Different IJN submarine types during WW 2

[La Rouge Beret]

The Imperial Japanese Navy operated one of the most diverse submarine fleets, with regards to types, during WW 2. If a senior Naval Officer decided to rationalise the number of submarine types operated by the IJN, in favour of a common build, that was predicated on attacking merchants not warships. What type of submarine would the IJN develop?

 

[CalBear]

Before or after the senior officer who dared to question the Decisive Battle doctrine was given command of a floating dry dock?

Japanese subs would have been very effective raiders as is. It simply violated 35 years of Japanese naval doctrine to "waste" them on anything but preparing the battlefield for the Decisive Battle. To prepare the battlefield meant one had to attack warships, cargo ships were almost beneath a true warrior's attention.

 

[La Rouge Beret]

Before or after the senior officer who dared to question the Decisive Battle doctrine was given command of a floating dry dock?

Japanese subs would have been very effective raiders as is. It simply violated 35 years of Japanese naval doctrine to "waste" them on anything but preparing the battlefield for the Decisive Battle. To prepare the battlefield meant one had to attack warships, cargo ships were almost beneath a true warrior's attention.

Could not agree more, this is research for an ASB TL that I am considering.

 

[Pangur]

If you want to go near ASB then you could do worse that have the I-201 class be built early. Perhaps having a stronger lin between the pre ww2 German and Japanese submarine fleets?

 

[zert]

I think a standard class with long range and an allowance for increased torpedo storage would be a plus. Plus the ability to acquire radar as soon as possible. Maybe include the ability to stay under for a longer time would be advisable to wait out Allied depth charges.

 

[Flying Sorcerer]

I think a standard class with long range and an allowance for increased torpedo storage would be a plus. Plus the ability to acquire radar as soon as possible. Maybe include the ability to stay under for a longer time would be advisable to wait out Allied depth charges.

Was it true that japanese submarines used inferior steels and couldn't dive as deep as US boats?

 

[La Rouge Beret]

Any prospective submarine class, would also need to review construction methods and other inputs (such as steel etc). Actually constructing the vessel will be the easy part, changing the organisational culture of the submarine arm, will be harder and more critical.

 

[Pangur]

Any prospective submarine class, would also need to review construction methods and other inputs (such as steel etc). Actually constructing the vessel will be the easy part, changing the organisational culture of the submarine arm, will be harder and more critical.

Which is what I was getting at when I mentioned working with the German Navy

 

[La Rouge Beret]

True, the way the USN was able to ruthlessly shape their submarine arm in the Pacific theatre to be a pretty effective capability, gives a better view of my eventual goals.

The question I have is the IJN better served by reverse engineering a Type IX submarine or utilising an existing class?

 

[Pangur]

True, the way the USN was able to ruthlessly shape their submarine arm in the Pacific theatre to be a pretty effective capability, gives a better view of my eventual goals.

The question I have is the IJN better served by reverse engineering a Type IX submarine or utilising an existing class?

I would think that the major design concerns would be range, being able to carry a decent load of torpedos and a design that can be built in large numbers. Would the Type IX cut it? I suspect not as the Japanese subs would surely be using Long Lance torpedos which were 9 m long as against the 7.163 m for German torps. For a sub when you include reloads thats a fair bit of difference in lenght

 

[La Rouge Beret]

I would think that the major design concerns would be range, being able to carry a decent load of torpedos and a design that can be built in large numbers. Would the Type IX cut it? I suspect not as the Japanese subs would surely be using Long Lance torpedos which were 9 m long as against the 7.163 m for German torps. For a sub when you include reloads that's a fair bit of difference in length

I would add habitability to the list above, which IMO leads us towards a Japanese equivalent to the Gato class.

 

[Pangur]

I would add habitability to the list above, which IMO leads us towards a Japanese equivalent to the Gato class.

Yep, habitability is big one

 

[eltf177]

Many good points here. I agree with La Rouge Beret and Pangur that habitability is a priority as IJN subs were not known for this.

I would go with the I-15 class but get rid of the catapult, hanger and seaplane for a second deck gun and storage. Give the fleet something like the KM's 'Milch Cows' to help keep them at sea.

However, the High Command has to use them against commerce as well as warships. And THAT'S going to be just about ASB...

 

[La Rouge Beret]

Many good points here. I agree with La Rouge Beret and Pangur that habitability is a priority as IJN subs were not known for this.

I would go with the I-15 class but get rid of the catapult, hanger and seaplane for a second deck gun and storage. Give the fleet something like the KM's 'Milch Cows' to help keep them at sea.

However, the High Command has to use them against commerce as well as warships. And THAT'S going to be just about ASB...

Resupply is going to be their Achilles heel, which means that attacking the coastal shipping on the western American seaboard is a step too far. The change to commerce raiding is the hard part, and one of the reasons it is going to go into the asb forum.

I'll do some digging on the I 15 class, would that also include cutting down the conning tower ala latter war American submarines?

 

[Pangur]

Resupply is going to be their Achilles heel, which means that attacking the coastal shipping on the western American seaboard is a step too far. The change to commerce raiding is the hard part, and one of the reasons it is going to go into the asb forum.

I'll do some digging on the I 15 class, would that also include cutting down the conning tower ala latter war American submarines?

There is little to no point in trying to raid the US seaboard however going after the US sea lines to its naval forces in the pacific is a very different matter. They have a clear military objective, they have an excellent idea where the ships would sail from and to were they would be going. If they were to patrol that close to the US then surely keeping watch on mass ship movements would give them a decent indication of a planned US invasion of some islands and with a decent range they could tail those fleets

 

[La Rouge Beret]

Long range maritime patrol aircraft, combined with Japanese version of coastwatchers would help in that regard.

 

[La Rouge Beret]

The next step to my mind is the sensor fit, and hopefully there are some more learned types around the forum. I also think a Japanese version of the TDC is a must.

 

[eltf177]

Long range maritime patrol aircraft, combined with Japanese version of coastwatchers would help in that regard.

The IJN had two excellent flying boats - the H6K "Mavis" and the H8K "Emily", but never enough of them. I agree about coastwatchers, they would definitely have helped.

The next step to my mind is the sensor fit, and hopefully there are some more learned types around the forum. I also think a Japanese version of the TDC is a must.

German technology would have helped, along with the snorkel. Also maybe try something along the lines of the German 'Flak Traps' to try and keep US aircraft at bay?

 

[mudhead]

If you want to go near ASB then you could do worse that have the I-201 class be built early. Perhaps having a stronger lin between the pre ww2 German and Japanese submarine fleets?

Another possibility: a closer post war - or pre-1922, anyway - link between the IJN and the RN. The 'R' class submarines were the first boats optimised for underwater rather than surface performance - 14 knots underwater, not bad for a 1917 design. IRL they were mainly scrapped postwar (no operational requirement, they couldn't fulfill peacetime patrol boat duties), bar two used for ASW training.

POD: they're sold (or the designs are) to the IJN, post war, rather than broken up. A fast submarine, if it could be developed - and the IJN was capable of putting a lot of development work into something it liked - might fit into existing Decisive Battle doctrine, and over time could be used as an ASW platform. Wikipedia basic, but seems accurate enough - here.

I would think that the major design concerns would be range, being able to carry a decent load of torpedos and a design that can be built in large numbers. Would the Type IX cut it? I suspect not as the Japanese subs would surely be using Long Lance torpedos which were 9 m long as against the 7.163 m for German torps. For a sub when you include reloads thats a fair bit of difference in lenght

IJN boats didn't use the Type 93 - the midgets used a Type 97 variant, but standard boats used 21" similar to other navies. There was a Type 95 variant of Long Lance designed for submarine use, but I don't know it it was issued at all, or widely used.

Basic information here

 

[Just Leo]

The Type 95 was issued, and widely used. Ask the Indianapolis.