What if Japan attack both Pearl Habor and Panama canal at the same time

[tchizek]

This works great, if one can get the merchant ship with commandos in the Canal. In a strange way, on this operation, the last 100 m to the target may be the easiest part. For the limpet mine option, I would be tempted just to hire some locals, or try to have a submarine unload 10-20 Japanese divers on the Panama coast on the first day of the war.

But if I could get a merchant ship through security that was poorly searched, i would just have 30,000 lbs of explosives deep in the cargo hold that I would explode. There is no reason to get cute, if the security is that poor.

The security was not that poor. The US searched every ship, to the level of confiscating handguns and cameras. Put a pilot and escort crew aboard, offloaded the whole crew in some cases. Turned back ships with any discrepancy in their cargo manifest. Non US flagged ship sometimes sat for a week or more while they were searched. Even US flagged ships were searched fairly closely. If they found 15 tons of explosive that were not on the manifest the ship would not go anywhere near the canal.

Many ships had their whole crew and passengers get a free train ride to the other end of the canal zone in a blacked out train, while the assigned pilot and canal crew took their ship through the canal.

This would not be easy if it is even possible.

 

[Gangster]

Panama

Anyone ever seen "Across the Pacific" Humphery Bogart, Mary Astor and Sidney Greenstreet?

Subject implausable, any Panamanian who could be bribed would know that
the US would offer 10X the $$$ for any info concerning an attempt on the Canal, the Japanese would know that any discovery of their plan prior to Dec 7 even by a few hours would require the whole mission plan to be scrubbed

Study the I-400's mission and plan of attack. IN 1945!

In 1941 the whole Zone was on the alert because they understood the potential for an attack, security was paramount particluarly at the locks.

 

[Shadow Master]

Um...

Why not just send a non-japanese ship loaded with around 1,000 tons of explosivies in the hold to detonate while in a lock?

 

[tchizek]

Um...

Why not just send a non-japanese ship loaded with around 1,000 tons of explosivies in the hold to detonate while in a lock?

Because they still have to get past the inspection that checks to see what you are loaded with and if the inspector is suspects anything he can either off load you and your whole crew and send your ship through under pilot and crew of a canal crew (at best), turn you back (second best), turn you back and revoke your canal privileges so you can never use the canal again (up to an including your whole company), arrest you and your whole crew for attempted sabotage (which might be better than the previous, depending on what country you are from).

The US took the security of the Canal very very seriously. If it was that easy the Germans and the Japanese would have done it during the war.

 

[Shadow Master]

I am assuming here that explosives laden merchant ships are traveling through the canal, and thus no attempt to conceal the explosives would be needed. As for the inspection and crew offloading, how hard is it to bury a one man detonation space within a ship of a size capable of carrying the explosives? Surely the inspectors are not going to be able to board a ship, completly off load the entire cargo (including the explosives), remove the crew, and only then sail the ship through to various locks?

Or am I off base about the explosives filled merchant ships being allowed to sail the canal no matter what flag they are flying?

 

[BlondieBC]

This would not be easy if it is even possible.

I never said easy, but let me ask you this question.

If I went to Seal Team 6, ask them to come up with a plan to destroy the canal with less than 40 men using only gear available in 1942, would there answer be "Mr. President, that is impossible"?

I doubt it. And as I said earlier it takes a POD at least a year before the war, because Japan will need a special forces unit focused on the mission.

Anyone ever seen "Across the Pacific" Humphery Bogart, Mary Astor and Sidney Greenstreet?

Subject implausable, any Panamanian who could be bribed would know that
the US would offer 10X the $$$ for any info concerning an attempt on the Canal, the Japanese would know that any discovery of their plan prior to Dec 7 even by a few hours would require the whole mission plan to be scrubbed

Study the I-400's mission and plan of attack. IN 1945!

In 1941 the whole Zone was on the alert because they understood the potential for an attack, security was paramount particluarly at the locks.

Great movie. Yes, but if I was the Japanese, I would look first at the Chinese in Panama. Find someone whose relatives live in an occupied area, and explain to them that they would both get a lot of money if it worked, but their entire extended family would be tortured to death if the double crossed Japan.

I doubt you could give them the date. More likely they would simply know to execute the attack after hearing in the media that Japan and the USA was at war. And yes, any operation is a high risk gamble. The payoff is the USA Navy is split in half for weeks, and it will take months to fix the canal. The down side is the loss of surprise at Pearl, or the risk unknown to the Japanese that codebreakers would learn of the operation. To me at least, this operation looks like it is less risky than the midget subs at Pearl, which could have also blown the surprise.

Um...

Why not just send a non-japanese ship loaded with around 1,000 tons of explosivies in the hold to detonate while in a lock?

Because they still have to get past the inspection that checks to see what you are loaded with and if the inspector is suspects anything he can either off load you and your whole crew and send your ship through under pilot and crew of a canal crew (at best), turn you back (second best), turn you back and revoke your canal privileges so you can never use the canal again (up to an including your whole company), arrest you and your whole crew for attempted sabotage (which might be better than the previous, depending on what country you are from).

The US took the security of the Canal very very seriously. If it was that easy the Germans and the Japanese would have done it during the war.

I largely agree with Tchizek here. This is so obvious, it does not work baring some massive breakdown of security by the USA. To get tons of explosives past the inspection probably requires something like a custom built ship with a false bottom to hold the explosives. I can see building this in secret in Japan, but then how do I get the ship into trade patterns that don't look suspicious to America.

I think the operation is possible, but not through a direct means such as light carrier raid, sub launched air raid, or freighter full of explosives. But I do think that a smaller operation might work, if kept totally secret and done early enough, ideally on the first 24 hours after Pearl Harbor while US personnel are making the transition from peace to wartime mindset.

 

[BlondieBC]

I am assuming here that explosives laden merchant ships are traveling through the canal, and thus no attempt to conceal the explosives would be needed. As for the inspection and crew offloading, how hard is it to bury a one man detonation space within a ship of a size capable of carrying the explosives? Surely the inspectors are not going to be able to board a ship, completly off load the entire cargo (including the explosives), remove the crew, and only then sail the ship through to various locks?

Or am I off base about the explosives filled merchant ships being allowed to sail the canal no matter what flag they are flying?

It takes one spy. All these ships likely have heavily screen personnel with security checks, so no Asians, Italians, or Germans. But if a spy is planted in the right place, yes, he could blow it up. But the same can be said of any USA warship. If Japan can get a suicide agent on the USS Enterprise, then there will be a fuel/bomb accident that destroys the ship. I would rate the difficulty of this the same as getting an agent on a USA capital ship, either at sea or at harbor.

 

[Gunnarnz]

Dams were blown in Europe by single airplanes, so it seems plausible.

No, they weren't. If you're referring to the efforts of 617 Squadron against the Ruhr dams, bear in mind it took several weapons to crack each dam, all delivered to the same spot. They were also using specially designed ordnance and a carefully rehearsed flight plan, and even so the casualty rate was very high.

 

[tchizek]

I never said easy, but let me ask you this question.

If I went to Seal Team 6, ask them to come up with a plan to destroy the canal with less than 40 men using only gear available in 1942, would there answer be "Mr. President, that is impossible"?

I doubt it. And as I said earlier it takes a POD at least a year before the war, because Japan will need a special forces unit focused on the mission.

Well it involves getting Seal Team 6 which involves a POD of more like 3-5 years before the war to get the training involved.

I suspect that the answer with <40 men gear available to the Japanese that they could carry in from a covert landing based on what they would be able to know in late 1941. The Seals would not want that mission - they don't like suicide missions and that's what it would be. The Japanese equivalent of the Seals would probably take it and would probably die trying but would more than likely fail. The distances are just to great (after they get on the ground) the difference in force is just to large, the target is just to hard (as in it takes a large amount of explosives or force to damage).

This would be like asking the British Commandos to take out the The Möhne and Edersee Dams rather than sending 617 squadron after them. Similar difficulty factor.

 

[BlondieBC]

No, they weren't. If you're referring to the efforts of 617 Squadron against the Ruhr dams, bear in mind it took several weapons to crack each dam, all delivered to the same spot. They were also using specially designed ordnance and a carefully rehearsed flight plan, and even so the casualty rate was very high.

Ok, but a damn is a lot thicker than lock gate. My point was the Japanese believed a single torpedo could bust a single lock gate, so this is likely correct.

 

[Grimm Reaper]

Japan's leadership believed many things proven false during WWII and the vulnerability of the lock gates to a single torpedo was just one of them.

 

[tchizek]

Ok, but a damn is a lot thicker than lock gate. My point was the Japanese believed a single torpedo could bust a single lock gate, so this is likely correct.

It is possible that a single torpedo could damage them, These gates range from 47 to 82 ft high, depending on position, and each leaf is 7 ft thick; the heaviest leaves weigh 662 tons; the hinges themselves each weigh 16.7 t (36,817 lb). The gates interleave two leaves making the total width of the gates when closed 14 ft thick with a total weight on the order of 1500 tons.

The other problem is that to hit the gates with a torpedo they have to drop from the correct side and they only have a width of 110 feet and a maximum depth of 43-64 feet to work with and a length of only 1000 feet to drop into. So basically they are threading a needle tighter than what 617 squadron did.

 

[Gunnarnz]

Ok, but a damn is a lot thicker than lock gate. My point was the Japanese believed a single torpedo could bust a single lock gate, so this is likely correct.

If you've got a torpedo with a shaped charge warhead, you might punch a hole in it I guess. According to Wikipedia the Type 91 aerial torpedo had a warhead weighing 320kg in it's biggest version, which is a goodly quantity assuming the jet forms and propagates correctly. This is a risky assumption, though, because shaped charge warheads were in their infancy during this period. And it's hard to imagine anything else being able to punch through a gate that's 7' thick, even with the tamping effect from the water.
As tchizek has pointed out, delivering the torpedo in the first place is also a non-trivial exercise, although if the Japanese start planning the raid early enough they might be able to drill the crews adequately.

Assuming it works, however, you still have to deal with the "so what?" issue. A shaped charge punches a fairly narrow hole which would be relatively easy to slap a patch on until a more permanent repair can be made. A conventional warhead might jar the gate enough so that it can't be opened, but again this isn't going to close the lock for long.

 

[BlondieBC]

It is possible that a single torpedo could damage them, These gates range from 47 to 82 ft high, depending on position, and each leaf is 7 ft thick; the heaviest leaves weigh 662 tons; the hinges themselves each weigh 16.7 t (36,817 lb). The gates interleave two leaves making the total width of the gates when closed 14 ft thick with a total weight on the order of 1500 tons.

The other problem is that to hit the gates with a torpedo they have to drop from the correct side and they only have a width of 110 feet and a maximum depth of 43-64 feet to work with and a length of only 1000 feet to drop into. So basically they are threading a needle tighter than what 617 squadron did.

Yes, to me, the hardest two parts are not being shot down, and dropping the torpedo correctly. And they build a custom sub and planes for this operation. To be likely to work, you would need something like a B-2 bomber and laser guided munitions, and 5000 pound custom designed bomb. Building the sub was a waste of resources, and would have been a waste prewar too. But dumber things were built such as midget subs for Japan and the USS Alaska for the USA. This is why i prefer the commando option, it is just as likely to work, and taking 40 of the best Infantry out of Manchuria has no real impact on the war. And there is multiple possible targets, either the lock or sinking some ships in a narrow channel. This option is similar to the Italian frogmen and Alexander. A very few men took huge, crazy risks, and made a difference. And even a failed commando raid might get the USA move extra resources to the Canal zone. The Zeppelin raids on the UK were a total waste of resources, but the UK overreacted, so the Zeppelin probably marginally helped the Germans.

But yes, it takes a POD probably by mid-1935, something like the IJN insisting on having a Panama Canal option that did not take capital ships.

 

[tchizek]

Yes, to me, the hardest two parts are not being shot down, and dropping the torpedo correctly. And they build a custom sub and planes for this operation. To be likely to work, you would need something like a B-2 bomber and laser guided munitions, and 5000 pound custom designed bomb. Building the sub was a waste of resources, and would have been a waste prewar too. But dumber things were built such as midget subs for Japan and the USS Alaska for the USA. This is why i prefer the commando option, it is just as likely to work, and taking 40 of the best Infantry out of Manchuria has no real impact on the war. And there is multiple possible targets, either the lock or sinking some ships in a narrow channel. This option is similar to the Italian frogmen and Alexander. A very few men took huge, crazy risks, and made a difference. And even a failed commando raid might get the USA move extra resources to the Canal zone. The Zeppelin raids on the UK were a total waste of resources, but the UK overreacted, so the Zeppelin probably marginally helped the Germans.

But yes, it takes a POD probably by mid-1935, something like the IJN insisting on having a Panama Canal option that did not take capital ships.

Yup with a POD 1935ish and probably more like 150-300 men plus the cost of a couple of subs yea they can try. And maybe get the US to move more forces to the canal zone - maybe, because the US was already putting a lot of effort into the canal zone so I am not sure they would need to put much more in. Maybe, and maybe the attack would make it more likely the US would feel the need to hold on the the canal long term - after all we actually had combat there!

 

[BlondieBC]

If you've got a torpedo with a shaped charge warhead, you might punch a hole in it I guess. According to Wikipedia the Type 91 aerial torpedo had a warhead weighing 320kg in it's biggest version, which is a goodly quantity assuming the jet forms and propagates correctly. This is a risky assumption, though, because shaped charge warheads were in their infancy during this period. And it's hard to imagine anything else being able to punch through a gate that's 7' thick, even with the tamping effect from the water.
As tchizek has pointed out, delivering the torpedo in the first place is also a non-trivial exercise, although if the Japanese start planning the raid early enough they might be able to drill the crews adequately.

Assuming it works, however, you still have to deal with the "so what?" issue. A shaped charge punches a fairly narrow hole which would be relatively easy to slap a patch on until a more permanent repair can be made. A conventional warhead might jar the gate enough so that it can't be opened, but again this isn't going to close the lock for long.

The Japanese had detailed engineering diagrams, and though the canal would be shut down for 6 months. They also planned to use 800KG bombs. The so what is that the lake is draining, and if the water level goes down enough, the canal is unusable until the lake refills, presumably in 6 months.

As to the real so what, how does this impact the war effort, my guess is not much. It takes a few weeks longer for ships release from the Atlantic to reach the Pacific, some supplies have to be unloaded to use the Panama railroad or unload in the USA and moved by rail. But since most of the stuff the USA used came from the USA, it likely means a few more freighters loading in California each day compared to OTL. There could be some strange butterflies, but they don't jump out at me.

Japan's leadership believed many things proven false during WWII and the vulnerability of the lock gates to a single torpedo was just one of them.

I understand you believe this, but do you have any evidence. Can you calculate how big a bomb is required to cut through 14 feet of steel if under water? Do you have a source where the USA studied the plans post war, and determined them to be flawed? Japanese engineers believed they were vulnerable if the locks were hit them.

 

[Grimm Reaper]

BlondieBC, how about offering some evidence that the Japanese assumptions, which the IJN was never able/willing to put to the test, were correct?

 

[usertron2020]

In 1942 the Japanese tried to use one of the seaplanes to cause a forest fire in the Pacific Northwest by sneaking to the West Coast and launching it right off the shore. Obviously, it didn't work.

This attack failed for the same reason the balloon bombs did. For all of Japan's knowledge of the Jet Stream, they never bothered to study American weather patterns in the Pacific Northwest. The attacks took place in the Spring. Thatis, during the height of the rainy season.

 

[usertron2020]

The problem with this is the time it would take and the size of the "spikes" you would be talking tons or tens of tons of metal twenty or thirty feet long driven into the bottom of the canal, one would not do, you would need what you say a "bed" so what ten or twenty of these things? So shall we say 5 tons each (light I think but we can go with it), 30 feet long (short but we can go with it) weld up an array of these 30x30 with "spikes sticking up at the corners and the middle? So 4 sides, 2 cross bars, 4 up from the corners, 2 in the middle, 12x5 tons? 60 tons to weld and move to the canal. Or make them 1 ton each and hope they don't just bend when a 6000 ton freighter hits them? that's still 12 tons, even if they can do this , the Patrols would notice.

Its workable. All you need is the enthusiastic support of the US Army Corps of Engineers.

 

[tchizek]

Its workable. All you need is the enthusiastic support of the US Army Corps of Engineers.

Well it would be used to attack the "enemy" aka the US Navy so you might be able to get that support.