WI: Pearl Harbor Had Been a Sea Battle

I put it to you that sitting your main carrier striking force off another nations main Pacific Base could only mean one thing and is a casus belli in its own right.

Yeah, somehow I see it being hard for Japan to say "Oh, we were just cruising innocently several thousand miles from home and all the sudden we were attacked by a whole bunch of battleships." Bullshit and the world knows it - You're right, there's only one reason they could be there and it certainly isn't a pleasure cruise.

THE IJN sailed in international waters - They always could say they did a fleet exercise - and the US attacked.

Even if you have strong hints that this is an attack, you are lacking proof.

(though the attack on the Phillies and the DEI/Malaya would later help to make your case)

Concerning the 400 or so US planes on Hawaii - they still need to fly out and actually FIND the Japanese fleet (in the dark if you want to attack at dawn)

Teh Japanese fleet would be out of reach (or at least at the outer edge) for Torpedo armed planes, so the US could only use dive Bombers (and Devastators armed with Bombs) - Take into account Take Off, Landing and getting into formation procedures...

I don't dount that the USN could deal a hard blow against Kido Butai if they

KNOW EXACTLY where to strike

And thats the big question if they could know.

Even AFTER the actual attack they did NOT find the Japanese fleet (they did not know that Japanese planes had a higher reach) and assumed them to be South or West of the Islands.

Assume they know of the attack (hich is plausible) they basically had no chance to KNOW where to strike.

Even if the Rader contact is correctly identified, the fleet would not be able to make contact with the Japanese ships.
 

Saphroneth

Banned
Here's a fun thing.

The first shots fired in the Pacific War were by the Royal Air Force - aircraft which attacked Japanese ships in the process of landing troops on the Malay peninsula.
That's before the Pearl attack actually went in.

So in the court of public opinion, it's going to be very, very hard for Japan to claim that they were on peaceful war exercises thousands of miles from their bases, right next to US bases, while also launching invasion convoys on American-held and Commonwealth-held islands and mainland areas, and then claim that they weren't the aggressors here!
 
The world doesn't work like that. Nobody would believe them, the explanation is not credible.

Its not the question what the world thinks its more like would an US Admiral (wuithout knowledge of his government) and no DOW by Japan really ATTACK a fleet in international waters or would he rather shadow this fleet and wait what they do. Formalities of war had a strong influence back then (even Germany tried to present a casus belli whe it attacked Poland - the Gleiwitz incident)

Here's a fun thing.

The first shots fired in the Pacific War were by the Royal Air Force - aircraft which attacked Japanese ships in the process of landing troops on the Malay peninsula.
That's before the Pearl attack actually went in.

So in the court of public opinion, it's going to be very, very hard for Japan to claim that they were on peaceful war exercises thousands of miles from their bases, right next to US bases, while also launching invasion convoys on American-held and Commonwealth-held islands and mainland areas, and then claim that they weren't the aggressors here!


Correct - but thats from a point when all facts are clear - with the Knowledge available to the US there is no attack on Malaya and even the Phillies the they approach Kido Butai.

OTL the US public was angry not the least because they were attacked without DOW. All the US could tell in this scenario that they attacked because they expected to be attacked (correctly).
 

Saphroneth

Banned
Its not the question what the world thinks its more like would an US Admiral (wuithout knowledge of his government) and no DOW by Japan really ATTACK a fleet in international waters or would he rather shadow this fleet and wait what they do. Formalities of war had a strong influence back then (even Germany tried to present a casus belli whe it attacked Poland - the Gleiwitz incident)




Correct - but thats from a point when all facts are clear - with the Knowledge available to the US there is no attack on Malaya and even the Phillies the they approach Kido Butai.

OTL the US public was angry not the least because they were attacked without DOW. All the US could tell in this scenario that they attacked because they expected to be attacked (correctly).
The US government will be able to say "We found a Japanese fleet thousands of miles from where it had any reason to be, well within attack range of our base at Pearl Harbour. The decision had to be made to engage it, and as events that very morning showed, across Asia and Oceania, the decision was correct - Japan was preparing a war of aggression against the United States."
 
If the surface action starts at dawn, the USN radars will already have picked up Fuchida and the first wave launching. 140 planes headed for Hawaii.

international waters notwithstanding, that's a casus belli right there.
 
If the surface action starts at dawn, the USN radars will already have picked up Fuchida and the first wave launching. 140 planes headed for Hawaii.

international waters notwithstanding, that's a casus belli right there.

I agree. its not like you could say a large force of armed aircraft could have anything other than non-peaceful intentions. What could they have said, "we weren't attacking you, the planes are the Mexican invasion force.:)" I can't see anyone not believing that.

However, the Americans were to have a good warning for this to happen, e.g. two days, might the Japanese realise their gambit has failed and run away. They won't get a second chance, but they are destroyed, that's every Japanese aircraft carrier gone. this would be a worse Battle of Midway if that happened. And It would be until May 1942, which was when the first Hiyo class was in service in OTL, for them to get some strength back.
 
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I agree with Nimitz. The Japanese would have the overall fleet speed to keep the strike force away from the US battlefleet, and an overwhelming advantage in aviation. The US ships would be relatively poorly equipped to defend themselves from dive and torpedo bombing attacks, and any ships sunk in the open ocean would stay sunk. My own opinion is that the resulting naval battle (if it occurred - other posters have pointed out that neither the Japanese nor US commanders would really have had the local authority to do this) would be just as devastating to the USN in terms of losses, and it would not have the emotional resonance that a "dastardy sneak attack" at Pearl did. This might actually give Yamamoto hope that the Americans could seek a negotiated peace some credence.
 

iddt3

Donor
I agree with Nimitz. The Japanese would have the overall fleet speed to keep the strike force away from the US battlefleet, and an overwhelming advantage in aviation. The US ships would be relatively poorly equipped to defend themselves from dive and torpedo bombing attacks, and any ships sunk in the open ocean would stay sunk. My own opinion is that the resulting naval battle (if it occurred - other posters have pointed out that neither the Japanese nor US commanders would really have had the local authority to do this) would be just as devastating to the USN in terms of losses, and it would not have the emotional resonance that a "dastardy sneak attack" at Pearl did. This might actually give Yamamoto hope that the Americans could seek a negotiated peace some credence.

I doubt there will be any issues if the IJN is attacked immediately after launching a strike that goes on to hit Pearl Harbor, an attack that precedes the DoW by a decent margin. The exact timeing won't be made an issue of, it will probably play something along the lines of "The dastardly Japanese tried to launch a surprise attack on us, but we were ready and gave 'em whatfor"
 

jahenders

Banned
Depends on Timing and Location

If the US gets some kind of advance warning, then the results of a conflict will depend on timing and location.

If the US finds out shortly before the strike, they can put out to sea and alert defenses on the island. Then it depends on who detects whom and when.

If the IJN detects the US fleet after the strike is launched, they'll almost ceratinly recall the planes to hit the fleet (and be closer for recovery) -- the main target is no longer at Pearl anyway. The IJN planes will kill or cripple several US battleships and the IJN fleet will avoid battleship slugfest range until/unless the US fleet is mauled. If one of the US carriers can participate it will result in less US fleet losses and heavier Japanese losses.

If the US has a few days warning, they'll have carriers and battleships together and the Japanese might waive off, or it'll be real bloody.

But, if it's a war at sea it will be quite different morally/politically. The US won't have hit "US soil" and the American public might be less inclined to press for war (or support is as strongly), especially if it might look like the US attacked first.
 

iddt3

Donor
If the US gets some kind of advance warning, then the results of a conflict will depend on timing and location.

If the US finds out shortly before the strike, they can put out to sea and alert defenses on the island. Then it depends on who detects whom and when.

If the IJN detects the US fleet after the strike is launched, they'll almost ceratinly recall the planes to hit the fleet (and be closer for recovery) -- the main target is no longer at Pearl anyway. The IJN planes will kill or cripple several US battleships and the IJN fleet will avoid battleship slugfest range until/unless the US fleet is mauled. If one of the US carriers can participate it will result in less US fleet losses and heavier Japanese losses.

If the US has a few days warning, they'll have carriers and battleships together and the Japanese might waive off, or it'll be real bloody.

But, if it's a war at sea it will be quite different morally/politically. The US won't have hit "US soil" and the American public might be less inclined to press for war (or support is as strongly), especially if it might look like the US attacked first.

I don't think it's hard to spin interrupting a surprise attack, after all, it's not just Pearl that's being hit. In OTL America was willing to fight Germany first despite Japan having presented a much more dire CB, if it gets into a Naval slug fest, it'll probably be spun as something like "US Fleet on exercise near Pearl is attacked by Japanese Invasion fleet". If the IJN still hits Pearl with the first wave, then it's the best of both worlds for the US, Pearl sustains moderate, photogenic, flag rallying damage, US strikes back and hits the IJN hard.
 
Given the relative speeds, unless the IJN are caught with USN ships in engagement range before they're noticed, it seems fairly unlikely the USN will managed to get in gun range of the carriers.

One possible scenario is that the USN's learned the IJN has despatched it's fleet near to Pearl Harbour. This isn't a clear DoW but it's also very clearly not friendly and they can't chance it so Kimmel sends Kidd to sea and Short has his defenses ready and such of his aircraft as are suited for it prepared to support the navy if called on - preferably with an hour or two of notice.

When the USN learned of the IJN approach and when the IJN learns the USN has put to sea are variables. In this scenario let's say the first is determined by interception and decryption of Japanese radio traffic by a west pacific US base on 5 or early 6 December reported to Pearl Harbour and leading to the USN ships (excluding the drydocked USS Pennsylvania) putting out on 6 September and the two carriers being recalled to join them west of Hawaii (the carriers won't arrive in time to be a factor). The IJN are not aware of this initially.

The IJN aircraft are picked up on radio and a patrol of P-40s is sent up from Wheeler Field to identify them. The patrol confirm these are Japanese bombers (B5N 'Kates') and since they're in US airspace and armed, the P-40s engage causing light losses and some disruption. Wheeler Field and other air fields start scrambling the fighters they can immediately, which isn't all of them but much better than OTL.

The first wave of bombers reach Pearl Harbour and report the absence of major warships. They drop their ordnance on whatever targets of opportunity they can see (USS Pennsylvania draws a lot of bombs but since it's in drydock it can't exactly be sunk despite the damage) and do their best to escape although they're now recipients of the attention of all available US aircraft. The airfields are caught launching their available aircraft as fast as possible, making them the focus of the initial defending aircraft.

Word reaches the USN of where the IJN aircraft came from - at least approximately - and they head in the necessary direction.

The IJN are alerted to the USN's absence. While the Second Wave of aircraft are sent in to do as much damage to the naval facilities and the airfields of Oahu as possible (the IJN would rather not have to battle land-based aircraft) this is clearly the last wave for that purpose and scout aircraft are sent out to try to locate the USN warships.

With more and more US aircraft in the air and not vulnerable on the ground, losses to the Second Wave aren't as severe as the those earlier in the day. Out of date fighters trying to take on Zeros take terrible losses though.

Meanwhile, using radar to track incoming and departing fighters, General Shorts HQ has more or less localised the IJN carriers and pass this to the USN at sea who were already heading in the right general direction. The IJN, for their part, are heading west and still searching.

IJN scout planes report the USN's location while the battleships and cruisers are still a good 100 miles from the carriers. Shortly thereafter B-17s from Pearl Harbour locate the IJN's location and bomb them (to no effect).

The IJN have had time to recover and rearm their aircraft from the first wave. They now launch an attack on the USN with 70 bombers (1/3 Kates with torpedos, 1/3 Kates with bombs, 1/3 Vals with bombs) escorted by 30 Zeros. The relative handful of US aircraft from Pearl that can be used to defend the fleet are sent to intercept - predominantly USMC and USN Wildcats. This isn't sufficient to break past the escorts in any substantial number and little damage is done to the attack force.

The 70 bombers engage the 7 Battleships and 8 Cruisers, taking AA fire from the ships and from the escorting destroyers. The Kates' bombs score very few hits although the Val's bombs are more accurate, in particular to the USS Nevada and USS Arizona (where a hit to the bridge kills Admiral Kidd). The Kates' torpedoes are the big winners though: USS Oklahoma and USS West Virgina, USS Helena and USS Raleigh all suffering multiple hits. Oklahoma, the worst hit, capsized with heavy loss of life and the two cruisers were abandoned when the same seemed likely to follow.

The IJN were now moving directly away from the USN and reports indicated there was no chance of catching up with them by the remaining USN battleships. Kimmel ordered the USN to close on Oahu so they could receive better air cover and survive to fight another day. An attempt was made to engage the departing IJN with a scratch air group from Oahu but this proved unsuccessful and many US aircraft and crews were lost in the attempt. This was, however, sufficient to convince the IJN leadership they had accomplished all they reasonably could and they withdrew.
 
would the battle be over before the Japanese ambassador delivered the declaration of war? could the Japanese stop that?
 
Its not the question what the world thinks its more like would an US Admiral (wuithout knowledge of his government) and no DOW by Japan really ATTACK a fleet in international waters or would he rather shadow this fleet and wait what they do. Formalities of war had a strong influence back then (even Germany tried to present a casus belli whe it attacked Poland - the Gleiwitz incident)

....

Roosevelt had already directed (in writing) to all US military commanders that any Japanese combat units appearing within attack range of US military facilities would be considered a act of war. They were authorized to make preemptive attacks on such Japanese military units. I cant remember the exact date that was issued. Probablly not later than the 'war warning' message sent in November.
 
Given the relative speeds, unless the IJN are caught with USN ships in engagement range before they're noticed, it seems fairly unlikely the USN will managed to get in gun range of the carriers.

One possible scenario is that the USN's learned the IJN has despatched it's fleet near to Pearl Harbour. This isn't a clear DoW but it's also very clearly not friendly and they can't chance it so Kimmel sends Kidd to sea and Short has his defenses ready and such of his aircraft as are suited for it prepared to support the navy if called on - preferably with an hour or two of notice.

When the USN learned of the IJN approach and when the IJN learns the USN has put to sea are variables. In this scenario let's say the first is determined by interception and decryption of Japanese radio traffic by a west pacific US base on 5 or early 6 December reported to Pearl Harbour and leading to the USN ships (excluding the drydocked USS Pennsylvania) putting out on 6 September and the two carriers being recalled to join them west of Hawaii (the carriers won't arrive in time to be a factor). The IJN are not aware of this initially.

The IJN aircraft are picked up on radio and a patrol of P-40s is sent up from Wheeler Field to identify them. The patrol confirm these are Japanese bombers (B5N 'Kates') and since they're in US airspace and armed, the P-40s engage causing light losses and some disruption. Wheeler Field and other air fields start scrambling the fighters they can immediately, which isn't all of them but much better than OTL.

The first wave of bombers reach Pearl Harbour and report the absence of major warships. They drop their ordnance on whatever targets of opportunity they can see (USS Pennsylvania draws a lot of bombs but since it's in drydock it can't exactly be sunk despite the damage) and do their best to escape although they're now recipients of the attention of all available US aircraft. The airfields are caught launching their available aircraft as fast as possible, making them the focus of the initial defending aircraft.

Word reaches the USN of where the IJN aircraft came from - at least approximately - and they head in the necessary direction.

The IJN are alerted to the USN's absence. While the Second Wave of aircraft are sent in to do as much damage to the naval facilities and the airfields of Oahu as possible (the IJN would rather not have to battle land-based aircraft) this is clearly the last wave for that purpose and scout aircraft are sent out to try to locate the USN warships.

With more and more US aircraft in the air and not vulnerable on the ground, losses to the Second Wave aren't as severe as the those earlier in the day. Out of date fighters trying to take on Zeros take terrible losses though.

Meanwhile, using radar to track incoming and departing fighters, General Shorts HQ has more or less localised the IJN carriers and pass this to the USN at sea who were already heading in the right general direction. The IJN, for their part, are heading west and still searching.

IJN scout planes report the USN's location while the battleships and cruisers are still a good 100 miles from the carriers. Shortly thereafter B-17s from Pearl Harbour locate the IJN's location and bomb them (to no effect).

The IJN have had time to recover and rearm their aircraft from the first wave. They now launch an attack on the USN with 70 bombers (1/3 Kates with torpedos, 1/3 Kates with bombs, 1/3 Vals with bombs) escorted by 30 Zeros. The relative handful of US aircraft from Pearl that can be used to defend the fleet are sent to intercept - predominantly USMC and USN Wildcats. This isn't sufficient to break past the escorts in any substantial number and little damage is done to the attack force.

The 70 bombers engage the 7 Battleships and 8 Cruisers, taking AA fire from the ships and from the escorting destroyers. The Kates' bombs score very few hits although the Val's bombs are more accurate, in particular to the USS Nevada and USS Arizona (where a hit to the bridge kills Admiral Kidd). The Kates' torpedoes are the big winners though: USS Oklahoma and USS West Virgina, USS Helena and USS Raleigh all suffering multiple hits. Oklahoma, the worst hit, capsized with heavy loss of life and the two cruisers were abandoned when the same seemed likely to follow.

The IJN were now moving directly away from the USN and reports indicated there was no chance of catching up with them by the remaining USN battleships. Kimmel ordered the USN to close on Oahu so they could receive better air cover and survive to fight another day. An attempt was made to engage the departing IJN with a scratch air group from Oahu but this proved unsuccessful and many US aircraft and crews were lost in the attempt. This was, however, sufficient to convince the IJN leadership they had accomplished all they reasonably could and they withdrew.

Would there not be a land based CAP for the USN fleet?

The British Carrier Ops in the Med often found that even a handful (litereal a handful) of fighters (in this case often Fulmars and Sea Hurricanes) was usually enough to seriously disrupt any attacking formation even when grossly outnumbered - so even if the CAP was a single Squadron of P40s this would seriously degrade any attack by the Japanese.
 
Roosevelt had already directed (in writing) to all US military commanders that any Japanese combat units appearing within attack range of US military facilities would be considered a act of war. They were authorized to make preemptive attacks on such Japanese military units. I cant remember the exact date that was issued. Probablly not later than the 'war warning' message sent in November.

AFAIK the directive by Adm Stark was that US forces are not allowed to open hostilities (27 Nov? - not sure) unless attacked by Japanese forces.
 
Given the relative speeds, unless the IJN are caught with USN ships in engagement range before they're noticed, it seems fairly unlikely the USN will managed to get in gun range of the carriers.
Nagumo approaches to launch the first wave under cover of darkness. If the fleets meet at that time, detection is indeed going to be within engagement range.

And if the seven battleships of the USN can disable the two refitted battlecruisers with Kido Butai before they can escape out of range, then the Leary's eight cruisers and twenty odd destroyers are actually faster than the Nagumo's carriers and outgun the rest of the escort significantly.


would the battle be over before the Japanese ambassador delivered the declaration of war? could the Japanese stop that?
Maybe. Depends on the scenario. A dawn action after the first wave is launched means the battle would finish before the declaration was delivered, but Nagumo might maintain radio silence (or not have transmissions received correctly) anyway. A chase where Leary's cruisers are detached to run down Nagumo over the course of the day while fending off air attacks (when most of the ordnance has been expended already) - maybe.
NB - it wasn't actually a declaration of war.

Would there not be a land based CAP for the USN fleet?
Probably not. Kido Butai would stay too far from Pearl. Japanese carrier aviation had better combat radii than USAAF pursuit planes in 1941.
 
Nagumo approaches to launch the first wave under cover of darkness. If the fleets meet at that time, detection is indeed going to be within engagement range.

And if the seven battleships of the USN can disable the two refitted battlecruisers with Kido Butai before they can escape out of range, then the Leary's eight cruisers and twenty odd destroyers are actually faster than the Nagumo's carriers and outgun the rest of the escort significantly.



Maybe. Depends on the scenario. A dawn action after the first wave is launched means the battle would finish before the declaration was delivered, but Nagumo might maintain radio silence (or not have transmissions received correctly) anyway. A chase where Leary's cruisers are detached to run down Nagumo over the course of the day while fending off air attacks (when most of the ordnance has been expended already) - maybe.
NB - it wasn't actually a declaration of war.


Probably not. Kido Butai would stay too far from Pearl. Japanese carrier aviation had better combat radii than USAAF pursuit planes in 1941.


How far out was the fleet? I know it was at least 150 NM as thats how far out the radar spotted them?

P40 has about 600 NM Range so the 3 odd sqaudrons on the Island could have performed a rolling CAP - but again only if the US Knew where the Japanese fleet was (Which Im assuming they did from the OPs comments)

Idealy I would move the US Fleet South East of the Island and keep it under Land based Air Cover while ordering Enterprise to join and the other Carriers to return ASAP - Maintain the doctrine of 'Fleet In Being' and deny the Japanese the option of sinking capital ships but thats not what the OP asked!
 

sharlin

Banned
If the USN knew the IJN was coming really the smart thing would be to sortee the fleet to the South East. AWAY from the IJN. Sure the IJN is light on surface escorts for this but you're going to be on the reciving end of 6 carriers worth of aircraft piloted by probably the best carrier pilots in the world at the time.

Going away from the threat preserves the fleet and lets the IJN vent itself on ground targets whilst being opposed by fighters etc.
 
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