn't list Midway, which also could be 'butterflied' away. In terms of air group losses, 150 aircraft could have been replaced from existing reserves. The step-in aviators could not fly as well, and they would be flying obsolescent aircraft, but it could have been done for the southern operation.

They only operated 81 (Kaga), 72 (Akagi, Shokaku, Zuikaku), and 54 (Hiryu and Soryu) aircraft each, and it took months to fully replace losses. Reduce that number by a quarter from 414 aircraft to 300 and basically that is both of the CVL out of action to train new airgroups. Knock a third (to 250) and now the Japanese are down to 3 CV. Knock out 50%, and at roughly 200 aircraft the Japanese can only operate 2 CV and 1 CVL.

To complete the southern drive they didn't need CV's at all.
 
so question for everyone, I do not know enough on this topic, but what kind of damage will the USN submarines and battleships and other ships do? How many would be lost?
 
Nevada was heading for open sea after taking a torpedo hit, then did beach patrol after being dive bombed. Zimm suggests the DB attack was a mistake, but it was this attack that created complications with the torpedo hit and led to uncontrolled flooding. If the Kaga leader made any serious mistake in the decision, it was attempting to sink the ship in the narrow channel rather than allowing her to move to sea, then trying to sink her there instead.



One serious error I think was in training - 1/3rd (18 aircraft) of the 5th division Kate squadron should have received specialist training in recce and not committed at all to the attack once at least one carrier was known to be at sea. Another error was in planning - they decided to go with two waves. They should have combined deck loads and done one wave, even if the second deck launch was understrength, (ie, 18 aircraft not 27).



Yamamoto was prepared to lose 2 CV's and 1/3rd of his air groups if the primary mission was achieved, which was securing the eastern sea front during the period of the southern operations.



None of what you list was particularly significant. I notice also that you didn't list Midway, which also could be 'butterflied' away. In terms of air group losses, 150 aircraft could have been replaced from existing reserves. The step-in aviators could not fly as well, and they would be flying obsolescent aircraft, but it could have been done for the southern operation.



To complete the southern drive they didn't need CV's at all.

no, they don't need the CVs for the Southern Resource Area campaign (well within land based range for all of it)

I think Midway is only going to happen if there is a Doolittle Raid, which I think requires a minimum of 4 US CVs being available for the Pacific. Even then it only happens if the Japanese have at least 4 CVs with their airgroups available. I would butterfly away the Aleutians too, although potentially it is an option even without the 1st Air Fleet (or so the Japanese would think as they don't know their codes were broken by then). If no Midway, the Japanese seek their "decisive battle" sometime in 1943 or wait until the Americans approach the Inner Defense Perimeter (Marianas). Although If I had been the Japanese High Command I would have pushed for a full scale Army and Navy push into eastern and southern India, not so much to conquer India as to finish off the isolation of Nationalist China and then pushing for a 1943 Icho-Go to bring about a Nationalist collapse (and finally free up some damn troops!). The RN could not have stopped it, and the situation in India was very shaky pretty much all of the 1942. While the Americans might have made some raids, and even landed somewhere important, they could not have threatened the Inner Defense Perimeter in 1942.

Ignoring the Nevada and putting those aircraft to use hitting the the American cruisers tied to the docks might be better cost benefit for the Japanese. You could easily argue either way though on that.

A time on target strike with everything at once would have been the optimum. However, those Japanese carriers lack catapults, and the heavily armed torpedo and level bombers needed a lot of ship to take off with. I am still researching this, but the impression I am getting is that the carriers of this era (lacking catapults) can only launch about half of their aircraft at a time. I can't find any examples of them launching much more than that but I am very open to being wrong on this. Apparently there was a problem on the Kaga with a rather slow elevator as well.

Because of those reasons I kept the strikes in my timeline the same size or less than the historic strikes. Anyone else have something on this issue?
 
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so question for everyone, I do not know enough on this topic, but what kind of damage will the USN submarines and battleships and other ships do? How many would be lost?

Unless the Japanese make a stab at Hawaii, or Alaska (not the Aleutians) the US BBs are not going to show up until late 1942 due to fuel constraints. There aren't enough oilers and other support ships to keep them going further west or in the South Pacific AND support the carriers too. The North Carolina class and the ones that follow were far more fuel efficient (indeed the most fuel efficient ship in the fleet were the Iowa's) and by the time they showed up, so did more oilers and other support.

Indeed if the Japanese had just sunk the 2 oilers at Pearl Harbor and bagged the other one that was en route they might have done more to limit US fleet operations west of Hawaii than actually doing the damage they did in OTL. Of the 6 BBs that were not total losses, 4 of them were back in service within weeks and the USN had 3 more it could easily transfer from the Atlantic without any significant issues But they sat in port or trained of the CA coast for nearly all of 1942 as the support ships they needed for offensive operations were not available until mid 1943
 
no, they don't need the CVs for the Southern Resource Area campaign (well within land based range for all of it)

Rabaul was the only out of range of land based air objective, and it could have been done with seaplane support I think, if necessary.

I think Midway is only going to happen if there is a Doolittle Raid, which I think requires a minimum of 4 US CVs being available for the Pacific.

If the Japanese carriers get spanked at Hawaii Midway might not happen, Doolittle or no.

A time on target strike with everything at once would have been the optimum. However, those Japanese carriers lack catapults, and the heavily armed torpedo and level bombers needed a lot of ship to take off with. I am still researching this, but the impression I am getting is that the carriers of this era (lacking catapults) can only launch about half of their aircraft at a time. I can't find any examples of them launching much more than that but I am very open to being wrong on this. Apparently there was a problem on the Kaga with a rather slow elevator as well.

Takeoff is at 6am and the planes should not be in the air more than 4 hours , (giving them about 3 hours leeway for damage and navigation). Launch and form up takes 15 minutes, cruise speed is about 125kt, , attack 30 min. Call it 60 minutes delay between waves. So, if the first wave waits for the second, it's like adding 125 miles to its launch range. Call it 400 miles (round trip) cruising (3.2 hr) and .5 hr attack, 1 hour waiting, that's 4.7 hours.

So it's all about shaving time where it can be shaved. Cut the second wave to 18 bombers per carrier (leave the other 9 on Kaga, Shokaku and Zuikaku in reserve or use for scouting after the 2nd wave departs). This cuts 20 minutes. Have the first wave depart when the second commences takeoff and do the form up en route. That cuts another 15 minutes. Make the round trip 360nm by moving the carriers closer to Oahu. That cuts 20 minutes. Total cuts are 55 minutes, dropping time from 4.7 hours to 3.8 hours, which is "in budget".
 
Rabaul was the only out of range of land based air objective, and it could have been done with seaplane support I think, if necessary.



If the Japanese carriers get spanked at Hawaii Midway might not happen, Doolittle or no.



Takeoff is at 6am and the planes should not be in the air more than 4 hours , (giving them about 3 hours leeway for damage and navigation). Launch and form up takes 15 minutes, cruise speed is about 125kt, , attack 30 min. Call it 60 minutes delay between waves. So, if the first wave waits for the second, it's like adding 125 miles to its launch range. Call it 400 miles (round trip) cruising (3.2 hr) and .5 hr attack, 1 hour waiting, that's 4.7 hours.

So it's all about shaving time where it can be shaved. Cut the second wave to 18 bombers per carrier (leave the other 9 on Kaga, Shokaku and Zuikaku in reserve or use for scouting after the 2nd wave departs). This cuts 20 minutes. Have the first wave depart when the second commences takeoff and do the form up en route. That cuts another 15 minutes. Make the round trip 360nm by moving the carriers closer to Oahu. That cuts 20 minutes. Total cuts are 55 minutes, dropping time from 4.7 hours to 3.8 hours, which is "in budget".

Looks reasonable to me... now the big question is why didn't the Japanese do that? Fear of discovery (and loss of surprise), concern about the sea state, or something else (the plan was somewhat rushed)?

Of course we have the benefit of looking over nearly a century of carrier operations, most of which are post Pearl Harbor, but the Japanese and Americans both had nearly 20 years of experience working with carrier operations at this point. It may be as simple as no one had realized the importance of a time on target attack in terms of effectiveness (or at least the Japanese hadn't maybe?)

I think Zimm is right in some of his criticisms of the Japanese attack plan and he does demonstrate in his book how more effective it could have been.

But hindsight is 20/20 it seems.

In my timeline I modeled some of the Japanese attack on Taranto (as it had been done recently) and some of what I think the Japanese would be able to do based on the historic attack and what they had available in terms of resources.

I ever do another one I will probably look at a best case (from a Japanese perspective) attack
 
Looks reasonable to me... now the big question is why didn't the Japanese do that? Fear of discovery (and loss of surprise), concern about the sea state, or something else (the plan was somewhat rushed)?

They did it at Darwin, so it was in the pipeline. I think the reason might have been mission overload. By cutting out a combined strike they simplified their training
and operational planning by dropping yet another thing that required an alteration of doctrine. After the strike, it was clear from the 2nd wave results it was a mistake though.


I think Zimm is right in some of his criticisms of the Japanese attack plan and he does demonstrate in his book how more effective it could have been.

Dunno. He lost me with flight leaders zipping around Oahu with flare guns doing provisional attack orders with various formations. Seemed more like a good desk idea than a good pilot idea. (When I looked at it, I wasn't confident that even a basic shift in orders to the second wave for a pre-planned change in targets was feasible).

When I read Zimm, I knew he was a naval officer and serious operational planner. So I expected a serious operational plan. He had some good points - more torpedo bombers and forget the level bombers, less focus on specialist attack methods. But he missed some really big issues, which were the one-strike planning assumption, failure to combine the strike waves, failure to curtail the assault period, failure to train a proper B5N2 scouting unit, failure to scout.

I ever do another one I will probably look at a best case (from a Japanese perspective) attack

On a two-wave strike, put Egusa in the first wave and have all the dive bombers hit the airfields. Planes must be on their way back by X minute (ie, 0830). The second wave is all level bombers with close escort (no strafing). This allows them to 'catch up' to the first wave and accelerates recovery by 1 hour. Have 5th Division and 8th CRU DIV throw in about 18 aircraft to scout to 300nm, this scouting wave departing with the second wave or just after, so that they're reaching their outbound dogleg 3.5 hr after the first wave departed, (ie, about 30 minutes before the 1st wave strikers start to return).
 
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