Dec.7'41: The Day That Panama was Bombed Too

robdab2

Banned
Blue Max responded with,

Okay, so the USA knows that there is a Japanese Carrier within striking range of Panama, and their interpretation of "not provoking Japan" involves sitting around defenseless ?

What is it with people here NOT ACTUALLY READING my scenario ? I know its a long one but come on gents, please READ IT before you comment.

Not at all. The submarine's radio deception broadcasts are intended to allow the Americans to believe that Chitose continues her delivery trip towards Argentina, a couple of thousand miles away from Panama.

However please see your Nov.28'41 USN war warning mesage order at http://www.ibiblio.org/hyperwar//PTO/EastWind/CNO-411127.html for "If hostilities cannot repeat not be avoided the United States desires that Japan commit the first overt act." Could it be ANY clearer ?

Sure, there's no HOSTILE INTENT there, just a matter of a communications breakdown in the end of November and a major war scare between Japan and the United States. Like this is not going to provoke a higher alert.

Against a single ship known (incorrectly as it would turn out) by RDF to be over two thousand miles away and receeding daily ??? Unlikely.

And then there is the part where you assume that in this higher alert posture, that Mavis Bombers are going to be allowed to cherry pick targets in the middle of what is likely to be a lack of tactical surprise. Indeed, if the USA is aware of Japanese Ships near Panama at this late point, why the hell won't they consider air recon or other efforts to keep alert?

The whole point of Japan's ATL deception efforts would be to ensure that Panama's American defenders would have NO IDEA AT ALL that Chitose was any closer than a couple of thousnd miles away and headed, on schedule, for Argentina.

This reader says: "Not impossible Feat" but not a very likely one, either. Accept the 1:100 chance and run with it, and then write about how Japan lost the entire force it sent to Galapagos.

You don't read very well, do you ?

I note that you have yet to provide any detail at all on how/why you feel that my entire ATL Panama attack force would/could be destroyed ?
 
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Three quick questions before I head to bed:
1) What is the size of your intended target?
2) What is your expected CEP?
3) How many hits are needed in order to cause the required level of destruction?

Just for a bit of comparison on this:
Further examination of the Marshalls experience only reinforced the conclusions originally derived. In terms of absolute number of hits on targets varying from 25 to 250 feet radius, the F4U and SBD were again almost even. Bombing a 25-foot circle, SBdD could expect to obtain 1.4 percent direct hits while Corsairs scored 1.1 percent. On 50-foot circles the respective figures were 5.4 and 4.5 percent, increasing to 19.9 and 16.7 percent against 100-foot circles. Both types passed the 50 percent margin on 200-foot targets. This was a dramatic increase, for where target size doubled, hits tripled. And attacking 250-foot circles, Dauntlesses recorded 75.1 percent hits while Corsairs scored 68.2 percent.

Corsair, pages 80-81, by Barrett Tillman

That's going to be a greater accuracy than you can achieve with your Mavises (Mavisi?), so consider the Corsair's performance an upper bound.
 
Okay, let's see, since you force me to nitpick the entire thing instead of accepting the short answer of the odds being low.

The USA is going to be...negative towards the whole cover mission in the first place. Argentina will NOT agree to these conditions, and the point of Ecuador getting into this (with the Galapagos and all).

Thus, justification shut down. You are using actions predating the US embargo with Japan to justify a trade with Latin America afterwards. Suffice it to say the USA will force Buenos Aires to decline. In your copious research have you somehow missed that the Argentine President, Roberto Ortiz, was pro-allied?

Your cover story is blown. Don't worry though, that's not all.

Your mission calls for a deception mission, and the Mavis' bombers are flying at different courses and speeds; of course this means that they will NOT all appear at the same time. That said, the USAAF would be keeping an eye on the Chitose because of its known mission (Duh!), the USAAF will probably know that something is up beforehand anyhow.

Also, your Japanese airmen are deliberately flying to avoid US Radar Systems with weaknesses that would require active communication, through a quixotic means of deception that the Japanese would have some cultural reluctance to accept.

With the Cover Story not bought and the USAAF keeping an eye on Chitose, the IJN probably cuts its losses and pulls out without attempting the mission.

It appears, for all of the criticism that I have been ignoring your points, it would also seem that you are ignoring the entire nature of the Panama drainage system (fine. Actual damage isn't going to be the real outcome, just pissing off the United States and forcing them to divert resources is all.)

So, this sounds like a great story. Maybe while we're at it, Japan can bomb Vladivostok. Wasting resources on a bizarre attack that the Japanese WOULD PROBABLY NEVER THINK OF and would almost certainly do little other than forcing a small diversion of US resources and could well spoil the element of surprise at Pearl Harbor, that's an intriguing way to begin a IJN Screwover...
 

robdab2

Banned
Bill Cameron wrote,

I checked my copy of McCullough's Path Between The Seas too and I can't believe that section is as weak as you believe it to be. We're still talking about a dam here and not an exhaust port on the Death Star.

It's funny how history and human nature repeat themselves isn't it ?

Short & Kimmel just couldn't believe that the Japanese could hit Oahu even though the USN's own annual training exercises had already done it three times over the years with nasty results. And Taranto had abley demonstrated the real wartime concept only the year before.

Neither did America see 9/11 coming even though a previous truck bomb attack had come close to dropping one of New York's Twin Towers.

Hindsight is 20/20 and easy. Its forsight which is the bitch. Too many places to look perhaps ?

You may not yet believe that the Canal was so vulnerable to Japanese attack but I'll attempt to further your education by asking you to read pages 299 & 300 of http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-8.html with my own highlites in red:

Reappraisal of Panama Canal Air Defenses

The critical examination of air defenses which had followed the Pearl Harbor attack naturally included a re-examination of the defense of the Panama Canal. Plans made in 1940-41 for protection of the canal had anticipated that the chief danger would come from the eastern approaches, but now the emphasis shifted.[SIZE=-1]160[/SIZE] Recently acquired Caribbean bases and operational rights and facilities provided by an understanding with Brazil came to be of primary importance as steppingstone on the ferrying route to Africa or for use in the maintenance of antisubmarine patrols. The real danger to the canal was from the Pacific side, where virtually nothing had been provided by way of outlying defense and where, geographically, the canal was most exposed to surprise attack.
Early in March 1942, both Secretary of War Stimson and Watson-Watt,

--299--
the British radar expert, examined Panama defenses and reported the existence of disturbing weaknesses. The canal, in the opinion of the British observer, fully justified the concern being shown for its safety, for it was "unique in the world, possessing only four vital points, each of small area, but each so fragile that a single projectile on any of the four could cut this vital line of communications, and two projectiles on any one of three could prevent its re-establishment within two years."[SIZE=-1]161[/SIZE] He agreed with American strategists that the most probable form of attack was a carrier-based raid from the Pacific and estimated that the Japanese could well afford to sacrifice four carriers in an attempt to block the use of the canal. Secretary Stimson reported to President Roosevelt his conviction that the planes from even one carrier could cripple the canal and that if two or more carriers participated in an attack there would be a strong probability fo success. Some means of intercepting carriers far to the west of Panama was urgently needed, because once "a carrier has released its planes for attack, no subsequent means of defense against those planes can sufficiently ensure the safety of the Canal."[SIZE=-1]162[/SIZE] An adequate defense required early detection--and destruction--of enemy carriers at a distance of 500 to 1,000 miles offshore, and since shore-based radars could not reach that distance, the only solution was long-range aerial patrol. Even with such surveillance, a carrier might escape notice long enough to launch its planes, and therefore patrols would need to be supplemented by an effective cordon of coastal radars to provide a twenty-minute warning to alert fighters and antiaircraft batteries for a "last-ditch" defense of the canal. An adequate patrol on the Pacific side of the canal would require coverage of an arc of 400-miles depth extending from an inner semi-circle 600 nautical miles west of Panama to an outer limit of 1,000 miles and from the coast of southern Mexico to northern Peru.[SIZE=-1]163[/SIZE] To patrol this extensive zone, aircrews needed the assistance of ASV radar, which could detect ships at distances of twenty-five to fifty miles, and of bases at Tehauntepec in Mexico, at the city of Guatemala of San José in Guatemala, on the Galapagos Islands, at Salinas in Ecuador, and at Talara in Peru. [See map on next page.] Of this proposed chain, only the bases at the city of Guatemala and Salinas were in use at the time of Mr. Stimson's visit to the Canal Zone. A field on the Galapagos was under construction in accordance with an agreement with Ecuador
--300--


Did you see my remarks about how where the damage to the spillway or the dam-to-spillway "seam" would determine how well the raid succeeded? If you hit nearer the top, you can more easily damage the structure but not release enough water to effect Canal operations. Hitting lower on the structure could release more water but that section is also far thicker.

Sigh.

YET AGAIN, I do NOT intend to bomb the concrete spillway structure.

NOT. NOT. NOT. NOT. NOT. NOT. NOT. NOT. NOT. Did I mention NOT ?

It is too massive to be much damaged by even an 800kg Japanese bomb. Even if a crack were created in that concrete, the rush of water would NOT be able to erode a channel down thru the remaining concrete (nor thru the spillway's rock foundation) so that Gatun Lake could drain out.

The mission is entirely possible, Robdab, but is it plausible? Japan in 1945 was desperate enough to attempt something close to this, but is Japan in 1941 equally desperate ?

Bill, come on.

Do you forget that on Dec.6'41 Japan was an embargoed nation of some 90 million ? Their leadership KNEW that their new Empire has less than 2 years before it ran out of "black gold" and would revert to stoneage survival techniques. Without fuel it couldn't even FEED all of it's own people every day.

They were also quite clear on the idea that Japan could NOT (that word keeps cropping up doesn't it ?) possibly win a long term production war against America.

Such a strategic "knock" against the US couldn't possibly come at a more shoestring price. Even if my ATL bombing FAILS to stop Canal operations, the mere attempt, in conjunction with the OTL Pearl Harbor raids, would send shockwaves thru all of America.

If America's 2 strongest Pacific fortresses were not safe from Japanese attack, could a West Coast invasion be far behind ?

Why couldn't this wheelchair bound President defend the nation ?

Why were incompetent Admirals and Generals in charge of the military ?

Why is Congress wasting our tax dollars on defenses that don't work ?

Lend/Lease should be stopped immediately so that Homeland defenses could be built up !!

To Japanese minds anyway, this would further encourage a morally bankrupt America to sign a quick ceasefire recognizing Japan's new ownership of the NEI's oil.

All at the possible cost of just 3 Mavis aircrews.

The IJN lost more airmen than that in Kido Butai training crashes during their preparations for the OTL PH raids.

I have already demonstrated that the 5 Japanese ships involved would not be missed from OTL Japanese operations.

Shoestrings couldn't come any cheaper.

I'm going to dig into my copy of the Pacific War Companion to see if I can find some short statements that describe Japan's pre-war war planning. Knocking the US back on it's heels with a Pearl Harbor attack was a very late addition to those plans, so any other direct attacks on US interests beyond the western Pacific would be late additions too.

Don't waste the time. I already agree. That is another reason that I think my ATL scenario to be plausible. The only time heavy change needed is the installation time for an existing heavier crane onto Chitose.

Japan's thinking was focused on forcing as much as 20% attrition on the USN as it broke through the defensive perimeter and than defeating it afterward. There had been no planning or thoughts about discomforting the US in the eastern Pacific and IJN planning always assumed the USN Pacific fleet would be reinforced by Atlantic assets before driving on the Phillipines anyway.

Yet draining the Panama Canal would add travel time and wear & tear to that USN Atlantic Fleet which gives Japan more time to secure her new Pacific Empire (and it's oil wells) before having to defend it, which is tough to do without sufficient fuel. Would not trading just 3 Mavis for 2 more months of preparation time be a wise decision ?

I just don't see how this is plausible. It's good, just not plausible.

We'll have to agree to disagree.

Such is always one possible, but dis-satisfying, outcome to any discussion.
 

robdab2

Banned
Blue Max responded with,

The USA is going to be...negative towards the whole cover mission in the first place.

So ? These are still sovereign nations. What better way to squeeze the US for better terms on anything than to begin trade with Japan ?

Argentina will NOT agree to these conditions,

Why not ? Page #118 of http://books.google.ca/books?id=ehd...X&oi=book_result&resnum=7&ct=result#PPA118,M1
indicates that 40% of her normal European trade had been cut-off by the war ongoing there. Japan would be a hungry new market for Argentinian goods.

and the point of Ecuador getting into this (with the Galapagos and all).

Ecuador wouldn't be involved at all. My ATL Chitose would be a totally unexpected and uninvited 12 hour visitor to Galapagos waters.

Thus, justification shut down.

I don't see how, so far. You offer not even a single verifyable source for your opinions.

You are using actions predating the US embargo with Japan to justify a trade with Latin America afterwards.

So ? It was the ongoing European war that closed Argentina's usual markets. The ABCD embargo (to which Argentina was not a party) was a motivating factor in Japan's search for new Latin American and South American suppliers.

Suffice it to say the USA will force Buenos Aires to decline.

How exactly ? Strongarm tactics are risky when dealing with firey Latin types that you want to build a continent wide alliance with.

I also notice that the US wasn't very successful in persuading Argentina to deny entry to escaping Nazis just a few short yeras later. I think that you greatly overestimate the real strength of American influence over Argentina.

In your copious research have you somehow missed that the Argentine President, Roberto Ortiz, was pro-allied?

That didn't seem to stop the Japan/Argentina trade deal that I have already mentioned, did it ? Money talks (and usually LOUDLY).

Your cover story is blown. Don't worry though, that's not all.

Not. You don't worry me at all.

Your mission calls for a deception mission, and the Mavis' bombers are flying at different courses and speeds; of course this means that they will NOT all appear at the same time.

If Mavis crews could find a tiny Pacific Island after a 2,800 mile overwater flight then I truely think that with RDF backup they could easily juggle speed and distance so as to arrive at the Gatun Dam from different directions, together.

Besides, if a "China Clipper" flyingboat, commonly seen in Panama's skies at the time, should circle some hill for a few minutes, why would anyone below possibly get upset about it ?

That said, the USAAF would be keeping an eye on the Chitose because of its known mission (Duh!), the USAAF will probably know that something is up beforehand anyhow.

Yet again you fail to comprehend that with radio deception, the Americans would believe my ATL Chitose to be a couple of thousnd miles away and going further towards Argentina by the hour. No USAAF warplane had such range to go and check visually , at the time. Even the PBY was only good for 800 nmiles out and then back.

Also, your Japanese airmen are deliberately flying to avoid US Radar Systems with weaknesses that would require active communication,

How so ? All 3 mavis would be flying low while over water, on differing courses and at differing speeds with the objective of arriving over the Gatun Dam at exactly 1300. What commo would be needed ?

through a quixotic means of deception that the Japanese would have some cultural reluctance to accept.

The only deceptions that I include are those done by the OTL Japanese for their PH attacks. They had no such "cultural reluctance" problems AFAIK. Can you offer some/any proof/source at all ?

With the Cover Story not bought and the USAAF keeping an eye on Chitose, the IJN probably cuts its losses and pulls out without attempting the mission.

Sorry, I can't see any of your totally un-supported points of view as being at all likely. Orders are orders and it wouldn't be good to disappoint the Emperor.

It appears, for all of the criticism that I have been ignoring your points, it would also seem that you are ignoring the entire nature of the Panama drainage system

Which is ... ?

Are you even sober ?

(fine. Actual damage isn't going to be the real outcome, just pissing off the United States and forcing them to divert resources is all.)

Whatever.

So, this sounds like a great story.

Thanks. I'd like to think so.

Maybe while we're at it, Japan can bomb Vladivostok. Wasting resources on a bizarre attack that the Japanese WOULD PROBABLY NEVER THINK OF and would almost certainly do little other than forcing a small diversion of US resources and could well spoil the element of surprise at Pearl Harbor, that's an intriguing way to begin a IJN Screwover...

Yawn. Tiime for sleep.
 
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Such is always one possible, but dis-satisfying, outcome to any discussion.


Robdab2,

It's dissatisfying because it's no longer a discussion. In a discussion, both sides listen and talk.

You've presented this idea or a similar version of it on two different boards to two different groups of people and have received the same feedback: it won't work, it completely ignores pre-war Japanese planning and thinking, and it's far too risky when measured against any possible rewards.

Sure it's possible. Nearly anything can be possible. Quantum theory can assign a possibility to my disintegrating into component molecules, zooming to Scotland, and reintegrating inside a vat of Glenfiddich where I'll drown in perfect contentment, but I'm not cutting back on my liquor sales if you know what I mean.

You did a lot of work but in the end it wasn't worth it. This idea simple isn't plausible. Sorry.


Bill
 
My major frustration with all of this is that robdab doesn't even THINK to challenge his own points and consider objections to his own scenario, instead looking for someone to believe his points of view on this forum under the guise of discussion.

Nonetheless, Robdab wants sources:

http://208.84.116.223/forums/index.php?showtopic=26906&

This blast from the past would certainly be a good exposition for the myriad of reasons why this would either not work or be unlikely.

Here is who is running Argentina at the time, for those of us who need sources to believe it:

http://en.wikipedia.org/wiki/Roberto_María_Ortiz

So you can make whatever economic claims you'd like, but at the end of the day a bizarre training mission in Argentina isn't going to go forward, and the Japanese ships' departure from its planned route WILL be noticed by the USAAF.

I think the evidence in on your head to determine why Argentina would make this kind of arrangement after Washington would have already pressured them to end trade agreements with Japan.

Finally, one more thing:

Robdab2: Are you even sober ?

Are you? You are the only one saying that this would work, failing to see how multiple levels of essentially deception (ie, lying by making a deal with Argentina, by concealing various items like BOMBS, by painting their aircraft to appear similar to historical flights.)

So what is likely to happen?
The ruse gets discovered. The Chitose is unable to explain why it is not following course to Argentina, assuming that Argentina doesn't simply call off the deal. Using a PRE-EMBARGO figure to justify a deal with Argentina when it is clearly pidgeonholing the requests of the United States suits the flavor of these events:

A series of unlikely and curious exploits.

So the Chitose's deviation is noted. You say that they'd press on the attack, fine, in which case there are fighters in the air when the second Mavis bomber appears, and if they might get four shots, not six, under fire.

Accuracy of a bomber while trying to evade interceptors--not the high degree you'd need.

Of course, you've cherrypicked the target--a dam, which looks like many other dams. Yes, the Mavis bombers might be able to pinpoint it IF they weren't busy trying to avoid getting shot to pieces.

I'd like to know about Japanese Intelligence in Panama--since you are clearly trying to circumvent US Radar despite Japan having no plausible way to know about its limitations.

And perhaps that's what frustrates me most about this whole scenario. There is no functional way for Japan to even consider this course of events. No one is going to stake their career on the course of these events--have you forgotten that Yamamoto threatened to resign to even launch Pearl Harbor in the first place? The IJN and IJA will not want to divert Chitose and its support craft on this adventure, and the proponent of said adventure oddly doesn't exist.

That's a far cry from "not defying an order from the Emperor." Indeed, the IJN will not even consider this attack and would have the commodore or whatever leading it punished for his departure from the larger plan of attacking the DEI...

So, you'd need a Japanese Spy Ring all over Panama. And they'd somehow give all of this information to Japan in advance of the actual attack. And Japan PROBABLY did not have all of the covert assets in play here.

You have plenty of information available to you. But are you willing to accept that realistically this plan has nearly zero chance of success? That so many things can go wrong and so many justifications don't exist that this whole plan is likely to be discarded in favor of simply using Chitose and its attendant vessels for something that is actually likely to work closer to home?

You called this thread a discussion. Do keep your word on that point and show a willingness to accept the unlikelihood/implausibility of this move.
 
Sigh. YET AGAIN, I do NOT intend to bomb the concrete spillway structure. NOT. NOT. NOT. NOT. NOT. NOT. NOT. NOT. NOT. Did I mention NOT ?


Robdab2,

This is an example of why this is no longer a discussion, even if it was one to begin with.

I've seen the pictures you've posted, I've read the materials you've posted, and I understand that you don't intend to damage the spillway directly. You don't need to repeatedly question my grasp of that point or Blue Max's sobriety.

However, you do need to read what we've posted and grasp what we're saying. You're targeting portion of the Gatun Dam where it "connects" with the spillway, the seam I mentioned. I'm calling into to question three problems with the assumption:

- The ability of the flying boats to hit such a target.
- The ability of the flying boats to damage such a target.
- The chances that the flying boats will hit adjacent targets.

First, the fact that you're "only" talking about the "seam" area is moot. Estimates of bombing accuracy before and during WW2 were notoriously overstated, wildly overstated, even by "experts" who should have known better. A large raid will have far better chances to find and actually hit the target than the type of raid you're proposing because it will using many more asset to drop much more ordinance.

Second, I've been able to find dimensions for the rest of the Gatun Dam and you claim the "seam" area is substantially thinner. Thinner, in fact, to point where it is easier to damage. Fine then. Show us the numbers. Show us the thickness at the top, thickness at the bottom, and width of this "seam". Show us how big the flying boats' target actually is and give us some indication of how weak it actually is. Give us an idea about how easily the target can be damaged. Until then all we have is your word.

Third, I don't want to hear about Fleet Problem 1 from 1923. Those "results" were were imposed by a referee modeling a much different raid. I also don't want to hear about the UK radar expert's opinion either, he was talking about a four carrier raid and all the ordinance such a raid could dump on a target, not a three flying boat raid and the pittance that type of raid can deliver. The period defense studies and reviews you're quoting assume a far larger raid dropping much more ordinance over longer period of time. You cannot dispute the vast differences between the raid they were worried about and the raid you're proposing.

Even assuming that the Japanese would authorize such an attack, an assumption I believe to be wholly false given the OTL example of the far less risky and potentially far more productive Pearl Harbor raid and how near it came to not being authorized, I still have significant issues with your "weak" point being actually hit and actually damaged. I would also like you to address an issue that I have repeatedly brought up in this thread, that damage to the dam itself, the spillway, or the "seam" area you're pinning your hopes on will only result in a loss of water.

There is some plausibility that Japan would conceive of such a raid in 1941 because they did so in much more desperate position in 1945, there is far less plausibility have they would specific intelligence required to plan such a raid, the various misdirections you've proposed have is even less plausibility of being attempted let alone working, and the least plausible aspect of all is that the flying boats will be able to travel over 800 miles separately, arrive over the spillway on time, hit the "seam" as planned, and damage it to the extent you imagine.

Taken all together, these various possibilities add up to something just north of zero. It's possible, because nearly anything is possible. It is also wholly implausible.

Finally, I'll repeat my previous last comments. You've presented this plan or another very like it on two boards now to two different sets of people and have received essentially the same responses; It Won't Work. That should call into question your assumptions, I know if I were in your place I question my own. You can take your idea to other boards, WW2 fora aren't hard to find, and put it to them. I'll predict now that their responses will be essentially the same as all the others you've already recieved; It Won't Work.

You did a lot of research, but that doesn't matter. I'm sorry, but it doesn't work on several levels.


Regards,
Bill
 

The Sandman

Banned
Here are my thoughts on this, after reading the thread.

First, since it appears that the I-400 class submarines were in fact available, and their plane complements could also carry 800-lb bombs, could they be sent along with the Chitose on this mission? Even another three planes increases the chance that something gets through.

Second, how might the ongoing Peru-Ecuador War affect the situation here? It might provide a good cover for the Japanese to be delivering the aircraft to one or the other of the combatants; the US may allow this one sale on the grounds that they don't particularly care about what Peru and Ecuador are doing and that this might give them the chance to acquire at least one of them in order to study it first-hand. On the other hand, I have no idea what if anything was operating in the Galapagos at the time due to the ongoing war.

If you really have huge brass balls (although I suspect the following is highly implausible at best), have the Japanese account for the fact that the US is likely to try to get the planes from Ecuador or Peru, and that the closest US facility for them to refuel and be transferred into American hands is the Canal Zone. That gives a legitimate reason for a flight of Mavis seaplanes to be heading right towards the Canal, with the last-minute diversion to bomb the spillway-dam junction an unexpected surprise. If the I-400 class is being used in this, their contribution might be done in the form of the aforementioned fake China Clippers, coming in from a different direction.

Third, I think we have to assume that the Japanese pilots are coming in as low and slow as possible. The whole point of the "surprise attack" part of it is that the US forces at the Canal won't realize what's happening until the Japanese planes are already headed into their bombing run, and I don't think that the planes on the ground could be scrambled quickly enough to stop the Japanese from having their shot at the Canal (although the Japanese will almost certainly lose most if not all of the force on the way home). Therefore, accuracy is likely to be less of an issue; the Japanese aren't having to try to bomb from any specific altitude, and the planes are all targeting the exact same spot with all of their weapons. At least one will probably hit on target, and even if the others don't they might still help weaken the structure of the dam or spillway a little.

Fourth, given that this is apparently occurring during the rainy season, the assumption seems to be that the dam will be filled up to near the top due to being in the "water-collecting" phase. Furthermore, it can be assumed that the dam will be continuing to fill later that very day from the rains, and that the spillway will be out of commission for at least a day or two due to repairs. Assuming that this suffices to create a leak between the concrete and earthen structures, instead of purely in one or the other, it seems plausible that the pre-existing join line would be more susceptible to catastrophic failure than the main bodies of either the dam or the spillway.

Fifth, the question we don't actually seem to be asking is "What would it take to get the IJN to authorize this?"; instead, we're just assuming that it would or wouldn't happen depending on the point we're trying to prove. So I'm asking: theoretically, what would it take for the IJN to approve this operation?
 

Ian the Admin

Administrator
Donor
Seems this guy has trolled many other forums and now he's an instant asshole here, so...

banhammer_wondertwins.jpg
 
First, since it appears that the I-400 class submarines were in fact available...


Sandman,

The three boats of the I-400-class weren't constructed until late '44/early '45. There are, however, boats in the A-1 and B-1 classes available in 1941 which also carry seaplanes.

FWIW, the IJN had some impressive submarines, both in terms of range, size, surface speed, and submerged speed. Fortunately, the IJN used those submarines very poorly.

Even another three planes increases the chance that something gets through.

Agreed.

Second, how might the ongoing Peru-Ecuador War affect the situation here?

That's an angle I completely overlooked, and a very intriguing angle too. What might be the US' response to arms sales from an Axis pact member to a nation in the Western Hemisphere?

The whole point of the "surprise attack" part of it is that the US forces at the Canal won't realize what's happening until the Japanese planes are already headed into their bombing run...

The Canal Zone, by virtue of it's having a sea frontier in both the Atlantic and Pacific, was actually more "at war" than Pearl was during this period. The US' undeclared ASW campaign didn't just involve destroyers off Iceland or shepherding convoys to the MOMP. Among other things, forces based in the Canal Zone were already flying regular ASW sweeps along both approaches.

Assuming that this suffices to create a leak between the concrete and earthen structures, instead of purely in one or the other, it seems plausible that the pre-existing join line would be more susceptible to catastrophic failure than the main bodies of either the dam or the spillway.

I've been unable to confirm Robdab2's claims regarding this weak "seam". The Gatun Dam itself is massive and the spillway only less so, so I find the idea of a "weak seam" between the two odd. The damage Robdab2 mentioned in Fleet Problem 1 was specifically said to involve the spillway while the testimony by the British radar expert didn't specifically mention what the four "weak points" exactly were. Robdab2's claims might very well be valid, I just can't back them up yet.

Fifth, the question we don't actually seem to be asking is "What would it take to get the IJN to authorize this?"; instead, we're just assuming that it would or wouldn't happen depending on the point we're trying to prove. So I'm asking: theoretically, what would it take for the IJN to approve this operation?

That is the question on which this whole WI turns and one that Robdab2 seemingly never asked. I cannot yet come up with a plausible reason for the IJN staff to authorize a mission of this type, but that doesn't mean others cannot.


Bill
 
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The Sandman

Banned
I've been unable to confirm Robdab2's claims regarding this weak "seam". The Gatun Dam itself is massive and the spillway only less so, so I find the idea of a "weak seam" between the two odd. The damage Robdab2 mentioned in Fleet Problem 1 was specifically said to involve the spillway while the testimony by the British radar expert didn't specifically mention what the four "weak points" exactly were. Robdab2's claims might very well be valid, I just can't back them up yet.

I was assuming here that the "weak seam" is due to the fact that the Gatun Dam, unless I horribly misread its description, is essentially two separate earthen dams going from the sides of the Chagres River valley to a hill in the middle, with the spillway constructed over the top of said hill. Since the spillway is more or less a separate concrete dam constructed in between two earthen ones, there should be some point where the concrete and the earth join. Get enough water flow through that point and you might be able to breach it by separating the earth from the concrete on one side.

That is the question on which this whole WI turns and one that Robdab2 seemingly never asked. I cannot yet come up with a plausible reason for the IJN staff to authorize a mission of this type, but that doesn't mean others cannot.

Given Yamamoto's apparent love of extremely complicated plans that involve repeatedly dividing his forces over vast distances, this would seem to be right up his alley. Just prove that it has a reasonable chance of working and that it isn't actually removing assets from places where they're already scheduled to be used, and Yamamoto might very well go "eh, what the hell" and throw it in.
 
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