# Mini Subs at Pearl Harbor??



## dutchman (Aug 25, 2013)

I was watch a TV show about the attack on Pearl. They had a photo from a Japanese plane that showed what looked like a torpedo trail in the water, heading for a battleship. At the other end of the trail was a disruption in the water. They were trying to make the point that it was a mini sub. I guess when they launched their torpedo the weight change often forced the mini sub to porpose and break the surface. 
Now I had heard there was at least 4 mini subs involved in the attack. But I've never heard about them having any real effect during the attack. There was one recovered inside the harbor they think but it was scrapped without any real hard look at it. They think it was a mini sub from Japan, but there was much debris in the harbor. It was just scrap in the way, I don't thinbk they even took photos of it. 

Has anyone any information about the mini subs and what they did at Pearl ??


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## Thorlifter (Aug 25, 2013)

The sub that was captured is alive and well at the Nimitz Museum in Fredricksburg Texas. I have picture of it somewhere. I'll see if I can dig it up.


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## Njaco (Aug 25, 2013)

The crews of the subs were hailed as heroes in Japan and had several artworks done about them. I will see if I can scan some tomorrow.


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## dutchman (Aug 26, 2013)

They also said on the TV show that the torpedoes carried by the mini subs were much more powerful then the air drops from the planes. But I think they only carried 2 torps?


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## Thorlifter (Aug 26, 2013)

That's correct. 2 torpedoes and they were the entire front of the sub. This isn't my picture, but it is the one at Fredicksburg. You can clearly see the nose of the 2 torpedoes. The whole thing is made to look like it's sitting on a regular I-class sub with the lights of Hawaii in the background.


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## N4521U (Aug 26, 2013)

And I believe there was one survivor was hailed as a traitor by the IJN?

I should stay out of these historical threads!


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## pattle (Aug 26, 2013)

I think one of these subs was destroyed by a destroyer outside the harbour before the air attack.


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## Shinpachi (Aug 26, 2013)

From my brief memory,
Second lieutenant Kazuo Sakamaki had become the first Japanese POW of the Pacific War.

There were five mini-subs and ten crew. Two boats successfully entered into the Pearl Harbor but were shot and sunk.
Other two were also sunk outside the harbor. Sakamaki and his partner Kiyoshi Inagaki(Sgt.) were unable to enter the harbor as their gyrocompass was out of order.

They gave up mission and decided to return but their boat had been stranded.
They destroyed the boat and swam to the beach nearby.
Sakamaki reached but had been captured.
This news was broadcasted on radio and Sakamaki had been excluded from the scheduled 10 heros.

Sorry for my clumsy explanation.

Photo: 9 mini-sub heros.


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## GrauGeist (Aug 26, 2013)

The famous photograph showing the torpedo wakes heading toward battleship row does confirm a mini sub. There is a "back wake" of sorts that was created when the launching torpedos kicked the sub backwards.

If I'm not mistaken, that particular sub got trapped in the back bay and was later discovered in the wreckage of Navy equipment that had been damaged in a blast and then later dumped at sea.


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## Njaco (Aug 26, 2013)

...and Shinpachi beat me to the picture!  Here is the supposed deployment of the subs.

.


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## Shinpachi (Aug 26, 2013)

A nice picture of subs deployment, Chris!

Yes, Sakamaki's mini sub was carried by I-24.




dutchman said:


> I guess when they launched their torpedo the weight change often forced the mini sub to porpose and break the surface.



As you pointed out, dutchman, the mini sub was so unstable in aiming and shooting torpedos IJN was obliged to develop the human (suicide) torpedo 'Kaiten' in the last stage of war.

************************

Sakamaki wrote a book about his experience after the war and a local TV visualized it in a drama two years ago.

_View: https://www.youtube.com/watch?v=ImnKroRrHmg_ is a short clip inside the mini sub.


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## dutchman (Sep 1, 2013)

The mini subs that Japan used at Pearl Harbor. How long could they stay underwater. Without the use of snorkel if they were so equiped???


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## parsifal (Sep 2, 2013)

There were midget submarine attacks allover the PTO in the opening months of WWII including an attack into Sydney harbour in June 1942

Australia Attacked - Sydney Harbour

"The bodies of the four Japanese crewmen from the midget submarines launched by I-22 and I-27 were recovered when these two midget submarines were raised. They were cremated at Sydney’s Eastern Suburbs Crematorium with full naval honours. Rear Admiral Muirhead-Gould, in charge of Sydney Harbour defences, along with the Swiss Consul-General and members of the press, attended the service. The admiral’s decision to accord the enemy a military funeral was criticised by many Australians but he defended his decision to honour the submariners’ bravery. He also hoped that showing respect for the dead men might help to improve the conditions of the many Australians in Japanese prisoner of war camps.

and 11 June 1942]After the recovery of the two midget submarines a composite was constructed using the bow section of one and the stern of the other. It was decided to use this composite midget submarine to raise money for the Royal Australian Navy Relief Fund and the King George Fund for Merchant Sailors. The composite submarine was first put on display at Bennelong Point, now the site of the Sydney Opera House, and people paid a small fee to see it. It was then transported by truck on a 4000-kilometre journey through south-eastern Australia raising further funds. Eleven months after the submarine raid, the composite submarine was installed at the Australian War Memorial in Canberra. 

In 1968, Lieutenant Matsuo’s mother travelled to Australia to visit the spot where her son had died. During her visit she scattered cherry blossoms in the water where her son’s midget submarine had been located and later she presented a number of gifts to the Australian War Memorial.

In November 2006, part of the mystery of the midget submarine from I-24 was solved when divers discovered the wreck of the submarine off Sydney's northern beaches. We will probably never know if Lieutenant Ban and his navigator, Petty Officer Ashibe Mamoru intended to rejoin their 'mother' submarine or whether they had no intention of returning and simply scuttled their vessel".

There was also a midget sub attack in madagascar 31 may 1942, in which the Bribattleship Ramillies was extensively damaged

Imperial Submarines


30 May 1942: 

About 10 miles E of Diego Suarez. At 1740 (local), I-16 launches Ensign Iwase Katsusuke and PO2C Takada Kozo's midget submarine M-16b to penetrate the harbor. 

At 1710, about 9 nautical miles E of Diego Suarez, I-20 launches Lt Akieda Saburo and PO1C Takemoto Masami's midget submarine M-20b. At 2025, Lt Akieda fires one of his two 17.7-inch torpedoes at RAMILLIES. The torpedo holes the bulge and bottom plating opening a 30-foot by 30-foot hole in the port bulge forward of "A" turret. The battleship's electrical system suffers damage and power is lost all over the ship. The six-inch armor belt above the site of the explosion is displaced and the forward magazines and shell rooms (15-inch main caliber and 4-inch AA) flood. At 2120, while corvettes drop depth charges nearby, Akeida fires his other torpedo and sinks 6,993-ton BRITISH LOYALTY in about 65 feet of water. 

31 May 1942:
Akieda and Takemoto depart the bay and head NNW. After the midget’s battery is depleted, M-20b is beached at Nosy Antalikely (Antali Keli) islet. Lt Akieda attempts to scuttle his craft, but the charge fails to explode. Both sailors reach shore and contact natives, who arrange transport to the mainland. Akieda and Takemoto head for the recovery area near Cape Amber where I-20 is to wait for two days. 

Iwase, Takada and midget submarine M-16b go MIA. The wreck of M-16b is never found. 

1 June 1942: 
I-18, still carrying her midget submarine M-18b, finally arrives at the recovery area and joins the search. 

Around 1100, Lt Akieda and PO1C Takemoto visit Anijabe village to buy some food. While most villagers are friendly, one contacts the British hoping to get a bounty for his information. 

2 June 1942: 
Amponkarana Bay (12-00S, 49-12E). In the morning. Lt Akieda and PO1C Takemoto are intercepted by Royal Marines' Commando No. 5 after the Japanese had made 48 miles on foot. During an ensuing gunfight both Japanese sailors and one Marine are killed. A watch and a pack of cigarettes with IJN markings are found, as well as a report addressed to the CO of I-20. 

That same day. the body of an unidentified IJN sailor, presumably M-16b's Iwase or Takada, is found on a beach off Diego Suarez. 

Destroyer HMS DECOY arrives with Constructor Captain H. S. Pengelly, RCNC, Fleet Constructor Officer, Eastern Fleet, aboard. Pengelly inspects HMS RAMILLIES and confirms she is fit for sea. however it will be many months before she is again operational. 

3 June 1942: 
After the other mother submarines depart the recovery area, I-20 surfaces and unsuccessfully tries to contact the midget submarines by firing flares and sending radio signals. At 1800, I-20 leaves the recovery area. 

Temporary repairs of HMS RAMILLIES are completed and she departs for Durban. 

9 June 1942: 
Mozambique Channel. The day after sinking Norwegian steamer WILFORD, LtCdr Otani Kiyonori, skipper of I-18 orders midget submarine M-18b jettisoned. 

1972: 
A makeshift monument is erected at the place where Akieda and Takemoto perished. 

10 November 1976: 
The Japanese Embassy erects a plaque at the same place with a text in both French and Japanese that says: "Here died two brave Japanese sailors on 3 June 1942". 

3 July 2001: 
Japan. The Japanese Maritime Self-Defense Force (JMSDF ) erects a monument to the four midget crews. Present are the crew of JMSDF training vessel KASHIMA and the ceremony is led by Rear Admiral Yasui Nobuharu. 

Lt ( j.g.) Kanda of HA-13 and his two crewmen were each promoted one rank, posthumously. 

Lt ( j.g.) Ota went on to become navigating officer of the ill-fated I-52 and perished with her in the Atlantic Ocean in 1944. 

Initially, the British thought another Vichy submarine made the attack and, therefore, did not alert the rest of the fleet. As a result, Sydney, Australia received no warning. After emergency repairs, RAMILLIES made for Durban, Union of South Africa where she was docked for temporary repairs from June to August 1942. Later, RAMILLIES returned to Plymouth, England where full repairs were completed from September 1942 to June 1943. In June 1944, RAMILLIES participated in the D-Day invasion. 

BRITISH LOYALTY was later refloated and towed to Addu Atoll where, on 9 Mar '44, she was torpedoed and damaged by German submarine U-183. On 15 Jan '46, BRITISH LOYALTY was scuttled and sank off Addu Atoll. 

The limited remains of Akieda and Takemoto's midget submarine "M-20b" were found about two weeks after the attack sitting upright on a reef within an area of volatile surf. According to historian/author Kimata Jiro, a recent NHK documentary showed the aft section (now completely submerged) in the same location. The propellers were salvaged and are on display at the midget submariners’ grave site


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## dutchman (Sep 2, 2013)

I was curious how long they could remain sumerged? If a mini sub had to avoid detection, or wait for a ship to come into a harbor so the sub nets would be opened, what kind of duration would one have before it was out of air. I would assume in shallow water they could bottom the boat and lay in wait??. I've seen figures on range submerged but next time factors.


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## Shinpachi (Sep 2, 2013)

Submerging time was 12 hours at longest.


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## Milosh (Sep 2, 2013)

The crews of midget submarines:

I-16tou, Masaji Yokoyama and Sadamu Uyeda; I-18tou, Shigemi Furuno and Shigenori Yokoyama; I-20tou, Akira Hiro-o and Yoshio Katayama; 
I-22tou, Naoji Iwasa and Naokichi Sasaki; I-24tou, Kazuo Sakamaki and Kiyoshi Inagaki.


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## dutchman (Sep 2, 2013)

Thank you Shinpachi that's exactly what I was looking for, I'm working on a problem here and in a week or so I'll post up another question here which should be interesting. Keep a watch for it, I'd like to hear your input.

Thanks again


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## GrauGeist (Sep 2, 2013)

They now have evidence that a mini sub did in fact participate in Pearl Harbor, unleashing it's two torpedos into Battleship row.

In this famous photograph, you'll see two torpedo tracks, *left of center*, heading towards the battleship (caught here the moment of impact). There are concentric rings and a "splash" shown at the head of the tracks. Experts have determined that this was not caused by a torpedo bomber, but in fact the mini sub. The "splash" seen is backwards, meaning that it is in the wrong direction for a dropped torpedo and could only be caused by the backward "kicking" of the midget sub during the launching of the torpedoes.

I will try and look to see if I can find a better photo that shows the launch and tracks better.


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## Shinpachi (Sep 2, 2013)

You are welcome, dutchman, if I could be of help. 

BTW, I have come across an interesting local video.
JMSDF crew visit the cenotaph of the 9 heros....

Anybody, any opinion?
In my opinion, they should not do it carelessly as Japan said good-bye to the prewar army and navy.
If they can do it with no hesitation, JGSDF also could visit the Yasukuni Shrine freely.
I am afraid such their innocent behavior often brings unnecessary misunderstandings about our country.
Sorry, guys, if I am nervous!


_View: https://www.youtube.com/watch?v=eQSUe4eF-dw_


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## Shinpachi (Sep 2, 2013)

Oh, nice find, GG!


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## GrauGeist (Sep 2, 2013)

Midget Sub #1 was shelled by the U.S.S. Ward, over an hour before the Japanese warplanes attacked. It remains where it sank, just outside the harbor.

Midget Sub #2 entered Pearl Harbor, but after missing its target with both torpedoes, the sub was destroyed by a pair of American ships. It was raised two weeks after the attack and buried as landfill.

Midget Sub #3 ran aground on the east side of Oahu, its captain became the first Japanese prisoner of war. Neither of its torpedoes had been fired. It is now on display in Texas at the National Museum of the Pacific War.

Midget Sub #4 turned up years later, several miles south of Pearl Harbor found in 1960, at Keehi Lagoon, and it still had its torpedoes in it. That midget submarine was shipped back to Japan and now stands outside the Naval Academy in Etajima.

Midget Sub #5 was recently found three miles south of Pearl Harbor in a pile of wreckage. It is believed that after the attack, the sub ended up stranded in an area of the back bay, called the West Loch near Waipoio penninsula. After being stranded there for several years, it became buried by debris during a disaster that happend in 1944 during the transfer of ammunition aboard an LST. Several hundred sailors were killed and injured and 6 LSTs were sunk...all on top of the midget sub. When they cleaned up the wreckage, the sub got scooped up with the debris and dumped out at sea. During the investigation, they found the topredo tubes to be empty. The control room of the Midget Sub is still sealed and it is believed the two crewmen may be aboard.

Here's an annotated photo of the one I posted above showing the diagnostics of the sub's attack:


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## dutchman (Sep 2, 2013)

I've seen the map of Pearl Harbor on Dec 7th showing the position of the ships before the attack. Does anyone know where the carriers would have been if they had been in port????


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## Thorlifter (Sep 2, 2013)

I don't know GG. I'd love to think a moment in history was captured the millisecond before the explosion, but I ask this. If we can assume that the first torpedo fired is the longer track headed towards the West Virginia, that would mean it would have to swing to fire its 2nd shot towards the Oklahoma. If that's the case, why is the "rectangular shape" aligned with the 1st shot?

If your answer is because it was starting it's turn out of the harbor, I find it hard to believe it would be perfectly lined up with the 1st shot.

I still tend it believe torpedoes were dropped by two planes and the torpedoes entered the water to the left of the mark you called "rooster tails". You can see their splashes in your first picture. The torpedoes could have porpoised causing the rooster tails. If my guess is correct, the Kate's would have been far out of the picture by the time the image was taken.

Also, it's my opinion the spot you marked are rectangular object is a flaw in the picture. It almost has a hard edge to it and everything else is a soft, almost blurry edge. But I'm no expert in object identification on 70 year old black and white film.


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## Matt308 (Sep 2, 2013)

I agree, Thor. These pics are subject to much debate. There has been many "experts" making claims of facts over these photos and best I can tell, nothing has been proven definitive.


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## parsifal (Sep 2, 2013)

> but I ask this. If we can assume that the first torpedo fired is the longer track headed towards the West Virginia, that would mean it would have to swing to fire its 2nd shot towards the Oklahoma. If that's the case, why is the "rectangular shape" aligned with the 1st shot?



That is not necessary. all WWII subs had a TDC, basically an analog computer into which bearing, range, target speed, and for more sophisticated computers, things like current and wash, could be fed in and estimates made for the torpedoes gyro setting. The second crewman would then adjust this before firing, for some more advanced torpedoes, its speed and pre-ignition settings could also be made.

There is no real technical difficulties to torpedoes being fired simultaneoulsy on diffrent headings


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## GrauGeist (Sep 3, 2013)

The annotated image is not mine, I've had it for some time on my drive. I have always been curious about the matter and have tried to find a copy of that image with a higher resolution. The photo was taken from the air during combat, so that's probably as good as it'll get.

The fact remains that they did find the 5th mini sub after all these years and they did confirm that it did launch it's torpedoes before coming to rest on the bottom of Pearl's back bay before disaster in 1944, eventually being scooped up and dumped to sea with the LST wrecks.


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## dutchman (Sep 3, 2013)

I agree that most subs could fire on multiple bearings, Firing a "spread" of torpedoes was common. I can understand the tower of the sub being their after the shot. The captain is going to watch the track as there is too much noise to confirm his hits. To be truthful, these crews knew they were on a one way ticket. Watching the hits would not be unreasonable. If there was much chance of making it out and home they would have submerged and evaded. As it was no one may have seen them anyway for 60 years or more as we still can't agree if the photo shows a sub.


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## GrauGeist (Sep 3, 2013)

The mini subs carried 1,000 pound torpedos...these were twice as heavy as airborn torpedoes. Launching from the mini sub would have caused the sub to violently "kick back", momentarily lifting the stern from the water. In addition to that, these early mini subs had a small rudder, making them difficult to manouver.

There was a report filed after Pearl Harbor that stated a large torpedo was found unexploded, but there is debate on a large torpedo strike on the West Virginia, which caused significant damage. This would be in keeping with the torpedo wakes seen in the photo.


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## Shinpachi (Sep 3, 2013)

The bow is said jumped up in experiment and it made the mini sub unstable for the immediate second shooting.


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## GrauGeist (Sep 3, 2013)

Shinpachi said:


> The bow is said jumped up in experiment and it made the mini sub unstable for the immediate second shooting.


Which is why the second torpedo most likely ran wide of it's target and ended up beaching. It was recovered after the attack, Admiral Nimitz made a mention of the torpedo finding in his congressional report.


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## Thorlifter (Sep 3, 2013)

I am certainly not saying you're wrong. In fact, I want to believe it and it would make the picture even more amazing. I guess I'm just getting too cynical in my old age.


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## dutchman (Sep 3, 2013)

The reaction of the mini sub when launching a torpedo would be somewaht violent. Once fired the sub would "recoil" from the launch which could make the stern rise. Then once the torpedo had cleared the tube you would be faced with a terrible weight shift to compensate for. The bow just became 1500 pounds or more lighter. So it will of course rise. To keep it under control would be a major effort. It would be a bit of a bucking bronco ride for the crew. I do know you can't fire the two torpedoes at the same time. That could have terrible results. I would guess and I say guess it would be 45 sec. before a second the torpedo could be launched.


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## Shinpachi (Sep 4, 2013)

Local wiki says, 

The Ko-hyoteki (mini sub's code name which means 'Target-A' ) was equipped with two torpedoes in its nose end. Type 97 oxygen torpedo with a diameter of 45 cm was used initially till the Battle of Solomon Islands (Guadalcanal) from the outbreak of the Pacific War. Shooting range was 5,000 m with speed of 50 knots.

After Type 97, Type 2 or Type 91 torpedo of 45cm diameter was used. Range was 3,900 m with speed 39 knots. These electric drive types showed superior maintainability to the oxygen type. Explosive charge weight was 350 kg for both types and the firepower of a Ko-hyoteki was equivalent to two attackers of aircraft. 

A pair of torpedos were housed in launch tubes and emitted by injecting air to the tube. Buoyancy of nearly 1 ton occurred when a torpedo was released. The bow bounced and jumped out to the water surface. Because of this unstable behavior, torpedo was shot out in the biased direction and did not necessarily catch the aimed target. It was about 30 seconds till stabled again. 

As the second torpedo was unable to be directed to the correct direction in such an unstable state at all, they could not adopt the ordinary tactics of putting enemy in sparging torpedos but performing single-shot shooting only. Optimum shooting distance to the enemy ship was said 800 m.

...............

I am unable to understand why the buoyancy was nearly 1 ton.
So, Please don't ask me. 
Thanks!


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## Wayne Little (Sep 4, 2013)

The referenced photo of battleship Row was apparently taken by Lt. Hirata Matsumura's navigator, Petty Officer 1st Class Takeo Shiro as they banked away from their aborted torpedo run on West Virginia, the photo shows Petty Officer 3rd Class Yasumi Oku's torpedo hit on West Virginia with the initial wave blast close against the ship, keen eyes will spot the beginning of the large water spout about to erupt into the air from the torpedo hit. 
Matsumura circled around and dropped back in between Akagi and Kaga's attack formations to release his torpedo also striking West Virginia.
Matsumura was the Second in command of the Torpedo attack in command of Hiryu and Soryu's torpedo bombers flying aircraft BII-320, while Oku's aircraft was BII-302 these pilots redirected their attacks on to battleship row from their assigned targets, slotting into the stream of Akagi and Kaga torpedo aircraft, and not wanting to waste their torpedoes on a lesser target than a Battleship.
The attack on battleship row by the torpedo aircraft was completed in a rather short duration of approximately 10 minutes during which some 27 aircraft attacked the ships, not all released their torpedoes, a few of the final Kates from Kaga were shot down before releasing their torpedoes, however some 20+ torpedoes were dropped in this short space of time providing plenty of torpedo wakes, waves and explosions in the waters of Pearl Harbor and this is more likely what can be seen rather than a mini sub.....


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## dutchman (Sep 4, 2013)

Okay folks here's a crazy idea. What if the Pearl Harbor attack was conducted differently. There are many things about the attack on both sides that bother me. But, with the advantage of hindsight that might be to easy to say. Now please don't take offence with this I'm not trying to start trouble I just want to look at this from a professional point of view without too much emotion. 

The attack was planned by some of the most brilliant minds in the military, so here's a point. Why mini subs at all? If you send 5 mini's in with a total of 10 torpedoes, do you really think that will tip the scales when you are about to hit with over 340 aircraft and drop 40 torpedoes and a almost a hundred bombs? I would think that the risk of one of the 5 subs being discovered and raise the alarm would outweigh any good they could have done during the attack. 

Why not modify the mini subs. They carried 2 torpedoes, remove one and replace it with a huge high capacity air tank. This should allow the mini to remain submerged for at least 36 hours. These mini subs could have made it into the harbor as at least one did. And then pick a point away from the ships and bottom the boats and wait. Let the planes do their thing. Then at a prearranged time say 0100 on Dec 8th slowly surface and look for targets of opportunity. The Enterprise would have been back in port by then. If the battleships were down and a carrier took 1-2 torpedoes in the side, it could be laid up for several months if not sunk. It would also have caused much confusion to the rescue and repair efforts if they weren’t sure the harbor was safe. Much the way a bomber formation would drop a percentage of bombs with time delay fuses. 

I was reading a report that claimed the attack was not as successful as they had hoped. The accuracy was less then expected. By about 20% with the bombs and a little more with torpedo. But you know the attack seemed sucessful enough to me!!!!


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## GrauGeist (Sep 4, 2013)

To commit assets to the attack, you want to have them have as much ordnance as possible to make the effort a success. A mini sub with a single torpedo cuts thier chances in half before they even start thier mission.

As it stands two made it into the harbor, one was caught and sunk, the other (#5 mentioned above) at least deployed it's torpedoes. The idea of mini subs supplementing the attack was to inflict the maximum amount of damage while they had the element of surprise. Nagumo called off the third wave when he saw that Pearl's defenses were more than they had counted on.

The Americans may have been caught sleeping, but they didn't take long to put up defensive fire. The other factor in Nagumo's decision, was that they didn't know that the carriers and thier support ships were out to sea. They had counted on the bulk of the fleet to be tied up that morning.


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## dutchman (Sep 5, 2013)

I understand that the mini subs were a minor factor in the battle. They carried a total of 10 torpedos but were only able to fire 2 torpedos at a maximum, one of which may well of missed it's target. So reducing to one torpedo per mini sub wouldn't have reduced the combat effectiveness of their portion of the attack much if any. There was speculation that they might have been trying to sink any vessel attempting to leave and by doing so plug the channels of the harbor. That would have closed it down for many weeks if it were a large ship. 

They did realize the carriers might not be there. The target assignments were complicated but navy command wanted the battleships as first priority. Genda who designed the attack saw battleships as obsolete and wanted to move the carriers to the top of the target list. There was also much effort to reduce duplication of hits. But the attack broke down and confussion set in. Many of the ships had more attacks then they were suppose to some had less. After the Battleships, the Carriers were next in their absence the Cruisers took the remander of the firepower.


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## GrauGeist (Sep 5, 2013)

The subs may have been more of a contributing factor, but too many things went wrong and only one made it to an attack position.

Had all 5 made it to thier designated positions and delivered all 10 torpedoes, this may have contributed to more destruction. The larger torpedoes had a significant destructive power over their airborn counterparts.

These early mini sub types had several problems which were addressed shortly after Pearl Harbor...one of the main problems being the rudder, which was too small.


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## Wayne Little (Sep 5, 2013)

dutchman said:


> I was reading a report that claimed the attack was not as successful as they had hoped. The accuracy was less then expected. By about 20% with the bombs and a little more with torpedo. But you know the attack seemed sucessful enough to me!!!!



Whilst i can't say much on the percentage for Bombing accuracy, the torpedo Accuracy was reasonably high from 40 torpedo aircraft, off the top of my head I can count at least 26 of 40 torpedoes hitting targets less 3 of 5 I think that were shot down without releasing torpedoes 26 of 37 does give a reasonable percentage of hits. now one would expect a pretty good accuracy count, the targets were stationary, and AA fire didn't react until more than half had dropped their torpedoes, once they got to firing, 5 of Kaga's last 7 aircraft to attack were shot down.


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## parsifal (Sep 9, 2013)

> Why not modify the mini subs. They carried 2 torpedoes, remove one and replace it with a huge high capacity air tank. This should allow the mini to remain submerged for at least 36 hours. These mini subs could have made it into the harbor as at least one did. And then pick a point away from the ships and bottom the boats and wait. Let the planes do their thing. Then at a prearranged time say 0100 on Dec 8th slowly surface and look for targets of opportunity. The Enterprise would have been back in port by then. If the battleships were down and a carrier took 1-2 torpedoes in the side, it could be laid up for several months if not sunk. It would also have caused much confusion to the rescue and repair efforts if they weren’t sure the harbor was safe. Much the way a bomber formation would drop a percentage of bombs with time delay fuses.




Japanese mini subs were designed as nuisance weapons only, and in this role were reasonably successful. Even when no observable results were the only result, this can be argued to be a good outcome. typically, following a nuisance raid there were extraordinary defensive measures that needed to be taken by the defending naval force across an entire region. The British experiences in the Med against the X MAS flotilla are typical. Despite the fact that X MAS delivered less than 5 successful attacks overall, the British throughout the Med were forced to adopt draconian and costly harbour defence procedures that also tied up large numbers of personnel and even quite a few ships. For the investment in men and materrial by the attackers, min sub operations were generally very good at tying down larger amounts of enemy resources. Japanese minisubs were in this category.

Following the Japanese attack at Pearl, the whole area went into complete lockdown, with ASW netting, active patrols, shore patrols, you name it. It would have been imposasible for a Japanese vessel of any size to lie undetected within the harbour. even the subs lying offshore had a hard time of it after the attack.


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## GrauGeist (Sep 9, 2013)

As it stands, two of the subs were caught and sunk on 7 December:
No. 20, at the mouth of the harbor, detected and sunk by The Destroyer Ward (DD-139) at 06:37
No. 22, inside the harbor, fired it's torpedos at the Speaplane tender Curtiss (AV-4) and at the Destroyer Monaghan (DD-354) which responded by sinking it at 08:43

So the U.S. Navy was aware of thier presence and any subs lurking after the attack would have been spotted and dealt with quickly.

The mini subs were also used on a similar mission at Sydney Harbor, 29 May 1942 where 5 subs mounted an unsuccessful attack.


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