Germany's Type XXI U-Boat

[Stuart Galbraith]

10 minutes ago, DougRichards said:

Did the Luftwaffe or Kreigsmarine have anything much more to add to the topic, apart from what has been mentioned above?  Or were neither of those services overly concerned about radar being used for anti-submarine warfare against RN submersibles? 

The Kreigsmarine may have become a bit more worried when RN / USN light forces started being able to locate, and kill, light forces by the use of radar.  If an S-Boot could be located and attacked, then the sail of a U-Boot would have been similarly vulnerable.

Well the Kriegsmarine were certainly exploring radar as a location or gunnery device. In fact Im led to understand that the Graf Spee had an early radar set on board when it sank. it was a boon for RN intelligence when it was discovered to be intact, and was sketched in situ, by Ian Fleming IIRC.

But I dont remember reading about much interest in submarines developing similar systems, presumably because they were so much closer to the water. There seems to have been zero interest in figuring out ways to avoid any allied radar systems, for reasons that are difficult to assess. Was it because they expected the war to be over quickly? Because they didnt believe Britain or France could develop systems better than what Germany had? Dont know.

Yeah well, the Luftwaffe was never really much interested in anything at sea, other than develop increasingly elaborate torpedo systems. Im not aware they ever mounted a search radar on the FW200 for example, and that might actually have proven useful, at least in locating convoys. I guess it might have proven useful in the Med against allied submarines, although the non permissive air environment would have made going after our Submarines there very expensive for them.

[DougRichards]

I wonder if the Luftwaffe ever tried their night fighting radars in an air to surface role?  Perhaps they didn't think about it.

[Stuart Galbraith]

They certainly used Wurzburg and some other air defence radars in the surface search mode. I bought a really interesting book from After the Battle on German coastal radars in France, and it was interesting to see how many of them were actually owned by the Kriegsmarine.

No, I cant say ive read of them using radar in a surface search mode. To be fair most of the air sets would have been within visual range anyway, but at least they would have been useful at night or in poor visibility. One of those areas Goering wasnt interested in I guess.

[shep854]

18 hours ago, Yama said:

Just for comparison, none of the US Fleet boat types had test depths over 400 feet (120 metres).

I was genuinely surprised when I finally learned that the Type VII boats had a test depth almost twice the US subs.

[MiloMorai]

A good book on the Type XXI

[glenn239]

10 hours ago, RETAC21 said:

No, it doesn't

Of course, in you heart you know the answer, Glenn.

 

Siebel ferries!

Siebel ferries were dangerous in the period 1940/1941  but by 1942 with the American in, that game was all done.  As a general rule of thumb, any Axis naval offensive in the European theatre outside the Black or Baltic Seas would have to be in the period before the US entry into the war.  

You were talking about the XXI as not being a war-turning weapon.  So the obvious question was, what do you propose that the Germans build in place of the XXI that was a war winning weapon?   From your answer, sounds like we all agree there was no such weapon system available.

[glenn239]

18 hours ago, Inhapi said:

And why would they do that ?

They could just wait for the German army to move west and then grab everything they could as fast as they could, cutting the German army off from its resupply and putting the western Allies before a fait accompli being stuck in a part of France.

Yes, that could certainly happen.  Germany would be overrun more quickly than historically, the Soviets would get further west than they actually did in 1945.  Then, the Allies would demand their occupation zones and the Red Army would have to fall back across the line of delineation.   That's one outcome, and its certainly possible.  Perhaps Hitler shouldn't have started a war on two fronts.  That being said, if the Soviets were to do as you say, they really don't gain anything geopolitically, because they'll have to fall back to their zone of occupation.

Edited August 3, 2022 by glenn239

[RETAC21]

13 minutes ago, glenn239 said:

 From your answer, sounds like we all agree there was no such weapon system available.

There you go. 

[Yama]

6 hours ago, shep854 said:

I was genuinely surprised when I finally learned that the Type VII boats had a test depth almost twice the US subs.

Yes it was a big surprise, everyone else but the Germans viewed that 100 metres was adequate operating depth (in WW1 many boats were rated only for 50 metres). As noted Type XXI was designed to go even deeper.

[Yama]

15 hours ago, RETAC21 said:

Of course, this starts out of the assumption that Type XXI were a new technology.

And they weren't. In fact they came about as stopgaps while the new technology was readied, the Walther turbine, and the intended boats were the Type XVII and XVIII, neither of which was ready by the war's end, and given Royal Navy experience post-war, would have been failures.

The only "new" thing was streamlining and increased battery capacity, soemthing so new that the RN's R class had already done it, in 1917. 

Well, it's bizarre then that Germans didn't use their experience with the R class...

But you are wrong, as they did have new technologies, most notably the modular construction method, and extensive use of hydraulics, both which ended up delaying the introduction of the boats: both were also arguably necessities - Type XXI was so obviously larger and more complicated than previous fleet boats, so streamlined methods were needed to make them affordable.

 

15 hours ago, RETAC21 said:

But again, it was you who was claiming they would make a difference, and no matter how you look at it, in the actual timeline they wouldn't and the only way would have been if they had been available in numbers in 1943 and with no allied counter to them. An impossibility, for a program launched on June 1943.

Original plan was to build fleet of 250 boats by summer 1945: as we now know, by summer -45 Third Reich was no more. However, two years earlier when the program was launched, it looked very possible that the war might go undecided for rather longer. Any 'what-if' scenario requires some of the premises changed, otherwise it wouldn't be a 'what-if' scenario. 

Perhaps more realistic scenario in terms of timetable is if the Walter boats had worked as was hoped, as the original plan had them available by mid-1944. By then it would have been too late for them to do much, if anything, about the invasion, or Arctic convoys, so the overall end result would have been the same. But they might have been a serious nuisance and caused losses and delays.

 

[Yama]

22 hours ago, R011 said:

I doubt that twenty thirty ton vessels represented as much shipbuilding resources as a single thousand ton corvette let alone a thirteen hundred ton submarine or a six thousand ton cruiser.  Nor would the maritime engineering resources, even if not modest, transfer over to gun making* or torpedo fusing.

Maybe not, I was just throwing examples around about projects which were left incomplete due to lack of resources. However, I doubt you can equate shipbuilding resources of specialized vessels like X-craft just in terms of tonnage "oh it's just 600 tons of warship, half a corvette."

My point is that this program probably was not very cheap, and certainly not 'minuscule' in terms of resources required.

[Yama]

15 hours ago, Stuart Galbraith said:

It strikes me that the only reason the Germans were not building XXI prewar, was a fixation of Doenitz with wolfpacking and surface attack. it was actually pointed out to Doenitz by a radar technician prewar that Radar would soon make surface attack obsolete, and the penny still didnt drop.

Wolfpacking and surface attacks were Dönitz's answer to the other tech which had supposedly made submarines obsolete - the ASDIC.

If Dönitz had started lecturing in 1938 how they needed wholly new type of expensive submarines, then Germany would not have had any kind of functional U-boat fleet when the war began. Actually, Kriegsmarine would have probably started new battleship projects...

At any rate, Dönitz fought for Walter boats in 1941/42, underlining the need for greater submerged speeds. So clearly he was not 'stuck' at the surface attack doctrine. Opposing him was Fuchs, who was leading the warship building programs.

I wonder, was the Japanese type I-201 submarine influenced by German plans? It has very similar premises and performance, but timetable looks just the same, if not earlier than the Type XXI.

Edited August 3, 2022 by Yama

[R011]

44 minutes ago, Yama said:

Maybe not, I was just throwing examples around about projects which were left incomplete due to lack of resources. However, I doubt you can equate shipbuilding resources of specialized vessels like X-craft just in terms of tonnage "oh it's just 600 tons of warship, half a corvette."

My point is that this program probably was not very cheap, and certainly not 'minuscule' in terms of resources required.

Those numbers look pretty miniscule to me, and shipbuilding in that era tended to correspond quite well with tonnage.

[Inhapi]

14 minutes ago, R011 said:

Those numbers look pretty miniscule to me, and shipbuilding in that era tended to correspond quite well with tonnage.

The X craft was just a very small submarine, for the rest there was really nothing groundbreaking about it that would need lots of effort by designers beyond: let's build a very small sub, the way we use to build subs.

it even used an existing bus diesel engine to power it....

The only thing that was out of normal was the addition of an airlock... hardly rocket science (pun intended)

Edited August 3, 2022 by Inhapi

[Stuart Galbraith]

7 hours ago, Yama said:

Wolfpacking and surface attacks were Dönitz's answer to the other tech which had supposedly made submarines obsolete - the ASDIC.

If Dönitz had started lecturing in 1938 how they needed wholly new type of expensive submarines, then Germany would not have had any kind of functional U-boat fleet when the war began. Actually, Kriegsmarine would have probably started new battleship projects...

At any rate, Dönitz fought for Walter boats in 1941/42, underlining the need for greater submerged speeds. So clearly he was not 'stuck' at the surface attack doctrine. Opposing him was Fuchs, who was leading the warship building programs.

I wonder, was the Japanese type I-201 submarine influenced by German plans? It has very similar premises and performance, but timetable looks just the same, if not earlier than the Type XXI.

Maybe not later, but he was not doing anything about it when it might actually have made a difference. They needed to have such designs ready for production prewar. By 1941, we can see now, it was already too late.

[RETAC21]

8 hours ago, Yama said:

Perhaps more realistic scenario in terms of timetable is if the Walter boats had worked as was hoped, as the original plan had them available by mid-1944. By then it would have been too late for them to do much, if anything, about the invasion, or Arctic convoys, so the overall end result would have been the same. But they might have been a serious nuisance and caused losses and delays.

8 hours ago, Yama said:

If Dönitz had started lecturing in 1938 how they needed wholly new type of expensive submarines, then Germany would not have had any kind of functional U-boat fleet when the war began.

Well, there you have the answer. 

So, to sum it up, no matter how much lead time the Type XXI would have had, it would have been irrelevant at best. 

Re the I-201 class, it was a parallel development, as, confronted by the same problems, the Japanese went for the same solutions.

[RETAC21]

27 minutes ago, Stuart Galbraith said:

Maybe not later, but he was not doing anything about it when it might actually have made a difference. They needed to have such designs ready for production prewar. By 1941, we can see now, it was already too late.

But I would argue this was only evident in hindsight. Remember Dönitz didn't have enough subs at the start of the war, so it took some time to get numbers up, continuously disrupted by distractions such as the Mediterranean or the entry of the US in the war. In 1942, things were looking rosy for the U boats and their command didn't see a need to revamp the whole construction program (best being the enemy of good enough) and then, in a couple of months in 1943, the whole house of cards came tumbling down. 

[Stuart Galbraith]

10 minutes ago, RETAC21 said:

But I would argue this was only evident in hindsight. Remember Dönitz didn't have enough subs at the start of the war, so it took some time to get numbers up, continuously disrupted by distractions such as the Mediterranean or the entry of the US in the war. In 1942, things were looking rosy for the U boats and their command didn't see a need to revamp the whole construction program (best being the enemy of good enough) and then, in a couple of months in 1943, the whole house of cards came tumbling down. 

Id argue its incredibly evident in hindsight, of course.

But Id suggest a more perceptive man would have grasped what a gamechanger Radar was prewar, even dimly perceiving what it would mean for surface attack. After all, other branches of the Kriegsmarine were adopting it, clearly they already saw its potential.

Id entirely agree he was concentrating on getting the maximum number of boats at sea, of course. But there doesnt seem to me to be a logical case for saying he couldnt have done better than the Type VII, if as you say, they had already experimented with streamlining in the previous war.

Hell, it was the 30's, even the railways were streamlining.

As I say, its just a personal opinion of mine. Im not going to go all Siebel Ferry over it.

 

 

[RETAC21]

52 minutes ago, Stuart Galbraith said:

Id entirely agree he was concentrating on getting the maximum number of boats at sea, of course. But there doesnt seem to me to be a logical case for saying he couldnt have done better than the Type VII, if as you say, they had already experimented with streamlining in the previous war.

Not the Germans, the Royal Navy...

[Stuart Galbraith]

38 minutes ago, RETAC21 said:

Not the Germans, the Royal Navy...

Ah, sorry, though you were implying that the Germans already had experience in it.

[MiloMorai]

1939:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Sep39 48/178,621
Oct39 33/156,156
Nov39 27/72,721
Dec39 39/101,823
Tot39 147 (36.75/month)/509,321 (127,330.25/month)
British merchant ship construction capacity from 1939-1941 did not exceed 1.2 million GRT per year.
US merchant ship construction in 1939 was 0.242 million GRT.

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Aug39 19/2
Sep39 3/0
Oct39 13/3
Nov39 10/1/1
Dec39 5/1/1
Tot39 50/7/2 (an average of 10 patrols per month and 14% lost)

Thus for 1939, an average of 2.94 ships were sunk per patrol and one U-Boat was lost per 21 ships sunk (note that throughout these averages will be slightly inflated since they do not include the minor contribution of the Italian submarine fleet.)

1940:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan40 53/163,029
Feb40 50/182,369
Mar40 26/69,826
Apr40 6/30,927
May40 14/61,635
Jun40 66/375,069
Jul40 41/301,975
Aug40 56/288,180
Sep40 60/288,180
Oct40 66/363,267
Nov40 36/181,695
Dec40 46/256,310
Tot40 520 (43.33/month)/2,462,867 (205,238.91/month)
US merchant ship construction for 1940 was about 0.5 million GRT.

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan40 8/2
Feb40 10/3
Mar40 10/2
Apr40 19/3
May40 8/0/2
Jun40 18/3/1
Jul40 4/0
Aug40 16/2/1
Sep40 12/0
Oct40 13/2
Nov40 14/1
Dec40 6/0
Tot40 138/18/3 (an average of 11.5 patrols per month and 13% lost)

Thus for 1940, an average of 3.77 ships were sunk per patrol and one U-Boat was lost per 28.89 ships sunk.

1941:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan41 23/129,711
Feb41 47/254,118
Mar41 41/236,549
Apr41 41/239,719
May41 63/362,268
Jun41 66/325,817
Jul41 26/112,624
Aug41 27/85,603
Sep41 57/212,237
Oct41 28/170,786
Nov41 15/76,056
Dec41 23/93,226
Tot41 457 (38.08/month)/2,298,714 (191,559.5/month)
US merchant ship construction 1941 0.804 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan41 10/0
Feb41 18/3/2
Mar41 15/3/3
Apr41 14/2/2
May41 21/0/2
Jun41 22/2/3
Jul41 24/1/9
Aug41 42/5/9
Sep41 38/0/2
Oct41 37/0/6
Nov 41 27/5/5
Dec41 49/4/6
Tot 41 287/25/49 (an average of 23.9 patrols sailing per month and 8.7% lost)

Thus for 1941, an average of 1.59 ships were sunk per patrol and one U-Boat was lost per 18.28 ships sunk.

1942:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan42 56/310,224
Feb42 72/429,255
Mar42 93/507,514
Apr42 81/418,161
May42 129/616,835
Jun42 136/636,926
Jul42 96/467,051
Aug42 117/587,245
Sep42 96/461,794
Oct42 89/583,690
Nov42 126/802,160
Dec42 64/337,618
Tot42 1,155 (96.25/month)/6,158,473 (513,206.08/month)
British and Canadian merchant ship construction 1942 1.8 million GRT
US merchant ship construction 1942 5.433 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan42 50/2/5
Feb42 29/3/2
Mar42 32/2
Apr42 37/2/2
May42 23/3
Jun42 39/9/5
Jul42 45/7/3
Aug42 58/10/4
Sep42 52/8/8
Oct42 62/6/10
Nov42 54/8/6
Dec42 59/8/7
Tot42 540/68/57 (an average of 45 patrols sailing per month and 12.6% lost)

Thus for 1942, an average of 2.14 ships were sunk per patrol and one U-Boat was lost per 16.99 ships sunk.

1943:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan43 44/307,196
Feb43 67/362,081
Mar43 110/633,731
Apr43 50/287,137
May43 46/237,182
Jun43 17/76,090
Jul43 46/237,777
Aug43 20/92,443
Sep43 16/98,852
Oct43 20/91,295
Nov43 9/30,726
Dec43 8/55,794
Tot43 452 (37.67/month)/2,510,304 (209,192/month)
US merchant ship construction 1943 13.081 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan43 61/13/11
Feb43 72/8/9
Mar43 59/16/10
Apr43 95/35/18
May43 55/23/9
Jun43 46/23/9
Jul43 39/27/7 (49 total patrols of all types)
Aug43 33/12/6
Sep43 32/11/10
Oct43 62/23/9
Nov43 36/9/4
Dec43 31/10/2
Tot43 621/210/104 (an average of 51.75 patrols sailing per month and 33.8% lost)

Thus for 1943, an average of 0.73 ships were sunk per patrol and one U-Boat was lost per 2.15 ships sunk.

So, overall, the most successful year for the U-Boats was 1940, before the expansion of the force allowed for an increase of more than about a dozen patrols sailing per month, and well prior to the entry of the US and its
 shipbuilding capacity into the war. Worse, the performance of the U-Boat force in 1941 and 1942 never exceeded its performance in the first months of the war. And, after 1943 the U-Boat campaign became ever less relevent 
to the outcome of the war.

Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Tot44 125/663,308
Tot45 63/284,476

US merchant ship construction for 1944 was 12.257 million GRT
US merchant ship construction for 1945 (through 1 May) was 3.548 million GRT

U-Boat Fleet to 1Sep42
On 19Aug39 there were 57 U-Boats in commission, 20 sea-going U-Boats and 18 ‘ducks’ were fully ready to put to sea
Total number U-Boats deployed to 1Sep42 275
Total number lost 94
Total number retired 10
Total number available 171

U-Boat Fleet 1Sep42 to 1May45
Total number deployed 1Sep42 to 1May45 531
Total number lost 1Sep42 to 1May45 568

British controlled merchant shipping over 1,600 GRT (number/in thousands of gross tons)
3Sep39 2,999/17,784
30Sep40 3,75721,373
30Sep41 3,608/20,552
31Dec41 3,616/20,693

Thus, despite the ‘success’ of the U-Boat force in 1940 (relative to its performance in 1941 and 1942) it had no appreciable effect in reducing the size of the British merchant fleet.

Numbers of ships arriving and losses in North Atlantic convoys inbound to Britain (ships arriving/losses)
1939 700/5 (7.1%)
1940 5,434/133 ((2.5%)
1941 5,923/153 (2.6%)
1942 4,798/80 (1.7%)
1943 5,667/87 (1.5%)
1944 7,410/8 (0.1%)

The operational U-Boat force from 1943-1945 never approached a "steady 400-500 boat[s]." Rather, during 1942 the peak strength of boats assigned to combat flotillas (including those under repair for combat-damage and 
breakdowns, but excluding those assigned to school flotillas, experimental projects, or otherwise retired from combat) was 202, during November. The low in 1942 was 89 in January. The average monthly strength during 1942 was
 143.83. The strength of the force peaked in May 1943 at 237. It had declined to a low of 159 by November. Average monthly strength during 1943 was 197.58. The peak strength during 1944 was 168 in February, the low was 146
 in November. Average monthly strength in 1944 was 157.83. The peak strength in 1945 was April with 165, the low was May with 134, prior to the surrender. <http://www.onwar.com/ubb/smile.gif>

At that, these were much better than 1939 (average of 19.5 monthly), 1940 (average of 18.75 monthly) and 1941 (average of 47.5 monthly). OTOH, the 'bang for their buck' was probably highest in 1940, which was also arguably
 the U-Boats most 'successful' year in terms of ships sunk per patrol and U-Boats lost per ship sunk (see my previous reply).

[Yama]

11 hours ago, R011 said:

Those numbers look pretty miniscule to me, and shipbuilding in that era tended to correspond quite well with tonnage.

I was not arguing the material costs, but the manpower resources: the mini-subs required high-quality, selected personnel who always were on short supply. Also, the support effort required ships and men (including conventional subs) which were away from doing something else.

If the program was so cheap, why wasn't it larger? There were lots of ports which could have been attacked, not just the Tirpitz. Obvious answer seems to be it wasn't easily scalable.

[Yama]

3 hours ago, Stuart Galbraith said:

Id argue its incredibly evident in hindsight, of course.

But Id suggest a more perceptive man would have grasped what a gamechanger Radar was prewar, even dimly perceiving what it would mean for surface attack. After all, other branches of the Kriegsmarine were adopting it, clearly they already saw its potential.

But basically you are suggesting that Dönitz should have thrown away his doctrine, which proved to be incredibly successful, for a prospective threat which was not materializing for some years.

Looking at the considerable success conventional U-boats were still having in 1942, it would have required a first-grade crystal ball to realize it was all going to collapse completely next year. Dönitz clearly thought he had more time to introduce new technologies.

Edited August 4, 2022 by Yama

[Stuart Galbraith]

2 minutes ago, Yama said:

But basically you are suggesting that Dönitz should have thrown away his doctrine, which proved to be incredibly successful, for a prospective threat which was not materializing for some years.

This was about 38 iirc, so it was all going to start falling apart in 1941 and 42, and be completely unworkable by the end of 1943. I submit, this is not a great distance away in time, and considering the amount of resources he was needing to get into the water to operate his strategy, it was beholden on him to get the right boats in time to do it. The happy time didnt last nearly long enough to laud him for having a successful strategy I think.

If he didnt have enough time to get the Type XXI into operation, ultimately its up to him to not correctly foresee what was going to happen and have a realistic alternative. Its worth reflecting on something here, the Walther testbed V80 was launched in April 1940. So clearly they understood prolonged underwater operation (and streamlining) was a good idea already before 1940 when they designed it. So why fixate on the Walther engine, when they already clearly understood diesel electric worked, and all they need to do was max out the batteries? There is nothing they were doing in 1945 they couldnt have done in 1940 at the very latest.

Ultimately if we point to Goering as being responsible for having the wrong kind of aircraft, its doesnt strike me as very unreasonable to suggest you simply have to blame Doenitz for having the wrong submarines. Its not even the worst procurement mistake on his watch either.

 

[seahawk]

6 hours ago, Stuart Galbraith said:

Maybe not later, but he was not doing anything about it when it might actually have made a difference. They needed to have such designs ready for production prewar. By 1941, we can see now, it was already too late.

That would first off all requite that Dönitz actually knows by 1938 which war is coming. It is pointless to debate how Germany would prepare for WW2 when nobody except Hitler thought about fighting WW2 in 1938. The U-Boats did quite well in the fight they were expected to fight against the British and the French.