How much damage could submarines do to Japan in the China Sea?

So, splitting off from my main thread on a German-aligned KMT China in a CP victory scenario, I was wondering about the naval situation.

Ittl, the Germans have invested a lot of material in China and one of the beneficiaries is the Chinese naval armament program, where rebuilt shipyards churn out submarines and cruisers.

Japan invades around the same time as in otl, but China has way more industry and professionally trained and equipped divisions and turns the war into a stalemate.

My question is, at this point, how much damage to the Japanese navy could a hypothetical Chinese submarine power do? Would they be able to sink warships or would they be more effective as strictly convoy raiders?
 
I think it depends on who supplies them the subs and training, if its the Germans I would think the could do serious damage ala what happened to the UK during the blitz and the battle of the Atlantic. It also depends if Japan is alone or has allies, if it is a straight up China v Japan I still would give it to Japan for tech reasons for at least 50-75 years due to a lot of internal problems the KMT had but they will make Japan bleed and the later it gets the more likely it becomes China could win.
 
I think it depends on who supplies them the subs and training, if its the Germans I would think the could do serious damage ala what happened to the UK during the blitz and the battle of the Atlantic. It also depends if Japan is alone or has allies, if it is a straight up China v Japan I still would give it to Japan for tech reasons for at least 50-75 years due to a lot of internal problems the KMT had but they will make Japan bleed and the later it gets the more likely it becomes China could win.

Well, ittl the Germans are providing both technical and training support so the crews are trained to a higher standard than otherwise and their subs are pretty modern. I can see Chinese subs essentially crippling outside supply of Korea and Manchuria, forcing the Japanese to rely more and more on native industries there, but I'm not sure how fast the Japanese ASW would adapt to a German-style submarine offensive, considering how poorly they did against the USA iotl.
 
The Japanese merchant fleet was sufficiently small that pressure from submarines could cause massive damage the Japanese economy.
 
Well, ittl the Germans are providing both technical and training support so the crews are trained to a higher standard than otherwise and their subs are pretty modern. I can see Chinese subs essentially crippling outside supply of Korea and Manchuria, forcing the Japanese to rely more and more on native industries there, but I'm not sure how fast the Japanese ASW would adapt to a German-style submarine offensive, considering how poorly they did against the USA iotl.
that seems plausible then, the thing is Chinese construction for a long time is iffy, numbers though might be China's strong suit. Subs could be China's Sherman tanks, they could overwhelm them even with significant losses. And as Naraic said do massive damage to Japan
 
Going with the 4-1 deployment schedule then if Germany sells China a dozen subs then there will be a average of three operating any one week. Another three will be refiting or training crews, while the other six are returned from patrol or near ready to patrol. I'm thinking the Germans would recommend smaller types since the near seas to China are filled with reefs, islands, shoals... If the Germans sell the Chinese on a complete coast defense package what sort of torpedo boats and 1930s style maritime patrol/strike aircraft would fall into Chinese hands?
 
The problem is the long time frame it will take for the Chinese to establish a submarine arm. For every sub crewman you'll need one more for the shore establishment for training. You'll need yards capable of doing repair and maintenance work of a very high quality, armorers who can maintain torpedoes, etc. All of this is starting from square zero where you have no crews trained, no maintenance people trained, and on and on. It will take 5-6 years to adequately train an officer from junior officer on a sub to commanding officer - yes folks got promoted faster in WWII but that was exceptional. How many years experience did the COB (chief of the boat) have in western navies, probably at least 10. Even if you magically had the boats, China in the 1920s and 1930s had almost no navy, and while the Chinese are certainly as POTENTIALLY capable as anyone else, the educational level in China for both potential enlisted and officers was limited - a small pool to choose from.

For China to build a submarine force of a dozen coastal submarines, you need to build the shore establishment at the same time. You'll probably need one base for the South China Sea and one for China's east coast - one of which is the major training and maintenance. A coastal submarine will have a crew of about 40 (looking at similar submarines in the IJN). So for a dozen submarines you'll need ~960 sub qualified personnel of whom perhaps 50-60 are officers. Some of these will be part of the technical shore establishment and some part of the training establishment at any one time. I can't imagine you'll need any less than 1,000 enlisted and 50 officers to run the base(s), manage repairs and shore based maintenance, etc. All of these roughly 2,000 people need to be highly trained and competent. I'm not counting the shore establishment that manages base services (logistics, messing, barracks - everything that makes a base run). Getting the non-technical personnel for base services is relatively easy.

If you start from zero, as China would have to, I would estimate it would take a minimum of 10 years to have an effective submarine force of 12 coastal submarines with all of the supporting facilities. This is assuming you don't have active military operations going on where the IJA is trying to overrun your base, the IJN or IJAAF bombing your facilities. This project will also be quite expensive, and require significant expenditures in hard currency to buy equipment, boats, torpedoes, trainers, salaries for foreign instructors. Naturally on top of the actual expenditures, you have the levels of corruption that existed in China at this time which will suction off funds raising the cost. China has neither the money, personnel, nor time to do all this.

Realistically China would need to start doing this in the mid-1920s, and even then they would be dependent on foreign sources for submarines, most spare parts, and torpedoes. China simply does not have the technical/industrial base to build submarines and torpedoes in the 1920s and 1930s. As an example look at the difficulties China had to build an indigenous air force where getting adequate personnel for pilot training and mechanic training was a struggle and you had Chinese being trained in the US for these roles.
 
Going with the 4-1 deployment schedule then if Germany sells China a dozen subs then there will be a average of three operating any one week. Another three will be refiting or training crews, while the other six are returned from patrol or near ready to patrol. I'm thinking the Germans would recommend smaller types since the near seas to China are filled with reefs, islands, shoals... If the Germans sell the Chinese on a complete coast defense package what sort of torpedo boats and 1930s style maritime patrol/strike aircraft would fall into Chinese hands?

Lets imagine that the Germans are selling a lot of weapons to the KMT (Since the German Arms industry wasn't constrained by Versailles and the demand for Chinese raw materials is high), so they're getting a lot.

The problem is the long time frame it will take for the Chinese to establish a submarine arm. For every sub crewman you'll need one more for the shore establishment for training. You'll need yards capable of doing repair and maintenance work of a very high quality, armorers who can maintain torpedoes, etc. All of this is starting from square zero where you have no crews trained, no maintenance people trained, and on and on. It will take 5-6 years to adequately train an officer from junior officer on a sub to commanding officer - yes folks got promoted faster in WWII but that was exceptional. How many years experience did the COB (chief of the boat) have in western navies, probably at least 10. Even if you magically had the boats, China in the 1920s and 1930s had almost no navy, and while the Chinese are certainly as POTENTIALLY capable as anyone else, the educational level in China for both potential enlisted and officers was limited - a small pool to choose from.

For China to build a submarine force of a dozen coastal submarines, you need to build the shore establishment at the same time. You'll probably need one base for the South China Sea and one for China's east coast - one of which is the major training and maintenance. A coastal submarine will have a crew of about 40 (looking at similar submarines in the IJN). So for a dozen submarines you'll need ~960 sub qualified personnel of whom perhaps 50-60 are officers. Some of these will be part of the technical shore establishment and some part of the training establishment at any one time. I can't imagine you'll need any less than 1,000 enlisted and 50 officers to run the base(s), manage repairs and shore based maintenance, etc. All of these roughly 2,000 people need to be highly trained and competent. I'm not counting the shore establishment that manages base services (logistics, messing, barracks - everything that makes a base run). Getting the non-technical personnel for base services is relatively easy.

If you start from zero, as China would have to, I would estimate it would take a minimum of 10 years to have an effective submarine force of 12 coastal submarines with all of the supporting facilities. This is assuming you don't have active military operations going on where the IJA is trying to overrun your base, the IJN or IJAAF bombing your facilities. This project will also be quite expensive, and require significant expenditures in hard currency to buy equipment, boats, torpedoes, trainers, salaries for foreign instructors. Naturally on top of the actual expenditures, you have the levels of corruption that existed in China at this time which will suction off funds raising the cost. China has neither the money, personnel, nor time to do all this.

Realistically China would need to start doing this in the mid-1920s, and even then they would be dependent on foreign sources for submarines, most spare parts, and torpedoes. China simply does not have the technical/industrial base to build submarines and torpedoes in the 1920s and 1930s. As an example look at the difficulties China had to build an indigenous air force where getting adequate personnel for pilot training and mechanic training was a struggle and you had Chinese being trained in the US for these roles.

Interesting. This is what I was looking for as I don't know as much about the logistics and infrastructure submarines require. What if the Germans are building the bases for their own subs and allowing the Chinese to use part of them (so German subs can strike at commerce in Asia should war break out) and is training them at the same time. Would a substantial investment on the side of the Germans starting in 1931 be enough to overcome many of these obstacles?

And also these shoreside estabilishments and ports would be prime targets by the IJN when war breaks out.

Agreed. However, if they're also German bases would the Japanese initially risk a war with the German Empire (who has a much more powerful fleet ittl)?
 
If you start from zero, as China would have to, I would estimate it would take a minimum of 10 years to have an effective submarine force of 12 coastal submarines with all of the supporting facilities.

Realistically China would need to start doing this in the mid-1920s, and even then they would be dependent on foreign sources for submarines, most spare parts, and torpedoes. As an example look at the difficulties China had to build an indigenous air force where getting adequate personnel for pilot training and mechanic training was a struggle and you had Chinese being trained in the US for these roles.

my thinking is you are correct but maybe the Chinese were more optimistic? details on small coastal u-boats ordered from Germany http://www.navypedia.org/ships/china/ch_ss_iib.htm

possible the Germans were to be involved in sub operations?
 

James G

Gone Fishin'
Maybe these Chinese subs do plenty of damage or maybe not. The Japanese surely react by doing what they did in OTL and taking all coastal ports. If the subs do really well and stop amphibious assaults then the Japanese go overland. Pre 1941 that was where their army focus was and they'll go south along the coast. Without ports for these subs it is bye-bye to a Chinese submarine arm.
 
Maybe these Chinese subs do plenty of damage or maybe not. The Japanese surely react by doing what they did in OTL and taking all coastal ports. If the subs do really well and stop amphibious assaults then the Japanese go overland. Pre 1941 that was where their army focus was and they'll go south along the coast. Without ports for these subs it is bye-bye to a Chinese submarine arm.
If you read the other thread you will see that the Chinese army has 60 German trained and equipped divisions by 1936. I guess that would be a challenge for Japan to face on land.

The question becomes can the Japanese equip and supply an equivalent force if the Chinese have managed to atria the Japanese merchant fleet.

I sat the answer is no. However if China was a peer nation I feel that Japan would be likely to have built up anow armaments industry (perhaps in Korea) to equip the Japanese army in China.

Who knows where the butterflies would bring us from there.
 

James G

Gone Fishin'
I haven't read nor know what that thread is. In addition, while the German trained Chinese divisions put up a fight in OTL, the Japanese had the will to take the losses and move on. Japan as an island trading nation not willing to bend to the will of others would have done whatever it took to not allow china to threaten it's trade. They would have gone after those submarine bases.
 
From what we know of Japanese bias regarding its conduct of submarine warfare and conversely anti-submarine warfare I would opine that even a few submarines could seriously disrupt Japan's thin merchant shipping resources. But I agree with others that China simply does not have the time if it only begins to pursue submarines mid-to-late 1930s and Japan keeps to schedule for war. Given greater trade surpluses with Germany I would assume more effort goes into a Chinese Air Force rather than bleeding off technical resources for a navy that in the short-term does not appear to change things enough. I suspect the 5 submarines ordered were long term planning and might get cancelled in the event of war beginning 1937 to 1939.

China has no good basing option and I doubt they want to reintroduce foreign personnel and naval power by having Germany build a base assuming Germany is that ambitious. My assumption is that Germany wants the benefits of trade here and slowly goes down the adviser path to something akin to Legion Condor at most. And the other powers would be wary of Germans stepping into China with troops, planes and ships to widen the war. Now might the Germans man those first five subs and train the Chinese covertly, pretending they are ROC crewed and tasked? If we get a secure base then it complicates things for Japan and might do best in souring her relations with the other players, especially the USA and UK as she reacts with a heavy hand.
 
given the collaboration with Soviets the German KM could launch more auxiliary cruisers into Pacific and help China equip same type of ship, that seems more realistic? (the German cruisers were expected to make return voyage north of USSR as transports at one point.)

a Chinese pirate fleet
 
I haven't read nor know what that thread is. In addition, while the German trained Chinese divisions put up a fight in OTL, the Japanese had the will to take the losses and move on. Japan as an island trading nation not willing to bend to the will of others would have done whatever it took to not allow china to threaten it's trade. They would have gone after those submarine bases.
Well it's linked on the OP.

In summary
Central Powers win ww1 but it's a negotiated peace and Germany doesn't get back its Asian possessions.

Germany pursues soft empire in China with major trading investment and military partnerships.

China has 60 German trained and equipped divisions for 1936. This compares with something like 11 divisions historically.

Yes Japan would have gone for submarine bases but this China is a peer nation so won't get them easily.
 
I goofed on reading the OP. In a CP win scenario there is more option for a Chinese naval build up. However the basics of what I wrote remain the same. If you have senior officers and petty officers who are German on the sub crews for the first 3-4 years with accelerated promotion for Chinese personnel who show potential. The timeline for training the force, building the base structure and so forth remains the same - having Chinese personnel on a selected basis going to Germany for training also helps however the language issue is huge. Submarine and aircraft carrier operations are the two most difficult of naval regimes to master. The Chinese could do this on a longer timescale but would be better off staring with light coastal forces up to destroyers first. As bad as Japanese ASW doctrine was in many ways, as the war went on they did make improvements in the face of a US submarine force much larger than anything China could have which also had the benefit of significant crypto support. While 3 coastal submarines at sea at any one time could certainly be painful for the Japanese, this force would be whittled down and replacing subs will be pretty much impossible.
 
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