What would it take for the Germans to launch Sealion?

I'm not asking about whether they'll succeed, because they won't. What I'm asking is what will it take to make OKW believe an invasion of the British Isles is something they should go ahead with. Is winning the Battle of Britain enough? Would a Sealion require postponing Barbarossa?

An awful lot of people posting here dont see to have read this initial post. We aren't talking about a successful SeaLion, just what would persuade the Germans to actually launch it.

Not sure if a better Dunkirk would make much difference. The germans thought that the amount of equipment captured meant the British had a load more stockpiled, and they know substantial numbers had been retrieved from southern France, and there we considerable forces in Britain. But Britain can be defended by one man and his dog, so long as the Royal Navy commands the Channel.

The reall success needs to be the air war, as its pretty obvious to the OKW that unless the LW can stop the Royal Navy, the sea crossing is toast. So the BoB has to go better, and to be perceived as going a LOT better. Micheles 'A Better Show'handles this very well.
The problem is that, unless we apply near-ASB levels of advantages, the LW can't do tremendoulsy better. But they can seem to do so to Goering,enough so that SeaLion could be launched.
 

hipper

Banned
An awful lot of people posting here dont see to have read this initial post. We aren't talking about a successful SeaLion, just what would persuade the Germans to actually launch it.

Not sure if a better Dunkirk would make much difference. The germans thought that the amount of equipment captured meant the British had a load more stockpiled, and they know substantial numbers had been retrieved from southern France, and there we considerable forces in Britain. But Britain can be defended by one man and his dog, so long as the Royal Navy commands the Channel.

The reall success needs to be the air war, as its pretty obvious to the OKW that unless the LW can stop the Royal Navy, the sea crossing is toast. So the BoB has to go better, and to be perceived as going a LOT better. Micheles 'A Better Show'handles this very well.
The problem is that, unless we apply near-ASB levels of advantages, the LW can't do tremendoulsy better. But they can seem to do so to Goering,enough so that SeaLion could be launched.

If you assume Downing is retired early and Big wings were adopted after the channel battles the lack of interceptions by fighter command be enough to convince the LW that they had some air superiority
 
Germans do better in BoB making Hitler and Göring convinced that they can do something more substantial than fart in the general direction of UK.
Serious civil unrest in Britain and a vocal "peace now" movement makes them think that if they land a force in England, resistance will crumble.
Adolf orders OKW to do it.
OKW says "f--- it" and goes ahead with anything it can scrape by.
Brits make bad war movies about it for decades to come.
 
OTL, the Atlantic Wall used 17 million cubic meters of concrete. A bit more than Hoover Dam. There's your start
If you allow for triple this, to cover stone and other fill, a distance of 40km and an average depth of 125m that'd be enough for a causeway 10m wide.

Now it's just an engineering problem...
 
Bah, Goering has promised to deal with them.

Oh and the actual depth of the channel around the narrow bit is less than 50m, so the causeway could be even wider.

This is a joke I know but is actually sort of entertaining, sort of a Alexander the Great Siege of Tyre 1km causeway concept but with modern economies of scale. Seems kind of Nazi like actually to try something like this.

In practice it probably would be pretty good bang for the buck. Start putting some concrete blocks in the ocean at Calais. Stack some flak and naval guns and radar around the site. Make a big propaganda production about it. Churchill would insist the British bombard the site with all sort of air and sea resources (kind of like his wanting to bomb V1 and V2 sites OTL). In practice a pretty good bomber sump. Maybe you end up with at least a pretty good protected mole for loading naval vessels at least.
 
I actually have no clue how much material would be required for a 2-lane Channel Autobahn... but I bet Speer would be willing to try :winkytongue:

Using the Nicholson Bridge as a template
img1d.jpg

it's a concrete arch bridge built in 1915. Biggest in the World for decades
724m long, 73m tall. Used 127,680 cubic meters of concrete 1030ton steel.

Now stretch that across the 32km Channel

5,643,314 cubic meters of concrete, 45,534tons of steel

Double it, so they can be mobile, floatable sections like the Mullberry Dock sections
M_Harbour_6___Main.jpg


11m tons... Do it Albert... it's not ASB territory
 
How difficult would ground combat be for the Heer if they successfully landed in Britain?

Totally.
The general logistical situation is that the landing force will be deprived of supplies. That alone kills the thing.
Assuming somehow that doesn't happen, the general strategic consideration is that they will be attacking on a ridiculously short frontage (*). Blitzkrieg was all about attacking where the enemy wasn't, outflanking them and destroying their LOCs behind them. This OTOH will look like WWI, frontal assaults.
Also, it's not "the Heer" as we know it that gets landed. The first wave is a puny infantry force, with no artillery to speak of, no transport vehicles, and with most of the accompanying tanks sunk in shallow water or bogged down on the beaches or destroyed in transit. Yeah, the second wave should be bringing in some artillery - save that the first wave will be destroyed/captured before that.

(*) that applies in spades to the cross-Tunnel bridge, dam, or tunnel, too, of course.
 

Saphroneth

Banned
"A Better Show" has it.

Basically, what you need is that the Germans look like they're doing well enough to kick it off. The Kriegsmarine knew it would be a disaster so they'd have to be browbeaten into agreeing, the Luftwaffe was confident so they'd probably be a "yes" vote, and the army were okay so long as they'd have a fairly broad front.
 
And unlike France, the Heer won't be picking up any supplies in England. All vehicles are immobilized and food/ammo/other moved or destroyed first.
 
I tend to think of September 1940 as the most likely time for a Sea Lion.

Here is a small number of pods that may help an attack happen but would not cause a successful attack.

1. During the invasion of France the ground components of 8 British airbases are caught and killed rendering them unable to evacuate at Dunkirk.

2. After Mers El Kebir and Dakar French retaliatory raids on Gibralter are much more significant than OTL sinking HMS Hood and HMS Valiant and HMS Ark Royale.

3. A ceasefire is agreed between Vichy France and the UK.

4. Italy pull a raid on Alexandria 6 months early badly damaging 2 battleships.

5. German bombers never let up on attacking RAF bases and achieve temporary air superiority.

Sea Lion wouldn't work but Germany might believe it could.
 
5. German bombers never let up on attacking RAF bases and achieve temporary air superiority.

This assumes that it will be possible for the Germans to achieve air superiority, even temporary, by continuing to attack RAF bases.
 
This assumes that it will be possible for the Germans to achieve air superiority, even temporary, by continuing to attack RAF bases.
I don't think it was on otl. That's why I had Britain get unlucky and have a big chunk of their airbase support staff in France caught.

One of the big British advantages is that damaged planes could land in their own base and be repaired.

If we take out the veteran personal a lot of the airbase staff might not be as good and Britain won't get as many damaged planes back in the fight. Also the British might not be as good at establishing and repairing airbases.

Is it enough? I don't know. Probably enough to give them an outside chance but not enough to win it.

Maybe after Frence reprisals for Mers El Kebir The RAF needs to move 50 first line fighters to Gibralter as well.
 
Mmm.

1. The crunch at the beginning of Septmber was much more as to truly experienced pilots than as to airplanes.
2. Additionally, the most important repair work was that done on the more seriously damaged fighters. That was mostly done by the CRO, a civilian organization that had not been deployed to France.
 
Mmm.

1. The crunch at the beginning of Septmber was much more as to truly experienced pilots than as to airplanes.
2. Additionally, the most important repair work was that done on the more seriously damaged fighters. That was mostly done by the CRO, a civilian organization that had not been deployed to France.
Maybe you are right.

On any given day the Royal Air force had a 90% serviceability rate for fighters. The Luftwaffe started the Bob with a 80% serviceability rate and ended with a 70% serviceability rate.

I figured that we might cut 5% off the British serviceability rate with the loss of some veteran aircrew and that maybe that would snowball. It's not just repairing damaged airframe but keeping ahead of the maintenance as well.

I'm not talking about Germany winning air supremacy but rather a temporary superiority. I wouldn't be surprised to see a Britain that is losing a battle of Britain pulling back to more northerly airbases to reconstitute and then returning South the instant there is a real threat of an invasion. Just because Germany thinks they have superiority doesn't mean do they do.
 
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