IJN Detected Before Pearl Harbor

[MUC]

Originally Posted by Kissinger

Wasn't the Japanese Battlewagons with them?

The Kido Butai sailed only with Hiei and Kirishima to execute the Pearl Harbor attack. The other Japanese battleships were busy supporting other operations in South East Asia.

[Basileus444]

If it comes down to a gun duel between the Japanese and American battle lines, the Kido Butai will be torn to shreds. The Pacific Fleet has something like a 7 to 2 advantage in battleships, and an even larger advantage in gun barrels, since Hiei and Kirishima only mount eight 14in guns, while the Nevadas have 10, and the rest have either 12 14in guns, or 16in guns. The only hope of the Kido Butai winning, or even surviving, a surface gun action would be the Long Lances. Whether or not that would work depends on the state of the Pacific Fleet's lighter forces, which I don't know much about.

However I'm not so sure as some posters seem to be that if the USN sallies, the battleships would be sent to the bottom by carrier aircraft. This is 1941, not 1944, and attacking a maneuvering, fully armed, crewed, prepared war fleet likely covered by land-based aircraft is a whole different thing from shooting a bunch of surprised, stationary, skeleton crewed ships.

[BlondieBC]

Take if for what it is worth, but the History Channel did a show on this where they gave retired admirals the actual orders, and gamed it. Seems like the US Navy had 2 hours warning. The immediately sailed the BB to a rally point south of Pearl and had the carriers race to the Fleet. The first strike still devastated pearls defenses. Later in the day, there were airstrikes back and forth. USA lost 4 BB. Japan lost 3 times as many planes as OTL, with their crews. USA had higher death toll from losing ships at sea, but also had 4 effective BB on day one of war. Pearl did not get the second strike so it was in better shape. All the carriers lived.

[The Kiat]

Originally Posted by eltf177

I was under the impression Kido Butai _was_ to retreat if discovered prior to launching the first strike, although trying to explain away a large task force that close to Pearl wouldn't be too easy...

Just being detected that close might lead to war. After all, what other reason would they have for having such a strike force in the middle of the Pacific? "It's bound for China; we're just taking the scenic route."

[Shadow Master]

Originally Posted by Delta Force

What if despite trying to evade detection, the IJN fleet was detected by the US military a few days or even hours prior to the surprise attack without the Japanese knowing (suppose a passing merchant ship or aircraft sees them)?

I'm going to have to go with submarine dection, as otherwise the IJN realizes they have been seen.

So lets go with a dection around 7PM dec 6th. Message is recieved and believed. Crews are recalled (It's a saturday night afterall) so lets say the fleet is not capable of sailing for at least 4 hours. Now lets say that with such short notice, a peace time fleet that is missing it's carriers is not going to head into a battle. Rather, the US fleet sails SSW at a fleet speed of 20 kts.

The Japanese first strike rolls in that morning to find all the BB's have sailed (with the possible exception of USS Pensylvania), and all of the AA defenses manned and ready. In addition, every fighter we have in Hawii is in the air, along with every other plane that is capable of shooting down a dive or torpedo bomber that is still carrying it's load.

Not sure what kind of damage they will succeed in inflicting on the harbour facilities, but they are going to take quite a bit more losses than OTL. If the USS Pensylvania is unable to leave drydock on such short notice, then we can say that she will become the sole capitalship target of the first strike and almost surely will be smashed hard.

After their rousing reception (not to mention the lack of capitolship targets), the KB is not likely to mount a second wave IMHO, but instead run for home.

So:
USN 1 BB bombed to scrap while in drydock, and some damage to the base facilities.
USAAF lots of aircraft losses, and some damage to their base facilities (but nowhere near OTL).

IJN many more aircraft lost, and not a whole lot to show for it.

[sharlin]

Originally Posted by Basileus444

.

This is 1941, not 1944, and attacking a maneuvering, fully armed, crewed, prepared war fleet likely covered by land-based aircraft is a whole different thing from shooting a bunch of surprised, stationary, skeleton crewed ships.

Yes, this is 1941 where you have probably the best trained carrier pilots of the whole war launching an attack on ships at sea most of which have deficient AA armaments, the 20mm is barely in service, the 40mm mount is a thing of smoke and vapor, the US BBs although tough are not the most modern ships in the world and their post pearl updates have not been applied so for the most part they are still a WW1 design, all be it a very good one. Also the attack would be on a scale never seen before in naval warfare, hundreds of aircraft against some slow battleships and their escorts.

The US planes and pilots have not encountered the Zero and the IJN's aircraft could safely launch and attack from well outside of the range of US land based cover.

[Delta Force]

What kind of impact would an early warning have on the attacks on the Philippines and British Empire (assuming it makes it through the UK chain of command fast enough)? Would the Philiphines command drag its feet on doing something and still end up surprised again like OTL (especially seeing the lack of urgency they displayed in responding to a confirmed attack, while this would just be a confirmed sighting)?

[Simon]

So basically we need to have the Japanese attack detected about an hour or less from the attack time so that the battleships don't have time to bring their boilers online from a cold start and sail out to get sunk, but enough to get the anti-air defences ready and alert and all the aeroplanes they can find pilots for up in the air waiting. The obvious answer is the old chestnut of news the of radar detection of the incoming first strike being passed on to somebody that puts two and two together, alternatively IIRC that the radar defences on Hawaii were meant to be fully operational by then but it had fallen behind for several reasons.

[MUC]

Most of you seem to think the USN would simply run away from the Japanese by sailing to the South of te islands. Is that, what the plan was? See the IJN come and run away from it? Or would the USN sail to meet the Japanese?

[33k7]

Originally Posted by MUC

Most of you seem to think the USN would simply run away from the Japanese by sailing to the South of te islands. Is that, what the plan was? See the IJN come and run away from it? Or would the USN sail to meet the Japanese?

this ALL depends on the time fram short-term knowledge of the attack before hand you can't get the ships of the harbor in that time probably every fighter craft would be up in the air and anywhere you could set up a antiaircraft gun or 50 caliber or pistol would be out it would be in the defense of US battle

US knows about the attacks in a few days before the attack that could go either way still FDR would not start the war and expect to win another term the Japanese have to attack first.

[eltf177]

Originally Posted by Simon

So basically we need to have the Japanese attack detected about an hour or less from the attack time so that the battleships don't have time to bring their boilers online from a cold start and sail out to get sunk, but enough to get the anti-air defences ready and alert and all the aeroplanes they can find pilots for up in the air waiting. The obvious answer is the old chestnut of news the of radar detection of the incoming first strike being passed on to somebody that puts two and two together, alternatively IIRC that the radar defences on Hawaii were meant to be fully operational by then but it had fallen behind for several reasons.

The big problem is that most of the fighters have empty fuel tanks and no ammo, an hour simply isn't enough to get everything into the air. Also don't forget it's Sunday, a lot of personnel aren't available and it takes time to get everybody out of the barracks and moving...

[GarethC]

Originally Posted by Delta Force

What kind of impact would an early warning have on the attacks on the Philippines and British Empire (assuming it makes it through the UK chain of command fast enough)? Would the Philiphines command drag its feet on doing something and still end up surprised again like OTL (especially seeing the lack of urgency they displayed in responding to a confirmed attack, while this would just be a confirmed sighting)?

The Philippines weren't surprised. MacArthur was refused to see Brererton until the B-17s which Brereton had got armed and airborne had burned too much fuel to carry out their planned attacks, so they landed to refuel.

It's likely that Brererton will get the go-ahead with his counterstrikes against IJA airfields in Formosa on the morning of the 7th (and not before then).

The B-17s will be attacking in poor visibility against targets they have not seen, let alone struck before; they will not have a great effect on the day. However, much more important is the likelihood that the FEAF defending fighters won't all have just landed to refuel when their airfields are attacked, so IJA casualties will be higher and the Philippines air war will not be over on the first day.

Force Z, Malaya, and Singapore are still as doomed though. Their losses are not down to strategic surprise so much as their commanders' decisions after the war began.

[Cook]

Originally Posted by Derek Jackson

Does Japan cancel the operation?

No. The Japanese had anticipated the possibility of being discovered and having to fight their way to the point where they could launch an attack on the Pacific Fleet.

Originally Posted by ModernKiwi

It wasn't until 1944 that carrier aircraft sunk capital ships at sea...

Originally Posted by ModernKiwi

Maybe. As I said, no-one sank a battleship at sea with carrier aircraft before 1944, despite trying. And Japanese battleships were WW1 rebuilds like the US ones and so just as vulnerable to being sunk.

The Royal Navy’s Fleet Air Arm, not an organisation that covered itself in glory during most of World War Two, torpedoed and crippled the Bismarck in May 1941 with carrier borne flying Swordfish biplanes and the Japanese torpedo bombers that sank the Prince of Wales and Repulse in December 1941 did so with the same torpedoes used by the carrier borne planes. Since the Japanese battleships were a screening force, well back from the Kido Butai, they’d have been very unlikely to be engaged.

American battleships were not attacked and sunk at sea in the first year of the Pacific War, not because the Japanese didn’t have the capability, but because following Pearl Harbour, those that were sea worthy were pulled back to the safety of the California Coast. The Japanese carrier aircraft successfully attacked and sank a string of ships at sea during the Indean Ocean raid and Coral Sea, including Cruisers and Carriers.

[gigalocus]

Originally Posted by Cook

The Royal Navy’s Fleet Air Arm, not an organisation that covered itself in glory during most of World War Two, torpedoed and crippled the Bismarck in May 1941 with carrier borne flying Swordfish biplanes

I was going to say this, but after reading his post, he has something like a get out clause that Battleships were only damaged enough that could be finished off.

But you are right, a cruiser is not going to sink the Bismarck until FAA had done enough damage to essentially destroy it. It could have been sunk by planes, but having cruisers about made it easier. I'm sure the USN would have done that to the IJN if it was possible. But Japanese fleets tend to have more screens then the Bismarck did, so it was not viable.

[BlondieBC]

Originally Posted by MUC

Most of you seem to think the USN would simply run away from the Japanese by sailing to the South of te islands. Is that, what the plan was? See the IJN come and run away from it? Or would the USN sail to meet the Japanese?

yes, the orders were to assemble the fleet, then attack. Even if you buy into the big gun wins battle idea, you still want your carrier scouts to find the enemy so you don't engage when the odds don't favor you.

[Bob in Pittsburgh]

Would MacArthur rather than Kimmel and Short become the sacrificial lambs for unpreparedness? Kimmel would have fought and, win or lose, would have been a hero.

[ModernKiwi]

Originally Posted by Cook

...
The Royal Navy’s Fleet Air Arm, not an organisation that covered itself in glory during most of World War Two, torpedoed and crippled the Bismarck in May 1941 with carrier borne flying Swordfish biplanes and the Japanese torpedo bombers that sank the Prince of Wales and Repulse in December 1941 did so with the same torpedoes used by the carrier borne planes. Since the Japanese battleships were a screening force, well back from the Kido Butai, they’d have been very unlikely to be engaged.

The Japanese aircraft that sank the PoW and Repulse were land based large bombers, not carrier capable aircraft.

And yes I did mention that they could damage and make other methods of sinking more probable.

[Paul V McNutt]

I think the ships would have been evacuated and the base is on full sorest. The Japanese find an empty harbor and the sky full of US planes. m Maybe the surrender is signed on the USS Arizona.

[Unconsensual]

Originally Posted by Rich Rostrom

But they'd still fare a lot better than on the ground, shooting down about 100 Japanese planes and losing about the same themselves. More Japanese planes would be shot down by the heavy AA fire. Nonetheless, they would press home their attack on Battleship Row, and sink one or two ships (damaging five or six).

Well AA is practically blind back then, it'll shoot whatever moves, especially with green troops. Though given the odds it'll probably hit Japanese fliers more often.

[sloreck]

Don't forget the radar set that had the ignored warning. With some warning even only an hour, the attack will be detected and some effort to vector fighters in can be made...not real GCI but still given general location & altitude it gives the fighters a decent chance to hit some bombers/torpedo planes on first pass before furball occurs.

With 2-3 hours warning most of the Army & Navy AA defenses will be manned and ready. Those ships that can't get out of Pearl will at least have full power going, batteries manned, and watertight doors shut (condition zebra). If an air attack is known to be coming, I hope that the a/c would be dispersed around the field rather than totally lined up....don't think there were many revetments they could be put in though. Those ships that could not sortie (and they would move away south until after attack to gather together & get scout info) before first strike have a chance now to get out before the second strike.

Overall the Japanese at a minimum lose way more a/c and importantly pilots/aircrew. Damage to the fleet and Pearl is less than OTL, certainly no third strike is contemplated & second may be seriously disrupted/aborted. I doubt that the US fleet and the KB will go head to head. After taking some serious hurt in the attacks the priority for the KB will be to get out of Dodge. Even if the US has a good fix on them when the last strike a/c are taken aboard the KB has too much of a lead to be caught..maybe a US sub could take some shots or B-17's from Hawaii take a shot but neither is likely to be effective.

IMHO the ONLY way things go better in the PI is if Mac gets a direct order to commence hostilities immediately...