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

robdab2

Banned
Gents (and any Ladies ?),

WHAT IF the Japanese had attempted to knock out the Panama Canal on Dec.7'41 ?

I believe that they might have done so at little cost and the following is my alternative timeline (ATL) scenario as to how they might have accomplished that feat at the same time as the original timeline (OTL) historical Pearl harbor air raids were going on. It is my hope that discussion generated here will prove to be entertaining (and educational) for all involved. Sorry that its so long and that I'm not a better writer ...

One source, http://www.history.army.mil/books/wwii/ ... s/ch12.htm indicates that, "Plans for protecting the Canal against sabotage during an international crisis of this sort had been drawn up in Panama and given constant study ever since the spring of 1936. Now, steps to put them into effect were quickly taken. Three basic measures had been provided for: first, the installation and operation of special equipment in the lock chambers, designed to detect underwater mines and bombs and to prevent damage from this cause; second, the restriction of commercial traffic to one side of the dual locks; and third, the inspection of all ships before they entered the Canal and the placing of (2-25) armed guards on vessels while in transit through it. These measures were instituted between 26 August, when the President gave Secretary Harry H. Woodring the signal to go ahead, and 1 September of 1941."

Page #48 of http://books.google.ca/books?id=8WJ...=X&oi=book_result&resnum=4&ct=result#PPA48,M1 does also indicate that US ship inspectors at the Panama Canal began tossing hydrogen cyanide gas into ship's holds in order to fumigate same, in 1923. This makes it far less likely, IMO, that the Japanese or indeed anyone else, would be foolish enough to attempt any "Trojan Horse" type freighter attack on the Canal.

Thus I would expect that the chances of blockship sabotage success there would be very unlikely.

The ATL Japanese surprise air attack that I have in mind instead would see just 3 H6K 4-engined "Mavis" flyingboats trundling in the 855 nautical miles from the Galapagos Islands at 1300 in the early afternoon of Dec.7'41, timed to match with the OTL strike on Oahu at 0755.

Sneaking a pre-war IJN surface warship across the busiest shipping lanes of the wide Pacific, un-noticed a la the Kido Butai, would most likely be impossible even in peacetime so a "show-the-flag" state visit voyage by the IJN seaplane tender Chitose would have to provide a peacetime cover story to get those 3 big flyingboats within their air range of Panama.

With official permission from the governments of the countries scheduled to be visited, naturally.

Page #118 of http://books.google.ca/books?id=ehda-fB ... &ct=result details some of the 1940 trade successes that Japan achieved with Latin and South American nations. My ATL suggests that part of the OTL barter deal signed with Argentina might have included the 1941 provision by Japan of 3 long-ranged Mavis flyingboats for the Argentine military. That elongated nation had much isolated ocean coastline to patrol against Chilean incursion afterall.

A triple Mavis delivery by Chitose would thus be easily justified and would not be expected to pass anywhere near the Panama Canal as the IJN delivery vessel would be sailing southeastwards, around Cape Horn, due to the "unofficial" US ban on Japanese vessels transiting the Canal .

What world power would be greatly worried about 1 lone seaplane tender on an announced peacetime flyingboat delivery mission many miles away from it's outposts ? Completely un-announced in the newspapers would be 2 detached fast IJN crewed tankers and Chitose's close escort bodyguard of 3 long ranged IJN submarines (detached from their historical role of patrolling around Hawaii with 27 others), each capable of 21 knots on the surface and folding seaplane equipped.

Chitose's OTL war assignment at Mindanao, PI could be fulfilled by the Japanese CVL Zuiho, itself detached from the mostly idle Combined Fleet which still had a second light carrier attached (the CVL Hosho) to provide it's historically Bonin bound battleships with CAP and observation services. Please see the TROMs at http://combinedfleet.com

Much as was done historically with the Tatsuta Maru's fake voyage thru Honolulu (see Prange's "At Dawn We Slept") Chitose's schedule of South American ports of call visits would be published in various newspapers by the local Japanese consulates but she would never arrive at any of them in my ATL Panama scenario. If spotted by US/UK/Dutch ships while on her way across the still peacetime Pacific prior to Dec.7'41, she would merely be reported as being on course and schedule for those already announced port visits.

Wherever possible she would refuel at the commercial ports of the still peacetime Pacific islands that she passed so as to reduce her need for any tanker support.

She would never even cross the 300 mile boundary of the US Neutrality Patrol zone which extended out from the coasts of Latin and South America.

As she neared South America her regular radio operator would board one of her submarine escorts which would then continue on alone along Chitose's announced course towards Argentina. All the while making the same regular fake radio transmissions designed to convince the peacetime Americans that Chitose was still on her Mavis delivery mission.

On the evening of Dec.6'41 my ATL Chitose (watched over by her remaining 2 IJN submarine escorts) would quietly anchor instead in a deserted lee bay somewhere in the numerous Galapagos Islands, all 126 of them, which were/are owned by Ecuador.

That South American nation had a substantial Japanese population in 1941, many of whom were fishermen or guano miners earning their living out on the Galapagos. Both being good covers for the pre-war scouting of a suitable anchorage for my ATL Chitose and her 3 big new flyingboats.

Chitose was originally built to handle 24 single engined seaplanes with 4 catapults and 5 cranes as per the painting to be seen at http://www.combinedfleet.com/chitosesp_t.htm so in order to hoist a much heavier/larger 4 engined Mavis aboard at least one of those midship cranes would have needed to be upgraded to one similar to that installed on the stern of the much smaller Akitsushima as seen at http://www.aeronautic.dk/Warship%20Akitsushima.htm At the same time as that crane installation was done, her central "platform" would be removed to provide enough clear deck storage space for 3 Mavis.

Once anchored, all 3 Mavis flyingboats would be hoisted over the side during the night, checked out, fueled and armed with twin 800kg type 80 land bombs.

After a sheltered bay water takeoff at dawn, all three would depart at different speeds and on differing courses, for Panama's Gatun Dam, some 855 nmiles away.

The reason for those seperate but co-ordinated flight approaches to Panama being the more than passing resemblance of the Mavis to the Pan-American Airline's "China Clipper" aircraft, the Sikorsky S-42. If pre-painted in Pan-Am's minimal colors, with round windows and markings, any observer expecting to see a lone "China Clipper" pass by overhead could certainly mistake a single Mavis for one of them instead. By no coincidence at all, Pan-Am was flying a daily "China Clipper" shuttle service on the Miami - Cuba - Costa Rica - Panama - Columbia - Venezuela - Buenos Aries route at the time. As well, PanAm's subsidiary, Panagra, was busy developing a trans-Pacific route to the Galapagos Islands at the request of the American and Ecuadorian governments..

Please compare for yourself at http://www.warbirdphotographs.com/NavyJB&W/H6K-8s.jpg and http://www.flyingclippers.com/S42.html . Both with 4 engines and twin tail fins.

Each Mavis could carry a pair of torpedoes as per http://www.warbirdphotographs.com/NavyJB&W/H6K-1.jpg so the fitting of two slightly lighter big HE bombs shouldn't prove to be much of a technical challenge for my ATL Japanese.

My 3 ATL Mavis would attempt "to hide in plain sight" by fitting easily detachable sheet metal tailcones on each of their 6x800kg bombs in an attempt to disguise them as long range wing strut mounted fuel tanks

The target of the 6 bombs carried by those 3 Mavises being the Gatun Dam (not the Gatun Locks) itself which held back the water in man-made Gatun Lake and thus, allowed the operation of the entire Panama Canal.

The Gatun Dam, a stone armored earthfill structure is far too thick to be affected by a torpedo warhead but the same cannot be said wrt the concrete wingwall located immediately adjacent to the central concrete spillway. As can be seen ringed in blue at http://i73.photobucket.com/albums/i234/phylo_roadking/dam.jpg and at http://community.webshots.com/photo/fullsize/1322277285048181265JyntdB
Don't miss http://www.czimages.com/CZMemories/Photos/photoof289.htm nor
http://www.autoridaddelcanal.gob.pa/eng/plan/multimedia/photos/target32.html

Certainly the US was aware of the vulnerability of the Gatun Dam spillway to BOMBING as early as 1923 when a training exercise called Fleet Problem I, which is documented at http://en.wikipedia.org/wiki/Fleet_P..._note-Wright-1 , which pointed that out quite dramatically.

I do know that 3 US interceptor squadrons, each of 10 x P-36 fighters, were flying in Panama's rainy season cloudy skies already but AFAIK the 71 more modern P-40s which had just arrived were not combat operational there until well after Dec.7'41 due to aircraft radio shortages.

I have also found several sources which do NOT present the other OTL American defences in a good light:

For example, page #349 of http://www.history.army.mil/books/wwii/ ... s/ch13.htm summarizes the state of Dec.'41 US defences at Panama against a surprise air attack: "He did, however, call to the attention of the War Department certain deficiencies in the defenses of the Canal. In General Andrews' opinion, the commandant of the naval district did not have enough planes or vessels under his control to conduct an adequate reconnaissance. The Aircraft Warning Service in the theater, he reported, was totally inadequate in personnel to supervise the installation of detectors on hand as well as to man the equipment when installed. Only two radar detectors were installed and in operation in the Panama Canal Department. The harbor defenses had less than one complete manning detail available. The antiaircraft artillery had insufficient personnel to man the armament being installed in the Canal Zone and only enough ammunition for one minute of fire per gun for the 37-mm. guns. There were no barrage balloons. The Air Force,General Andrews continued, was totally lacking in night pursuit planes and in very-high-frequency radio equipment with which to direct pursuit in air. Only 8 modern long-range B-17C bombers and 12 modern AC-20 light bombers were available..."

Only one minutes worth of AA fire hardly inspires any confidence that a surprise IJN air attack could be prevented from reaching good positions to launch unexpected bombing attacks on the Gatun Dam's spillway. The US Army itself estimated that loss of all of the water stored in Gatun Lake would have prevented all Canal operations for a period of at least two years and possibly three, depending on the refill rates dictated solely by local rainfall amounts. This ATL attack scenario hopes to drain all of the Canal's water reserves as the Gatun Dam itself would be split open and exposed to complete destruction by erosion, thus emptying most of Gatun Lake.

Although not exactly identical, the Baldwin Hills Dam failure video to be seen at http://www.youtube.com/watch?v=kIeNM8cm6J8 aptly demonstrates the same type of quick progressive erosive failure that I predict for the earthfill Gatun Dam if those 6 big Japanese bombs can crack it's concrete upstream face open. It would take days however for the 164 square miles of Gatun Lake to drain into the Caribbean via the Chagras River.

Page #274 on http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-8.html provides the assertion of: "The problems involved in providing a serviceable radar screen to alert the inner defenses of the Canal were less easily solved. Equipment in use at these stations was "inadequate" for early warning and "quite useless" for purposes of controlled interception. Sites had been selected for four British-type radars, the sets to be supplied from Canadian production, but improvement in equipment could not overcome deficiencies of operating personnel. Operators in Panama were largely untrained, had been given no indoctrination in the need for precision standards, and were frequently unenthusiastic about their assignment. Radar crews had made no effort to plot the permanent echoes in their search areas, and therefore could not discriminate between such "echoes" and "live" targets. The combination of inadequate equipment, poor site selection, and untrained operators produced such inefficiency that even the best station in Panama was "far below any acceptable standard of operational utility." The elimination of all the deficiencies noted depended on action by the War Department to provide improved equipment and better trained crews. No complete remedy was available to local commanders."

Since they had a little OTL knowledge of the American Panama radars via their spymaster there, Akiyama (please see http://www.ibiblio.org/pha/timeline/411122ax2.html ), my 3 fake ATL "China Clippers" will fly low over the Bay of Panama in an attempt to avoid it. Considering the high probability of rainy season cloud cover over Panama's mountains though, such would not be at all safe over land. Fortunately for my scenario, it seems that those same OTL radars would not likely have posed much of a detection/interception threat to my 3 ATL flyingboats anyway. Being of the same type of air warning radar as installed on Oahu, the one US radar set facing the Pacific Ocean would also have suffered from the same 20 mile minimum "blindspot" experienced by those Hawaiian radars.

Pages #424-426 of http://www.history.army.mil/books/wwii/ ... s/ch16.htm provide: "Although General Andrews recognized the U-boat campaign as "a definite menace to our war effort," he considered the canal to be "the one real enemy objective" and its protection to be his "paramount mission." Although he was somewhat concerned about the possibility of German surface raiders penetrating [from] the Caribbean, he was more than ever convinced that the principal threat was by carrier-borne aircraft from the Pacific.

The means for detecting an enemy carrier force before it launched its planes and for sighting the enemy planes before they reached the canal were the nerve center of the Panama defenses. Patrol planes, operating at about the 900-mile radius, were depended upon for the initial warning of an enemy's approach. Long-range radar (the SCR-271 and its mobile version, the SCR-270) was relied upon for the detection of enemy planes at distances up to about 150 miles. Still closer-in, the fixed antiaircraft defenses relied upon short-range, height-finding radar (SCR-268) for searchlight and fire control.

AFAIK there were only 12 PBY scouts (without RADAR) assigned to search the Pacific to the west of Panama out of the 70 (with RADAR) that were estimated to be able to provide a proper long ranged search.

At the time of the Pearl Harbor attack however, serious deficiencies existed in the warning and detection system. There were not enough planes and operating bases to carry out the search as planned. There were only two SCR-271 radars in operation, one at each end of the Canal. Although three additional sets arrived by the end of December and were being installed on the Pacific side of the Isthmus, the work was slowed down by a shortage of trained radar engineers and mechanics.

There were nevertheless certain deficiencies which were not entirely the result of a shortage of equipment and trained men. Tests in Panama repeatedly disclosed that low-flying planes approaching directly over the Bay of Panama were not detected by the radar system. Visiting British experts had noted this characteristic in American sets and attributed it to a basic defect of the equipment, but the Signal Corps insisted that, properly placed and operated by competent crews, the American equipment in this respect was just as good as, if not better than, the British radar. Whatever the cause, the blind spot remained. Furthermore, neither the SCR-270 nor the SCR-271 was designed to show the elevation of the approaching plane, and neither gave a continuous tracking plot. These qualities were indispensable for ground-controlled interception (GCI), which British experience had demonstrated to be the most successful method for conducting an air defense."

Pages #160-166 of: http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-5.html detail the poor overall situation in Panama: "The vital importance of this phase of Canal defense was revealed in an estimate of enemy capabilities prepared by the Caribbean Defense Command in the latter part of November 1941. Japan was regarded in respect to the Canal itself as the primary potential enemy, and a carrier-based attack from the Pacific was considered "not an improbable feat." Other possibilities were taken into account, but it was concluded that in any event the most important defensive measure was "increasing and thorough reconnaissance and observation of the air, sea, and land approaches to the Canal Zone." Existing forces in the area were regarded as sufficient to repel any probable initial attack on the Canal provided they were given "timely warning" of the approach of hostile forces. The inability of defending naval and military air forces to perform the required amount of reconnaissance and to provide the "timely warning" constituted perhaps the chief weakness in the defenses immediately prior to American entry into the war. It was a weakness which was recognized by both Army and Navy commanders, their expressed hope lay in the postponement of attack by an enemy until the defending forces could achieve the proper degree of co-ordination and the necessary equipment for complete coverage of the vast sea frontiers."

THUS IT IS REVEALED THAT THE PRIMARY US PACIFIC DEFENSE OF THE PANAMA CANAL IN DECEMBER 1941 RELIED SOLELY ON THEIR MERE HOPE THAT THE JAPANESE WOULD NOT ATTACK THEM ANYTIME SOON !!!

Just how pathetic was that ?

Had the Japanese but known ... or dared ...

Your thoughts & constructive criticisms (with sources), please.



Veni, Vidi, Velcro. - I came, I saw, I Stuck Around
 
Robdab2,

I think if you explain what makes the spillway so important to the operation of the Gatun Dam and why the dam is so important to the operation of the Canal people will begin with a better grasp of what you're trying to accomplish.


Bill
 

robdab2

Banned
I think if you explain what makes the spillway so important to the operation of the Gatun Dam and why the dam is so important to the operation of the Canal people will begin with a better grasp of what you're trying to accomplish.

Thanks for the suggestion. Having done the research, I often forget that most others don't have the background knowledge.

The simplest approach might be a good read of http://en.wikipedia.org/wiki/Panama_Canal

My own shorter version is that the Panama Canal is an above sea level waterway the uses Panama's abundant but seasonal rainfall to provide an 8,000+ mile (and 4-6 weeks) shipping shortcut between America's Atlantic and Pacific coasts.

The mostly earthen Gatun Dam, seen in overhead drawing form at http://content.lib.washington.edu/c...OT=/fishimages&CISOPTR=38664&CISOBOX=1&REC=11
stores that seasonal rainwater in Gatun Lake for the Canal's use throughout the year.

Since the Canal runs ships thru Gatun Lake, the loss of all of that stored rainfall puts the Canal out of operation, period.

That Dam is a prime target but is far too thick in most locations to be blown open by any reasonable number of bombs/torpedos. If ever overtopped by water's erosive flow however, it's lifespan would be measured only in hours so the concrete arch spillway was constructed in the centre of the Dam to ensure that Gatun Lake could never rise too high. It's 14 steel gates could be used to release excess Gatun Lake waters into a concrete drainage channel fully protected against water erosion. Peacetime problem solved.

If somehow destroyed in War however, Gatun Dam could be repaired by 4-6 months of earthmoving BUT it would take 2-3 YEARS of Panama's rainy season to refill Gatun Lake and thus restore the Canal's operations.

This ATL scenario suggests that the connecting point between the earthen Gatun Dam and it's own centre concrete spillway section was an un-intentional weakspot designed into that dam in 1911, some three decades before Japan's 800kg bombs (and the warplanes capable of delivering them) even existed. Technology marches on.

The OTL Japanese exploited their newly developed technology to attack Pearl Harbor in the form of minisubs, underway at sea re-fueling, radio mis-direction, long range drop tanks for their Zero fighters, AP bombs made from 16" battleship shells and shallow water launch capable torpedos.

I believe my ATL Japanese could also have used just 6 of their 1938 800kg type 80 blockbuster bombs, delivered in surprise by 3 fake "China Clipper" Mavis flyingboats, to crack open the Panama Canal's keystone Gatun Dam on Dec.7'41.

Lunchtime in Panama (0800 on Oahu) would never be the same again.
 
Great post, great research. Here are my thoughts:
1. The IJN was leery of Pearl Harbor as it was; Panama doubles the number of attacks, doubles the chances of something going wrong, detection, etc. Of close, closing the canal is a tremendous strategic blow, so maybe it's worth it.
2. The CHITOSE is hardly a vast stragetic asset, so it's loss would be acceptable if the canal was closed.
3. Would the three bombers be enough? I don't know. What about bad weather?
4. Timing: It wouldn't have to be perfect - I mean the Phillippines had hours of warning and Mac was still caught unawares.
5. The US still wins. There's no doubt this helps, but the bulk of the fleet was still in the Pacific. Japan is toast on Dec 8th 1941; this might mean Japan lasts until later in 1945, and gets a few more a-bombs for it's trouble.

Mike Turcotte.
 
Didn't we do this last year, or was it only at tank-net where you posted this (and everyone laughed at how absurd it was)? Thread in question, looks the exact same

I don't think you ever did answer how you expected them to get a reasonable degree of success aiming at 6 small individual point targets, just hand-waving it with "Well, they got 50% hits on much larger targets at Pearl Harbor"

And there was always Paul's excellent post on page 9.

During the period running up to American attack on Panama, I led a 'Tiger Team" which crawled around the canal facilities looking for ways to sabotage it. It can be done, but not too easily.

The Gatun Dam, and its later companion, Maden Dam (also prewar) provide the water needed for the canal's operations. While they are obvious targets, they are not the weakest links in the chain. Both lakes would have naturally extended much further than they do, thanks to the use of several dozen small earthen dams. A breach in any of these would cause the lake to drain. Some of these dams are remote, maintenance teams visit them once or twice a year to inspect and prevent the encroachment of the jungle. These teams travel by boat.

A couple of sabotage teams could blow several of these dams at once, and (depending on how wildly you wish to let your imagination run) delay repair efforts. Both Madden and Gatun Lakes would have to be targeted. Madden provides a ready backup for Gatun should it alone be attacked.

The two dams are unremarkable in their construction. (Persistent stories are told that Madden Dam is an exact copy of a dam in the TVA.) Madden is a huge hunk of concrete, while Gatun is an earth-fill dam with concrete spillways. It is freakishly large and so liable to attack. But it is also an obvious target, and so during the runup to WWII protected by antiaircraft batteries. (Of course Pearl Harbor had air defense too.)

Still, a successful attack on such a dam would have been a very tough nut even large, ground-based planes, and just at the edge of silliness for a carrier-based raid. And remember, if you only take out Gatun Dam, it can be repaired and the water from Madden can be released. So you can interrupt operations, but not destroy the canal.

As for a fireship, it could have been done. It does presume a suicide crew, and that is the sort of detail that makes it tough to pull off. In the prewar period, ships from Axis powers and some neutrals were boarded and searched before being allowed transit. If these two hurdles anc be overcome, the detonation of several hundred tons at exactly the right time and place could have been catastrophic.

Repair and recover capabilities during this period were impressive. Work along the Cut never ends, but was at a higher level then than now. Further, military construction capacity in the theatre were employed in building lots of stuff all over the region. All that capacity could have been brought back to patch up the canal.

In the modern era, there are dozens of ways of causing trouble to the Canal. Some methods would effectively close the canal, but these techniques are not applicable in wartime.

Does this help?

DKTanker said it best though:
You asked for a critique yet you still are intent on having your fantasy affirmed.
 

robdab2

Banned
MikeTurcotte wrote,

1. The IJN was leery of Pearl Harbor as it was; Panama doubles the number of attacks, doubles the chances of something going wrong, detection, etc. Of close, closing the canal is a tremendous strategic blow, so maybe it's worth it.

There is no question that doing anything at all different from what was done in the OTL might increase the risk of a timely warning being deliverd to Oahu before the PH attacks. Considering the "slow as molasses" peacetime responses demonstrated on Oahu though, I can't see Panama's US defenders responding any more quickly nor getting a sleepy Oahu to quickly recognize any such advanced warning that Panama might deliver. Even the American Forces in the Philippines were caught unprepared some 8 hours AFTER the PH air strikes occured. AFAIK, the American military in the Pacific was largely "asleep at the wheel" for that last peacetime weekend.

2. The CHITOSE is hardly a vast stragetic asset, so it's loss would be acceptable if the canal was closed.

Considering that she would be awaiting her returning fake "China Clippers" in the Galapagos, some 855 nmiles west of Panama, while being protected by 2 IJN submarines and several of her own seaplane fighter aircraft, how might she be lost ?

Panama's Pacific defenders only had 12 PBYs of which only 4 flew long range Pacific sector searches each day, without on board radar. Out of the 70+ radar birds needed to do that job well. Those 4 flew without bombs/torpedos in order to maximize their fuel loads. The other 8 were sidelined for aircraft repair and aircrew rest each day.

A scenario variation could see her running west at 29 knots right after the dawn launch of her 3 fake Mavis. She would then be 7x29 = 200 nmiles west of the Galapagos when the first 800kg bomb fell. As was planned by the OTL Japanese at PH, the 2nd of her 3 submarines would have instead been ordered east towards a rendezvous point nearer to Panama to pickup the survivors of her 3 flyingboat aircrews.

3. Would the three bombers be enough? I don't know.

Neither do I for sure. I have been unable to locate cratering data for Japan's 800kg type 80 bombs but such data for US 2,000lb GP bombs dropped from only 1,000' indicates that one hit in the right place would have started the water flow thru that dam's weakspot. 1 hit out of 6.

What about bad weather?

The weather is never guaranteed but Panama's Pacific coast rainy season predictably delivered ultra high humidity hazy sunny mornings followed by heavy early afternoon downpours. Ideal for my 3 fake "China Clippers". Sunny for their approach navigation, hazy so that any other aircraft would not get a good view of their details in the distance and with heavy cloud cover to mask their escape after bomb drop.

4. Timing: It wouldn't have to be perfect - I mean the Phillippines had hours of warning and Mac was still caught unawares.

True but my ATL Japanese atackers wouldn't have that hindsight knowledge. Those 3 "Clipper" pilots would be ordered to NOT drop their bombs before 1300 Panama time NO MATTER WHAT, so as to minimize any chance of Oahu being warned. Later than 1300 would mean more risk for the 3 Mavis crews but the OTL PH air raids could NOT be risked.

5. The US still wins. There's no doubt this helps, but the bulk of the fleet was still in the Pacific. Japan is toast on Dec 8th 1941; this might mean Japan lasts until later in 1945, and gets a few more a-bombs for it's trouble.

With the benefit of 20/20 hindsight, quite true. I've never suggested otherwise. It is hard to trump US submarines (once they have a working torpedo) and firebombing B-29s let alone (2) A-bombs, with more "in the pipeline".

Without hindsight my 1941 ATL Japanese war planners could not know that those were all under development so I think it not too "off the wall" an idea that they might have hit the Panama Canal in a further attempt to bluff the US into an early ceasefire. Especially if the most likely cost was just 3 flyingboats.
 

robdab2

Banned
Mote wrote,

Didn't we do this last year, or was it only at tank-net where you posted this

My previous scenario proposed a 3 Mavis launched 6 torpedo attack on the Gatun spillway's 14 steel gates rather than a 6 bomb attack on the Gatun Dam itself. Similar but not identical.

I hope to access a wider/different field of knowledge here at the Alternate History Discussion Board.

I don't think you ever did answer how you expected them to get a reasonable degree of success aiming at 6 small individual point targets, just hand-waving it with "Well, they got 50% hits on much larger targets at Pearl Harbor"

This ATL scenario proposal calls for dropping 6 bombs on just 1 dam target point weakspot. My readers here will have to decide for themselves if they think that the Japanese could achieve that level of bombing accuracy, or not.

And there was always Paul's excellent post on page 9.

As I responded to Paul at the time, my 3 "China Clippers" could indeed have been used to fly in 3 teams of "suicide demolition engineers" with their explosives, except for two facts of that time.
1.) Yamamoto had ordered that none of his Pearl harbor attacks be intentionally designed as suicide missions. I follow that order for my ATL Panama attack planning. There must be a reasonable way home for my ATL Japanese even if, as some did at PH, a wounded pilot might voluntarily choose to crash his big 4 engined warplane into say, a dam's electrical generation powerhouse.
2.) AFAIK there were no early war historical examples of the Japanese using any such airborne commando style raiders. There were JSNLF parachute battalions used in Feb. '42 IIRC but they were not historically trained by Dec.7'41. They jumped months later with the intent of being relieved by IJA ground troops, not with the intent of deliberately dying there.

You asked for a critique yet you still are intent on having your fantasy affirmed.

Why would I not explain/defend my ATL scenario proposal here ? Is this not a site named the ALTERNATIVE HISTORY DISCUSSION BOARD ?

Thanks for joining in that very discusion.
 
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Why would I not explain/defend my ATL scenario proposal here ? Is this not a site named the ALTERNATIVE HISTORY DISCUSSION BOARD ?

Thanks for joining in that very discusion.

You missed the point of that comment. There is a wide difference between "discussion and critique" and your continual attempts to promote something while ignoring all of the very valid critiques mentioned.

Looking at your proposed target, you're trying to hit a pair of small point targets with only six bombs (and relying upon the defenders to be entirely asleep in order to do this) and doing so by means of horizontal bombing. Not exactly the world's easiest thing to do and probably outside of the skill (not to mention a plan that is doomed to failure if there are any clouds, fogs, etc.) of the pilots given the technology of the day.

The destruction of the spillway in Fleet Problem 1 looks to be administrative, not necessarily realistic.

Still think that the Mavis delivery is an absurd cover that wouldn't fly with the Americans nor prevent them from sending a ship to watch and make sure they didn't do anything. Especially once they ask pointed questions of why they're painted in PanAm colors when they're a military shipment or indeed why they're being taken by tender at all instead of just flying there.
 
I see nothing wrong with this ending in a failed attack on Panama. Why not?

The Japanese are trying to hit a 1% chance of success, they don't hit it but they scare the USA into putting more forces on defense.

Let's not kid ourselves, however, into turning this kind of shoestring operation into a winning move. This is an error that will probably lead to the loss of all units involved; if the IJN wants to lose they can make this kind of loser move that bombs a giant hunk of concrete and fails due to all of the backups and controls in place.

Considering that this would involve taking away forces that would have to be otherwise dedicated to Japan's very successful operations elsewhere, I think this is one of the options that leads to a shorter and easier Pacific War.
 
If the Japanese had come up with the following aircraft carrying Submarine earlier then maybe they could have used it at the beginning of there war with the US against the Panama Canal.

Sentoku Type (I-400, I-401, I-402)

Main article: I-400 Class Submarine




Sentoku Type (I-400, I-401, I-402)
Main article: I-400 class submarine
An I-400 class submarine

The Sentouku I-400 class displaced 5223 tons surfaced and measured 400 ft 3 in (122m) overall. They had a figure-eight hull shape for additional strength to handle the on-deck hangar for housing the three Seiran aircraft. In addition, they had four anti-aircraft guns and a large deck cannon as well as eight torpedo tubes from which they could fire the 21 inch (53cm) Type 95 torpedo.

Three of the Sen Toku were built (I-400, I-401, and I-402). Each had four 1825 horsepower (1360 kW)[3] engines and range 37,500 nm at 14 knots (26 km/h).

The submarines were also able to carry three Aichi M6A Sei ran aircraft, each carrying an 800 kilogram (1764 lb) bomb 550 nautical miles (1,020 km) at 360 miles per hour (580 km/h). To fit the aircraft in the hangar the wings of the aircraft were folded back, the horizontal stabilizers folded down, and the top of the vertical stabilizer folded over so the overall profile of the aircraft was within the diameter of its propeller. A crew of four could prepare and get all three airborne in 45 minutes launching them with a 120 foot (37 m) catapult on the fore deck of the giant submarine.
Each submarine had four 3,000 horsepower (2.2 MW) engines and fuel enough to go around the world one-and-a-half times, more than enough to reach the United States from either direction. It displaced 6,500 tons and was over 400 feet (120 m) long, three times the size of ordinary submarines. It had a figure-eight hull shape for additional strength to handle the on-deck hangar for housing the three sei ran aircraft. In addition, it had four antiaircraft guns and a large deck cannon as well as eight torpedo tubes from which they could fire the Long Lance
Before the War ended the Japanese had a plan to use that Submarine against the Panama Canal.
Read story on "the world’s first purpose-built underwater aircraft carrier":
http://www.historynet.com/japans-panama-canal-buster.htm
 
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robdab2

Banned
Blue Max writes,

The Japanese are trying to hit a 1% chance of success, they don't hit it but they scare the USA into putting more forces on defense.

Whether a success or a failure, the mere attempt on the Canal would certainly further worry an American military and public already greatly upset by the OTL Pearl Harbor attacks.

Let's not kid ourselves, however, into turning this kind of shoestring operation into a winning move. This is an error that will probably lead to the loss of all units involved;

I can certainly see the 3 Mavis being dispatched by USAAF fighter aircraft after bombing the Gatun Dam but what American weaponry do you suggest would be able to finish off the Chitose, 3 IJN submarines and the two Japanese tankers in distant support ?

if the IJN wants to lose they can make this kind of loser move that bombs a giant hunk of concrete and fails due to all of the backups and controls in place.

Except that my ATL scenario proposes the low altitude 800 kg bombing of the earthfill dam BESIDE that concrete spillway structure, not on the concrete spillway itself. AFAIK there were no "backups and controls in place" to deal with that type of attack.

Please describe for us, the details of all the ones that your research has uncovered.

Considering that this would involve taking away forces that would have to be otherwise dedicated to Japan's very successful operations elsewhere, I think this is one of the options that leads to a shorter and easier Pacific War.

As my initial shoestring attack posting describes:
The 2 tankers were otherwise idle.
The Chitose's OTL mission at Mindanao could be done instead by the CVL Zuiho which only sailed with the Combined Fleet's battleline out and around the Bonin Islands.
The three IJN submarines come from the 30 attached in the OTL to Nagumo's Hawaiin raid.

I don't see any of them being re-directed to Panama as likely changing the OTL historical outcomes of any other early war Japanese operations.

Why do you feel that such might be the case ?
 
Panama Canal, obviously, has a lot of naval traffic.

If the Japanese are moving with this kind of force in advance of December 7th, they have an excellent chance of getting spotted, including the Chitose in this adventure.

Furthermore, the USA has the Japanese codes cracked. This attack hinges on surprise and non-detection; the Chitose happening to be at the Galapagos Islands...

Do the Japanese even KNOW all of the information you are presenting here? Would they even know what dam to hit? This is an a time where bomber wings often didn't hit the right CITY. I guess Japan could make the attempt, but given that you are throwing three bombers (none of which has the pinpoint accuracy, and probably not even the needed intelligence) to make this call, they'd flub the first attempt and get shot out of the sky for their trouble. If the Japanese Fleet happens to be at the Galapagos Islands, Quito will simply tell Washington that on Pearl Harbor Day.

That force is probably not going to get home alive. Even if they do, all they've done is divert a modicum of forces to Panama...
 
If the Japanese had come up with the following aircraft carrying Submarine earlier then maybe they could have used it at the beginning of there war with the US against the Panama Canal.


Metro,

Yes, those could have been possibly built earlier and used. In fact, the IJN already has seaplane-carrying submarines in 1941. In the thread which spun off this one, A More Coordinated Pearl Harbor Attack or some such, I wrote about the A1 and B1 classes and the aborted 1945 attack using the I-400s. Robdab2's use of Chitose allows for larger planes carrying bigger bombs however.

Returning to Robdab2's idea, while I believe the Japanese might have been able to plan such an operation, I must agree with the other posters' comments regarding the plan's chances. The idea of Chitose reaching the Galapagos unobserved and/or unbeknownst to the US, let alone the chances of damaging the spillway significantly enough to drain Gatun, are close to nil.

Chitose and her escorting submarines can make it to the eastern Pacific, they may be able to launch the flyingboats, they may even be able to get home, but the chance of effecting the Canal's operation are below 1%. That chance of success, in my opinion, that makes it wholly unlikely that the IJN command will approve the operation. Nearly anything is possible, however but few things are plausible.

Some comments:

- With tensions so high between Japan and the US in 1941, the USN made great efforts to locate IJN warships through radio intecepts, "hum-int", and plain old patrolling. With the exception of the Pearl strike force which was observing radio silence and whose assets' presence was indicated elsewhere by deliberate broadcasts, the USN was almost completely successful in that effort.

- Steaming to the west coast of South America on what is supposedly a peaceful delivery of seaplanes, Chitose wouldn't even be observing radio silence and couldn't benefit from the deceptive broadcasts as the Pearl strike force did. When Robdab2 asks What world power would be greatly worried about 1 lone seaplane tender on an announced peacetime flyingboat delivery mission many miles away from it's outposts? the only plausible answer can be, given the tensions of the time, Any world power with a room temperature IQ.

- The US had been "jumpy" with regards to the Canal since before it's construction was complete. As Robdab2 correctly points out, fleet problems had examined attacks on and defense of the Canal since 1928. During November and December of 1941 the US might not have been at war, but it was also far from being at peace. Expecting the US to allow a unit of the Imperial Japanese Navy to visit, announced or not, the west coast of South America without being monitored in some fashion is expecting the US to be far too stupid for far too long. Yes, Pearl Harbor was surprised and MacArthur failed to heed the warnings given him, but expecting the Canal Defense Command to complete such a "trifecta of stupidity", especially after the reaming the same command had been given over defense preparations that very summer, is simply asking too much.

- Assuming Chitose is able to loiter off the Galapagos, assuming she is able to launch the three flying boats, assuming they reach the Gatun Dam unmolested, and assuming they damage the spillway, it still doesn't necessarily follow that Gatun Lake will be drained or that the operation of the Canal effected. For those of you who haven't yet read the information regarding dams, spillways, and the Gatun Dam's role in the Canal let me use these rough analogies.

- A spillway acts like that hole or slit near the top of your bathroom sink. When the water in your sink gets too high, it flows through the hole and prevents the sink from overflowing. A spillway works the same way for a dam. In the case of an earthen dam like Gatun, the spill way is concrete-lined to combat erosion; you don't want the overflow eating into the dam as it flows away. So that the spillway can used at nearly anytime, the surface of the Gatun Lake is kept 15 feet or so higher than the top of the spillway. Huge gates are then used to keep the lake from passing over the spillway.

- The Gatun Dam and the lake behind it act like the tank on the back of your toilet. They store the water that allow the Canal's locks to function just as the tank stores the water that allows your toilet to function. Each time a ship transits the Canal something like 50 million gallons of water are used in the locks and that water comes from the lake.

- Damaging the spillway will result in a loss of water in the Gatun Lake. However, all the water in the lake will not necessarily be lost. The lake's designed depth is roughly 90 feet, the top of the spillway is 16 feet lower than that, which leaves 74 feet of water below the spillway. If the bombs damage a gate, the lake could drop to 74 feet. Drops in depth after that will depend on where the bombs hit with lower hits releasing more water. However, the lower we go on the spillway, the thicker the dam is behind it and the harder it will be to cause a fracture. So the easier fractures will release less water and be less likely to effect the operation of the Canal.

- Next we need to look at repair capabilities. It won't be necessary to return the spillway to full operation in order to return the Canal to full operation. All you need do is plug the holes. When you remember that earth moving on a massive scale is still a daily chore within the Canal in 2009, you'll realize that the US will have all the means to rapidly plug the leaks in the spillway on it's fingertips.


Summing up, while Robdab2's idea is a nice one, and a nicely detailed one too, I must agree with the posters here and elsewhere that it is essentially a non-starter. The chances of the mission succeeding is nearly nil, the spillway is too hard to damage in any meaningful way, the US defenses at the Canal are not idiots, the deceptions involved with the mission are not enough, and the assets used for the mission will do far better good on other missions in other places. The Japanese of 1945 may have seen this as a worthwhile gamble and did launch something akin to it, but the Japanese of 1941 are not that desperate yet. They would not have taken such a gamble with such a negligible rate of return.

It's a nice idea and a well put together idea, but a wholly implausible idea, I'm afraid. :(


Bill
 
Except that my ATL scenario proposes the low altitude 800 kg bombing of the earthfill dam BESIDE that concrete spillway structure, not on the concrete spillway itself. AFAIK there were no "backups and controls in place" to deal with that type of attack.


Robdab2,

That earthen dam has to following dimensions according to Wiki:

The gap is filled by an earth dam, 640 metres (2,100 ft) thick at the base, 2,300 metres (7,500 ft) long along the top, 121 metres (400 ft) thick at the water level, and 30 metres (98 ft) thick at the top, which is 9 metres (30 ft) above the normal lake level.

What are 800lb bombs going to do to 30 or more meters of rammed earth?

This is a nice idea and you put a lot of work into it, but it just doesn't work. I'm sorry it doesn't, very sorry as a matter of fact, but it just doesn't work.


Bill
 

robdab2

Banned
Mote writes,

You missed the point of that comment. There is a wide difference between "discussion and critique" and your continual attempts to promote something while ignoring all of the very valid critiques mentioned.

Mote, I don't think so. Your pointing out my previous thread on another discussion board proves that your statement is not at all true. I evaluated the critiques discussed on that other board and have presented a modified bombing scenario here, rather than a torpedo attack scenario as was done there.

Looking at your proposed target, you're trying to hit a pair of small point targets with only six bomb

Actually only one small area target, not a pair of point targets.

(and relying upon the defenders to be entirely asleep in order to do this)

That seems to have worked out ok for the OTL Japanese over most of Oahu.

and doing so by means of horizontal bombing. Not exactly the world's easiest thing to do and probably outside of the skill (not to mention a plan that is doomed to failure if there are any clouds, fogs, etc.) of the pilots given the technology of the day.

Tell that to the crew of the USS Arizona.

The destruction of the spillway in Fleet Problem 1 looks to be administrative, not necessarily realistic.

I didn't present that 1932 Fleet Problem as an example of what the Japanese might accomplish in 1941 but rather as an acknowledgement that the American KNEW that the Gatun Spillway was a target for anyone that might want to stop Canal operations.

Still think that the Mavis delivery is an absurd cover that wouldn't fly with the Americans nor prevent them from sending a ship to watch and make sure they didn't do anything.

You are certainly entitled to your own opinion but I would point out that FDR had specifically ordered that Japan would be allowed to make the first move in any upcoming war. Intercepting an IJN warship, on a legal mission, in International waters, thousands of miles from the nearest US territory could EASILY escalate into just the kind of Causus Belli that FDR feared Japan was looking for.

AFAIK USN commanders of 1941 were not eager to ignore direct Presidential orders.

Especially once they ask pointed questions of why they're painted in PanAm colors when they're a military shipment

My initial posting #1 included, "Please compare for yourself at http://www.warbirdphotographs.com/NavyJB&W/H6K-8s.jpg and http://www.flyingclippers.com/S42.html . Both with 4 engines and twin tail fins." so that you could see for yourself the minimal PanAm cliper markings in use at the time. I see no great difficulty for the Chitose's crew to paint fake windows and registration numbers on the 3 Mavis only as that ship neared the Galapagos Islands.

or indeed why they're being taken by tender at all instead of just flying there.

Perhaps a brief analogy might help ? If I were to exchange much cash for a brand new Volkswagon Beetle (all of which are built inn Mexico these days) would I want it to be highway driven all the way to Canada for delivery to me, as a new car ? I think that I'd prefer that a nice safe combination of railway carriage and car transport truck be used to get it to me instead.

Long range flights over the Pacific were still a dangerous task in 1941 and even a Mavis didn't have the range to fly direct from Japan to Argentina.

I don't think you ever did answer how you expected them to get a reasonable degree of success aiming at 6 small individual point targets, just hand-waving it with "Well, they got 50% hits on much larger targets at Pearl Harbor"

Sorry for my delay in responding to this earlier point of yours but I needed to access my records on my home computer to properly respond to your torpedo vs spillway gate question from a previous thread discussion.

I direct your attention to page #99 of http://books.google.ca/books?id=WOyJD1_PcIwC&pg=PA98&lpg=PA98&dq=%22Hwachon+Dam%22&source=bl&ots=9MsCJNO9dp&sig=QY3f40CNwXmizEhPo37IeyYwzYg&hl=en&ei=3SeUSf6tHsSJmQfUyL2VCg&sa=X&oi=book_result&resnum=5&ct=result#PPA99,M1
which details the 1951 torpedo attack (using WW2 vintage Mk13 torpedos) by US pilots on Korea's Hwachon Dam. Despite the handicap of never before having trained on dropping any torpedo, those airmen holed 3 of that dam's steel gates. Considering the hours of torpedo practise undertaken by the Kido BUtai's pilots prior to the PH attacks, I don't think it unrerasonable to suppose that 3 Mavis crews might also have been highly trained in precision torpedo attacks before being sent to attack the Panama Canal. Not that such would seem to have been necessary given that US experience in Korea.

Realtime video footage of that actual Korean dam torpedo attack is available for purchase at http://www.militaryvideo.com/store/store.cfm?titleID=CARRIERSKOREA&do=detail for the truely skeptical. 'Tis interesting.
 

robdab2

Banned
Blue Max typed,

Panama Canal, obviously, has a lot of naval traffic.

Really ?

Over the entire 1941-45 period the average was only 14 transits per day

If the Japanese are moving with this kind of force in advance of December 7th, they have an excellent chance of getting spotted, including the Chitose in this adventure.

Blue, forgive me for pointing this out but in this ATL scenario she isn't trying to hide, at least initially. Her aircraft delivery route and schedule would be PUBLISHED and her regular radio transmissions would allow the American RDF types to accurately track her progress across the Pacific towards Argentina.

Furthermore, the USA has the Japanese codes cracked.

AFAIK at this time, only Japan's diplomatic codes were an open book to the Americans. In any case, what great naval secrets would Chitose have to broadcast back to Tokyo other than something vague like, "Progress on schedule, mission ok." I can't imagine her broadcasting something like, "BANZAI, BANZAI, WE ATTACK THE PANAMA CANAL THREE DAYS FROM NOW !! BANZAI, BANZAI". Can you ?

This attack hinges on surprise and non-detection; the Chitose happening to be at the Galapagos Islands...

Sorry but what was your point here ?

Do the Japanese even KNOW all of the information you are presenting here ?

I believe so or I wouldn't have presented it.

I think that including sources greatly forwards a discusion since details AND CONTEXT can be checked by any reader here. You might consider trying it.

Please see http://www.ibiblio.org/pha/pha/magic/x12-0022.html for transcripts of American intercepts from Panama's Japanese spy contingent. Please carefully note that the interception dates and the code breaking/translation dates are often MUCH seperated. 'Tis interesting to speculate on just how many other messages were missed by the Americans. It certainly shows that the Japanese network was widespread in Panama and could find out much about the American Canal defenses.

Would they even know what dam to hit?

I believe so or i wouldn't be suggesting that in an ATL scenario.

Please see "Report from the foreign resident,NO8" from
http://jpimg.digital.archives.go.jp/kouseisai/word/pqrs.html for a 1913 record of a Japanese inspection visit to the then still under construction Gatun Dam. The record is stored in the Japanese National Archives and clearly shows that the Japan was gathering important military information about the Panama Canal even BEFORE it was completed.

Japan's engineers weren't at all stupid.

This is an a time where bomber wings often didn't hit the right CITY.

I believe that you forget that Fuchida historically used peacetime American commercial radio station homing to guide his 1st wave KB strike force towards Honolulu before hitting Pearl Harbor. Confirmation can be found in Prange's ADWS if you'd like to stretch yourself ?

Panama had at least three peacetime commercail radio stations in December 1941, all likely to be broadcasting from about dawn. Ideal for a Mavis aircrew to use to triangulate their exact position if cloud cover was heavy, although such was unlikely for a typical rainy season morning there.

Please, try to remember that Mavis aircrews regularly flew 2,000+ nmile recon. missions over open Pacific ocean distances where their very lives depended on their pinpoint navigation skills.

The ATL hop that I propose is but 855 nmiles (only 805 being over water) and comes with peacetime American radio station homing already provided gratis. I have no doubt at all that my 3 fake "China Clippers" would find the Gatun Dam, on schedule.

I guess Japan could make the attempt, but given that you are throwing three bombers (none of which has the pinpoint accuracy, and probably not even the needed intelligence) to make this call, they'd flub the first attempt and get shot out of the sky for their trouble.

You are certainly entitled to your own opinins but so far, they don't seem to be supported by any verifyable sources.

If the Japanese Fleet happens to be at the Galapagos Islands, Quito will simply tell Washington that on Pearl Harbor Day.

A simple Wiki check at http://en.wikipedia.org/wiki/Gal%C3%A1pagos_Islands would have revealed to you that the Galapagos Islands are a large spreadout archapeligo of many islands, large and small.
"The Galapagos Archipelago consists of 7,880 square km (3,042 sq. miles) of land spread over 45,000 square km (28,000 miles) of ocean." And: "The group consists of 13 main islands, 6 smaller islands, and 107 rocks and islets."

I believe that in a time of difficult communications and on a sparsely settled and poor archipeligo consisting of 126 bits of land, my ATL Chitose could have found some deserted cove to anchor in overnight, without being detected by anyone in a position to radio Quito.

That force is probably not going to get home alive. Even if they do, all they've done is divert a modicum of forces to Panama...

Whatever.
 

robdab2

Banned
That earthen dam has to following dimensions according to Wiki:
The gap is filled by an earth dam, 640 metres (2,100 ft) thick at the base, 2,300 metres (7,500 ft) long along the top, 121 metres (400 ft) thick at the water level, and 30 metres (98 ft) thick at the top, which is 9 metres (30 ft) above the normal lake level.

What are 800lb bombs going to do to 30 or more meters of rammed earth?

This is a nice idea and you put a lot of work into it, but it just doesn't work. I'm sorry it doesn't, very sorry as a matter of fact, but it just doesn't work.

Bill, perhaps you would be convinced if you actually read my posting #1 and then LOOKED at the images that I sourced there ?

I am glad that you have finally figured out that my ATL bomb attack is directed at the earthen dam section BESIDE the concrete spillway rather than AT the concrete spillway itself. Why then did you post Wiki dimensions for the main Gatun Dam rather than for the section BESIDE that concrete spillway ?

Wrt your dam dimensions, even one look at http://www.autoridaddelcanal.gob.pa/eng/plan/multimedia/photos/target32.html which I provided in my posting #1 would have clearly indicated to you that the dam's thickness and height were/are greatly reduced immediately BESIDE the concrete spillway. That small weakspot IS THE TARGET that I intended for Japanese bombing, not the main body of the dam itself.
 
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?

:confused::confused::confused::confused::confused:

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.

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?

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.
 
Bill, perhaps you would be convinced if you actually read my posting #1 and then LOOKED at the images that I sourced there ?


Robdab2,

I did look over your photos. As I said more than once, your research is very impressive. I'm just drawing different conclusions from the same facts, that's all.

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.

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.

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?

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. 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.

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

We'll have to agree to disagree.


Bill
 

robdab2

Banned
Bill Cameron replied with the deeply flawed,

Returning to Robdab2's idea, while I believe the Japanese might have been able to plan such an operation, I must agree with the other posters' comments regarding the plan's chances. The idea of Chitose reaching the Galapagos unobserved and/or unbeknownst to the US, let alone the chances of damaging the spillway significantly enough to drain Gatun, are close to nil.

Bill, as I have mentioned several times now, my bombing attack is not at all directed at the concrete spillway but rather at the much thinner earthen dam section immediately BESIDE it.

Chitose and her escorting submarines can make it to the eastern Pacific, they may be able to launch the flyingboats, they may even be able to get home, but the chance of effecting the Canal's operation are below 1%. That chance of success, in my opinion, that makes it wholly unlikely that the IJN command will approve the operation. Nearly anything is possible, however but few things are plausible.

Perhaps the scenario wiould seem more plausible if you actually READ IT ?

Some comments:

- With tensions so high between Japan and the US in 1941, the USN made great efforts to locate IJN warships through radio intecepts, "hum-int", and plain old patrolling. With the exception of the Pearl strike force which was observing radio silence and whose assets' presence was indicated elsewhere by deliberate broadcasts, the USN was almost completely successful in that effort.

Just as I intend that they would be completely successful in tracking Chitose and later, her submarine replacement broadcasting deliberately to indicate her presence elswhere other than near the Galapagos. I include the historical deception techniques used by the OTL Japanese in my ATL scenario in the pursuit of more realism.

- Steaming to the west coast of South America on what is supposedly a peaceful delivery of seaplanes, Chitose wouldn't even be observing radio silence and couldn't benefit from the deceptive broadcasts as the Pearl strike force did. When Robdab2 asks What world power would be greatly worried about 1 lone seaplane tender on an announced peacetime flyingboat delivery mission many miles away from it's outposts? the only plausible answer can be, given the tensions of the time, Any world power with a room temperature IQ.

Umm Bill,

Your comments might carry more weight if you realized that Argentina is situated on the SOUTHEASTERN coast of South America rather than on it's western side. Perhaps an atlas or Wiki might help ...

Also, if you had actually READ my ATL scenario posting #1 you would know that my Chitose would indeed benefit from ongoing deceptive radio broadcasts from one of her bodyguard submarines.

- The US had been "jumpy" with regards to the Canal since before it's construction was complete. As Robdab2 correctly points out, fleet problems had examined attacks on and defense of the Canal since 1928. During November and December of 1941 the US might not have been at war, but it was also far from being at peace. Expecting the US to allow a unit of the Imperial Japanese Navy to visit, announced or not, the west coast of South America without being monitored in some fashion is expecting the US to be far too stupid for far too long. Yes, Pearl Harbor was surprised and MacArthur failed to heed the warnings given him, but expecting the Canal Defense Command to complete such a "trifecta of stupidity", especially after the reaming the same command had been given over defense preparations that very summer, is simply asking too much.

My ATL scenario includes publication of a Chitose schedule and route that has her sailing around Cape Horn, at the southern tip of South America (for those geographically challenged as Bill seems to be) before turning north to Argentinian ports. The deliberate and historically used radio deception techniques that I have included should satisfy the American (as they did in the OTL SEA) need for monitoring her location.

The continuously expanding American Neutrality Patrol (directed against German commerce raiders) around South American shores was well known to the entire world and so it's 300 miles offshore limit would be carefully avoided by both Chitose and my fake Chitose radio deception I-boat.

- Assuming Chitose is able to loiter off the Galapagos, assuming she is able to launch the three flying boats, assuming they reach the Gatun Dam unmolested, and assuming they damage the spillway, it still doesn't necessarily follow that Gatun Lake will be drained or that the operation of the Canal effected. For those of you who haven't yet read the information regarding dams, spillways, and the Gatun Dam's role in the Canal let me use these rough analogies.

Yet again, I don't intend to bomb the concrete spillway but rather the thinner earthen dam section BESIDE the concrete spillway.

- A spillway acts like that hole or slit near the top of your bathroom sink. When the water in your sink gets too high, it flows through the hole and prevents the sink from overflowing. A spillway works the same way for a dam. In the case of an earthen dam like Gatun, the spill way is concrete-lined to combat erosion; you don't want the overflow eating into the dam as it flows away. So that the spillway can used at nearly anytime, the surface of the Gatun Lake is kept 15 feet or so higher than the top of the spillway. Huge gates are then used to keep the lake from passing over the spillway.

In this case the concrete sill of the Gatun Spillway was built at an elevation of 69' above sea level. 14 steel gates, each 45' wide by 20' high were mounted above that elevation and were used to maintainn the normal level of Gatun Lake at 85' asl. Towards the mid-December end of the rainy season, it's level was allowed to rise to 87.5' asl in order to retain more rainwater for dry season Canal usage.

- The Gatun Dam and the lake behind it act like the tank on the back of your toilet. They store the water that allow the Canal's locks to function just as the tank stores the water that allows your toilet to function. Each time a ship transits the Canal something like 50 million gallons of water are used in the locks and that water comes from the lake.

Please note that in 1932 the smaller Madden Dam was built in Panama's mountains above Gatun Lake in an effort to store even more of Panama's rainwater. It also provides a third hydro-electric power source for the Canal and Panama's military & civilian populations, in that order.

- Damaging the spillway will result in a loss of water in the Gatun Lake. However, all the water in the lake will not necessarily be lost. The lake's designed depth is roughly 90 feet, the top of the spillway is 16 feet lower than that, which leaves 74 feet of water below the spillway. If the bombs damage a gate, the lake could drop to 74 feet. Drops in depth after that will depend on where the bombs hit with lower hits releasing more water. However, the lower we go on the spillway, the thicker the dam is behind it and the harder it will be to cause a fracture. So the easier fractures will release less water and be less likely to effect the operation of the Canal.

Here we disagree. Nothing less than several Barnes-Wallis style "dambuster" bombs, which weren't even perfected by the British until 1943, was going to break the thick mass concrete of the Gatun Spillway below 69' asl, the level reached after the loss of the spillway's steel gates.

The canal was kept dredged to a depth of 40' asl with a minimum 2' safety margin in case the area's regular landslides should send rock into the Canal and reduce it's navigation depth. Ship's propellers and rudders don't respond well to being dragged thru rocks.

Thus the Canal had a usual navigation depth of 85'asl - 40'asl - 2' safety margin = 43' although it could indeed be deeper in some flooded valley sections of Gatun Lake
At the end of the rainy season that was increased to 87.5'asl - 40'asl - 2' safety margin = 45.5'

My previous torpedo attack scenario, which MOTE pointed out, was ultimately rejected because a torpedo attack on the 14 steel spillway gates could only, at best, reduce the canal's navigation depth to 69'asl - 40' asl - 2' safety margin = 27' which is still deep enough for most American carriers if lightened by their flying off aircraft etc. for the duration of their transit

- Next we need to look at repair capabilities. It won't be necessary to return the spillway to full operation in order to return the Canal to full operation. All you need do is plug the holes. When you remember that earth moving on a massive scale is still a daily chore within the Canal in 2009, you'll realize that the US will have all the means to rapidly plug the leaks in the spillway on it's fingertips.

Once again, my ATL scenario does NOT intend the concrete spillway to be a bombing target. Rather the thinner and very erodable earthen dam section BESIDE the concrete spillway will be broken thru to allow water flow as per the Baldwin Hills dam failure video that I sourced earlier.

In such a case there won't be nearly enough time to even begin to "plug the holes" before that rapid water flow cuts down thru the Gatun Dam's earthfill mass.

While destroyed by a foundation leak rather than a top down leak, I refer you to http://www.youtube.com/watch?v=KEdM6Ys6spA for a video view of the failure of the earthfill Teton Dam.

Summing up, while Robdab2's idea is a nice one, and a nicely detailed one too, I must agree with the posters here and elsewhere that it is essentially a non-starter. The chances of the mission succeeding is nearly nil, the spillway is too hard to damage in any meaningful way, the US defenses at the Canal are not idiots, the deceptions involved with the mission are not enough, and the assets used for the mission will do far better good on other missions in other places. The Japanese of 1945 may have seen this as a worthwhile gamble and did launch something akin to it, but the Japanese of 1941 are not that desperate yet. They would not have taken such a gamble with such a negligible rate of return.

Obviously, I find your analysis and conclusions to be fataly flawed because you have yet to actually READ my ATL scenario as proven by your elementary mistakes above. I am embarassed for you.

It's a nice idea and a well put together idea, but a wholly implausible idea, I'm afraid. :(

I believe that still remains to be determined by other actual READERS.

You have maintianed your initail approach of criticising BEFORE ACTUALLY READING my ATL scenario.
 
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