WI: Combined Fleet spotted days before Pearl Harbor attack?

[imsoth]

By pure chance on the early morning of December, 4th a destroyer or another radio-equipped US vessel nearly collides with a japanese cruiser and immediately starts radio transmission. Astonished japanese admiral reads the message. It starts with some encrypted junk, then a repeated plain text "40 -163 BB CA VISUAL CONTACT".

What happens next?

 

[Geon]

At this point very little happens. The USN notes a destroyer has nearly run into a Japanese cruiser and possibly a battleship. Given the heavy seas and bad weather visibility I suspect was a problem. Their in international waters. At this point there's no real alarm sounded I think.

 

[kclcmdr]

USN Intel will wonder why would the IJN send a BB n a CA approx heading East in the North Pacific about three days travel time at 20 Knots toward the Hawaiian Is. And four to five days from reaching the US pacific states..

Pearl Naval HQ will probably order their DD/CA TF to shadow the IJN TFZ and ascertain their destination every hour or half hour...

 

[Carl Schwamberger]

President Roosevelt had already approved the War Warning orders in late November. Admiral Kimmel had received and passed on the Consider Hostile order. This directed US military to attack any Japanese ship or aircraft approach US territory.

In this case Kimmel redirects air reconisance to the NW of Hawaii. The two carriers may be redirected to reconnoiter North, and some cruisers sent back out.

 

[Carl Schwamberger]

USN Intel will wonder why would the IJN send a BB n a CA approx heading East in the North Pacific about three days travel time at 20 Knots .....

No wondering. The War Warning messages sent 25/26 November. Made it clear war with Japan was expected within days or a few weeks. Kimmel had participated in the fleet exercises testing attacks on Oahu. It would be fairly obvious the Japanese we're headed to attack positions.

 

[docfl]

But would the Japanese abandon the attack if spotted?

 

[Dathi THorfinnsson]

I thought the Japanese had orders to turn around if discovered like that.

 

[docfl]

Thats what I thought. What effect of an abort make?

 

[marathag]

At this point very little happens. The USN notes a destroyer has nearly run into a Japanese cruiser and possibly a battleship. Given the heavy seas and bad weather visibility I suspect was a problem. Their in international waters. At this point there's no real alarm sounded I think.

U.S.S. ENTERPRISE

At Sea
November 28, 1941


BATTLE ORDER NUMBER ONE

1. The ENTERPRISE is now operating under war conditions.

2. At any time, day or night, we must be ready for instant action.

3. Hostile submarines may be encountered.

4. The importance of every officer and man being specially alert and vigilant while on watch at his battle station must be fully realized by all hands.

5. The failure of one man to carry out his assigned task promptly, particularly the lookouts, those manning the batteries, and all those on watch on the deck, might result in great loss of life and even loss of the ship.

6. The Captain is confident all hands will prove equal to any emergency that may develop.

7. It is part of the tradition of our Navy that, when put to the test, all hands keep cool, keep their heads, and FIGHT.

8. Steady nerves and stout hearts are needed now.


G. D. MURRAY,
Captain, U.S. Navy
Commanding

Approved: November 28, 1941.
W. F. HALSEY,
Vice Admiral, U.S. Navy,
Commander Aircraft, Battle Force

Those International Waters are very far away from the closest Japanese territory.

War conditions means any unidentified vessel must be identified

 

[Geon]

U.S.S. ENTERPRISE

At Sea
November 28, 1941


BATTLE ORDER NUMBER ONE

1. The ENTERPRISE is now operating under war conditions.

2. At any time, day or night, we must be ready for instant action.

3. Hostile submarines may be encountered.

4. The importance of every officer and man being specially alert and vigilant while on watch at his battle station must be fully realized by all hands.

5. The failure of one man to carry out his assigned task promptly, particularly the lookouts, those manning the batteries, and all those on watch on the deck, might result in great loss of life and even loss of the ship.

6. The Captain is confident all hands will prove equal to any emergency that may develop.

7. It is part of the tradition of our Navy that, when put to the test, all hands keep cool, keep their heads, and FIGHT.

8. Steady nerves and stout hearts are needed now.


G. D. MURRAY,
Captain, U.S. Navy
Commanding

Approved: November 28, 1941.
W. F. HALSEY,
Vice Admiral, U.S. Navy,
Commander Aircraft, Battle Force

Those International Waters are very far away from the closest Japanese territory.

War conditions means any unidentified vessel must be identified

Narathag I am uncertain what war conditions means. Does this allow them to initiate hostile action if necessary?

 

[marathag]

Narathag I am uncertain what war conditions means. Does this allow them to initiate hostile action if necessary?

yes, as USS Ward did on Dec. 7th

 

[SsgtC]

Narathag I am uncertain what war conditions means. Does this allow them to initiate hostile action if necessary?

The War Warning message FDR sent out in late November essentially opened the hunting season on the IJN and KM. All US Naval vessels were authorized to shoot first and ask questions later at that point.

 

[wcv215]

At this point there's no real alarm sounded I think.

Nope. The thing you have to remember is where they actually are in the world. There's nothing nearby which the Japanese could be heading to OTHER than American territory. And since the fleet is sailing with no known destination, nor any form of warning there is only one conclusion to draw: a sneak attack. This is completely in character for the Japanese who pulled the same move against Russia in their war, as well as aggressive moves against China. Basically, there are two possibilities. Either the Japanese decided on a lark to go and cruise the Pacific, which is absurd, or they are preparing to attack the US fleet. Only one of these is realistic, meaning that any further advances will be met by the Americans. And within hours everything that can go scout the Kido Butai is going to be moving that way. Pearl Harbor will be going on a war footing literally as soon as the message is received. Any chance of surprise is gone for good.

Which does present a rather horrible dilemna for Japan. Their chance to cripple the American battle line is gone, and continuing will lead to significant losses. So should they continue? It would be a snap decision, though the IJN themselves leaned toward no as I recall. Without the possibility of an attack without a declaration of war they likely won't risk it.

 

[eltf177]

I thought the Japanese had orders to turn around if discovered like that.

Thats what I thought. What effect of an abort make?

It's my understanding that Nagumo had orders to turn around if spotted before ready to launch. Assuming he follows orders Japan's ambassadors start coming up with excuses as to why Kido Buitai was there, which aren't bought.

Agreed, there's no good reason for them to be there and the US gets VERY suspicious...

 

[Carl Schwamberger]

I thought the Japanese had orders to turn around if discovered like that.

I can't recall the exact date, but discovery early on allowed Nagumo to abort. At a later date, the 5th perhaps, Nagumo was directed to attack the US fleet where he could find it. The reason was by the 5th (6th Maylasian time) the invasion fleet for Maylasia was underway. The logic was the fleet needed to strike even if complete suprise was lacking.

Yamamoto did have the option to override Nagumos decision, but I'm unsure how likely that was.

 

[DDM]

Nagumo's orders were if detected more than 1 day in advance to turn back. I have not seen anywhere where the rest of the offensive is also to be postponed. If Nagumo is turned back after being discovered then that takes care of Pearl Harbor but I wonder what affect this would have on the rest of the offensive. Would allied forces perform better or pretty much the same.

 

[marathag]

Would allied forces perform better or pretty much the same.

Considering how Dugout Doug dithered after an actual attack, hard to see the PI going much different from OTL: maybe worse, as he would have even more times to rush even more troops and supplies to undefendable beaches

 

[Tonrich]

So lets say the PH attack force turns around. What about the operations against Wake, Gaum and the Kra peninsula. Those operations were on a time table so what would happen there?

This is an interesting question.

 

[Carl Schwamberger]

So lets say the PH attack force turns around. What about the operations against Wake, Gaum and the Kra peninsula. Those operations were on a time table so what would happen there?

This is an interesting question.

The Kra landing operation was at sea on the 5th - US time & spotted by Commonwealth reconissance on the 6th. The Brits knew they were coming.

 

[eltf177]

I'd say everything else goes as planned. But with Pearl not attacked maybe an earlier offensive? Would the battleships actually be sent into combat? Be interesting to have one or more of the old BB's early in the Guadalcanal fight...