AHC: Make Sealion very unlikely

[ennobee]

Curious thought, but might a LONGER battle of France actually help Sealion?
1) more English Resources used up defending Paris or Rouen. Of course, there will be more German casualties too, but overall with Germany being victorious, they will still have more men and guns left in the end.
2) Germany having more time to build up Dunkirk and Calais while the British ports are busy ferrying supplies to Normandie. By the time France is defeated, Germany would have working S-boat and U-boat squadrons in Belgium and the north of France. While still no match for the Royal Navy, they could still deprive the English at least the uncontested rule of the sea.
3) Finding out that Britain will not roll over dead on command, Germany will already have to think at least seriously about landing on the island. Each day the war in France drags on, it will have one more day to plan the invasion and to design and manufacture the hardware needed. Yes we might still see the Germans using seized Dutch river barges, but just as well, they will have their share of purpose-built commando-lighters or even giant sailplanes and more importantly, they will have their share of ferries and packetboats in place to run the supply chain for the second wave once the beaches are secured.

 

[Post]

It seems you're talking about a few months longer campaign in France. In a few months you don't build a whole lot of S-boats and U-boats, not nearly enough to tip the scale in a meaningful way. Besides a longer campaign means you'll miss the slot to do Sealion in 1940.
That means postponement to 1941, which gives more time to prepare, but also gives the UK more time to prepare.

 

[Garrison]

Curious thought, but might a LONGER battle of France actually help Sealion?

Not really, Germany needed a fast victory in 1940 owing to the severe limits of its logistics. Following the fall of France they looted the French railway system for rolling stock because of the dire state of the Reichsbahn, which is just one way they raided France for resources. Nazi Germany was walking a tightrope in 1940 and without overrunning France so shockingly quickly they are in deep trouble. Also if Germany is bogged down fighting in France don't count on Italy to declare war, so no Mediterranean distractions for the British.

 

[ScrewySqrl]

The disparity of forces between the KM and RN is easy to underestimate. During the WAllied withdrawal from Narvik, the number of RN destroyers covering the operation was greater than the number of KM destroyers afloat at the outbreak of hostilities. Thanks to Warspite et al, the number of German destroyers available for any Sea Lion is significantly lower than that starting figure.

The LW can't stop the RN getting to the barges, and the KM sure as hell doesn't have enough hulls to make it vaguely competitive.

Sure, you can attempt to rectify this by a PoD or PoDs but: a) there will be a reacting in the UK (and other countries); b) the scales are still massively weighted against them; c) something else isn't getting built, which will have an effect, likely in the Battle of France.

And that last one is the main problem. These ideas always treat the BoF as a foregone conclusion. It wasn't. Treating it as such will not only cause great consternation in German high command (with potential reactions to said concern); the diverted attention towards Sea Lion decreases the chance of Case Yellow's success.

This disparity is why my (wild) idea was Zeppelins.

If you aren't ever going to beat the Royal Navy in this lifetime, you have to bypass them somehow.. gotta go over or under. Under the channel means either digging a tunnel -- something tech 50 years later took a decade to do, or Subs. Subs of the day (an even now) would never have serious cargo capacity to make this work. This leaves going over.

The one tech Germany has in the 1930s that MIGHT have the carry capacity to move an army division through the air is Zeppelins.

As noted, there are plenty of *other* potential problems (weather, relatively slow speed making them targets, etc), but it does bypass the Royal Navy, which is the single largest impediment to invading. Preventing that is something the Navy was basically for since 1588, after all.

 

[Garrison]

This disparity is why my (wild) idea was Zeppelins.

If you aren't ever going to beat the Royal Navy in this lifetime, you have to bypass them somehow.. gotta go over or under. Under the channel means either digging a tunnel -- something tech 50 years later took a decade to do, or Subs. Subs of the day (an even now) would never have serious cargo capacity to make this work. This leaves going over.

The one tech Germany has in the 1930s that MIGHT have the carry capacity to move an army division through the air is Zeppelins.

As noted, there are plenty of *other* potential problems (weather, relatively slow speed making them targets, etc), but it does bypass the Royal Navy, which is the single largest impediment to invading. Preventing that is something the Navy was basically for since 1588, after all.

I know you aren't being entirely serious, but really this is a nonstarter. it took 5 years to build the Hindenburg, which had the following stats(from Wikipedia):

Crew: 40 to 61

• Capacity: 50–70 passengers
• Length: 245 m (803 ft 10 in)
• Diameter: 41.2 m (135.1 ft 0 in)
• Volume: 200,000 m3 (7,062,000 ft3)
• Powerplant: 4 × Daimler-Benz DB 602 (LOF-6) diesel engines, 890 kW (1,200 hp) each

Performance

• Maximum speed: 135 km/h (85 mph)

A single WWII Division consisted of 10000-15000 troops. Be generous and assume you could halve the space per person and halve the crew number to make room and maybe 200 troops per airship, not allowing anything for equipment. So that's 50 Hindenburg class airships for one division, with no equipment. Now imagine trying to unload these monsters somewhere in the English countryside, with no support infrastructure on the ground and bearing in mind that building this fleet of airships is hardly going to be something Germany could keep secret and that the British have had ample time to prepare countermeasures. Basically this is an elaborate way to donate a lot of Aluminium to the British war effort.

 

[ScrewySqrl]

I know you aren't being entirely serious, but really this is a nonstarter. it took 5 years to build the Hindenburg, which had the following stats(from Wikipedia):

Crew: 40 to 61

• Capacity: 50–70 passengers
• Length: 245 m (803 ft 10 in)
• Diameter: 41.2 m (135.1 ft 0 in)
• Volume: 200,000 m3 (7,062,000 ft3)
• Powerplant: 4 × Daimler-Benz DB 602 (LOF-6) diesel engines, 890 kW (1,200 hp) each

Performance

• Maximum speed: 135 km/h (85 mph)

A single WWII Division consisted of 10000-15000 troops. Be generous and assume you could halve the space per person and halve the crew number to make room and maybe 200 troops per airship, not allowing anything for equipment. So that's 50 Hindenburg class airships for one division, with no equipment. Now imagine trying to unload these monsters somewhere in the English countryside, with no support infrastructure on the ground and bearing in mind that building this fleet of airships is hardly going to be something Germany could keep secret and that the British have had ample time to prepare countermeasures. Basically this is an elaborate way to donate a lot of Aluminium to the British war effort.

you can probably do more than that. The Ocean liners that were converted to troop transports increased the carrying capacity as troopships by 10-fold and that for a week-long trip. This would be for only a few hours at most. so with a 100 ton capacity, you could probly increase the troops held to 600 per zep (or about 30-40 zeps for a division), with their basic equipment. A days combat supply for an infantry division would be about 7 zeps worth (700 tons). your landing facility would be captured ahead of time by a traditionally landed Parachute-and-glider division or two.

Its still a massive undertaking (and the zeps are built using the metal *not* used in making 4 battleships and an aircraft carrier), will have odd consequences (Britain And france respond with more aircraft capacity? maybe primitive rockets to shoot zeps down?) and how even a slow-moving airmobile force could change warfare in Poland and France (just leapfrog Maginot to say Nancy or Luneville and drive on Paris?)

 

[Cryhavoc101]

Marinefahrpram gets designed earlier and cranked out in as much secret as possible, U-boats sink the Dunkirk rescue fleet, and magnetic mines are held in strategic reserve until the landings.

These alone bump the odds from "Battle of France goes OTL well" odds, up to simply poor as hell.


Cram most of the U-boat and E boat fleet into the channel to screen capital ships along with the Mines, and perhaps diversionary raids by the Deutschlands and Scharnhorsts, and you'll for sure have a few days to ferry shit over.

After that it depends entirely on how panicky and stupid the British become.

Their was extensive mine fields either side of the area of the Dunkirk evacuation and about 30 odd DD - as well as huge tidal surges throught the straights along with very shallow waters + sand banks etc - not a good environment for Uboats!

 

[DaveBC]

The only way you could realistically weigh different statistical outcomes is if you had a load of precedents to compare it to.

Yet for some reason, I can't find any historical examples where an improvised amphibious fleet attempted to cross an ocean and land on a shore defended by an enemy force with naval superiority. Unless Crete or Exercise Tiger count.

The difference between 0% and 1% is something you couldn't possibly qualify through hypothetical scenarios.

All of that said, perhaps I'm biased by having my boots squarely -- and safely -- planted in the 0% camp. If you're incapable of holding the Channel, then for all that it's only a couple dozen miles away, southern England may as well be on the Moon.

 

[Barry Bull]

The problem with building landing craft is that it will alarm everyone in the baltic and make the UK narrow its eyes. Also the Germans would have to be prescient...

...As a tour de force in how to do a tech change story well. Because even with the main character being a man who has our level of hindsight, he runs into the realities of things, industrial problems, beuaracratic obstructionism etc, poor leadership and management etc etc. And the battles to get things done and changed which he knows WILL work, are often struggles against the most bitter of opposition.

The Germans suddenly building landing craft, in the baltic, in the 30's literally makes NO sense. Who's your target? Why are you wasting resources on them on the off chance that when you beat france you can threaten the UK that you can't possibly know will happen without hindsight or being able to see the future.

You sir, win the Internet.

 

[DaveBC]

Don't worry - I'm sure the Brits aren't likely to see a massive fleet of purpose-built landing craft as any reason to shore up their defences. Historically, Britain made very little effort to counter other empire's ship-building efforts and the Royal Navy was almost ridiculously reluctant to appear aggressive in the face of the enemy.

 

[Cryhavoc101]

Don't worry - I'm sure the Brits aren't likely to see a massive fleet of purpose-built landing craft as any reason to shore up their defences. Historically, Britain made very little effort to counter other empire's ship-building efforts and the Royal Navy was almost ridiculously reluctant to appear aggressive in the face of the enemy.

Yep. The phrase “just because we are paranoid doesn’t mean they are not out to get us” has absolutely no bearing on the Admiralty and Whitehall in general. Nope. Not even a little bit.

 

[TDM]

These boats were very simple and to a large degree made of concrete. The US faced the same situation with their LST needs and build them in new shipyards at rivers inland. So it is possible. The tricky thing is to prioritize it before the Fall of France.

They had concrete in them, and compared to other sea going vessels they were relatively simple but that doesn't make them something you can knock up in any workshop in the land by pouring a bit of concrete. As you say the the US had to make the shipyards in the inland rivers. So like I said you are not just keeping making a fleet of these things secret but now the shipyards you're going to make your secret boats in, secret.

And as you point out in terms of resources and scale and availability of stuff, Germany in the 30's is no US in the 40's

 

[TDM]

Curious thought, but might a LONGER battle of France actually help Sealion?

In general as pointed out the longer the battle of France goes on for the less likely Germany is to win it, or win it quickly and decisively, or be in any position to contemplate invading another country let alone doing so amphibiously.

1) more English Resources used up defending Paris or Rouen. Of course, there will be more German casualties too, but overall with Germany being victorious, they will still have more men and guns left in the end.

Thing is with this, is that the BEF being used up but the British putting more troops in. means that Britain has fully mobilised , which means that those material shortages issue tend to go away. However what it really means is France is still in the game and fighting, That is a lot of resources against Germany, including stuff like the French navy that might have a knock on effect on what we're discussing here.

2) Germany having more time to build up Dunkirk and Calais while the British ports are busy ferrying supplies to Normandie. By the time France is defeated, Germany would have working S-boat and U-boat squadrons in Belgium and the north of France. While still no match for the Royal Navy, they could still deprive the English at least the uncontested rule of the sea.

If we're picturing a scenario where the Germans have seized Calais but we're still supplying british troops in France there's no way the RN and the RAF will leave Calais in any shape to support the Germans doing anything (sorry Calais)! Also If Germany is still fighting in france that's going to take more resources than not fighting in france and building up a Sealion fleet, so they'll be less likely to devote extra resources to S(E)-Boats and U-boats.

S-Boat and U-boats also aren't much good against a RN in the North Sea and channel operating much more stuff.

3) Finding out that Britain will not roll over dead on command, Germany will already have to think at least seriously about landing on the island. Each day the war in France drags on, it will have one more day to plan the invasion and to design and manufacture the hardware needed. Yes we might still see the Germans using seized Dutch river barges, but just as well, they will have their share of purpose-built commando-lighters or even giant sailplanes and more importantly, they will have their share of ferries and packetboats in place to run the supply chain for the second wave once the beaches are secured.

I agree the idea that the idea of avoiding fighting Britain all the way will disappear, but the reality is if your still fighting in France that's what you are concentrating on not invading Britain. If you're Germany every day the fighting draws on its not really an extra day to plan your next invasion, it another day closer to losing momentum and getting another WW1, where they get ground down. German army blitzkrieg etc, has to win and win quickly. Then you have wider theatre stuff, like if German get caught up in France, maybe Stalin gets ideas with his army already sitting on half of Poland. Hell if the Great Fuhrer's promises start looking more like a rerun of WW1 he might face more kick back from home!

The problem Germany has is it's tight on resources, and blitzkrieg is a resource intensive way to fight (they lost 1000+ planes and 800+ tanks in 45 days in france as it is), they have to win and seize more resources or they run dry.

I think there's a tendency to forget just how lucky Germany got in 1940 OTL, it's already about as good as it's likely to get for them.

 

[DaveBC]

I think there's a tendency to forget just how lucky Germany got in 1940 OTL, it's already about as good as it likely to get for them.

This sums it all up, really. Germany willingly provoked or declared war with four major powers and achieved victory over precisely one of them. Even in baseball, a .250 record is pushing towards the mediocre side of average.

That said, one of the enduring questions of these interminable Sea Lion threads to me remains whether Germany could have just declared the war over after the fall of France. That wouldn't give a 1% chance of Sea Lion being pulled off, but it would probably be at least a 1% chance of ending the war with Britain for the time being.

 

[eltf177]

I find the mines question interesting, I have read they needed around 7000 to cover both sides of the invasion route, but I struggled to find out how they would be laid or exactly where. I don’t even know if they were actually available.

I do think the Germans would have had quite a few minelayers - a consequence of the pre-war expectation of needing to lay and maintain various minefields along their coastline. That said I doubt they anticipated their minelayers operating in contested waters, I assume the small boats on patrol, coastal guns and their radar in places like Dover would have made it very tough to lay mines near the British side of the English channel.

A book I read on the Z-Plan says the mines weren't available, nor were sufficient number of minelayers. And when you realize the RN is going to contest laying these fields the KM is going to run short of minelaying craft very quickly.

And the tides are going to pose problems for maintaining the fields...

 

[ScrewySqrl]

wouldn't a lot of the mines be sub-deliverable?

 

[DaveBC]

wouldn't a lot of the mines be sub-deliverable?

How many subs were available and does Germany really want to risk comparatively expensive, specialized craft on such a mission?

Good thing the British can neither sweep German mines nor lay mines of their own or I would say this was a fruitless exercise...

 

[TDM]

wouldn't a lot of the mines be sub-deliverable?

Subs don't have much payload, and unless they're on the surface they are slow, and there aren't that many subs.

This touches on what I was saying earlier about the myth of subs.


The type VII had a payload of 14x torps or 26 TMA or 39 TMB mines, depending in the type (mainly the TMA mines) Although I know that on occasion they crammed more torpedoes in at times so I'm guessing you could up that mine payload a bit especially if it's not a long trip..


The problem is Subs take up a lot of their capacity just being subs!

 

[yulzari]

This all drives towards my POD of France joining the Axis which instantly gives a huge increase in naval forces and in coastal, river and oceanic transports. Small stuff supporting the German USW to the east and long distance/larger stuff for the French USM to the east. I would like to throw in the Italians (and Spanish?) but the Royal Navy has the spare capacity to engage and sink them in transit to France. It does not solve the naval mismatch but does give a better chance of getting a lodgement and maintaining some sort of supply for some worthwhile period.

Is it likely? No, but not totally inconceivable. In OTL France and Britain fought in Morocco, Algeria, Gibraltar, Syria, Senegal, French Somaliland, Madagascar, Egypt and Syria and most French POWs refused to join the Free French and were repatriated. General Catrouox was the Governor General of French Indo-China a the time of the Armistice and contacted the British for support before the Japanese arrived in June 1940. Notwithstanding the actual ability of British forces to actively aid him, an injection of British forces into Indo-China could be a causus belli for a French declaration of war. Catroux was dismissed for his actions and became a Gaullist General.

 

[Gudestein]

They had concrete in them, and compared to other sea going vessels they were relatively simple but that doesn't make them something you can knock up in any workshop in the land by pouring a bit of concrete. As you say the the US had to make the shipyards in the inland rivers. So like I said you are not just keeping making a fleet of these things secret but now the shipyards you're going to make your secret boats in, secret.

And as you point out in terms of resources and scale and availability of stuff, Germany in the 30's is no US in the 40's

I’m not saying its logical to prepare Sea lion IOTL april 1940. I’m saying that building Marinefahrpramen outside normal naval yards is possible and not that complicated. The Italians made hundreds for operation Hercules.
That is all I’m saying here.

It does not by itself make Sea lion a success and it takes quite a pod to prioritize it before the Fall of France. I have this as the next upcoming update in my current TL (List Regiment at Havrincourt), and I use a 1917 pod. So it, to make it completely clear, it is not something I see as a Sea lion easy fix.