No Plan Z, early Uboat expansion

[Deleted member 1487]

I check the search function and couldn't find a post about this specific POD, so please hold the hate.

What if instead of starting Plan Z in January 1939 Hitler instead opts to expand the Uboat force?
http://en.wikipedia.org/wiki/Plan_Z

Plan Z was a combination of a strong battle fleet capable of challenging the British and a big U-boat fleet for commerce raiding. The plan was initially focused on building large surface ships. If war broke out early in the plan, before the large ships were nearly operational, the large ship building program would be halted. This happened in reality when war started in September 1939. The U-boat production was then given priority and the large ship program was stopped.

In the short time from the introduction of Plan Z on January 27, 1939 up to the beginning of war with the United Kingdom on September 3, 1939 only two of the plan's large ships, H class battleships, were laid down (a third one was only days from receiving its keel). At the time components of the three battlecruisers were in production.

At the beginning of the war the large ships ordered before Plan Z were 1 aircraft carrier, 4 battleships, 3 heavy cruisers and 6 light cruisers which were either ready for action or would be ready in the next months. 1 aircraft carrier, 2 heavy cruisers and 3 light cruisers were in early of stages of construction.

With the outbreak of World War II work on the H class battleships, the battlecruisers and even on some cruisers and the two aircraft carriers laid down before Plan Z was introduced was halted, because these large and expensive construction projects would require too much of war essential materials and the materials were diverted to the construction of U-boats.

As it was the construction of capital ships turned out to be a total waste of resource (materials, dock space, and scarce skilled labor) and ended up delaying the Uboat expansion needlessly.
The added benefits of starting the Uboat expansion in 1939 is that training can be started in peace time for large numbers of crews, more experience gained producing Uboats, which reduces construction times, and the British won't be moved to start expanding their escort forces, as they thought they had enough to handle up to 100k tons of Uboats as it was and the Germans won't be able to manufacture up to 100k by the time September 1st rolls around.

The numbers I'm thinking would be just moving up historical production up a year.

http://uboat.net/technical/shipyards/
Historical numbers:

U-boat production:
1935 (14)
1936 (21)
1937 (1)
1938 (9)
1939 (18)
1940 (50)
1941 (199)
1942 (237)
1943 (284)
1944 (229)
1945 (91)

Total: 1153

So that would mean this in my scenario:
1939: 50
1940: 199
1941: 237
etc.

Here are historical losses:

1939
57 U-boats were capable of going out to sea when the war began in September 1939. When the year ended 9 of them had been lost.

1940
24 boats were lost in 1940. U-31 was actually sunk twice so she appears twice in that number.

1941
35 boats were lost during 1941.

1942
The U-boat fleet lost 86 boats during this year, most of them in the latter half the year. A sign of things to come ...

Losses were pretty low until late 1942-1943, which was the result of the US entering the war and finally closing the Atlantic Gap with patrols AND production finally ramping up enough to properly escort convoys and make good losses.
That was also about the time that there were 100 Uboats on station, which was far too late to make a difference.

Here though the production numbers would mean that in mid-1941 there would be over 300 Uboats in service so would then have 100 Uboats on station, which was Admiral Dönitz's 'magic number'. This would also be before the US enters the war and the convoy system gets good at sinking German subs.


Still even in 1940 the Germans would have a massive increase in Uboats, meaning there would be around 150 Uboats available by July-August for operations in the Atlantic (not including the coastal subs still operating in the North Sea.
That would be a massive increase (50) over OTL, which saw less than 20 Uboats on station at that period:
http://uboat.net/ops/combat_strength.html
That's more than 3x the number that were available to be on station during the period that the convoys were at their weakest and the Germans had broken the convoy codes.
IOTL they lacked the numbers to really intercept all of the convoys they knew were coming (17% of convoys actually engaged in 1940), while here they won't really. There will be plenty of chances to form Wolf Packs, which exponentially increased losses, especially in this period (1st Happy Time).

http://en.wikipedia.org/wiki/Battle...me.27_.28June_1940_.E2.80.93_February_1941.29

'The Happy Time' (June 1940 – February 1941)

The early U-boat operations from the French bases were spectacularly successful. This was the heyday of the great U-boat aces like Günther Prien of U-47, Otto Kretschmer (U-99), Joachim Schepke (U-100), Engelbert Endrass (U-46), Victor Oehrn (U-37) and Heinrich Bleichrodt (U-48). U-boat crews became heroes in Germany. From June until October 1940, over 270 Allied ships were sunk: this period was referred to by U-boat crews as "the Happy Time" ("Die Glückliche Zeit").[26] Churchill would later write: "...the only thing that ever frightened me during the war was the U-boat peril".[27]

The biggest challenge for the U-boats was to find the convoys in the vastness of the ocean. The Germans had a handful of very long-range Focke-Wulf Fw 200 Condor aircraft based at Bordeaux and Stavanger which were used for reconnaissance. The Condor being a converted civilian airliner, this was a stop-gap solution for Fliegerführer Atlantik. Due to ongoing friction between the Luftwaffe and Kriegsmarine, the primary source of convoy sightings was the U-boats themselves. Since a submarine's bridge was very close to the water, their range of visual detection was quite limited. The best source proved to be the codebreakers of B-Dienst.

Instead of attacking the Allied convoys singly, U-boats were directed to work in wolf packs (Rudeln) coordinated by radio. German codebreaking efforts at B-Dienst had succeeded in deciphering the British Naval Cypher No. 3, allowing the Germans to estimate where and when convoys could be expected. The boats spread out into a long patrol line that bisected the path of the Allied convoy routes. Once in position, the crew studied the horizon through binoculars looking for masts or smoke, or used hydrophones to pick up propeller noises. When one boat sighted a convoy, it would report the sighting to U-boat headquarters, shadowing and continuing to report as needed until other boats arrived, typically at night. Instead of being faced by single submarines, the convoy escorts then had to cope with groups of up to half a dozen U-boats attacking simultaneously. The most daring commanders, such as Kretschmer, penetrated the escort screen and attacked from within the columns of merchantmen. The escort vessels, which were too few in number and often lacking in endurance, had no answer to multiple submarines attacking on the surface at night as their ASDIC only worked well against underwater targets. Early British marine radar, working in the metric bands, lacked target discrimination and range. Moreover, corvettes were too slow to catch a surfaced U-boat.

Pack tactics were first used successfully in September and October 1940, to devastating effect in a series of convoy battles. On September 21, convoy HX 72 of 42 merchantmen was attacked by a pack of four U-boats, losing eleven ships sunk and two damaged over two nights. In October, the slow convoy SC 7, with an escort of two sloops and two corvettes, was overwhelmed, losing 59% of its ships. The battle for HX 79 in the following days was in many ways worse for the escorts than for SC 7. The loss of a quarter of the convoy without any loss to the U-boats, despite very strong escort (two destroyers, four corvettes, three trawlers, and a minesweeper), demonstrated the effectiveness of the German tactics against the inadequate British anti-submarine methods. On December 1, seven German and three Italian submarines caught HX 90, sinking 10 ships and damaging three others. The success of pack tactics against these convoys encouraged Admiral Dönitz to adopt the wolf pack as his primary tactic.

Nor were the U-boats the only threat. Following some early experience in support of the war at sea during Operation Weserübung, Fliegerführer Atlantik contributed small numbers of aircraft to the Battle of the Atlantic from 1940 onwards. These were primarily Fw 200s and (later) Junkers Ju 290s, used for long-range reconnaissance. The Condors also bombed convoys beyond land-based fighter cover and thus defenceless. Initially, the Condors were very successful, claiming 365,000 tons of shipping in early 1941. These aircraft were few in number, however, and directly under Luftwaffe control; in addition, the pilots had little specialized training for anti-shipping warfare, limiting their effectiveness.

Allied tonnage sunk by U-boats
Year Tons sunk
1939 0,6 million
1940 2,3 million
1941 2,2 million
1942 5,8 million
1943 2,3 million
1944 0,6 million
1945 0,2 million
14 million Total

Seeing as how vulnerable British shipping was in 1940 after the Fall of France, I think it is generous to assume that with more than three times more Uboats on station that losses would tripled, as the primary reason the Uboats IOTL didn't inflict even more losses was the lack of numbers.

I figure the following for shipping losses to Uboats alone:
1939: 1.2 million
1940: 6 million
1941: 6 million
1942: 10 million
1943: 5 million

With numbers like these at what point do Allied operations become badly effected and the British drop out of the war? Remember too that shipping losses were actually higher than this because of losses to mines, aircraft, surface warships, etc.
http://www.usmm.org/wsa/shiploss.html
IOTL over 22 million tons of shipping were lost up to 1943, with 13.2 million caused by Uboats. Here Uboats cause 28.2 million tons of losses, while the remainder, 9.8 million, as all other causes. That's 38 million tons of shipping, which was the total launched by the US from 1939-1945.

Also what about butterflies? If the Uboats increase pressure on the British so much, perhaps the Bismarck slips through into the Atlantic because the British lack enough warships to pursue her.
What are your thoughts?

 

[David S Poepoe]

And the British do nothing in light of this increased production?

 

[phx1138]

What are your thoughts?

My first thought:

The Brits were in big trouble even OTL, & by June '43 were considering abandoning convoy as ineffective. This was at a time when they'd effectively defeated the U-boat.

I figure the following for shipping losses to Uboats alone:
1939: 1.2 million
1940: 6 million
1941: 6 million
1942: 10 million
1943: 5 million

Those numbers look accurate to me, & frightening. I think you need to round down a trifle, since the more-rapid expansion is going to hurt crew quality more TTL than OTL; the difference won't be major, but it'd be noticeable: 5.8-5.9 mil in '40, say.

Still even in 1940 the Germans would have a massive increase in Uboats, meaning there would be around 150 Uboats available by July-August for operations in the Atlantic (not including the coastal subs still operating in the North Sea.
That would be a massive increase (50) over OTL, which saw less than 20 Uboats on station at that period

With 50 more boats, you get about 12-13 more on station in the Atlantic at any given time, with the rest en route or in training: 200 boats is 50 on station. (I'm ignoring the Type IIs.) This is serious stuff.

Now, if they're all Type VIIs, you've still got issues of endurance, which puts more pressure on BdU to introduce the Type XIV, which gives Bletchley opportunities to find & sink them.

Also, with more boats, you increase the chances to compromise KM Enigma, or to have RN capture it. (Given Dönitz won't tell them to shut up, which by all appearances is ASB....)

This would also be before the US enters the war and the convoy system gets good at sinking German subs.

This was the American approach. The Brits preferred to avoid, thinking (correctly IMO) the convoy getting through was more important.

Which brings me to Brit CM. Does the greater threat compel Winston & his Air Minister (Wood or Hoare {I had to look it up}) & CinC Bomber Command (Portal {I had to look it up, too}) to give more attention to Coastal Command? Does CC get ex-BC Stirlings? IMO, they'd almost certainly get ASV before BC gets H2S TTL.

Does CC get Stirlings in Newfoundland in '40-'41? This would negate BdU's advantage: finding a convoy at sea is much harder than finding it at, or right after, departure, & patrol a/c in NF could keep U-boats down in the crucial stage.

Do Newfoundland, HMG, & Canada, build an escort-refit yard in St John's? (There wasn't one OTL.) This would enable work otherwise done in Britain (already overstretched) or Halifax (far from the warzone) to be completed expeditiously.

Does RCN get any ex-RN DDs, complete with crews? OTL, RCN didn't have the trained manpower to run their own, & putting green crews in corvettes on the slow (& most-exposed) convoys was a recipe for ruin even OTL; TTL, it almost doesn't bear examining.

Does RCN specify gyroscopes for its corvettes? This is necessary for Hedgehog--but Canada couldn't produce her own, so domestic-built corvettes weren't even wired for them...

Does RCN get more Type 268/equivalent radars? A St John's yard would help with installing them; you still need to push RCN senior officers to specify them, & the SOs didn't appreciate the value... (Had this been done, the sets could have been built in Canada & installed at completion--if Canadian-built sets could be kept out of American hands, where many went OTL.)

You've probably made the Battle of the Atlantic a very, very near-run thing indeed. You've probably forced a fuel crisis in Britain (which might ground much of Bomber Command for a time), & contributed to earlier famine in Bengal (which was a result of Britain redistributing shipping to cope with a tanker crisis). You've also probably butterflied any Italian adventure; the shipping just doesn't exist. You also likely impacted PTO ops, tho maybe less than I think: there was considerable waste in the PTO loading/unloading, so fixing that could actually free up bottoms compared to OTL.

OTOH, if CC gets patrol planes in NF & Iceland in '40-1, U-boat losses go up a fair bit, & convoy losses go way down, even over OTL, despite more U-boats at sea. (A/c still control the chokepoints; more boats actually makes it easier.)

I wonder if more patrol aircraft leads BdU to develop an AA missile, comparable to IDAS. (Too sophisticated for the tech?) Or to introduction of a "sub-Raketenwerfer" (like the deck-mounted system proposed, but in-hull)?

My first thought is, you've effectively made the Type XXI moot, & the Walther boat, too: KM doesn't need them. (Postwar, this also means no Exploder & Excruciator, either. Probably no GUPPYs, either.) As I think of it, if facing a greater air threat, an improved Type IX with more battery for greater udw endurance or attack speed isn't out of the question. Knowing Dönitz, I consider it unlikely to reach service before war's end.

Short answer: you've made it a much more interesting war...if only for the changes wrought on Bomber Command.

BTW: subscribed.

 

[Deleted member 1487]

And the British do nothing in light of this increased production?

Initially no, because their construction plans and existing fleet expected that it would be able to handle a Uboat fleet of over 100k tons, which would be more than Germany could build by the start of WW2. Once the extent of German construction becomes clear though the British will behave as they did IOTL, by building up major escort assets, which will take years.

Eventually I imagine the British, depending on how quickly they are spooked, will shift BC assets to CC, though I expect that like IOTL they will slavishly maintain the failed Hunter-Killer groups until 1941.

Part of my hope for this thread is that we can have a discussion of what British reactions would be, when they would happen, and what the consequences to the war effort of those changes would be.

I realize posters are sick of Teutono-wanks, but I'm not proposing one necessarily; I'm laying out a case and am looking for push back on the other perspective from someone that is familiar with the British side of the hill.
Can we get some thesis, anti-thesis, synthesis going?

 

[phx1138]

I expect that like IOTL they will slavishly maintain the failed Hunter-Killer groups until 1941.

I fear so...& the results will be disastrous.

Part of my hope for this thread is that we can have a discussion of what British reactions would be, when they would happen, and what the consequences to the war effort of those changes would be.
...
Can we get some thesis, anti-thesis, synthesis going?

I do hope so. I'd be very interested knowing if I'm alone thinking the "Newfoundland option" was the best one, just for a start.

 

[Deleted member 1487]

With 50 more boats, you get about 12-13 more on station in the Atlantic at any given time, with the rest en route or in training: 200 boats is 50 on station. (I'm ignoring the Type IIs.) This is serious stuff.

50 more for combat availability overall, as there would be about 150 total operational.

I'm basing the 1/3rd on station from the following:
http://uboat.net/ops/combat_strength.html

Chief of U-boats Karl Dönitz estimated he needed 300 U-boats to defeat the Allied convoys and force Britain into submission. When war broke out on 3 Sept 1939 he had 26 ocean going U-boats. The 300 U-boat figure was calculated by him to mean that from this figure 100 boats would be in repairs, rest and working-up, 100 more on their way to and from operational areas - leaving on average 100 U-boats in actual combat areas. This meant about 200 U-boats would have been at sea at any one time, but with the French and Norwegian bases resulting in shorter transit times the ideal figure would be somewhat lower.

So 150 boats means 50 on station at any one time.

Now, if they're all Type VIIs, you've still got issues of endurance, which puts more pressure on BdU to introduce the Type XIV, which gives Bletchley opportunities to find & sink them.

I'd imagine we'd get an OTL spread. Not all of these boats would be in the Atlantic either, as the bigger boats would be able to travel farther into the South Atlantic, Indian Oceans, etc. which of course spreads British warships even further hunting down the greater threat.

Also, with more boats, you increase the chances to compromise KM Enigma, or to have RN capture it. (Given Dönitz won't tell them to shut up, which by all appearances is ASB....)

This is a problem, but seeing as it was pretty much solved in 1941 anyway, I don't know what more effect it could have, especially as the decoding usually happened after the information was useful and the best effect was gained from triangulating the location of transmission.

 

[BlondieBC]

Some thoughts. It looks like U-boats preWW2 took 6-18 months from keel laying to commissioning. This is an improvement from up to two years preWW1. It also took several months from ordering to keel laying. So you numbers look a bit high for numbers of U-boats. So lets take a sample ramp up in peace time.

Jan 1939 - Hitler signs off on priority switch.
Late Feb 1939 - Navy sends out orders to ship yards.
April 1939 - First new keel of new order laid. It will take several more months to get all the keel order in 1939 under construction.

So, gaining 6 months, not a full year on production seems more reasonable. Using a half year gain, we get:

1939 43 U-boats (18+50/2)'
1940 125 U-boats (50/2+199/2)
1941 around 200-225.

And I think this is a bit optimistic. Looking at the historical numbers, it looks like only after the Fall of France did the real push begin. With France still undefeated, I strongly suspect the extra steel and other strategic materials will be consumed by the Heer and Luftwaffe. At least a high % of these materials. I think there is a little too much foresight in these ramped up numbers. And who ever built more than 25 submarines in one year in peace time, ever? Then why is it all or nothing on Plan Z. Wouldn't it be more likely to keep some of the order ships but cancel only a few of them? I think a large push would look more like this rate.

Prewar orders:
1939 24 (Two full squadrons is a lot per year)
1940 24
1941 24
1942 24

If we build 2 squadrons per year, we will have 213 U-boats by the end of 1945. Sure he wants 300 U-boats, but did anyone outside of the U-boat command ever seriously consider this number pre WW2?

Then you might end up with a rise more like.

1939 36 (Rushed production of half of next year orders. This is bit on high end)
1940 72 (Doubling is big increase. And France is still undefeated for most of year)
1941 240 (Ok, now we are in full swing)

 

[Riain]

Plan Z was to build upon the foundations of the existing Kreigsmarine of 2 battlecruiser, 3 panzerchliffe and 5 light cruisers with 2 carriers, 2 battleships and 3 heavy cruisers on the slips being built. What happens to this force? Is work slowed or stopped on the ships being built, are the existing ship raided for officers and men?

These are the questions I ask myself when uboat-wanks are proposed.

 

[BlondieBC]

Ok, now to take your numbers on face value on ship construction. Yes, I think you get a strong British reaction, but I do not think it will be as strong as some other posters on this tread seem to think. Again, back to time line and the fact governments make decisions slowly. If Hitler decides to go heavy U-boats in January 1939, we have to ask when British Intelligence (Sea Lords) understand this decision has been made. I would guess it would be over the summer as they see the large number of new keels being laid. So lets say that by April, intelligence has some indication of what is happening. It could easily be June before the UK adjusts its strategy. So say Germany gets a 6 month jump on building, but the UK gets a 3 month jump on reacting. I think you will have to pull many British countermeasures forward in time. I don't know the dates of these in detail, so I can't give you an opinion on this matter beside the UK will react faster than OTL.

From what I have seen in WW1, I do believe the "300" magic number is correct. If you have 300 at start of war, you can break the UK. This means 300 quality U-boats with well train crews by peace time standards and the supporting aircraft. You estimated losses look reasonable for your given ship losses. The trick will be that the UK will react. Convoy will be moved up sooner. More bombing focus on U-boats. At some point before defeat, the War Cabinet will be told that U-boats must be number one target for all command or the war will be lost. At this point, the bomber Generals will focus on U-boats. As ships are sunk, there are fewer targets at sea at any given time. Fleet carriers can be used to escort convoys. More commando raids will be done. For a good TL, you have to adjust for these. By the end of mine, I had a 35% or so reduction in U-boat effectiveness factor. I found it was easier to set the forces at play and adjust every couple of months, you seem to be taking the approach of planning ahead the whole TL. I found that as one went month by month, it becomes obvious what the Royal Navy will do. At least narrow down to a few choices.

British drop out of war when they run out of food. About 1400-1700 calories per day per adult. September 1940 to December 1941 is a very short period of time to break the will of a nation. The first winter will not be too bad, and by the height of the second winter there is hope of the USA. Also, Churchill will starve India before giving up. He only removed 60% of merchant shipping from the India Ocean OTL. He likely goes well above 90% ITTL. And units on the defensive consume less supplies. And the UK does not really have to have tea and coffee. You just have to look at the details and make a call. For example, what % of tonnage that went to England IOTL was non-essential (tea, toys, clothes not required for survival, etc). And there are other ways to free up shipping. Not attacking Italian East Africa and keeping the troops in say Australia saves a lot of merchant tonnage.

Butterflies: There are many huge ones.

1) Japan is big winner as Pacific is stripped. I can even see USA and UK making a deal with Japan (no embargo). Churchill said he make a deal with Satan to stop Hitler. Tojo is nicer guy than Satan, and Churchill might have been speaking the truth.

2) Yes, Bismark might slip through. Or other merchant raiders do better. You should just pick a few as butterflies and run with it. No way to know for sure which ones work.

3) Italy does a lot better. With fewer supplies, UK does not attack into Libya. I doubt Malta is seriously defended. Then we get no Africa Korp. Whole series of butterflies.

4) Probably cancel Greece operations too. I tend to think a truly desperate UK allows Italy to dominate Med without challenge.

5) Surprise for the invasion of USSR might be lost.

6) USA could easily be changed. A lot of extra ships are being sunk.

7) A lot more people might be sent to Canada. I know the sent some children, but they could send all children and elderly not need for war if desperate enough.

8) If truly desperate, look at things to get more help from Empire. Things like Dominion status for India in exchange for more help might be consider. Or more concessions to South Africa. The UK know what is at stake, and will take desperate actions.

 

[Deleted member 1487]

Plan Z was to build upon the foundations of the existing Kreigsmarine of 2 battlecruiser, 3 panzerchliffe and 5 light cruisers with 2 carriers, 2 battleships and 3 heavy cruisers on the slips being built. What happens to this force? Is work slowed or stopped on the ships being built, are the existing ship raided for officers and men?

These are the questions I ask myself when uboat-wanks are proposed.

The ships being built would probably continue work, just at IOTL, as they would be ready by 1941 (the aircraft carrier A though was IOTL pillaged for sale of parts to the USSR) and carrier B would be stopped before OTL I'd think if it was no longer needed when this Plan Z is commissioned. Its keel probably gets broken up; if not it gets stopped in 1939 when the war breaks out.
The existing ships wouldn't be raided for men, as this was not needed to staff all of the 1000+ uboats built IOTL.

Some thoughts. It looks like U-boats preWW2 took 6-18 months from keel laying to commissioning. This is an improvement from up to two years preWW1. It also took several months from ordering to keel laying. So you numbers look a bit high for numbers of U-boats. So lets take a sample ramp up in peace time.

Jan 1939 - Hitler signs off on priority switch.
Late Feb 1939 - Navy sends out orders to ship yards.
April 1939 - First new keel of new order laid. It will take several more months to get all the keel order in 1939 under construction.

So, gaining 6 months, not a full year on production seems more reasonable. Using a half year gain, we get:

1939 43 U-boats (18+50/2)'
1940 125 U-boats (50/2+199/2)
1941 around 200-225.

And I think this is a bit optimistic. Looking at the historical numbers, it looks like only after the Fall of France did the real push begin. With France still undefeated, I strongly suspect the extra steel and other strategic materials will be consumed by the Heer and Luftwaffe. At least a high % of these materials. I think there is a little too much foresight in these ramped up numbers. And who ever built more than 25 submarines in one year in peace time, ever? Then why is it all or nothing on Plan Z. Wouldn't it be more likely to keep some of the order ships but cancel only a few of them? I think a large push would look more like this rate.

Prewar orders:
1939 24 (Two full squadrons is a lot per year)
1940 24
1941 24
1942 24

If we build 2 squadrons per year, we will have 213 U-boats by the end of 1945. Sure he wants 300 U-boats, but did anyone outside of the U-boat command ever seriously consider this number pre WW2?

Then you might end up with a rise more like.

1939 36 (Rushed production of half of next year orders. This is bit on high end)
1940 72 (Doubling is big increase. And France is still undefeated for most of year)
1941 240 (Ok, now we are in full swing)

http://en.wikipedia.org/wiki/Plan_Z

Plan Z was the name given to the planned re-equipment and expansion of the German Navy (Kriegsmarine) ordered by Adolf Hitler on January 27, 1939.[1] The plan called for a Kriegsmarine of

10 battleships,
4 aircraft carriers,
3 battlecruisers,
3 old panzerschiffe,
12 new panzerschiffe,
5 heavy cruisers,
36 light cruisers M Class,
24 light cruisers typ spähkreuzer,
68 destroyers,
90 torpedo boats
249 U-boats

To be ready by 1945

I assume that we could suggest instead that Uboats are favored for the Plan Z of TTL instead of surface vessels. We can still call it Plan Z. Apparently two building plans were laid out for Plan Z either a massive surface fleet backed up by Uboats or a commerce raiding fleet primarily of Uboats (pretty much a Jeune Ecole fleet).

Given the scale of production that IOTL was laid out for the massive H class battleships and other surface fleet vessels, I don't see why it would be so strange to assume that a larger commerce raiding fleet would built up on a larger scale than 24 units per year, especially as Germany was planning on being ready for war by 1942. A naval war wasn't planned before 1945, but could be planned for sooner, because Uboats, torpedo boats, mine layers, destroyers, and light cruisers take far less time to built and commission than the large fleet planned IOTL. Even if 300 were the number selected, which if Uboats are favored I think it would actually be more, then I think they'd be shooting for 75 units per year to be ready for 1942, by which time all of the capital projects would be ready for a major European war. IIRC 1945 was also the year that Hitler thought he'd have to fight a world war, not just a European war.
So he planned 1942 to fight in Europe and 1945 to fight the world/the US.

The final numbers you give for the predicted amount of construction I think is too low. You're probably right that my numbers are too high, so your first set of numbers is probably the closest. Even without France defeated, Germany is figuring that it is stuck fighting a long war and is thus planning to fight a commerce war to interrupt the flow of US trade to France and Britain. IIRC right before the May 1940 invasion OKW was planning on seizing the Netherlands and bogging down if Manstein's plan didn't work, so were then planning on fighting an attrition war with their new forward air bases and naval bases.

 

[Riain]

OK, so the invasion of Norway occurs as per OTL as does the threat of Sea Lion? Because so much of the possibilities of a Uboat campaign rests on these events.

In my mind the whole 'scrap the surface fleet, wank the Uboat TL' means that while the Uboats slowly squeeze Britain the war on land goes much better for Britain, negating the Uboat efforts.

 

[Deleted member 1487]

OK, so the invasion of Norway occurs as per OTL as does the threat of Sea Lion? Because so much of the possibilities of a Uboat campaign rests on these events.

In my mind the whole 'scrap the surface fleet, wank the Uboat TL' means that while the Uboats slowly squeeze Britain the war on land goes much better for Britain, negating the Uboat efforts.

I didn't say scrap the surface fleet, rather prevent the ships that were scrapped anyway from even getting started and instead focus that effort into Uboats. As it was lots of metal and effort were wasted on ships that were laid down 6-7 months they were cancelled, while the Uboat fleet then get the resources that were focused on those ships. So instead of waiting for the Uboat fleet expansion that happened anyway in September 1939, why not start it when Hitler decided he wanted to build up the navy anyway in January 1939? As it was there needed to be effort to scrap the keels of the ships that were cancelled, tying up precious dock space, skilled labor, and wasted much of the metal, including the metal that had been machined and was waiting delivery.

Yes, the Norwegian campaign still happens, because the ships that took part in them were not part of Plan Z and were already far advanced or were completed and would thus not be affected by the POD.

Sea Lion would probably still be going on even without my POD, as nothing about the Uboat expansion or Plan Z affected anything to do with Sea Lion.

http://www.german-navy.de/kriegsmarine/zplan/battleships/schlachtschiffh/history.html

Construction was stopped on October 10th, 1939 as the focus in German naval construction switched to the construction of more U-boats instead of battleships. Up to this day, 1200 tons of steel was already used for the Schlachtschiff H , 3500 tons were in construction and another 12000 tons were already ordered. (Schlachtschiff J was still in an earlier phase of construction). In 1940, the used material was wrecked on the shipyard and used elsewhere.

 

[Riain]

Your PoD is quite sensible, but many TLs of this type go back further and don't have Germany build a surface fleet to speak of at all. This denies the Germans the ability to conduct the Norwegian campaign, the ability to conduct the Atlantic operations that occured in 1941, and the threat to the Russian convoys that lasted until very late in the war.

In my mind the best thing to do would have been to accelerate the construction of the most complete ships such as Seydlitz and Graf Zepplin (without the heavy guns, which were sold to the Soviets) at the expense of ships like the Lutzow and Peter Strasser and especially the H BBs and M CLs.

 

[Deleted member 1487]

In my mind the best thing to do would have been to accelerate the construction of the most complete ships such as Seydlitz and Graf Zepplin (without the heavy guns, which were sold to the Soviets) at the expense of ships like the Lutzow and Peter Strasser and especially the H BBs and M CLs.

The Graf Zeppelin was never completed because its fire controls system was sold off to the Soviets and it would have taken too long to build another. Both the Seydlitz and Graf Zeppelin should have been scrapped, as neither were every used for anything and given Germany's fuel shortages, they would have been too much of a drain to justify the fuel costs. The Lutzow was sold to the Soviets, but I think should have been scrapped, the Strasser was scrapped anyway and should have been stopped in January 1939 when this Plan Z is enacted, and obviously the rest should never have been started.
None of the ships above would have added anything to the German war effort that an equivalent number of Uboats wouldn't offer for less resources (fuel, metal, manpower, time); even scrapping the ones started before 1939 would still offer Germany the metal, which would have been useful for more Uboats, especially considering most ended up scrapped anyway or sunk postwar for no gain for Germany. At least the metal would have helped.

 

[Blackfox5]

The added benefits of starting the Uboat expansion in 1939 is that training can be started in peace time for large numbers of crews, more experience gained producing Uboats, which reduces construction times, and the British won't be moved to start expanding their escort forces, as they thought they had enough to handle up to 100k tons of Uboats as it was and the Germans won't be able to manufacture up to 100k by the time September 1st rolls around.

I think there's a flaw in this logic. If the British think they can handle 100k tons of U-Boats and notice their prime potential enemy is increasing production of U-Boats, then they don't wait until 100k are manufactured or war breaks out before they begin to do something about it.

If they wait too long before producing on their own, then that 100k tonnage is quickly bypassed. The smart thing to do is plan when that tonnage will be met, and already have new escorts, frigates, and destroyers being commissioned to deal with it at or before that time.

Ramping up U-Boat production from 18 to 50 (an almost 200% increase), and knowing future years will see more U-Boats, will cause the British to start building their ASW weapons earlier to deal with that threat. The British will probably be several months behind the Germans because it takes time to notice this and then formulate a response. But I don't think several months start will be decisive.

The British have a very robust ASW system. German U-Boats can't be much of a threat until France falls in May 1940. By March 1941, the British were winning the Battle of the Atlantic. I don't think this scenario changes that decisively once you factor in expected British responses.

Of course, in a Second Happy Time scenario where the US goofs off and forgets to embrace standard ASW procedures in the first six months of their entry in the war, this could be real trouble. Of course, having all those extra U-Boats out there may cause FDR and King to put more thought in how the US will need to react if they suddenly enter the war.

Only a few things need to change for the US and UK to dramatically improve their ASW performance. Using aircraft patrols more effectively, instituting convoys near US coasts, and increasing escort production are very simple to do. If the U-Boats ever become dangerous enough to really cause existential concern, I suspect that will all happen far quicker than they did IOTL.

 

[Riain]

I think that not completing an aircraft carrier because you've sold the FCS for the 15cm guns is about the dumbest reason ever. Just build the carrier without them! In my mind if the GZ did a single cruise and then sat in port for a few years it would have made a significant contribution to the German war effort considering how close she was to completion when war broke out. We're not talking about an empty shell here, we're talking about a ship which was launched in Dec 38 complete with 200,000shp of machinery.

 

[BlondieBC]

The ships being built would probably continue work, just at IOTL, as they would be ready by 1941 (the aircraft carrier A though was IOTL pillaged for sale of parts to the USSR) and carrier B would be stopped before OTL I'd think if it was no longer needed when this Plan Z is commissioned. Its keel probably gets broken up; if not it gets stopped in 1939 when the war breaks out.
The existing ships wouldn't be raided for men, as this was not needed to staff all of the 1000+ uboats built IOTL.

http://en.wikipedia.org/wiki/Plan_Z


I assume that we could suggest instead that Uboats are favored for the Plan Z of TTL instead of surface vessels. We can still call it Plan Z. Apparently two building plans were laid out for Plan Z either a massive surface fleet backed up by Uboats or a commerce raiding fleet primarily of Uboats (pretty much a Jeune Ecole fleet).

Given the scale of production that IOTL was laid out for the massive H class battleships and other surface fleet vessels, I don't see why it would be so strange to assume that a larger commerce raiding fleet would built up on a larger scale than 24 units per year, especially as Germany was planning on being ready for war by 1942. A naval war wasn't planned before 1945, but could be planned for sooner, because Uboats, torpedo boats, mine layers, destroyers, and light cruisers take far less time to built and commission than the large fleet planned IOTL. Even if 300 were the number selected, which if Uboats are favored I think it would actually be more, then I think they'd be shooting for 75 units per year to be ready for 1942, by which time all of the capital projects would be ready for a major European war. IIRC 1945 was also the year that Hitler thought he'd have to fight a world war, not just a European war.
So he planned 1942 to fight in Europe and 1945 to fight the world/the US.

The final numbers you give for the predicted amount of construction I think is too low. You're probably right that my numbers are too high, so your first set of numbers is probably the closest. Even without France defeated, Germany is figuring that it is stuck fighting a long war and is thus planning to fight a commerce war to interrupt the flow of US trade to France and Britain. IIRC right before the May 1940 invasion OKW was planning on seizing the Netherlands and bogging down if Manstein's plan didn't work, so were then planning on fighting an attrition war with their new forward air bases and naval bases.

Ok, I see where you are going. Sort of flip the build order around. So you get something closer to my first set of numbers. With some luck, the UK might not react as strongly to the Germans just reordering production priorities. They could see it as more problems with capital ships construction than building U-boats faster. As much as anything, the German navy gets lucky.

On the 1/3 rule of ships on station, it is about right from Germany to west of British Isles. But I saw rates as high as 50% on station in the Med in WW1 due to shorter travel times. With the French ports being used, you might get a peak sustained rate of over 33% due to shorter distances. At least until British air power pushes the ships out to more distant locations.

Another butterfly is that you might find some of the quality issue with German subs and torpedoes earlier. More ships is more chance to figure out the torpedoes are not working right. Also more chance to fix items like hatches installed backwards. Your POD is really something that could go a lot of ways. In a German bad case scenario, the Germans lose surprise on Russia. They also spook FDR and the RN into more aggressive counter actions. Things like bomber command using bombers to hunt for U-boat and bombing the U-boat bases as #1 priority would help the UK a lot. Or in a German good case scenario, we can have Italy thriving without German help, extra units for the attack on Russia which is still done with surprise achieved, and vastly worse logistics for the UK. Later on vastly worse logistics for the UK/USA for D-Day. With the USSR hit much harder and the USA looking like it is dragging its feet even more, a peace deal might look pretty good to Stalin.

 

[Deleted member 1487]

I think there's a flaw in this logic. If the British think they can handle 100k tons of U-Boats and notice their prime potential enemy is increasing production of U-Boats, then they don't want until 100k are manufactured or war breaks out before they begin to do something about it.

If they wait too long before producing on their own, then that 100k tonnage is quickly bypassed. The smart thing to do is plan when that tonnage will be met, and already have new escorts, frigates, and destroyers being commissioned to deal with it at or before that time.

Ramping up U-Boat production from 18 to 50 (an almost 200% increase), and knowing future years will see more U-Boats, will cause the British to start building their ASW weapons earlier to deal with that threat. The British will probably be several months behind the Germans because it takes time to notice this and then formulate a response. But I don't think several months start will be decisive.

The British have a very robust ASW system. German U-Boats can't be much of a threat until France falls in May 1940. By March 1941, the British were winning the Battle of the Atlantic. I don't think this scenario changes that decisively once you factor in expected British responses.

Of course, in a Second Happy Time scenario where the US goofs off and forgets to embrace standard ASW procedures in the first six months of their entry in the war, this could be real trouble. Of course, having all those extra U-Boats out there may cause FDR and King to put more thought in how the US will need to react if they suddenly enter the war.

Only a few things need to change for the US and UK to dramatically improve their ASW performance. Using aircraft patrols more effectively, instituting convoys near US coasts, and increasing escort production are very simple to do. If the U-Boats ever become dangerous enough to really cause existential concern, I suspect that will all happen far quicker than they did IOTL.

The Brits were already building up their escort assets prior to the outbreak of the war and still have massive trouble with Uboats until 1941-2. My point is that they already planned and acted on the threat and they thought they had a massive cushion before Uboats would be a threat. They wouldn't build up more escorts then they already were in 1939, because they thought their pre-war fleet was enough to handle 100k tons of Uboats and then they built more on top of that because they thought they were building up an overkill margin. It turns out they were severely underkilling it, because they badly misused their escort assets escorting warships on Hunter-Killer missions until 1941, tying up much of the escort cushion until they finally realized they weren't sinking enough Uboats to justify the HK groups.

That was what I was getting at in the first post, that the British wouldn't build any more escorts than IOTL prior to September 1939 because they didn't think they had any reason to build more, as with their construction plans in place by March 1939 had them countering the new German building AND counter the increasing threats of Japan and Italy. Britain was constrained by the threats in the Mediterranean and Pacific too, so they were building for all eventualities and the extra 25-40 Uboats laid down prior to September in this version of 1939 (IOTL there were already 18 laid down prior to September 1939), wouldn't really result in a change of British building strategy, because they thought they had it more than handled because of ASDIC. It turns out they were badly wrong and (re)learned several harsh lessons.

I think that not completing an aircraft carrier because you've sold the FCS for the 15cm guns is about the dumbest reason ever. Just build the carrier without them! In my mind if the GZ did a single cruise and then sat in port for a few years it would have made a significant contribution to the German war effort considering how close she was to completion when war broke out. We're not talking about an empty shell here, we're talking about a ship which was launched in Dec 38 complete with 200,000shp of machinery.

But to what end? What did the Graf Zeppelin offer the German fleet in terms of capabilities? Sea Planes could do the recon work, especially as the GZ had very low aircraft capacity and was poorly designed for Atlantic service (just as many of the German capital ships proved, which is why they needed the Atlantic bows and engine upgrades...but an aircraft carrier poorly designed for rough sea launches is no upgradeable). Anything in the North Sea can be handled by land based aircraft, especially once Norway falls.

Ok, I see where you are going. Sort of flip the build order around. So you get something closer to my first set of numbers. With some luck, the UK might not react as strongly to the Germans just reordering production priorities. They could see it as more problems with capital ships construction than building U-boats faster. As much as anything, the German navy gets lucky.

On the 1/3 rule of ships on station, it is about right from Germany to west of British Isles. But I saw rates as high as 50% on station in the Med in WW1 due to shorter travel times. With the French ports being used, you might get a peak sustained rate of over 33% due to shorter distances. At least until British air power pushes the ships out to more distant locations.

Another butterfly is that you might find some of the quality issue with German subs and torpedoes earlier. More ships is more chance to figure out the torpedoes are not working right. Also more chance to fix items like hatches installed backwards. Your POD is really something that could go a lot of ways. In a German bad case scenario, the Germans lose surprise on Russia. They also spook FDR and the RN into more aggressive counter actions. Things like bomber command using bombers to hunt for U-boat and bombing the U-boat bases as #1 priority would help the UK a lot. Or in a German good case scenario, we can have Italy thriving without German help, extra units for the attack on Russia which is still done with surprise achieved, and vastly worse logistics for the UK. Later on vastly worse logistics for the UK/USA for D-Day. With the USSR hit much harder and the USA looking like it is dragging its feet even more, a peace deal might look pretty good to Stalin.

I agree much of this is based on speculation and its really hard to determine what would have happened, as it is very personality and randomness dependent. Still diverting BC away from bombing Germany sets back that offensive pretty badly with no additional effort from the Germans. It could very well set back the Allies in all sorts of ways even in the worst case scenario for the Germans, as the Allies work to counter the threat instead of focusing on historical efforts...especially if the German inflict a-historic shipping losses, which means the Allies have less than IOTL to work with.
The point about discovering the torpedo problem and construction issues has major potential for interesting PODs. If part of the torpedo problem is solved by the time of the Norwegian campaign, then the RN is going to take some very serious losses:

http://www.uboataces.com/articles-wooden-torpedoes.shtml

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”.

Owing to torpedo failures, on April 26, Grand Admiral Raeder released the U-boat Force from Norwegian operations. Meanwhile, design flaws were being discovered back at the Torpedo Directorate. Often times, when a problem was discovered and corrected, other new problems were uncovered as a result of the fix. Problems fell into three main categories: contact detonator, magnetic detonator and depth keeping ability.

 

[Blackfox5]

Britain was constrained by the threats in the Mediterranean and Pacific too, so they were building for all eventualities and the extra 25-40 Uboats laid down prior to September in this version of 1939 (IOTL there were already 18 laid down prior to September 1939), wouldn't really result in a change of British building strategy, because they thought they had it more than handled because of ASDIC. It turns out they were badly wrong and (re)learned several harsh lessons.

Again, I heavily disagree with this logic. The British won't be seeing, "Hey, it is only 32 more U-Boats". They will be seeing Germany building capacity for 200% more U-Boats in 1939 and continuing at that level or beyond. It's 32 more U-Boats by end of 1939, and an extra 100 or more by 1940 than previous projections. That means the British will know in early 1939 that that 100 ton limit will be broken sometime in 1940. Knowing that, they'll analyze and make changes accordingly.

Once you see your enemy greatly increase his ability to build a weapon so that your previous projections are outdated, you'll begin countermeasures. And increasing production by 200% is going to attract attention.

 

[Deleted member 1487]

Again, I heavily disagree with this logic. The British won't be seeing, "Hey, it is only 32 more U-Boats". They will be seeing Germany building capacity for 200% more U-Boats in 1939 and continuing at that level or beyond. It's 32 more U-Boats by end of 1939, and an extra 100 or more by 1940 than previous projections. That means the British will know in early 1939 that that 100 ton limit will be broken sometime in 1940. Knowing that, they'll analyze and make changes accordingly.

Once you see your enemy greatly increase his ability to build a weapon so that your previous projections are outdated, you'll begin countermeasures. And increasing production by 200% is going to attract attention.

They certainly would after they completely their currently locked in building program. By late 1939 they will be planning for their 1940 building program, which IOTL saw that massive increase in escort production. My point is they wouldn't change their pre-war building program, as it was deemed sufficient until they could start their next one in 1940, which would then address the Uboat expansion. They wouldn't necessarily know where the Germans were planning on stopping Uboat construction, so they wouldn't want to unbalance their fleet by loading up on escorts, when they still needed to deal the with surface fleets of German, Japan, Italy, and who knows who else. I agree they would address it by 1940, but pre-war their building plans were set to deal with the triple threat of the Axis fleets in a balanced way and when 1940 rolls around they will be freed up to counter the growing Uboat concern if it materializes because escorts require significantly less time to build than Uboats.

Remember that Italy and Japan were building up their much larger surface fleets and the RN needed to plan to deal with them, especially as Germany was a relatively minor naval threat in comparison in 1939. You're certainly right that naval building is reactive, but Britain isn't reacting to just Germany or necessarily mainly to Germany. The RN pre-war thought was that the Uboat problem was solved by ASDIC, so a German Uboat build up, while concerning, isn't the main threat in the minds of the RN, because they were still stuck in the battleship mindset (as Raeder was too) and thought that technology and WW1 experience conquered the threat from the Uboats. Except it turns the Uboat captains learned from their mistakes in WW1 and operated on the surface at night many times, confounding the British, who thought the Germans were operate as anticipated, instead of 'asymmetrically', among many other tactics that the British were not prepared for.