AHQ: U-boat sinking rate to achieve victory?

This thread orignally raised the question... (Yes, a bit of thread necro...:eek::eek: )
If the Germans want to sink more shipping, they can either:
  • Increase the number of U-boats (more pre-war production, better survivability, or give U-boat construction priority during the war)
  • Increase U-boat time on patrol (better fuel economy, bigger fuel tanks, or underway replenishment)
  • Increase tonnage sunk per U-boat per day at sea (OTL this number was about 750 tons. The Germans could increase this number by fixing their torpedoes during the opening months if the war, or by using effective air reconnaissance to vector U-boats towards ships, instead of U-boats having to make a picket line and hope to stumble on a ship)
  • Increase the tonnage sunk through other means (mines, aircraft, surface raiders, etc) I have no clue how to do this.
These are the usual proposals.

Let me counter the usual.

More U-boats is an obvious non-starter. The Brits will never go for it.

Better fuel economy is problematic. (Diesels are pretty efficient, & carrying more fuel is a space issue.)

More time on station actually isn't beneficial. Getting to the patrol station faster, or reducing turnaround time between patrols, is. Reducing the refit time safely is problematic, given the experience with Scorpion.

That being so, faster U-boats is a good idea, & more powerful engines can be developed fairly covertly. Moreover, they have uses as railway engines, so there's an obvious excuse. So, a somewhat bigger U-boat (nearer a Type IX, to be able to reach the U.S.) that's also faster would be roughly ideal.

More torpedoes isn't, necessarily, a good thing.

Better torpedoes do require better testing prewar (not necessarily hindsight...). Larger warheads, able to sink ships with single shots, would be good. Better firecontrol gear, able to ensure more hits as a percentage of shots fired, would definitely help. (AIUI, German wartime gear was pretty crude by U.S. standards, & even then, the U.S. doctrine was spreads of three.)

Increased use of submarine-laid mines, especially in the period when German torpedoes were problematic, would be good. Developing a better sub-laid mine, especially a magnetic mine, would be a good idea.

Developing a method to track convoys by their TBS emissions would be an excellent idea.

I'll leave off the schnornchel & electroboot ideas; they both seem to demand wartime experience with Allied ASW.

Did I miss anything? ;)
 
The only possibility I can think of is getting a treaty with Franco's Spain to establish a naval base in either the Canaries or Spanish Morocco pre war. The problem with that is the British reaction to such a treaty is very obvious and Franco wasn't stupid enough to risk Britain's wrath.
 
Bomber bases in Ireland carrying out a mining of ports campaign such as Operation Starvation against Japan in the last six months of the war.

Lessons from Aerial mining: https://www.rand.org/content/dam/rand/pubs/reports/2006/R1322.pdf
I really, really don't see Ireland (never mind the Brits :eek: ) going along with that.

And let's not forget the effect of convoying:
:openedeyewink: 10-4, Rubber Duck.

More seriously...
I've seen estimates that the convoy system cost Britain 25 to 30% of import tonnage without a ship being sunk.

So sinking ships is important, but so is bollixing up harbors and docks with mines, air raids of docks, supporting dock strikes by workers and even false sub reports that forces a convoy 20 miles out of the way. Everything that is done that forces a ship to sit longer then it should have helps the goal. The goal being reducing tonnage into Britain.

People get fixated on sinking ships (and that is important) but the crisis in 1940, 41 and 42 was more due to the reduced capacity (and higher need in wartime) then in actual submarine activities.
That's absolutely true. Even declared (but entirely fictional) minefields could have salutary effects.

There's also the lesson learned by the Pacific Fleet Sub Force, one Dönitz seemed to ignore: sink the tankers, you cripple the war effort. Concentrating on tankers out of Venezuela & Texas would have enabled Dönitz to maximize the impact of the small numbers of boats he could (at first) place off North America. He never even thought of it, AFAIK...:rolleyes:
 
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Let us, like a sane strategic force, work backwards.

Assume that we need to sink the Norwegian, French, British and US merchant marine in the Atlantic to the point where France and the UK are incapable of war against Germany.

At what point of import loss do these economies "tank?"

How many tonnes of merchant marine must be sunk to achieve this? How many tonnes of merchant marine can be constructed by France, Norway, Britain and the US before they experience negative economic consequences from having to construct merchant marines causing them to exit the war?

How long can Germany sustain a war against France and Britain?

How do we achieve the required sinking in 3 years, or the length we can sustain war against France and Britain, which ever is lesser.

What form of evidence would we use to track reality against our planned capacities and requirements?

Can we do so? At what cost? Do we even have the capacity to expend that cost?

Those are the questions I'd ask before transit times, submarine livability, etc.
 
A lot of the Air Forces objection is a reaction to the loopy orders of 42 which tasked the bomber force with attacking heavily defended and invulnerable U boat bases
They were right on that score. The number of heavies lost (not committed, just lost) just bombing Lorient, to exactly zero effect, had they been sent instead to Newfoundland, could have shut down a large percentage of the U-boats' ability to make early contact with convoys & so predict their routes, which improved the chances for sinkings. (Not in the convoys alone, but among the rompers {who got out ahead} & stragglers.)

IMO, it didn't require anything like 400 a/c.
Let us, like a sane strategic force, work backwards.

Assume that we need to sink the Norwegian, French, British and US merchant marine in the Atlantic to the point where France and the UK are incapable of war against Germany.

At what point of import loss do these economies "tank?"

How many tonnes of merchant marine must be sunk to achieve this? How many tonnes of merchant marine can be constructed by France, Norway, Britain and the US before they experience negative economic consequences from having to construct merchant marines causing them to exit the war?

How long can Germany sustain a war against France and Britain?

How do we achieve the required sinking in 3 years, or the length we can sustain war against France and Britain, which ever is lesser.

What form of evidence would we use to track reality against our planned capacities and requirements?

Can we do so? At what cost? Do we even have the capacity to expend that cost?

Those are the questions I'd ask before transit times, submarine livability, etc.
Fair points, all. AIUI, a sustained sinking rate of 750000 tons/mo for 24mo (I've also read 12, IIRC, but don't quote me) would do it--but that's 18 million tons of shipping, which seems fairly extravagant, given the Brits started with only 19.5 million (if that's accurate...). What's the sustained force needed? 120 boats (i.e., 30 on station)? Can enough boats be built in the period from 9/39 to achieve & maintain that? Can more be built, & more kept on station? Can the per-patrol sinking rate be increased?

OTL, sinking of 14 million tons in 3584 patrols is a per-patrol rate 3906 tons (which is actually less than the Pacific Fleet rate...). Achieving the 14 million tons sunk before mid-'43 (42 months) requires a sustained force of (roughly) 85 boats on station. (Fewer, if the transit time is less, from faster boats: it's about 14mil/{3906x0.5x42} to get the sustained force {I think; for PTO, it was 4mil/(4278x0.375x65) to get war's duration}.)
 
They were right on that score. The number of heavies lost (not committed, just lost) just bombing Lorient, to exactly zero effect, had they been sent instead to Newfoundland, could have shut down a large percentage of the U-boats' ability to make early contact with convoys & so predict their routes, which improved the chances for sinkings. (Not in the convoys alone, but among the rompers {who got out ahead} & stragglers.)

IMO, it didn't require anything like 400 a/c.

Fair points, all. AIUI, a sustained sinking rate of 750000 tons/mo for 24mo (I've also read 12, IIRC, but don't quote me) would do it--but that's 18 million tons of shipping, which seems fairly extravagant, given the Brits started with only 19.5 million (if that's accurate...). What's the sustained force needed? 120 boats (i.e., 30 on station)? Can enough boats be built in the period from 9/39 to achieve & maintain that? Can more be built, & more kept on station? Can the per-patrol sinking rate be increased?

OTL, sinking of 14 million tons in 3584 patrols is a per-patrol rate 3906 tons (which is actually less than the Pacific Fleet rate...). Achieving the 14 million tons sunk before mid-'43 (42 months) requires a sustained force of (roughly) 85 boats on station. (Fewer, if the transit time is less, from faster boats: it's about 14mil/{3906x0.5x42} to get the sustained force {I think; for PTO, it was 4mil/(4278x0.375x65) to get war's duration}.)
Also the assumption needs to be made pre war that the Norwegian and French bases are available, which changes everything as the German army did not plan conquering France in a single campaign and no plan to invade Norway. Without that you have to contend with the MN ASW force, including its ASW air bases, the ability to reroute convoys so the Western Approaches are not as important - the Channel route is which extends the transit time and makes the operational area one dominated by allied air power.

And more training which requires more boats. As it is the Entire U boat arm in 1940 has 54 crews. in 41 250 crews and 350 pa thereafter thats trained so less losses plus survivors.

So if you want 85 boats on station from anywhere that's 255 trained crews re war and if you want them in Type IX thats increasing production from 9 boats to 285.

Not going to happen unless you scrap the entire navy and if you are not building Bismarcks and Graf Spee the brits change their build as well and react differently to events pre war.
 
They were right on that score. The number of heavies lost (not committed, just lost) just bombing Lorient, to exactly zero effect, had they been sent instead to Newfoundland, could have shut down a large percentage of the U-boats' ability to make early contact with convoys & so predict their routes, which improved the chances for sinkings. (Not in the convoys alone, but among the rompers {who got out ahead} & stragglers.)

IMO, it didn't require anything like 400 a/c.

Fair points, all. AIUI, a sustained sinking rate of 750000 tons/mo for 24mo (I've also read 12, IIRC, but don't quote me) would do it--but that's 18 million tons of shipping, which seems fairly extravagant, given the Brits started with only 19.5 million (if that's accurate...). What's the sustained force needed? 120 boats (i.e., 30 on station)? Can enough boats be built in the period from 9/39 to achieve & maintain that? Can more be built, & more kept on station? Can the per-patrol sinking rate be increased?

OTL, sinking of 14 million tons in 3584 patrols is a per-patrol rate 3906 tons (which is actually less than the Pacific Fleet rate...). Achieving the 14 million tons sunk before mid-'43 (42 months) requires a sustained force of (roughly) 85 boats on station. (Fewer, if the transit time is less, from faster boats: it's about 14mil/{3906x0.5x42} to get the sustained force {I think; for PTO, it was 4mil/(4278x0.375x65) to get war's duration}.)
It took 3 years for Germany to achieve the 100 boats 'at sea' that Dönitz had 'wanted' on 8th Aug 42

The maximum U-boats on Station was achieved in April 43 - just before Black May (when 41 u-boats were lost) - about 160 boats at which point an alignment of Tactics, equipment, weapons ( FIDO, Hedgehog) operational skills of the USN and RCN matching the RN, Numbers of escorts reaching that magic 700+ , newer and better warships, escort carriers and a massive increase in LR MPA such as the LR Liberator as well as a massive and sustained improvement to the code breaking machines and their numbers.

One of the biggest reasons for the Uboat's successes was not only large numbers of boats but also the problems the allies had in cracking Enigma for much of 42

As I maintained in the earlier thread - the quicker answer that the allies would come to is to throw more aircraft at the problem - something they should have done earlier than they did anyway.

So here lies the issue

Germany in order to win the BotA has to achieve a Uboat build up far far quicker than they did - before the technological, geographical and number advantage of the Allies increasingly enjoy make it impossible (OTL this was probably at some point during 1942 and certainly by May 43)

So I think they have to achieve a crippling loss rate (i.e. mid/late 42/early 43 numbers) and do it by the end of 1941

I personally think that this is impossible all other things being equal in Sept 1939.
 
The combined tonnage of the American and British merchant fleets never dipped below 30,000,000 tons during the war. In order to even have a prayer of accomplishing this they would need to begin building large number of submarine and training crews and operating at sea at long distances probably (and this is just a guess) around 1930 at the latest and that will likely provoke a change in British naval strategy and policy assuming British leaders are not drinking lead paint.
 
You will need better trained crews and more aggressive submarine captains. A lot of submarines achieved abysmal performance with number of patrols outnumbering the number of sinkings. A lot of people didn’t want to be there and risk their lives. They still suffered for it.

Fixing the magnetic torpedo problem would pay great dividends but that requires testing outside of German waters with active warheads and targets in order to notice the problem. All of which would be noticed by other powers who at best may not take kindly to it and at worst will discover what you’re up to.

I believe the following steps would need to be taken:

Realize that realities of war will change and Britain will inevitably arm merchants and organize convoys. Thus after the initial period deck guns will become useless. However in the early period they can even form the basis of submarine tactics. Thus I’d have a peacetime design focusing on gunnery numbering around 40 subs or so with a wartime design doing away with deck gun completely and focusing on underwater speed.

Prepare for modular design and construction of submarines. Build engines and long build items before the war but without the subs.

Come up with a snorkel sooner if possible. It’s not a revolutionary invention and I’m amazed it too so long for them to adopt it.

Develop a slow, 12-20 kt changeable speed noisemaker torpedo capable of doing zig zag patterns to emulate a mannouvering submarine.

Discover and understand thermal layers and their impact on sonar performance. Train the crews on understanding it and using it to avoid detection or facilitate escape when possible. Understand the underwater performance of submarines and cavitation creation due to X speed at X depth.

Long range Wire guided torpedos allowing the use of periscope and hidrophone to guide a torpedo into target.

Train the crews to perform submerged attacks without use of periscopes. If that is possible design submarines capable of deep strike rather than designs capable of only sub 100ft attacks. Being able to strike from 100 meters underwater would be a great boon.
 
Another obvious thing is to more rapidly change the codes and increase the time it takes for the allies to break the code - in 1941 the British were breaking them in hours - but for much of 42 - 10 months in fact until Pettard's brave crew boarded U559 and recovered several code books (with 2 of the 3 men drowning) - the Change to more advance encryption really hamstrung the British efforts to read their 'emails' and apart from having more boats at sea it was this that prevented the British from diverting convoys around known concentrations of Uboats as they had done in 41 and explains the massive raise in shipping sunk

So moooor Enigma would help
 
Wasn't the whole point of why the German's effort to starve Britain out of the war was that they only had a 3rd of the fleet required to do this at the start of WW2 and by the time they finally increased production of boats to do this they where being sunk faster than they were building them?

Much obliged!
 
Wasn't the whole point of why the German's effort to starve Britain out of the war was that they only had a 3rd of the fleet required to do this at the start of WW2 and by the time they finally increased production of boats to do this they where being sunk faster than they were building them?

Much obliged!
Shouldn't have been a problem if their torpedoes actually worked:
In fact, one of the earliest torpedo failures took place on September 14 during an encounter with the Ark Royal. Gerhard Glattes of the U-39 chanced upon the most formidable and modern aircraft carrier of the Royal Navy, sailing alone and into the crosshairs of his periscope. She had turned into the wind to launch aircraft and as a result, had fallen four miles astern of her destroyers. Glattes fired a fan of three torpedoes at the carrier. All three detonated prematurely. Now alerted of the presence of a U-boat, her destroyers rushed to the scene and depth charged and sank U-39 through a series of coordinated attacks. The U-39 was the first U-boat to be lost in the war.
The Torpedo Directorate dismissed initial reports citing inexperience and incorrect settings of the torpedoes. But soon after, even top aces and Knight’s Cross holders Prien and Schultz began complaining. During the attack on Scapa Flow, Prien reported that his first salvo of three torpedoes fired from the bow and one from the stern resulted in only one explosion. In another incident on October 30, the U-56 under Wilhelm Zahn spotted the battle group Nelson, Rodney and Hood. Carefully eluding the escorts, Zahn attacked and fired three torpedoes at Nelson, and heard two of them thump harmlessly on the target’s side. Worse yet, the third torpedo detonated prematurely and alerted the escorts. Zahn was so demoralized by the incident that Donitz granted him extended leave upon his return.
As expected, the Norwegian seas were filled with Allied ships. Almost immediately, the U-boats began attacking. Every day and every hour, U-boats were attacking warships or were being attacked themselves. Day in, day out, night after night, the U-boats fired their torpedoes one after another, relentlessly against their targets. Not one of them exploded. Their efforts remained completely fruitless. Worse yet, when the data was analyzed back at BdU, it was found that four attacks were launched on the battleship HMS Warsprite, fourteen on cruisers, ten on destroyers, and a further ten on transports – yet only one transport was sunk. Discounting marginal attacks, Donitz concluded that had the torpedoes not failed, the U-boats would have “probable sinkings” of one battleship, seven cruisers, seven destroyers, and five transports. In summary, about twenty enemy warships had escaped certain destruction because of torpedo failures.
By the end of the Norwegian campaign, the men of the U-boat Force had lost all faith in their torpedo and had not much heart to resume the fight. On April 19, Prien refused to attack when he spotted a convoy of ten transports and several destroyers. He still had four torpedoes left, but had so little faith in them that he sailed away silently. Upon his return, in explaining his refusal to attack, he told Donitz that he “could hardly be expected to fight with a dummy rifle”
 
The basic problem is the start date is 1935. There are some things that can be done in advance but not a whole lot and the German position is starting with nothing and very limited knowledge. With the KM in third place for resources and severe restrictions on what resources are available. In particular steel and non ferrouns metals which you have to buy in with actual money.

You can't train without training boats, and crews skilled enough to undertake training. OTL with a start date of 1927 you end up with a plan for 54 crews in1940 rising to 250 pa in 41. This is using all the boats they can build.

As to the other suggestions.

Most, overwhelmingly most U boat sinkings were of ships not in convoy. As I said on another recent one the highest rate of sinkings was on the SC convoys, it amounts to just about 2.5% of sailings, with an equal number being stragglers from the convoy, i,e. not escorted. Attacking a convoy with a decent escort is a bad idea. In the best of circumstances you are going to be attacked so you dive and the convoy speeds away at 2-3 kts. In the worst of circumstances you are dead.

So 40 U boats at the start of the war. There are 26 ocean going boats OTL including any used for on type training. So Double the resource allocation. After the Luftwaffe and Heer have finished kicking you around the room because they have to deal with Poland, France and not enough ammunition you will settle for whats left, or get kicked around the room again until you get the message.

Modular design. Basically does not work in the era. Speer tried this when he tried to speed up late war production. As the Shipbuilders told him this wont work. The final proof was when they fit them all together there were gaps in the hull the prospective captain put his fingers into. Your assumptions are that a) noone will notice your cunning plan, b) assembly is faster than new build c) that everyone is working to the same tolerance and QC can control this and d) when you put the parts together and put them under pressure the parts will respond in the same way and not fall apart.

'Within this transformation-turning flat steel into a submarine hull-there are numerous processes that have the potential to impact the variation of the product. This research effort will focus on the variation which may result from such areas as: geometric design parameters, joining methods, alignment techniques and datum control, material properties, measurement methods, cutting and forming practices, and others. Each of these areas consists of many different processes and actions, some automated, others manual, that contribute ever-greater levels of complexity and variation to the end product. '

With all the drawings being hand copied and part being filed to fit.

Schnorkel is of limited utility you can recharge underwater but are limited to 6 kts. or the snort breaks, and you will be injuring your own crew at first and always sending out a plume of highly visible exhaust, not to mention the feather wake from the snort mast. So yes you can recharge the batteries, if you move at 6kts but have limited fuel and are visible from the air and by radar. And you cant use your own hydrophones while its deployed.

Noisemaker. Pretty useless. The allies are not using homing torpedoes mainly so sending off a noisemaker moving faster than a sub is a clear indication that ITS NOT THE SUB and if you use it prior to detection it just puts everyone at general quarters not looking for the thing moving faster than the sub.

Thermocline. Not sure what your point is, As soon aa diesel boat dives it starts to lose relative speed. mission kill.

Wire guided torps are a 1960s design so pointless as the RAF will have nuked Berlin day 1.

Submerged attacks. 50 merchants, 8 escorts - what's the target for your attack without a periscope? And if its a single ship, why bother. the acoustic torps used were specifically intended to attack escorts as they had different acoustic characteristics, but you still have to deal with the cone the torp tracks in.

Mines. Handy things, but to attack a target you need to lay a mine in a shipping channel . The dastardly Royal Navy had a habit of laying its own minefields at a depth so that ships could pass happily above but submarines get to go boom boom for no apparent reason. They also did not tell people about them. Its handy briefly at the start of the was but as the days pass getting a sub close enough to anywhere where its better than dropping them off mid ocean/random chance is very unlikely - and very very dangerous.

Magnetic warheads. Handy if you firing at a warship over cruiser size, pointless on a crappy merchant that will sink anyway. The problem with the magnetic pistol was everyone got it wrong which suggests something fundamental in the technology not apparent to anyone. The US problem was not just that they refused to admit the problem but they had several other problems as well. The RN and KM did not have those issues, so they switched to contact detonation oh that works.
 
The only possibility I can think of is getting a treaty with Franco's Spain to establish a naval base in either the Canaries or Spanish Morocco pre war. The problem with that is the British reaction to such a treaty is very obvious and Franco wasn't stupid enough to risk Britain's wrath.

Actually the Germans did use the Canaries during the war, but it was very intermittent and not a full-fledged base.

 
I know it's easy to throw around stats but in this case they are important. As I stated earlier, at no point in the war did the combined US and British merchant fleets go below 30,000,000 tons and in 1942, a year the Germans sank about 6.1 million tons of shipping, British, Canadian, and American shipyards produced 7.1 million tons of shipping.

I would argue there is nothing the Germans can do that the Allies cannot counter and the Allies have superior resources and can afford to divert resources to the Battle of the Atlantic much more than the Germans can and for the Germans to succeed in this endeavor they are going to have to sink millions of tons more of shipping every year than they did OTL.
 
There does need to be a miracle for Britain to lose the battle of the Atlantic in such a way that forces them out of the war.

Most importantly it needs a big jump in the early war. Pulling the Norwegian merchant fleet completely out of the war (circa 4 million tonnes of shipping) would be a minimal but useful start.

Can this be done in peace negotiations with norway (even partially).

It would be more than the u boats did in the first year of the war I'd say.

Can't have the british taking over a chunk of the Italian merchant marine or the French or Dutch or Belgian fleets too.
 
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You will need better trained crews and more aggressive submarine captains. A lot of submarines achieved abysmal performance with number of patrols outnumbering the number of sinkings.
I don't think the basic problem here (unproductive patrols) was training. U-boat crews underwent rigorous training in the Baltic. The problem was that from late 1942 onward--when most of the boats began operational service--the odds were just too long against them. Had ASB made it possible to have the u-boat fleet of April 1943 in 1939-40, there would've been a massacre of shipping.
Just like fighter pilots, tank gunners etc, there were a small number of aces in the ubootwaffe. Few have the chops to be great at such a tough job, so unless the Germans, anticipating the need for great commanders 20 years earlier, figured out how to clone the best uboatmen, there was nothing they could do about that.

Come up with a snorkel sooner if possible. It’s not a revolutionary invention and I’m amazed it too so long for them to adopt it.
Blair wrote that u-boat crews hated snorts, which rendered a boat deaf and blind during use. And they weren't for continuous use just recharging.
 
Most, overwhelmingly most U boat sinkings were of ships not in convoy.
Sure. I think the performance of the uboatwaffe would've been improved, and its effectiveness prolonged, perhaps considerably, if three changes were made. First, emphasize Type IX construction. Considering that the bulk of sinkings and the most remunerative patrols occurred in remote, peripheral areas, the Germans should've invested more in long range boats. Second the IXs should not have been used in anti-convoy operations, not even on their first patrols when coming out of the Baltic. Third, they should've maintained absolute radio silence, save for emergencies, when transiting to or from patrol areas.

Attacking a convoy with a decent escort is a bad idea...
Well, even if the Germans emphasized long range boats they still had to attack convoys, at least occasionally, with the VIIs they had so the allies had to maintain the convoy system, to the detriment of efficient shipping circulation.
 
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