What if the Type 21 U-Boats became operational in 1940?

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Takao
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Re: What if the Type 21 U-Boats became operational in 1940?

Post by Takao » 16 Dec 2019 17:54

TheMarcksPlan wrote:
15 Dec 2019 12:37

Absolutely. The prudent course for an earlier T21 would have been to use, say, half of the ways/docks for old-style construction from keel up and the other half for assembling modules. Then as you work out the predictable bugs in the system you shift to all-modular. That at least guarantees operational experience with the new type and live training of crews on it.
Your assuming that the Germans will be rushing production of the this earlier XXIs. That was the root of the modular production troubles. Had the Germans proceeded at a norma pace, and made sure that the companies producing the modules had all their ducks in a row,the problems would have been far less. However, the Germans were in too much of a rush to complete the XXIs.


TheMarcksPlan wrote:
15 Dec 2019 12:37
I was just making the point that even if Germany made the same choice earlier as it did OTL as a desperation shot, they'd still have produced a potentially war-winning weapon.
The XXI was never a war winning weapon, nor could it ever be, as the Type XXI could never sink ships at a much greater rate than the U-Boats then in use. The U-Boats were so successful because the British lacked enough escorts early in the war. Once the British were producing escorts in numbers, the Type XXI would face all the same problems that the U-Boats then in use faced.

TheMarcksPlan wrote:
15 Dec 2019 12:37

I'd also think T21 would have been supplemented by 1945 with further enhanced eBoats. Like a 3-4x larger one that can do 25 knots and therefore chase down fleet assets (30kn+ max speed for most fleet task forces but they dont steam at those speeds because only the capital ships have meaningful range at the highest speeds).
The only boats that could be capable of such high speeds were the Walther boats - Which were projected to do 23 knots for 5-6 hours, and those were not much larger than the XXIs. Indeed, most of the paper project U-Boats were smaller more maneuverable ones that could better evade escorts. The largest was the XXIc which was fitted with an additional module of torpedo tubes amidships, but had no increase in speed.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by Takao » 16 Dec 2019 18:10

We should also remember that the British one-upped the Germans, by converting HMS Seraph into a high speed submarine, and using her to conduct attack trials against. The Brits also informed the Americans of their intel, resulting in the US converting the old R-1(SS-78) into a high speed target submarine. The British also converted two other of their S-Class submarines into high speed targets for ASW training exercises. The Western Allies also focused on improving existing technologies to counter the threat, as well as developing new ones.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by T. A. Gardner » 16 Dec 2019 20:02

What you would see here is the Allies reacting more strongly to the threat they're presented with. If the Type XXI represented a greater threat at sea to merchant shipping the British and then the US would have responded more strongly to that threat. By the end of 1940 most of the necessary weapons and sensors to defeat the Type XXI were in development. The weapons and sensors to defeat more conventional Type VII and IX boats were in use. So, development took a normal pace.
If the need for those weapons and sensors were greater they'd be pushed into service sooner and the Type XXI facing weapons and sensor systems that can defeat them becomes the new norm.

The Walther boats would have proved unserviceable operationally, just as H2O2 boats did in other navies that tried them post WW 2. The British built two H2O2 submarines Explorer and Excalibur. They were derisively called Exploder and Excruciator by their crews for the danger they posed. The Soviets tried this with a couple of their Zulu class subs but found the problems insurmountable and gave up because of the danger.
It's like using liquid sodium for coolant in a reactor system on a sub. It sounds like a good idea on paper but it's a nightmare in practice.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by Takao » 16 Dec 2019 20:34

The US also tried H2O2 on the SS X-1 in the mid-50s...with similar explosive results, and promptly converted her to diesel-electric propulsion.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by TheMarcksPlan » 17 Dec 2019 04:19

Takao wrote:Your assuming that the Germans will be rushing production of the this earlier XXIs. That was the root of the modular production troubles. Had the Germans proceeded at a norma pace, and made sure that the companies producing the modules had all their ducks in a row,the problems would have been far less. However, the Germans were in too much of a rush to complete the XXIs.
True, I did make that assumption.
OTOH Germany rushed weapons like the Panther that grabbed Hitler's attention so I'd lean towards rushing T21 also. But maybe not.
Takao wrote:The XXI was never a war winning weapon, nor could it ever be, as the Type XXI could never sink ships at a much greater rate than the U-Boats then in use.
Upthread I've said that I doubt T21 would be more effective at sinking ships than historical Uboats were pre-May43. So we agree there.
But it's not the per ship stats that matter, it's the total tonnage. OTL Uboat production peaked just as the Uboats were becoming useless. By extending the Uboat campaign past 1943, Germany might have been able to build enough of them to render the U.S. land contribution negligible and to weaken Britain's output.

That alone doesn't win the war if the Red Army keeps grinding the Ostheer into a pulp. I said "potential" war winning weapon, meaning Germany also has to avoid losing on other fronts.
Takao wrote:The only boats that could be capable of such high speeds were the Walther boats
OTL yes, ATL maybe not. A larger sub has a lower ratio of displacement to drag (square-cube principle), so requires less HP and batteries to achieve/sustain a given speed. 25kn is probably a bit high...

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by TheMarcksPlan » 17 Dec 2019 07:30

T.A. Gardner wrote:What you would see here is the Allies reacting more strongly to the threat they're presented with. If the Type XXI represented a greater threat at sea to merchant shipping the British and then the US would have responded more strongly to that threat. By the end of 1940 most of the necessary weapons and sensors to defeat the Type XXI were in development. The weapons and sensors to defeat more conventional Type VII and IX boats were in use. So, development took a normal pace.
If the need for those weapons and sensors were greater they'd be pushed into service sooner and the Type XXI facing weapons and sensor systems that can defeat them becomes the new norm.
You're not the first to make this point but, like the others, you still need to explain which "weapons and sensors" would have defeated T21.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by T. A. Gardner » 17 Dec 2019 18:39

TheMarcksPlan wrote:
17 Dec 2019 07:30
T.A. Gardner wrote:What you would see here is the Allies reacting more strongly to the threat they're presented with. If the Type XXI represented a greater threat at sea to merchant shipping the British and then the US would have responded more strongly to that threat. By the end of 1940 most of the necessary weapons and sensors to defeat the Type XXI were in development. The weapons and sensors to defeat more conventional Type VII and IX boats were in use. So, development took a normal pace.
If the need for those weapons and sensors were greater they'd be pushed into service sooner and the Type XXI facing weapons and sensor systems that can defeat them becomes the new norm.
You're not the first to make this point but, like the others, you still need to explain which "weapons and sensors" would have defeated T21.
The first would be the sonobuoy. The AN/CRT 1 to 4 models would be made available sooner. The US was testing a prototype in September 1941 before the British suggested the idea to them. That could be pushed up considerably. Add radar and you have a plane with a combination of sensors that can hunt down a Type XXI. Speed would be of little value here just as it was in the 50's and 60's versus ASW aircraft with essentially the same equipment.

Add in an earlier use of FIDO and other homing torpedoes. Same thing. You can't run and you can't hide a WW 2 sub from these weapons.

For ships, the biggest change would be going to a scanning sonar like the QGA or SQS 4 rather than the much slower "searchlight" manually swept ones used for much of the war. Again, the technology was in development but not rushed because production of the adequate searchlight sets took precedence.

US DE type escorts are fast enough to deal with a Type XXI so that doesn't need changing. The US might need to build the 1000+ they planned rather than the about 500 they actually built. Actual destroyers could be used too. Sure, the British would find the Flower class almost useless, but it would still be better than nothing.

The US in particular could build faster merchant ships like the Victory Ship. That complicates the Type XXI's attack patterns.

Pushing more aircraft earlier into ASW work would help as well. Although the US didn't deck over merchant ships into makeshift carriers, they could have to put more flight decks at sea quicker

Pushing out better ahead thrown weapons like say trainable hedgehog with a longer range, Squid / Limbo, or even something like Weapon Alpha, is all very doable on a shorter timetable.

Basically, you get the ASW weapons of the late 40's in the early 40's when they were being developed at lower priorities, because they get pushed up to higher priority.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by JAG13 » 17 Dec 2019 20:00

T. A. Gardner wrote:
17 Dec 2019 18:39

The first would be the sonobuoy. The AN/CRT 1 to 4 models would be made available sooner. The US was testing a prototype in September 1941 before the British suggested the idea to them. That could be pushed up considerably. Add radar and you have a plane with a combination of sensors that can hunt down a Type XXI. Speed would be of little value here just as it was in the 50's and 60's versus ASW aircraft with essentially the same equipment.

Add in an earlier use of FIDO and other homing torpedoes. Same thing. You can't run and you can't hide a WW 2 sub from these weapons.
FIDOs and sonobuoys need a prompt...

That means sonar and radar.

A proper ESM as envisaged for the Type XXI means radar will NEVER detect a sub, the signal will simply warn the sub well before the radar can get a return and the sub will dive.

Same for the sonar, an active sonar means it is the first target for a guided torpedo, great for the merchants, quite a danger for the emitting escort.

Of course, a Type XXI doesnt need to penetrate a convoy screen, can simply launch its six torpedoes against the convoy and set the sound tracking to activate when arriving at the estimated position of the convoy, less accurate and no clue on the results, but far safer, let the escorts guess where the torpedoes came from...

...and newer and different torpedoes were in the pipeline as well.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by T. A. Gardner » 17 Dec 2019 20:41

JAG13 wrote:
17 Dec 2019 20:00
FIDOs and sonobuoys need a prompt...

That means sonar and radar.

A proper ESM as envisaged for the Type XXI means radar will NEVER detect a sub, the signal will simply warn the sub well before the radar can get a return and the sub will dive.
Driving a diesel boat down and keeping it down is almost as effective as sinking it. A Type XXI can only stay submerged so long before the batteries give out. Snorkeling means giving the ASW ships and planes a radar target. It also means greatly increased noise running the diesels. Sure, its safer than being surfaced, but it has limitations and you can't do it when there's a search plane in the vicinity.

Also, even with proper ESM, German U-boats often got detected by radar so it's no panacea against that.
Same for the sonar, an active sonar means it is the first target for a guided torpedo, great for the merchants, quite a danger for the emitting escort.
Except there is no sonar homing torpedo in existence at the time, German or Allied. The Germans had one by mid war that homed on noise in general but that quickly got countered by ships trailing a Foxer decoy.
Of course, a Type XXI doesnt need to penetrate a convoy screen, can simply launch its six torpedoes against the convoy and set the sound tracking to activate when arriving at the estimated position of the convoy, less accurate and no clue on the results, but far safer, let the escorts guess where the torpedoes came from...

...and newer and different torpedoes were in the pipeline as well.
Torpedo range remains the issue here. A convoy properly run is spread out sufficiently that random torpedoes are going to generate few hits. Doesn't matter if they're pattern runners, or whatever. The further out you fire from the shorter the time the torpedo has left when it reaches the area of the target. This is accepting fewer enemy losses for your own safety. If those losses are at a sustainable level then the U-boat has failed it's purpose.

Also, the Germans still have the problem of centralized control and daily reporting in that gives their position away to Allied HF/DF stations. Doesn't matter one whit that the Allies can or can't read the code and messages sent. What matters is the location of the transmission is pinpointed. That gives the Allies a place to start looking for the boat.

Of course, there's also the Allies doing things like bombing the snot out of U-boat shipyards, pens and docking facilities, etc.

It's just like in physics. For every action, there's an equal an opposite reaction. Only in this case it isn't always equal...

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by JAG13 » 17 Dec 2019 21:22

T. A. Gardner wrote:
17 Dec 2019 20:41
JAG13 wrote:
17 Dec 2019 20:00
FIDOs and sonobuoys need a prompt...

That means sonar and radar.

A proper ESM as envisaged for the Type XXI means radar will NEVER detect a sub, the signal will simply warn the sub well before the radar can get a return and the sub will dive.
Driving a diesel boat down and keeping it down is almost as effective as sinking it. A Type XXI can only stay submerged so long before the batteries give out. Snorkeling means giving the ASW ships and planes a radar target. It also means greatly increased noise running the diesels. Sure, its safer than being surfaced, but it has limitations and you can't do it when there's a search plane in the vicinity.
By necessity the aircraft has an even shorter autonomy than the Uboat on batteries, moreover, it would lack the prompt to stick around and seriously bother the sub.
Also, even with proper ESM, German U-boats often got detected by radar so it's no panacea against that.
No, had the KM had PROPER ESM in WW2 they wouldnt have gotten detected by radar, they kept screwing up and ignoring microwaves until late war.
Same for the sonar, an active sonar means it is the first target for a guided torpedo, great for the merchants, quite a danger for the emitting escort.
Except there is no sonar homing torpedo in existence at the time, German or Allied. The Germans had one by mid war that homed on noise in general but that quickly got countered by ships trailing a Foxer decoy.
Not countered, reduced its effectiveness, it still got hits and the Germans were fielding/about to field improved versions including an active homer which would have made countermeasures ineffective.
Of course, a Type XXI doesnt need to penetrate a convoy screen, can simply launch its six torpedoes against the convoy and set the sound tracking to activate when arriving at the estimated position of the convoy, less accurate and no clue on the results, but far safer, let the escorts guess where the torpedoes came from...

...and newer and different torpedoes were in the pipeline as well.
Torpedo range remains the issue here. A convoy properly run is spread out sufficiently that random torpedoes are going to generate few hits. Doesn't matter if they're pattern runners, or whatever. The further out you fire from the shorter the time the torpedo has left when it reaches the area of the target. This is accepting fewer enemy losses for your own safety. If those losses are at a sustainable level then the U-boat has failed it's purpose.
The KM experimented with torpedoes with extra batteries and a 9Km range and found them too heavy, but if an absolute need had been identified...
Also, the Germans still have the problem of centralized control and daily reporting in that gives their position away to Allied HF/DF stations. Doesn't matter one whit that the Allies can or can't read the code and messages sent. What matters is the location of the transmission is pinpointed. That gives the Allies a place to start looking for the boat.
Kurier would have certainly at the very least degraded that capability if not eliminated the problem altogether:

(Battle of the Atlantic Vol. VI, Technical intellegence from Allied Communications Intellegence (SRH025), Chapter VIII.8 says: "Obviously this system was designed as a counter-measure against D/F. Further security was obtained in the use of frequencies, in that deviation from a given basic frequency of as much as 200 kcs plus of minus was provided for. In no case were KURIER transmissions ever D/F'd, and it is significant that if this system had been brought into effective operational use, the Allied D/F organization would gave been rendered helpless until counter-equipment could have been devised."

Quoted from a post by delcyros here:

https://www.tapatalk.com/groups/warship ... -s190.html

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by TheMarcksPlan » 17 Dec 2019 21:23

@T.A. Gardner I might respond in more detail later and I thank you for your detailed response.

What I guessed you meant by "defeat the T21" was something total domination of the vessels akin to T7/9's fate.

My point is that unless the Wallies achieve something like that, the KM can reasonably expect a massive edge in submarine attrition warfare to persist. Even if your ASW advances limit the average T21 to, say, 4 Liberty Ships sunk (~30k GRT), that imposes a ~6:1 economic attrition ratio on Wallies. In a Wallies vs. Germany fight (i.e. no eastern front or German victory there) that's negates Wallies' economic edge if Germany spends just 10% on subs.

That's all I mean by potential war winner. I hope it's clear from my suggested 30k tonnage average that I don't think T21 was impervious to ASW or something. I just don't think the Wallies would have been able to dominate the BoA as in later OTL and I think they need Atlantic battlefield dominance to win.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by T. A. Gardner » 18 Dec 2019 05:21

JAG13 wrote:
17 Dec 2019 21:22
T. A. Gardner wrote:
17 Dec 2019 20:41
JAG13 wrote:
17 Dec 2019 20:00
FIDOs and sonobuoys need a prompt...

That means sonar and radar.

A proper ESM as envisaged for the Type XXI means radar will NEVER detect a sub, the signal will simply warn the sub well before the radar can get a return and the sub will dive.
Driving a diesel boat down and keeping it down is almost as effective as sinking it. A Type XXI can only stay submerged so long before the batteries give out. Snorkeling means giving the ASW ships and planes a radar target. It also means greatly increased noise running the diesels. Sure, its safer than being surfaced, but it has limitations and you can't do it when there's a search plane in the vicinity.
By necessity the aircraft has an even shorter autonomy than the Uboat on batteries, moreover, it would lack the prompt to stick around and seriously bother the sub.
Aircraft can be rotated on station. Typically, ASW carrier planes of the time could stay aloft for several hours. Maritime patrol planes could fly for as much as close to a day (like the B-24). They could easily call for another plane to relieve them on station if that were necessary.
Blimps, like the US used, could stay up for days.

Tactics also play a role. Take VP-63 for example. They came up with a operational method that fit the bottleneck of the Straight of Gibraltar they called "The Fence." It was a constantly patrolled barrier that would catch any sub trying to enter the Mediterranean Sea. See my article on their unique weapon the Retrobomb they used to sink several that tried.

https://www.navalhistory.org/2019/10/08/the-retro-bomb
Also, even with proper ESM, German U-boats often got detected by radar so it's no panacea against that.

No, had the KM had PROPER ESM in WW2 they wouldnt have gotten detected by radar, they kept screwing up and ignoring microwaves until late war.
The US had proper ESM in the Pacific on their subs. They found that mounting and using radar was a better proposition than ESM. US sub captains thought that was a bad idea until a combination of operations researchers and naval officers developing tactics showed them in training that it wasn't. Once they knew how to use their gear to best advantage they came to love using radar.

The German problem is there won't be any such systematic training. Instead, each sub commander will have to work it out for himself and then try to swap information with other commanders, assuming he survives his patrol.
Same for the sonar, an active sonar means it is the first target for a guided torpedo, great for the merchants, quite a danger for the emitting escort.

Except there is no sonar homing torpedo in existence at the time, German or Allied. The Germans had one by mid war that homed on noise in general but that quickly got countered by ships trailing a Foxer decoy.

Not countered, reduced its effectiveness, it still got hits and the Germans were fielding/about to field improved versions including an active homer which would have made countermeasures ineffective.
Foxer was relatively effective. Mk 6 Fanfare its replacement was even better. The later duplicated a ship's screws much closer than the relatively simple Foxer.
Of course, a Type XXI doesnt need to penetrate a convoy screen, can simply launch its six torpedoes against the convoy and set the sound tracking to activate when arriving at the estimated position of the convoy, less accurate and no clue on the results, but far safer, let the escorts guess where the torpedoes came from...

...and newer and different torpedoes were in the pipeline as well.


Torpedo range remains the issue here. A convoy properly run is spread out sufficiently that random torpedoes are going to generate few hits. Doesn't matter if they're pattern runners, or whatever. The further out you fire from the shorter the time the torpedo has left when it reaches the area of the target. This is accepting fewer enemy losses for your own safety. If those losses are at a sustainable level then the U-boat has failed it's purpose.

The KM experimented with torpedoes with extra batteries and a 9Km range and found them too heavy, but if an absolute need had been identified...
The Allies have the edge on agility to make new weapons and countermeasures simply by virtue of having more resources to put into this. It isn't that the Germans were stupid or something, they simply don't have the kind of resources-- and in the US case the industrial organization-- to match what the Allies can do.
Also, the Germans still have the problem of centralized control and daily reporting in that gives their position away to Allied HF/DF stations. Doesn't matter one whit that the Allies can or can't read the code and messages sent. What matters is the location of the transmission is pinpointed. That gives the Allies a place to start looking for the boat.

Kurier would have certainly at the very least degraded that capability if not eliminated the problem altogether:

(Battle of the Atlantic Vol. VI, Technical intellegence from Allied Communications Intellegence (SRH025), Chapter VIII.8 says: "Obviously this system was designed as a counter-measure against D/F. Further security was obtained in the use of frequencies, in that deviation from a given basic frequency of as much as 200 kcs plus of minus was provided for. In no case were KURIER transmissions ever D/F'd, and it is significant that if this system had been brought into effective operational use, the Allied D/F organization would gave been rendered helpless until counter-equipment could have been devised."

Quoted from a post by delcyros here:

https://www.tapatalk.com/groups/warship ... -s190.html
I read this. Kurier is a very late war system that used skywave burst transmissions. It would have fixed a lot of the HF/DF problems but it wasn't around in 1939-40 when the scenario is occurring. So, unless you want the Allies to be were they were in 1944-45 too, it's sort of unfair and one-sided to say the Germans would have 1944-45 equipment all around and the Allies are stuck with 1939-40 equipment.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by TheMarcksPlan » 18 Dec 2019 12:20

T.A. Gardner wrote:Add in an earlier use of FIDO and other homing torpedoes. Same thing. You can't run and you can't hide a WW 2 sub from these weapons.
T21 was faster than FIDO - top speed of 15kn.

What was the development timeline of homing torpedoes significantly faster? My understanding is the limit wasn't the torp itself - obviously there were faster ones decades earlier- but on the ability of the homing mechanism to work at faster speeds.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by JAG13 » 18 Dec 2019 15:24

T. A. Gardner wrote:
18 Dec 2019 05:21

Aircraft can be rotated on station. Typically, ASW carrier planes of the time could stay aloft for several hours. Maritime patrol planes could fly for as much as close to a day (like the B-24). They could easily call for another plane to relieve them on station if that were necessary.
Blimps, like the US used, could stay up for days.

Tactics also play a role. Take VP-63 for example. They came up with a operational method that fit the bottleneck of the Straight of Gibraltar they called "The Fence." It was a constantly patrolled barrier that would catch any sub trying to enter the Mediterranean Sea. See my article on their unique weapon the Retrobomb they used to sink several that tried.

https://www.navalhistory.org/2019/10/08/the-retro-bomb
If its 1940 forget about carrier ASW... specially radar equipped.
The US had proper ESM in the Pacific on their subs. They found that mounting and using radar was a better proposition than ESM. US sub captains thought that was a bad idea until a combination of operations researchers and naval officers developing tactics showed them in training that it wasn't. Once they knew how to use their gear to best advantage they came to love using radar.

The German problem is there won't be any such systematic training. Instead, each sub commander will have to work it out for himself and then try to swap information with other commanders, assuming he survives his patrol.
The USN had no ASW opposition, the IJN was utterly clueless in that regard, a point proven precisely by the fact that the USN could use radar with impunity, usually a no-no for submarines since it broadcasted its presence.
Foxer was relatively effective. Mk 6 Fanfare its replacement was even better. The later duplicated a ship's screws much closer than the relatively simple Foxer.
Which is why they were about to deploy the active Geier and even a wire-guided torpedo steered by the sonar operator.
The Allies have the edge on agility to make new weapons and countermeasures simply by virtue of having more resources to put into this. It isn't that the Germans were stupid or something, they simply don't have the kind of resources-- and in the US case the industrial organization-- to match what the Allies can do.
Lets see what Adm. Nimitz really thought of the type XXI and its effect, after extensive trials of course:

"These tests (...) have demonstrated that this particular submarine can with relative immunity attack a convoi or task group screened by the usual means and in deep water is virtually immune by any ship or aircraft or combination of both yet developed."

From a leter to Truman in June 1946.

So no, the Germans made a significant leap forward with the sub and the USN had a VERY hard time trying to detect the sub in tests, much less in actually setting up an attack.
I read this. Kurier is a very late war system that used skywave burst transmissions. It would have fixed a lot of the HF/DF problems but it wasn't around in 1939-40 when the scenario is occurring. So, unless you want the Allies to be were they were in 1944-45 too, it's sort of unfair and one-sided to say the Germans would have 1944-45 equipment all around and the Allies are stuck with 1939-40 equipment.
And that is the problem of this scenario, the Type XXI was a child of war, you simply cant get it without the 3 years of war development that molded it.

However you can wonder what aspects or elements of it you could have gotten with a bit more foresight, such as modular construction for mass production as the RN feared pre-war, working torpedoes, snorkel, ESM and that is it...which is quite a lot already.

The Type XXI displaced twice as much and yet required 2/3 the man hours to build, apply such design considerations to an hypothetical Type VII designed for mass production and the KM can ramp up production in 1938 once the AGNA is scrapped, that alone would be a huge problem for the RN.

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Re: What if the Type 21 U-Boats became operational in 1940?

Post by T. A. Gardner » 18 Dec 2019 17:47

JAG13 wrote:
18 Dec 2019 15:24

If its 1940 forget about carrier ASW... specially radar equipped.
Why? Aircraft with ASV I or II sets were in use in 1940, that includes some Albacore on carriers. The USN had manufacturing of similar sets underway for their aircraft.
The USN had no ASW opposition, the IJN was utterly clueless in that regard, a point proven precisely by the fact that the USN could use radar with impunity, usually a no-no for submarines since it broadcasted its presence.
Not true. The Japanese tried to mount an effective ASW campaign and did equip many ships and aircraft with radar like this B5N.

Image

The problem was their tactics were sloppy and everything was in short supply. They were simply fighting a war way in over their heads.
Which is why they were about to deploy the active Geier and even a wire-guided torpedo steered by the sonar operator.
For every measure, there's a counter-measure. The Germans were just as frustrated by Allied technological advances, and the Allies have the advantage of greater resources to come up with a counter-measure.
Lets see what Adm. Nimitz really thought of the type XXI and its effect, after extensive trials of course:

"These tests (...) have demonstrated that this particular submarine can with relative immunity attack a convoi or task group screened by the usual means and in deep water is virtually immune by any ship or aircraft or combination of both yet developed."

From a leter to Truman in June 1946.
That's at the time. Often the hindsight of history shows us a different picture. That's why we have these historical "what if's" for example. One of the most widely debunked is that Germany could have carried out Seelöwe successfully. At the time, Britain really believed they might manage it and took defense of England very seriously. Hindsight shows the British almost panic to get a defense in place was overblown.
So no, the Germans made a significant leap forward with the sub and the USN had a VERY hard time trying to detect the sub in tests, much less in actually setting up an attack.
Yes, the Type XXI did make a big advance in submarine technology, but not for high underwater speed. There were other fast underwater subs prior to it. The British R class in WW I. The Japanese I 201 and Ha 201 classes, as two examples. The GHG Balkon sonar

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Now, that was a huge surprise to the Allies.
And that is the problem of this scenario, the Type XXI was a child of war, you simply cant get it without the 3 years of war development that molded it.

However you can wonder what aspects or elements of it you could have gotten with a bit more foresight, such as modular construction for mass production as the RN feared pre-war, working torpedoes, snorkel, ESM and that is it...which is quite a lot already.
The ESM you can't get without a need for it. The Germans were very slow to react to Allied developments in electronics and when they did it was often haphazard initially like the Naxos detector.
The Type XXI displaced twice as much and yet required 2/3 the man hours to build, apply such design considerations to an hypothetical Type VII designed for mass production and the KM can ramp up production in 1938 once the AGNA is scrapped, that alone would be a huge problem for the RN.
But without the impetus of war German companies are not going to look for such production methods. The meister system of skilled professionals and strong unions would have resisted this. Even the Nazis actively trying to undermine that system really never were able to. It was the wartime need to do production in the face of declining numbers of skilled craftsmen (often drafted for service a mistake the Japanese shared) and the use of semi- and unskilled labor that drove much of the process. Modular construction dispersed that making it less prone to being bombed out, a major reason the Germans adopted such measures.

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