Smallest Event That Can Prevent Pearl Habour

Clearly several people did consider it. I quoted a few secondary sources in a previous post https://www.alternatehistory.com/discussion/showthread.php?p=2620226#post2620226 and I can add that the initial IJA plan was written by Lieutenant-Colonel Nishiura Susumu (from "The Origins of the Second World War in Asia and the Pacific" by Akira Iriye, page 102 which quotes Daihonei Rikugumbu, 2: 42,48).

The point is that OTL, the IJN was happy to lose the advantage of surprise in the PI by attacking Pearl. I am not suggesting ignoring the PI, just not attacking first. Move aircraft to Formosa and make plans to attack Clark, keep enough ships available to deal with the 3 cruisers of the Asiatic Fleet and prepare for an invasion if war comes. However, the US cannot send anything in less than weeks, so watch US politics and see if war is coming.

Note that you are quoting an Army plan here.. I'm sure the IJN would just have clapped in glee and gone along with it....!!:p

Army are well known for making wonderful plans without actually having any idea about the naval side of it...

Basically, the Japanese navy was as fixated on their concept of the decisive battle as the Allied air forces were on strategic bombing (and about as rationally...)
Even PH was intended to work towards this - it would weaken the USN to a point where they could be lured into battle at better odds (the original plan was to lure them west and use attrition to bring the odds more in Japanese favour, but as time went on this looked less likely to result in the USN losses needed).

And you dont get and win a decisive battle by sticking your navy out at the end of a long supply line with your major foes fleet and bases sitting alongside it...not unless you can COVER that supply line, which the Japanese couldnt.
 

Bearcat

Banned
Pretty much everything you said here was wrong.

QFT.

On topic:

Recently read that Kimmel kept his Catalinas at Kaneohe and Ford Island unused - no major scouting - because he expected to lure the Japanese into a major fleet battle in the mid-Pacific soon after the war started and wanted them all in good shape. That comes second hand from Ed Miller, who wrote the book on Warplan Orange.

Question though, is how Kimmel could do that? Jaopan had long planned to lure the USN into its mandate area, attrit it with land-based air and subs, and then win the fleet engagement. Sounds like each side wanted the fight on their terms. Would one side roll the dice, or would the battle not happen until about the historical date of Midway? A fleet engagement early favors the IJN, but the USN I still think will not fight on the IJN's home turf. A later engagement allows the Hypo breakthrough, and gives the IJN time to figure out that they need to precipitate it by taking something the US won't want to lose.
 

Markus

Banned
QFT.

On topic:

Recently read that Kimmel kept his Catalinas at Kaneohe and Ford Island unused - no major scouting - because he expected to lure the Japanese into a major fleet battle in the mid-Pacific soon after the war started and wanted them all in good shape. That comes second hand from Ed Miller, who wrote the book on Warplan Orange.

I read different. He could have to keept the entire 180° sector west of Oahu under surveillance but in this case the PBYs would have worn out faster than replacements were comming forward, so only the most likely route of attack, the sector south-west of Oahu was patrolled.An understandable measure of economy, less understandable was Kimmel not telling the Army about the lack of air recon in the north.
 

Bearcat

Banned
I read different. He could have to keept the entire 180° sector west of Oahu under surveillance but in this case the PBYs would have worn out faster than replacements were comming forward, so only the most likely route of attack, the sector south-west of Oahu was patrolled.An understandable measure of economy, less understandable was Kimmel not telling the Army about the lack of air recon in the north.

Here's a partial copy of the email I received:

> From: Ed Miller <edmiller@verizon. net>
> Date: Wednesday, November 25, 2009 6:28:15 AM
> Subject: Husband Kimmel
>
> <snip>
> 3. My book War Plan Orange, chapter 25, describes
> completely Kimmel's war plan of July 1941, approved by the
> CNO and SecNav in September 1941. He planned to lure Yamamoto
> into a mid-Pacific battle in the first three weeks of a war.
> His seven squadrons of long range flying boats were not
> patrolling Oahu despite war warnings because they were
> grounded in top shape for the battle. This account is not in
> other books.

I had never heard this anywhere else either.
 
I suppose it could be argued PH was actually too successful!

The Japanese ideal was to lure a weakened US Pacific fleet forward, attrit it, then destroy it. The obvious bait was the PI.
But by pretty much wiping out everything except the carriers, there was no way the USN was going to do any relief of the PI because they didnt have anything to relieve it with!
 

Bearcat

Banned
I suppose it could be argued PH was actually too successful!

The Japanese ideal was to lure a weakened US Pacific fleet forward, attrit it, then destroy it. The obvious bait was the PI.
But by pretty much wiping out everything except the carriers, there was no way the USN was going to do any relief of the PI because they didnt have anything to relieve it with!

The thing to notice is, Kimmel had no intention of being lured to the PI even IF his fleet was intact - he wanted to fight the IJN in the mid-pacific, where the odds would be more favorable.

Which makes me wonder if a battle would possibly just not happen immediately, as each side tried to figure out how to bring it about on their respective terms.
 
Both on & off topic:

I have been going through archives rather extensively for research on my MA thesis (USMC, Navy, at Quantico, Navy Yard, Nat'l Archives etc). One thing that became clear was even as early as the early 1920's war planners realized that the PI would have to hold out for a LONG time on their own & that any relief from the Navy would not happen easily. Basically an expectation that the odds were good the PI would fall.
 
The thing to notice is, Kimmel had no intention of being lured to the PI even IF his fleet was intact - he wanted to fight the IJN in the mid-pacific, where the odds would be more favorable.

Which makes me wonder if a battle would possibly just not happen immediately, as each side tried to figure out how to bring it about on their respective terms.

Thats very true, but even with a less successful attack surely Kimmell would have been replaced as in OTL? (I suspect Nimitz would have been even less likely to go west...??)

I was thinking more of the political pressure to relieve the PI rather than the USN's attitude - after all, whats the point of building the fleet if it just sits there and lets our brave boys die in the Phillipines....:D
 
To answer the question asked by the parent:

A gnat in the eye of a British Swordfish pilot during the Battle of Taranto that makes his aim less steady, causing his torpedo to miss, causing less damage to the Italian fleet, causing the Japanese to take less notice of the attack, butterflying away the Pearl Harbor attack.
 
Hi this is my first topic on AH.com.

What would be the smallest event, in example, involving only few persons or things, that could make Japan scrap the Pearl Habour plan.
Let's say POD is between 18 months before to December 6th, 1941.

What if FDR does not approve of the oil embargo against Japan or what if FDR does not move the Pacific fleet to Pearl Harbor.
 
To answer the question asked by the parent:

A gnat in the eye of a British Swordfish pilot during the Battle of Taranto that makes his aim less steady, causing his torpedo to miss, causing less damage to the Italian fleet, causing the Japanese to take less notice of the attack, butterflying away the Pearl Harbor attack.

That isn't going to affect anything. The importance of Taranto was that it proved you could use torpedoes in such a shallow harbour. Not that the Japanese couldnt work this out for themselves, but having it proved put the proponents of such a strike in a much stronger position.
 
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