December 28th, 1941: The Day of Infamy

[Tom_B]

http://aa.usno.navy.mil/cgi-bin/aa_pap.pl

This is an interesting time-line. Good luck with it.

Some constraints on delaying Pearl:

1) The Pensacola convoy would reach the Philippines. That's a major increase in the firepower (especially artillery) available to the US forces there. In theory it is a major increment in air power too, but planes were shipped without key components. I don't know if those components would have made it before crunch time in this scenario, but I suspect they would be a top priority--maybe even flown in on B17s if there was enough fuel capacity to get there with a small load.

2) December 7th was a full moon, which allowed the Japanese to launch pre-dawn more easily and without lighting up their ships. Not sure what the phase of the moon was Dec 28th.

3) In much of Southeast Asia, the monsoons made military movements much more difficult and cut down on the effectiveness of aircraft. That was especially true in Burma, where large-scale warfare essentially shut down for several months during the monsoon season. Historically, the Japanese timed their attack partly so that they could establish their perimeter before the monsoon season started. Delaying the attack three weeks would cut into their margins in terms of reaching all of their objectives.

One advantage for the Japanese I can think of off the top of my head: They'll have time to make more of the converted naval shell bombs that they used at Pearl. Historically they weren't able to make as many as they wanted to.

U.S. Naval Observatory
Astronomical Applications Department


Sun and Moon Data for One Day

The following information is provided for Pearl Habor (longitude W157.2, latitude N21.4):

Sunday
28 December 1941 Universal Time - 10h

SUN
Begin civil twilight 06:41
Sunrise 07:05
Sun transit 12:30
Sunset 17:56
End civil twilight 18:20

MOON
Moonrise 14:03 on preceding day
Moonset 02:57
Moonrise 14:41
Moon transit 21:12
Moonset 03:46 on following day


Phase of the Moon on 28 December: waxing gibbous with 81% of the Moon's visible disk illuminated.

First quarter Moon on 25 December 1941 at 00:44 (Universal Time - 10h).

 

[DaleCoz]

More on the Philippines: The US was making reinforcement of the Philippines their top priority in the last half of 1941. The big bottleneck was shipping. As of November 1941, over a million tons of supplies meant for the Philippines was piled up in US ports or depots. A lot of that stuff was supposed to be sent to the Philippines in December 1941, with the last of the convoys set to sail on December 20. As of Dec 5th, 100,000 tons of supplies were in route to the Philippines, with twice that amount ready to go as soon as shipping arrived.

How much of that stuff would have reached the Philippines by Dec 28th, I don't know, and how much of it would have actually been operational I also don't know. Getting stuff to the Philippines obviously didn't make it automatically ready to go. For example, the army had seven radar sets in the Philippines on Dec 7th, but only two were installed and operational. The US was frantically trying to get the 557th Air Warning Battalion to the Philippines to help out, but they only arrived in San Francisco on Dec 6th.

Historically, a lot of the stuff that got shipped to the Philippines hadn't been unloaded yet on December 7th and a lot of the planes there weren't fully operational--for a lot of "for want of a nail" type reasons.

Bottom line here: The Philippines would be a considerably tougher nut to crack in this scenario, but then again the US would lose considerably more men and supplies if/when defenses ultimately did fold.

 

[DaleCoz]

Other considerations: Wake would have probably gotten the radar unit that was apparently sitting in port in Hawaii waiting to get shipped, and they would have probably had revetments completed for their fighters. Not sure how that would have influenced the fighting there. They lost a substantial portion of their small air contingent in a surprise attack historically, but it's hard to say if that would have been avoided in this scenario. The Philippines had radar and still got a good hunk of their air power caught on the ground historically.

Speaking of which, when I look at the historical circumstances that led to the bulk of US air power in the Philippines sitting on the ground fully fueled and ready to take off, but not in the air when the Japanese main airstrike came in, I have to think that the Japanese essentially rolled double sixes. It is not likely that a similar attack three weeks later would have had the same set of coincidences in its favor. In all likelihood the Japanese would still win the air battle, but probably with much higher losses, and the victory would probably take more time. Japanese pilots killed there obviously wouldn't be around for subsequent parts of the campaign, and tying up those planes would have some impact..

 

[Bearcat]

1) The Pensacola convoy would reach the Philippines. That's a major increase in the firepower (especially artillery) available to the US forces there. In theory it is a major increment in air power too, but planes were shipped without key components. I don't know if those components would have made it before crunch time in this scenario, but I suspect they would be a top priority--maybe even flown in on B17s if there was enough fuel capacity to get there with a small load.

Also you could fly them in by PBY or China Clipper. So long as its nothing heavy.

2) December 7th was a full moon, which allowed the Japanese to launch pre-dawn more easily and without lighting up their ships. Not sure what the phase of the moon was Dec 28th.

First quarter. Moon sets a little after midnight. No pre-dawn light. So maybe the first wave rolls in a little later in the morning.

This also makes the whole Khota Bharu landings far dicier. They need to wait for light or try to land in pitch dark. Either more landing boats get shot up, or more drift out of the LZ, get swamped, etc. Either way, its quite possible it could tip the very slim balance there.

3) In much of Southeast Asia, the monsoons made military movements much more difficult and cut down on the effectiveness of aircraft. That was especially true in Burma, where large-scale warfare essentially shut down for several months during the monsoon season. Historically, the Japanese timed their attack partly so that they could establish their perimeter before the monsoon season started. Delaying the attack three weeks would cut into their margins in terms of reaching all of their objectives.

Yamashita's margin of error is razor thin in Malaya. Even if the 8th is gone, if he doesn't move as quickly in the early going, it won't help - he'll run out of ammo and supplies short of Singapore.

 

[DaleCoz]

Anybody know what the weather was like over Pearl Harbor on the morning of December 28th? Early World War II airforces were generally pretty much fair weather forces.

 

[Bearcat]

Anybody know what the weather was like over Pearl Harbor on the morning of December 28th? Early World War II airforces were generally pretty much fair weather forces.

Only way you might find that info is to have a member in Hawaii look it up in old Honolulu newspapers on microfiche at the library. That kind of thing is just not on the web.

 

[Dave in St. Louis]

Only way you might find that info is to have a member in Hawaii look it up in old Honolulu newspapers on microfiche at the library. That kind of thing is just not on the web.

Apparently, it is available on a web site - weather-warehouse.com. But they want to be paid to allow you to access the information. I'll nose around further and see if I can find a site that will cough up the information for free.

 

[Dave in St. Louis]

U.S. Naval Observatory
Astronomical Applications Department


Sun and Moon Data for One Day

The following information is provided for Pearl Habor (longitude W157.2, latitude N21.4):

Sunday
28 December 1941 Universal Time - 10h

SUN
Begin civil twilight 06:41
Sunrise 07:05
Sun transit 12:30
Sunset 17:56
End civil twilight 18:20

MOON
Moonrise 14:03 on preceding day
Moonset 02:57
Moonrise 14:41
Moon transit 21:12
Moonset 03:46 on following day


Phase of the Moon on 28 December: waxing gibbous with 81% of the Moon's visible disk illuminated.

First quarter Moon on 25 December 1941 at 00:44 (Universal Time - 10h).

Kido Butai turned into the wind at 0550 on December 7, 1941. Prange says that "The weather delayed takeoff twenty minutes." (pg 490), citing interviews with Genda, Fuchida & Amagi and page 121 of Shinjuwan Sakusen Kaikoroku. This means that Itaya (commanding the Zeros of Akagi and the first pilot to takeoff) probably takes off between 0610 and 0620. Anyone have a better number?

Without the full moon (or even a waning gibbous moon), the earliest I can see a launch on December 28 taking place is 0645. This pushes the commencement of the attack back to after 0800. If any of you have been in the service, you'll know that things do pick up a bit after morning colors (0800) as "night/morning" routine pushes pushes into "work day/business day" routine. It won't be as significant as if it were a Monday, but I think Pearl puts up at least a slightly better fight.

Agree? Disagree?

 

[DuQuense]

disagree - This is the Sunday between Xmas and New Years, Lots of Men will have taken leave for the week, and others will be on Generous Liberty.
Morning Mess will be over, with lot of the remaining men headed for Church.

 

[DaleCoz]

Kido Butai turned into the wind at 0550 on December 7, 1941. Prange says that "The weather delayed takeoff twenty minutes." (pg 490), citing interviews with Genda, Fuchida & Amagi and page 121 of Shinjuwan Sakusen Kaikoroku. This means that Itaya (commanding the Zeros of Akagi and the first pilot to takeoff) probably takes off between 0610 and 0620. Anyone have a better number?

Without the full moon (or even a waning gibbous moon), the earliest I can see a launch on December 28 taking place is 0645. This pushes the commencement of the attack back to after 0800. If any of you have been in the service, you'll know that things do pick up a bit after morning colors (0800) as "night/morning" routine pushes pushes into "work day/business day" routine. It won't be as significant as if it were a Monday, but I think Pearl puts up at least a slightly better fight.

Agree? Disagree?

I tentatively agree, but I think it depends to some extent on the way the political situation plays out. If the Japanese accompany their military delay with trying to draw out negotiations, so that the negotiation breakdown happens about the same time distance from the attack on Pearl as it did historically, then US forces would be getting their "War Warning" not long before Christmas. The US still had peacetime bad habits, but I suspect that a war warning would have some impact on the usual Christmas to New Year's activities.

 

[Grimm Reaper]

There is also one other factor to consider.

This delay means that the Soviet counter-offensive is well underway and, far from expecting a Soviet collapse, Japan is now wondering just how bad the situation has suddenly become for Germany.

 

[DaleCoz]

Interesting little data point: John Costello's The Pacific War 1941-1945 talks about how on December 6th, "Mrs. Dorothy Edgars, a new Japanese linguist on the OP 20 G team had begun the task of translating a second-priority message cabled in low-grade code by the Japanese consul general in Honolulu. The contents indicated an extensive interest in shipping movements at Pearl Harbor which so roused Mrs. Edgar's curiousity that she brought the intercepts to the notice of her senior officer. Overtaxed(...) they told her, "It can wait until Monday.""

That little tidbit in and of itself probably wouldn't have alerted Pearl when a bunch of other things didn't, but it does illustrate the reality that another three weeks of delay would give US intelligence another three weeks to piece clues together and figure out what the Japanese were up to.

 

[DaleCoz]

It's interesting that the US fighters on the Philippines were so short of 50 caliber ammunition that they were not allowed to test the guns on their P40s. They had about two loads on average per plane. The Penscola convoy would have brought another 500,000 rounds of 50 cal, and would have reached the Philippines quite a bit before Dec 28th.

 

[DaleCoz]

Here is an ironic possibility: The US might have delayed the delivery of planes to Wake and Midway under this scenario. The US wanted the fighters on the islands partly to protect the flights of B17s to the Philippines, but they wanted to wait until the last minute to deliver the planes for a variety of reasons, among which were that at least Wake wasn't really ready for them. So, you might have the carriers taking on the same missions they were on at Pearl about three weeks later. That would still leave one carrier in Pearl I guess. I would have to look into what went into the timing of the deliveries to know if they would be delayed in that way.

 

[Rickshaw]

Pedant.

Why? 'cause I read what you type?

This was point I was making:

Then you should have made it.

 

[Gridley]

OK, some comments. If you look at post #41, you'll see that search radar did indeed reach Wake in the extra three weeks. This prevents 2/3 of the fighters there from being destroyed on the ground, which in turn means more kills by VMF 211... until Hiryu and Soryu show up on the backswing from Pearl and wipe them out. Wake holds an extra couple of days.

Quite a bit of additional supplies and equipment have reached the Philippines. This won't change the final outcome of the campaign, but it will play out rather differently.

On the political side, the Japanese did indeed spin things out longer than OTL, and TTL's equivalent of the 14-part message was sent on the 27th/28th. The longer period of tension and warnings has had mixed results, just as OTL; some units are tired of hearing about wolves, others have take the time to work themselves into a higher readiness state.

I haven't addressed whether Germany declares war on the US for the very simple reason that I'm not sure if/when they will, and as I'm writing in a non-sequential set of updates at the beginning I can get away with that. War between them eventually is inevitable at this point, but the Pacific War will remain the focus.

On weather: weather played a major role is many if not most (arguably all) campaigns in the Pacific Theater. The weather three weeks later will be different, but in most cases I don't have good weather data for that period. Please bear in mind that the Quantum Weather Butterflies came out of their cocoons back in early November. By the Pearl Harbor raid they've been flapping their wings for almost two months; they certainly haven't changed long-term weather patterns, but they WILL have changed some of the details from OTL.

 

[Dave in St. Louis]

Here is an ironic possibility: The US might have delayed the delivery of planes to Wake and Midway under this scenario. The US wanted the fighters on the islands partly to protect the flights of B17s to the Philippines, but they wanted to wait until the last minute to deliver the planes for a variety of reasons, among which were that at least Wake wasn't really ready for them. So, you might have the carriers taking on the same missions they were on at Pearl about three weeks later. That would still leave one carrier in Pearl I guess. I would have to look into what went into the timing of the deliveries to know if they would be delayed in that way.

What route were the B-17s going to take to the PI? Does anyone know?

 

[DaleCoz]

Also on Pensacola convoy: apparently 3 million rounds of .30 calibre ammunition, which would have been a major help if it got to the troops. Historically Philippine units in Mindanao were so short of ammunition that they weren't allowed to actually fire their rifles in training--so they were actually firing their rifles for the first time in combat. That obviously didn't go well.

 

[DaleCoz]

What route were the B-17s going to take to the PI? Does anyone know?

The first several flights went Midway, Wake, Port Moresby, Darwin and then to the Philippines. That wasn't considered safe in event of war, so the US was looking into a South Pacific route.

 

[Dave in St. Louis]

The first several flights went Midway, Wake, Port Moresby, Darwin and then to the Philippines. That wasn't considered safe in event of war, so the US was looking into a South Pacific route.

1) So Wake can handle B-17s?

2) That doesn't make any sense. The Wake to Port Moresby hop seems very odd. Running the Wake to Port Moresby hop through NOAA [1], I get a figure of roughly 3250 nm. That is a long haul for a B-17. And why not stop at Guam?

[1] http://www.nhc.noaa.gov/gccalc.shtml