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Japanese I-400 Class Submarine World Naval Ships Forums Archive

Japanese I-400 Class Submarine

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Japanese I-400 Class Submersible Seaplane Carrier. Specially built to attack the Panama Canal. Five were built, three launched, but none served the original purpose. The Japanese built five (three were launched) giant, seaplane carrying submarines. One made a trip around the Horn of Africa to Germany. Another was converted as a tanker. A submarine fleet was formed intending its aircraft to torpedo the Gatun Locks, Panama Canal, but was diverted to attack the US anchorage at Ulithi just as the war ended. The I-400 series submarine had an energy absorbing skin, snorkel, radar, degaussing, and a range of 1-1/2 times around the world and four months duration. Two submarines hulls were welded together with a waterproof compartment on deck for three disassembled torpedo bombers. Hanger deck is a watertight compartment. Each plane to be assembled on deck. The I-1400 carried three Aichi M6AI Serian float planes specially build for torpedo bombing of the strategic Panama Canal. Aichi, builder of the D3A "Val" carrier bomber and the late-war B7A "Grace" torpedo bomber, also build the E13S "Jake" long range reconnaissance seaplane that flew at Pearl Harbor. A specially designed version was purpose built for the I-400 class submarine to carry an aerial torpedo to attack the strategic Gatun Locks to stop the flow of ships and supplies from the Atlantic needed to fight in the Pacific. Fortunately the war came to an end before this was carried out. A model kit is available. See the final pic.
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Clearly both the Panama and Suez canals were obvious targets. I wonder if there were plans to attack the Suez canal? Remember how easily it was blocked during the 1956 kerfuffle.

Most definitely a fascinating subject. If anybody is interested I came across a couple of sites dealing with this amazing submarine... [url]http://www.soest.hawaii.edu/HURL/I-401.html[/url] [url]http://www.webenet.net/~ftoon/memory/japsub.html[/url] Regards astraltrader/Exeter/Devon

Absolutely sensational. Thanks for adding this. Great photos too. How incredibly interesting. Better give us your first name. Can't keep calling you Australtrader.

Ok Squire - Fair dinkum - although it`s Astraltrader not Australtrader! Anyhow how about - Best wishes Terry. Exeter/Devon.

Interesting thought, an attack on the Suez Canal. Unlike the Panama Canal, Suez has no locks and therefore it is difficult to see how any lasting damage could be done. German aircraft did, of course, lay mines in the canal several times throughout the war but these were cleared fairly quickly. Any attempt at a long term blockage by the Axis powers would have proved difficult if not impossible. I know the Egyptians did it during the Suez Crisis but the canal is in their Country which makes the logistics a whole lot easier. The only real way to deprive the allies of the use of the canal was for the axis powers to capture and take control of it. This is, of course, what they tried to do but unfortunately for them, Montgomery had other ideas. Similarly, in an attempt to deprive the allies of the use of the Canal in WW1 the Germans persuaded the Turks to mount an attack on it. The attack was made in Feb 1915 but the Turks were unsuccessful and lost in the region of 2000 men. Although the Turks did not capture the canal the attack made the British wary of the possibility another attempt being mounted. This led to more troops that would otherwise have been sent to Gallipoli being stationed along the Canal to guard it. Regards...John

Don't forget our poor old M.2 seen here as a seaplane carrier and also when she was fitted with the 12" gun.
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Three definitive photos of the 400 class. 1.I-400. 2.I-401. 3.I-402.
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[B][U][I]I-400[/I][/U][/B] Chief Equipping Officer - Cmdr. Toshio Kusaka - 15 December 1944 - 30 December 1944 Cmdr. Toshio Kusaka - 30 December 1944 - 1 September 1945 [B][U]Toshio Kusaka[/U][/B] Commanding Officer, SS [I]I-121[/I] - 20 March 1939 - 15 August 1939 Commanding Officer, SS [I]RO-63[/I] - 15 October 1940 - 9 February 1942 Commanding Officer, SS [I]I-174[/I] - 9 March 1942 - 15 November 1942 Commanding Officer, SS [I]I-180[/I] - 15 January 1943 - 14 September 1943 Commanding Officer, SS [I]I-26[/I] - 18 September 1943 - 1 August 1944 Promoted Commander - 1 May 1944 Chief Equipping Officer, SS [I]I-400[/I] - 15 December 1944 - 30 December 1944 Commanding Officer, SS [I]I-400[/I] - 30 December 1944 - 27 August 1945 [B][U][I]I-401[/I][/U][/B] Lt. Cmdr. Nobukiyo Nambu - 8 January 1945 - 1 September 1945 [B][U]Nobukiyo Nambu[/U][/B] Commanding Officer, SS [I]RO-63[/I] - 15 October 1942 - 16 March 1943 Commanding Officer, SS [I]I-174[/I] - 12 November 1942 - 23 February 1944 Promoted Lieutenant Commander - 1 May 1944 Commanding Officer, SS [I]I-362[/I] - 23 May 1944 - 1 December 1944 Commanding Officer, SS [I]I-401[/I] - 18 January 1945 - 15 August 1945 [B][U][I]I-402[/I][/U][/B] Cmdr. Otoji Nakamura - 24 July 1945 - 15 August 1945 [B][U]Otoji Nakamura[/U][/B] Commanding Officer, SS [I]I-53[/I] - 19 March 1938 - 30 July 1938 Commanding Officer, SS [I]I-68[/I] - 25 July 1941 - 31 January 1942 Promoted Lieutenant Commander - 1 February 1942 Commanding Officer, SS [I]I-5[/I] - 5 February 1942 - 28 February 1942 Commanding Officer, SS [I]I-402[/I] - 24 July 1945 - 15 August 1945 As you can see, all three COs of these monster subs were veteran members of the IJN's submarine service, well-deserving of such prestigious commands. -Matt

I read today about the 'Sensuikan Toku' (special submarines) which was a massive submersible aircraft carrier. Here is the link; [url]http://rmhh.co.uk/files/files2/submarine_carriers.pdf[/url] What an impact this would have made in WW2. joboy

Interesting post. Is that a DB601 engine that I see on that airplane?

There has already been a thread about this type of submarine so I have moved the posts there.

Hi. Some photo. Best regards Alex
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In the Daily Telegraph today. I hope they make a documentary of it. Cheers, Bob.
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Bob, they have made a program of it and it is on the National Geographic Channel tonight at 21.00 GMT. It is called "The Hunt for the Samurai Subs" or something like that.

[QUOTE=emason;84252]Bob, they have made a program of it and it is on the National Geographic Channel tonight at 21.00 GMT. It is called "The Hunt for the Samurai Subs" or something like that.[/QUOTE] Playing here in USA tonight to on the NGC at 21.00 Eastern.

One wonders what the results would have been had these submarines actually been able to deploy before war's end. I would presume that the surface and air Anti-Submarine Warfare assets at the Panama Canal would have been in place, but how effective, after years of patrolling without much action would these units actually be? These would have been "second echelon" forces, not the honed sea hunters operating in the Pacific and Atlantic. On the other hand, these huge submarines were highly vulnerable to sonar detection, very noisy, cumbersome to maneuver underwater, and therefore a juicy target for a destroyer or destroyer escort with a modern anti-submarine fit. With aircraft on board, they might well have been able to launch outside the area of likely detection late at night, but then, on the surface, would have been a real sore thumb for an air-borne centimetric radar set on a PB4Y or the like. Interesting scenario if they had any success at all this late in the war. Wouldn't have changed a thing, though, the A-bombs would still have gone off and all that followed.

Don, you asked the rhetorical question:- "[I]One wonders what the results would have been had these submarines actually been able to deploy before war's end."[/I] The answer as you say is practically zero. With a bomb load of only 800lb each, and three aircraft per submarine, the result would only have been a pinprick, nuisance value only. That is if the aircraft even managed to locate it's target and score a bull's eye with each bomb, a most unlikely scenario. One wonders at the mentality that devised such a useless weapon, especially if one takes into account the manpower, cost and time taken to develop and deploy. Hardly a war winning weapon. Transporting three aircraft across the Pacific Ocean in a huge submarine to deliver a pinprick, when each component (the sub and planes) would have been far more effective in their proper role elsewhere, strikes me as being (almost literally) not much bang for their bucks.

You got that entirely right, Bill. If you look at the sub books, you find that Japan built many classes of submarine, just before and during the war, each with some sort of "special scenario" attached to it to meet a specific naval objective. What they didn't do was standardize a single good design and build the hell out of it as we did, making improvements to the basic design as time passed and retrofitting the older boats when possible. This was enormously wasteful of naval funding...they were actually restricted in the number of subs built by having to have so many different special parts and fittings, etc., to say nothing of power plants, etc. The I 400s, as you said, could only deliver a pinprick, despite the enormous expenditure of yen devoted to them. More of the "too little, too late" that both Germany and Japan experienced. It seems to me, broadening this out to the whole navy and the war, Japan did itself no favors in the ship design department due to the conflict between what the Imperial Naval Headquarters desk jockeys though useful and the laws of physics, regardless of the protestations of excellent ship designers. If you read the histories, of the heavy cruisers, for example, they built about six classes, some "specialized" for specific purposes such as scouting for the aircraft carriers and providing AA cover (Tone, Chikuma). They could never figure a proper aircraft fit for a ship that was always half what you needed. Poor design there, wasted yen. Then the Mogami's, found at construction to be fatally weak in welded joints and unable to bear the stress of gun firing. There went millions into fixing these flaws. plus they were overweight and had to have bulges fitted (due primarily to headquarters insistence on torpedo tubes.) Plus they changed out the guns for 8" pieces...More millions ....etc. through many classes of ship, and all due to the desire to pack as much punch in an individual ship as possible. Then the Nachis and Takao's were loaded with torpedo tubes as well...double the initial fit, resulting in the need to bulge them out and correct some trim problems. They paid the price in combat for that much explosive loaded above the main deck, too. Japan built some eventually powerful (and still overweight) heavy cruisers, but there could have been say 8 more of them if they didn't have to re-design and rebuild them twice over before getting a satisfactory ship. Japan's naval constructor's common sense was overridden by the demands of the senior staff for what they thought was more firepower. Fortunately, we had a better system going that paid off quite quickly. Our megatons of new ships to the fleet, built in huge batches of the same classes, mostly became active in 1944. By the end of 1944 the Japanese had been absolutely butchered on all fronts by the push from this amount of technology.

Don, I would have to agree with your comments. Also remember that the USN did in fact study these submarines for their operational capabilities before using them for target practice, or just flat sinking them. Regards Charles

One of the US Submarine commanders who brought back one of the smaller Japanese submarines said, other than the overpowering stench, there wasn't much that stood out, and nothing much to recommend from any of these boats from a practical seafaring point of view. You can bet the superb Japanese binoculars went to the officers right off the bat! I understand some of the mechanical design of the aircraft stowage space was of use in designing the US' first round of missile carrying subs. (Looking on my library shelf, it was Paul Schratz in "Submarine Commander.") I think the fact that they became torpedo targets says about all there is to say about there utility in the post-war navy! Regards,

As far as "wasting" yen refitting 8" into the Mogamis: it was-per everything I've read, including the IJN Cruiser "Bible" by L+W- always the intent to do that. The original 6.1" allowed them to build a class of "light" cruisers that were in fact heavies designed to carry 8" from the outset. Their CA allowance was pretty much used up. After the Mogamis appeared the USN replied with 15-6" gunned Brooklyns and RN went up to much larger CLs with 12-6". All of their CAs from Nachis on were anything but the [I]10,000 tons [/I]of the Treaty. So simply put...they cheated to build in the attributes that, on paper, made them superior to RN and USN 10,000 ton CAs. The Mogamis did need the hull bulging, etc you referred to to get their seakeeping up to snuff tho. The Nachis and Atagos gained more wt. during refits as well. IJN CA against Allied[I] prewar [/I]CA they were very powerful vessels by 1940 standards, but against the AIRPOWER that the USN developed and deployed....they came off THIRD best out of two, as the record of many of the IJN CAs' sinkings does show!! OTOH, the USN's Baltimore class of WW 2, without Treaty restrictions were, I believe, superior in both offensive and defensive power to any of the IJN CAs. Getting back to the I-400s: I'd certainly agree they were a waste of the IJN's limited resources and effectively they accomplished nothing. Rather like the monstrous Yamatos, for that matter! DFO ;) Some details of these subs: [COLOR="Red"]Ship History[/COLOR] The submarine included radar and radar detectors and watertight hanger for three Aichi M6A1 Serian seaplanes. The submarine had a range of 37,500 nautical miles. Construction began on January 18, 1943 at Kure Dock Yards under heavy security. Completed on December 30, 1944 and assigned to Captain Tosho Kusaka. Wartime History It was planned to use the I-400 along with the I-401, I-13 and I-14 to participate in a daring plan to attack the Panama Canal and disable its locks. In June 1945 the decision was made to switch targets to hit USN anchorage at Ulithi Atoll. The plan was code-named Arashi (storm) for the I-400 and I-401 to use its Serians on Kamikaze attacks on any carriers based there. The two subs departed Ominato on July 23, 1945. At sea, the sub suffered an electrical fire on August 5th that forced it to surface to repair the damage, but successfully reached their rendezvous point, 100 miles miles south of Ulithi on August 14th, but the I-401 was not there. The strike date was set for August 17th, but Japan surrendered on the 15th. Surrender After hearing of the surrender, the Captain elected to return to Kure, to surrender in Japanese home waters. They jettisoned their Serain aircraft. Spotted on August 27th off northern Honshu by Avengers from the USS Bennington. Destroyers USS Blue DD-744 and Mansfield DD-728 pursued the sub and boarded it to accept its surrender. The following day, the USS Weaver DE-741 arrived to again accept its surrender. After surrender, the sub was sailed to Hawaii, and evaluated by the US Navy. Sinking History On June 4, 1946 off Barber's Point, Oahu sunk by USS Trumpetfish SS-425 on during a tests of the Mark 10-3 exploder. After being hit by three Mark 18-2 electric torpedoes, the sub sank in deep water at 12:10, sinking by the stern. Over the course of several days four captured subs were sunk including I-201, I-14, and I-401.
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Great post, designer! I agree the Mogamis were planned from the get-go to have 8". My point was that they spent yen they didn't have to, once again, to get the ship they should have just designed and built to start with, rather than play "games" with the treaty they were violating to start with. This point I guess was a bit off-track on the I-400s, but the IJN built all these subs to fill some Imperial Headquarters concept of a "role" for the sub, instead of building a standard series like we did which was so enormously wasteful of yen that it clearly restricted the number of subs they could have on hand when it counted. This philosophy also created enormous tubs like the I-400s with extremely limited utility and that would have been a sonarman's dream, much less the lads on Hedgehog or Squid launchers (was it Squid that came out during the war, or a predecessor thrower?). The record of Japanese shipbuilding of war vessels overall shows that they must have spent enormous amounts of money taking ships back in hand to correct problems that surfaced when the ships were actually in use. The cruisers, thanks to the book you mentioned, is just the most well-documented example of this wasteful tendency, forced by the Imperial Headquarters on the ship designers. You are probably well aware of the Tomozuru incident, where a ship capsized due to overweights forced from the Headquarters staff. The ship designer, a more junior member of the design bureau, was of course blamed, had a stroke, and died, while the Headquarters staff dined at a nice restaurant featuring fine saki, geisha's and fugu. Admiral Hiraga, the IJNs main man in the design bureau was most senior before the war came about, so his solution to the problem was to retire with a clean record and let the Headquarters divas do as they pleased. While Japan was doing all this refitting, the US developed standard designs and built hell out of them. Baltimores, Clevelands, the ten battleships and two battlecruisers, Fletchers and Gearing's, the Gato and descendants. All clearly excellent equipment overall, quite capable of dealing with their counterparts. I've always been of the opinion that the design flaws of Japanese ships, plus the design philosophy of making so many "specialized" designs and trying to make each ship superior to potential enemies vice a standard design went a long way toward making things easier on the United States and Allied navies when the time came to square off. We faced far fewer ships that could have been available, and less capable ones when we did face them, with the exception of those massive heavy cruisers who were real tough brutes -- but vulnerable to upped deck disaster with all those torpedoes on board. The Japanese had their successes early on, of course, but then, as ships went down, there were no replacements, no "new squadrons" ready to sail because they had broken the bank with what they had and it was too late to correct that error. Regards,

OTOH then there is the USN's new LPDs and LC$ "designs"...oopzzz. To go from the excellent WW2 USN designs in mass production to now, really SAD!........DFO :eek:

designer....OTOH I figured out, but what's DFO? We rookies are curious. Also...who put the sorcerer's hat on the new Darings? Looks like a modern American design :). I like the old ones better! :rolleyes:

hi!every one I'm just new on this site!so! please to be your friend!? I'also heared about the japanese I-400 class sub,it is a very terific ship I hope to see a new version of it in the mere future!

The US channel PBS just aired a program on the "Secrets of the Dead" series about the I-400 Super Submarines. There was little new information, but there were interviews with crewmen and a lot of photos I had never seen before. If you get to see this series do so.

Thanks my friend. When it crosses the pond I will look forward to seeing it. [URL]http://www.worldnavalships.com/forums/showthread.php?t=736[/URL]

I have just seen this show here. Very interesting set of photos and films, and the interviews with former crew were interesting. As usual these days, the producers try to make far too much drama over these "super subs" and fail to take in to account the realities of the time in which these subs operated. They were huge for the day, innovative and also highly vulnerable. They might well have carried out their planned attack on the Panama Canal, but at that late stage of the war, they would probably have failed and been quickly hunted down and disposed of. Big, unwieldy, slow to dive and huge sonar targets, they cost huge amount of yen that could have been better spent on more conventional submarines that could have caused more serious damage to our fleets. Overall though, an excellent show.

I searched for the previous thread on the I-400, but didn't find it. Sorry. Merge them if you want to.

I saw the program as well. Amazing how they got on pretty well once the final gong was sounded. But i agree with Don, what would any navy prefer, 20 I-400's or 20 Essex Class, subs very overated, almost desperate measure.

[quote=John Odom;114087]I searched for the previous thread on the I-400, but didn't find it. Sorry. Merge them if you want to.[/quote] It has now been done!

[QUOTE=The Sailor;2333]Japanese I-400 Class Submersible Seaplane Carrier. Specially built to attack the Panama Canal. Five were built, three launched, but none served the original purpose. The Japanese built five (three were launched) giant, seaplane carrying submarines. One made a trip around the Horn of Africa to Germany. Another was converted as a tanker. A submarine fleet was formed intending its aircraft to torpedo the Gatun Locks, Panama Canal, but was diverted to attack the US anchorage at Ulithi just as the war ended. The I-400 series submarine had an energy absorbing skin, snorkel, radar, degaussing, and a range of 1-1/2 times around the world and four months duration. Two submarines hulls were welded together with a waterproof compartment on deck for three disassembled torpedo bombers. Hanger deck is a watertight compartment. Each plane to be assembled on deck. The I-1400 carried three Aichi M6AI Serian float planes specially build for torpedo bombing of the strategic Panama Canal. Aichi, builder of the D3A "Val" carrier bomber and the late-war B7A "Grace" torpedo bomber, also build the E13S "Jake" long range reconnaissance seaplane that flew at Pearl Harbor. A specially designed version was purpose built for the I-400 class submarine to carry an aerial torpedo to attack the strategic Gatun Locks to stop the flow of ships and supplies from the Atlantic needed to fight in the Pacific. Fortunately the war came to an end before this was carried out. A model kit is available. See the final pic.[/QUOTE] Greetings to The Sailor. Interesting posting. I must confess to not knowing of the two incomplete ships of the class. New facts duly noted. A thing puzzling me, (apologies for being petty), but you mentioned that one made a trip from Japan to Germany around the Horn of Africa. As the Horn is the point directly opposite to Aden, at the southern entrance to the Red Sea, just how did the submarine overcome the problem of the Suez Canal passage, that waterway being in the hands of the British at that time. Once again my apologies for being petty, please accept my regards.

Sorry Abbeywood - The Sailor has sailed off to different climes and has not been seen in the forum since March 2008!! :D

Re: One made a trip from Japan to Germany around the Horn of Africa. Didn't happen. See [url]http://www.combinedfleet.com/sensuikan.htm#tromsi[/url] HTH Bob

(From CBC News) [B]Japan's WWII super-submarine found scuttled off Hawaii[/B] "[I]Scientists plumbing the Pacific Ocean off the Hawaii coast have discovered a Second World War era Japanese submarine, a technological marvel that had been preparing to attack the Panama Canal before being scuttled by U.S. forces. The 122-metre "Sen-Toku" class vessel — among the largest pre-nuclear submarines ever built — was found in August off the southwest coast of Oahu and had been missing since 1946, scientists at the University of Hawaii at Manoa said[/I]." Complete article here: [url]http://www.cbc.ca/news/world/japan-s-wwii-super-submarine-found-scuttled-off-hawaii-1.2448985[/url]

An interesting [URL="http://aolbroadband.welcomescreen.aol.co.uk/video/spy-sub-discovered-67-years-later-off-hawaiis-coast/518034993/"]re-discovery[/URL]. Not sure if the its whereabouts were completely unknown, due to the fact that U.S. forces scuttled her. Jim

from the cnn report "Finding it where we did was totally unexpected," lab operations director and chief submarine pilot Terry Kerby said in a university statement. "All our research pointed to it being further out to sea." Nigel

You'd think someone would have put a mark on a map when she was sunk in '46, wouldn't you ? In retrospect, they probably did and promptly filed the map wherever it is today. I-401 was discovered in the general vicinity ca. 2005. Still an interesting find. Bill

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