Failed first move: What if Kido Butai defeated at Pearl Harbour

[mutiafarida3]

POD :

US Intelligence crack Japanese Naval Codes in early December 1941, thus able to decipher the exact plan of Japanese attack against Pearl Harbour and warned the base at December 6th. When Japanese planes arrived, they found the entire base at full alert. The battleships already powering their weapon systems, the coastal AA battery readied, and the airbases in the process of launching most of their fighters. Japanese first wave took heavy loses and the second wave effectively wiped out.

When it was reported that no aircraft carrier sighted at the port, Nagumo realized that he can be in turn counter attacked by US carrier strike, not to mention all the land based bombers. He promptly ordered a retreat and left the area. Kido Butai loses more or less 2/3 of it aircrafts, Pacific fleet suffered several warship moderately damaged and several dozen aircraft destroyed.

What will happen with the Pacific War after this? Will US attempt attack Japanese Home Island immediately with a full scale naval offensive? Or they will wait until the Essex class and Iowa class completed?

Will Japan be defeated at 1943-1944, instead 1945?

 

[Onkel Willie]

With 2-3 days warning, the Pacific Fleet could actually have steamed out of PH, which would have been worse. With a few hours warning your scenario could have happened, which would have cost Japan a lot of experienced airmen that could have been used elsewhere.

 

[johnboy]

With 2-3 days warning, the Pacific Fleet could actually have steamed out of PH, which would have been worse. With a few hours warning your scenario could have happened, which would have cost Japan a lot of experienced airmen that could have been used elsewhere.

I would not go that far. No Pacific Fleet at Pearl means no raid. The Japanese were well enough informed as to what lay at anchor up to the day before.

 

[rob2001]

I would not go that far. No Pacific Fleet at Pearl means no raid. The Japanese were well enough informed as to what lay at anchor up to the day before.

It depends on whether or not the officers of the First Air Fleet, have enough sense to go after other targets at Pearl Harbor. Namely, the oil tank farms, the dry docks, the work shops, and the submarine docks. If they take out the oil tank farms, it will destroy the entire fuel reserves of the entire Pacific fleet.

 

[Shaby]

It depends on whether or not the officers of the First Air Fleet, have enough sense to go after other targets at Pearl Harbor. Namely, the oil tank farms, the dry docks, the work shops, and the submarine docks. If they take out the oil tank farms, it will destroy the entire fuel reserves of the entire Pacific fleet.

Only first, they have no orders to do that. Those come into play only in prolonged war, which Japanese did not want and knew would lose. The purpose of Raid was to shock the US into accepting Japanese terms.

Two: they couldn't do that. It was physically impossible. The US had an entire underground storage that was invulnerable to anything Japanese brought to bear in the Raid. The same goes, only to a larger extent to dry docks and other pretty heavy stuff.

 

[Shaby]

I would not go that far. No Pacific Fleet at Pearl means no raid. The Japanese were well enough informed as to what lay at anchor up to the day before.

If Kimmel got really clever, and the US scored improbable intelligence coup in knowing the Japanese orders, he'd leave the fleet at anchor, sail out the carriers and put the planes in revetments. Then as the Japanese are detected on radar launch his ground planes, meet the first wave in the air and order carriers to hit Kido Butai as they launched the second wave.

 

[Anarch King of Dipsodes]

POD :

US Intelligence crack Japanese Naval Codes in early December 1941, thus able to decipher the exact plan of Japanese attack against Pearl Harbour and warned the base at December 6th.

Can't happen. The orders for the Pearl Harbor attack were never transmitted by radio.

However. One could have Kimmel decide to send a few PBY patrols NW, and have one of them sight Kido Butai. Even if that happens early 7 December, that still provides Pearl Harbor with a couple hours of warning - which is vastly more than they had OTL, and possibly enough to put up an effective defense.

Kido Butai loses more or less 2/3 of it aircrafts, Pacific fleet suffered several warship moderately damaged and several dozen aircraft destroyed.

What will happen with the Pacific War after this? Will US attempt attack Japanese Home Island immediately with a full scale naval offensive?

The USN can't get there. U.S. priority would be defending Wake Island, Guam, and the Philippines, and the last two are almost certainly hopeless.

After that would come defending New Guinea, the Bismarck Islands, perhaps the Gilbert Islands.

One very big difference: Kimmel will be CINCPAC instead of Nimitz.

 

[King Augeas]

I suspect that had the US determined Japanese intentions, either by codebreaking (the nonexistent messages!) or simply by recon finding the KB near Hawaii, they would have attacked it immediately.

War warnings had already been sent out and there was only one reason for the KB to be cruising towards strike range of Pearl. It might take a while for the necessary permissions to be given though.

 

[Glenn239]

POD :

US Intelligence crack Japanese Naval Codes in early December 1941, thus able to decipher the exact plan of Japanese attack against Pearl Harbour and warned the base at December 6th. When Japanese planes arrived, they found the entire base at full alert. The battleships already powering their weapon systems, the coastal AA battery readied, and the airbases in the process of launching most of their fighters. Japanese first wave took heavy loses and the second wave effectively wiped out.

When it was reported that no aircraft carrier sighted at the port, Nagumo realized that he can be in turn counter attacked by US carrier strike, not to mention all the land based bombers. He promptly ordered a retreat and left the area. Kido Butai loses more or less 2/3 of it aircrafts, Pacific fleet suffered several warship moderately damaged and several dozen aircraft destroyed.

What will happen with the Pacific War after this? Will US attempt attack Japanese Home Island immediately with a full scale naval offensive? Or they will wait until the Essex class and Iowa class completed?

Will Japan be defeated at 1943-1944, instead 1945?

First, the total anti-aircraft firepower of Oahu in December 1941 was more like 4 or 6 battleships by 1944, so the losses might be around 60 aircraft assuming altered defences, double that for heavily damaged planes - mostly to USAAF fighters, (which would also take a pounding to Zeros).

That being said, assuming KB lost 2/3'rds of its aircraft at Hawaii, it returns to Japan with approximately 135 aircraft operational, out of a normal capacity of about 390. The CVL's could make up some of the difference, and there were shore units with older type carrier aircraft as well - old aircraft, pilots not nearly as well trained. KB would need to recover before joining the Southern Operation, and when it did, it may be the case that at least the 5th Carrier Division would be operating obsolete types with poorer pilots, (A5M, B5N1, D1A), and perhaps the 2nd CAR DIV as well.

 

[Glenn239]

I would not go that far. No Pacific Fleet at Pearl means no raid. The Japanese were well enough informed as to what lay at anchor up to the day before.

If Oahu were alerted it lights off like a Christmas tree with radio signals. Also, the Japanese spies would report the sharply increased activity. Unless almost right on top of Hawaii, Nagumo turns around and sails for home.

 

[Nik]

How long to secure the hatches etc ??

How long does it take from 'anchor watch' to close a big ship's water-tight doors ? To man the AAA guns ??

The former would have saved several big ships sunk on 'Battleship Row'. The latter could have taken a nasty chunk out of the attackers...

And, given enough warning to launch air-craft, there would have been an expensive fur-ball rather than a turkey shoot...

IIRC, marine archaeologists recently found remains of one of the IJN mini-subs whose sightings had been thought 'urban legend'...

Previous posters called it right-- If quorum of USN fleet was 'closed up' or had sea-room, the IJN would have no alternative but to abort attack lest their hyper-trained pilots be mauled and/or their carriers be shot from under...

 

[fred1451]

How long does it take from 'anchor watch' to close a big ship's water-tight doors ? To man the AAA guns ??

The former would have saved several big ships sunk on 'Battleship Row'. The latter could have taken a nasty chunk out of the attackers...

And, given enough warning to launch air-craft, there would have been an expensive fur-ball rather than a turkey shoot...

IIRC, marine archaeologists recently found remains of one of the IJN mini-subs whose sightings had been thought 'urban legend'...

Previous posters called it right-- If quorum of USN fleet was 'closed up' or had sea-room, the IJN would have no alternative but to abort attack lest their hyper-trained pilots be mauled and/or their carriers be shot from under...

When I was in Navy we were supposed to have the doors closed and be at battle stations ready to go 6 minutes after the alarm was called. Now it was a carrier, but it was also twice the size of the BBs at Pearl. I think a bigger hit would have been the fact that a good number of the crews might have been on liberty.

 

[Glenn239]

The former would have saved several big ships sunk on 'Battleship Row'. The latter could have taken a nasty chunk out of the attackers.

The biggest difference is in the torpedo bombers. Instead of 5 shot down, maybe 20 or 25?

 

[marathag]

After the War Warming of I think Nov 22, all unidentified Ships were to be assumed hostile and attacked.

With enough Magic decrypt, could/would the Fleet sortie for a meeting engagement north of Hawaii, before Nagumo sent out scouts, to try and
'Dogger Bank' the IJN before they launched to 'Toranto' the USN at Pearl?

 

[sloreck]

The USN meeting the Kido Butai at sea is a bad thing for the USN. Most folks agree that the USN would come out on the short end, and more ships would be permanently lost in deep water and more sailors killed than OTL PH. Even if the air groups are decimated, the carriers are fast enough so that when the US fleet shows up they, with appropriate escort, can run away leaving the heavies to slug it out.

If the US fleet does not sortie until very early am 12/7, the Japanese embassy can't warn the KB. The smart thing to do would be to take the fleet south of PH, the Japanese can't sped any effort searching for them...so when the first wave arrives over PH they have nothing to hit (at least torpedo planes), and of course ground AA & fighters are waiting for them. Not sure what will happen to the 2nd wave.

After the air is clear the fleet can come back to PH, top off, and go after the Japanese if they want to...they will have realized (hopefully) how many carriers were with the KB roughly, and expect the escort (heavies & others) to be quite large. Even with 30-60% of the air group out of action a fleet action of the US forces with maybe one carrier against the KB is not a smart move.

 

[Johnrankins]

I suspect that had the US determined Japanese intentions, either by codebreaking (the nonexistent messages!) or simply by recon finding the KB near Hawaii, they would have attacked it immediately.

War warnings had already been sent out and there was only one reason for the KB to be cruising towards strike range of Pearl. It might take a while for the necessary permissions to be given though.

No permission needed. The war warnings plus the fact that Japanese Fleet would have no reason being near Pearl Harbor except to attack it was all that was required. If the Japanese fleet is spotted heading to Pearl it is going to be attacked , no permission necessary.

 

[Carl Schwamberger]

The USN meeting the Kido Butai at sea is a bad thing for the USN.

That was not in the plans.

The smart thing to do would be to take the fleet south of PH

The intent was SE. Any Japanese raid was expected from the direction of Truk, to the South West. Positioning the fleet to the SE puts it on the flank of the hypothetical enemy & means they have to contend with carrier strikes from one direction and land based strikes from another.

Kimmels war plan WPP-46 can be found with a brief google search. It is a tough read, but worth the effort for the understanding of how the USN would act once it knew it was at war.

 

[Shaby]

The USN meeting the Kido Butai at sea is a bad thing for the USN. Most folks agree that the USN would come out on the short end, and more ships would be permanently lost in deep water and more sailors killed than OTL PH. Even if the air groups are decimated, the carriers are fast enough so that when the US fleet shows up they, with appropriate escort, can run away leaving the heavies to slug it out.

Well, that would not be a given conclusion, IMHO. First, the Japanese, as has been said are under orders to retreat if the surprise is lost to the point the US fleet sails to meet them. Their pre-war wargames assumed that without surprise they lose carriers. IIRC, 2 or 3.

Second, as has been pointed out, US fleet sails south, southeast. They expected the Japanese will come from that direction.

Third, if the BBs are on the move, it would negate the most lethal weapon the Japanese employed - modified artillery shells, ones which caused most damage on the USN ships. Also, torpedo bombers would have a lot harder job if their targets are manouvering on open sea, plus shooting on them from every AA gun they have. Dive bombers, the only that could reliably hit BBs in those conditions, would not be able to hurt them.

Fourth, the Japanese would be facing the ships in Material Condition Zebra. All watertight hatches and stuff would be closed, and the integrity of the ships at maximum.

So Japanese would not win automatically.