Operation Sea Lion (1974 Sandhurst Wargame)

[Zincwarrior]

Your hypothesis is that in the case that the British army in England was 1 soldier, and in the case that the British army was 1,000,000 soldiers, the size of the required amphibious landing would still be the same? Absolutely not. A weak British army would allow a much weaker Sealion to succeed, while a strong British army would require a much stronger Sealion. Hence, the reason that Overlord was so much stronger than Sealion, because the German army in France in 1944 was so much stronger than the British army in Britain in 1940. In both cases, the strength, training, leadership, fortification and reserves of the defending army defined much of the amphibious requirements.

No one has opened up the size of the invasion, but followed what the Germans were considering under the plan. If the plan involved 90K troops then that is what is being discussed. Whether or not they had 670 divisions on France are irrelevant. The only thing is relevant is the plan and transport capacity they were using in the plan.

If you are arguing the Germans only needed one division and the British would surrender then show support for that. you will need a lot of support though as this is home ground and not Greece or Crete or France.

 

[Glenn239]

You're arguing it takes the Prince of Wales two hours to sink a barge thats about twice the size of one of the lighters it carries? Thats not a lucid statement.

I stated 80 RN warships sink targets at a hypothetical tempo of 80 ships per 2 hours. The tempo, or rate, at which ships are sunk will decrease with the size and scale of the forces engaged. That is to say, it will take 100 ships much longer to sink 100 targets than it will 1 ship to sink 1 target. So, if the RN engages the invasion in daylight, it's in a battle of tempo with the Luftwaffe, with the RAF also attempting to disrupt the Luftwaffe's tempo. If the LW tempo proves greater than the RN's tempo, the RN will not be able to achieve its mission. On a related note, from well provisioned and prepared base, and for a short number of days, a Stuka could fly up to 10 attacks per day.

British ships of the line and submarines are the spear, engaging the KM. Destroyers flank and go after the barges. Armed smaller vessels stand a line and stop anything that gets through. RAF fighters go after the LW ala BoB. RAF bombers and naval aircraft first go after the KM, then begin strafing the barges.

Where do you think Sealion is taking place, in the Thames River? The RAF goes after the LW like in the Battle of Dunkirk, not like the Battle of Britain.

Meanwhile, UK divisions fill in defensive positions and lines. Mobile units prepare to block movement inland. Artillery prepares to slaughter anything on the beach.

This is not Sparta. This is madness.

So if the British react energetically they can contain a beachhead and if they fuck it up they are in trouble? Yes, that is correct. But what I find "madness" is that you'd assume it would be one and could not be the other. Oh wait, it's 79 years after the fact - you can type whatever you want.

 

[RodentRevolution]

Your hypothesis is that in the case that the British army in England was 1 soldier, and in the case that the British army was 1,000,000 soldiers, the size of the required amphibious landing would still be the same? Absolutely not. A weak British army would allow a much weaker Sealion to succeed, while a strong British army would require a much stronger Sealion. Hence, the reason that Overlord was so much stronger than Sealion, because the German army in France in 1944 was so much stronger than the British army in Britain in 1940. In both cases, the strength, training, leadership, fortification and reserves of the defending army defined much of the amphibious requirements.

You know people have tried to point out the key difference is the massive logistical underpinning of Overlord and that in addition the Allies sought out magnitude order advantages in the concentration of air and sea power versus the defenders. In addition the Allies began training operations in November 1943 for Overlord while the Germans are expecting to land mid-September having only first issued instructions for an invasion to be prepared on the 2nd July.

So the Germans have a negative sea force correlation, nothing like the margin of aerial superiority in fact they are equal in the crucial count of single engine fighters, a situation on land that is at best equally difficult and is supported by a much weaker logistical structure and in addition needs to retain force cohesion despite lacking any kind of dedicated amphibious training.

Looks good...

 

[Glenn239]

Or - radical and shocking idea here - both elements of the RN engage the invasion flotilla at the same time. There’s plenty of targets for everyone.

Seems to me the 30kt warships in formations attack in strength before the slow trawlers spread out on patrols. So, back to the question you didn't answer - which is it - do the warships repel the invasion on the French side of the Channel and don't need the aux. warships, or does Sealion with heavy air support bludgeon its way through the warships and the trawlers come in in strength as it approaches the British shore?

 

[DaveB]

On the question of tidal streams and navigational difficulties, it’s worth remembering (I’m sure it’s been pointed out on this thread before) that long stretches of beach along the target coastline are backed by shear chalk cliffs.

 

[varyar]

Seems to me the 30kt warships in formations attack in strength before the slow trawlers spread out on patrols. So, back to the question you didn't answer - which is it - do the warships repel the invasion on the French side of the Channel and don't need the aux. warships, or does Sealion with heavy air support bludgeon its way through the warships and the trawlers come in in strength as it approaches the British shore?

I did answer it. That you reject the answer doesn’t make it go away.

But if you insist, very well. Under your scenario, the British destroyers and cruisers defeat the invasion force on the French side of the Channel.

 

[DaveBC]

On the question of tidal streams and navigational difficulties, it’s worth remembering (I’m sure it’s been pointed out on this thread before) that long stretches of beach along the target coastline are backed by shear chalk cliffs.

No problem. Just issue each landing ship with a large trampoline.

 

[RodentRevolution]

I did answer it. That you reject the answer doesn’t make it go away.

But if you insist, very well. Under your scenario, the British destroyers and cruisers defeat the invasion force on the French side of the Channel.

Once they engage the chaos of battle Glenn insists on will descend. Chaos is the enemy of orderly beach landings, Operation Sealion enters a failure cascade of epic proportions.

 

[Glenn239]

Let's take your numbers: 80 hulls sunk out of the first wave... The total shipping available for the invasion may number 4000ish , but you wanna provide timely resupply and reinforcements for the first wave? That kinda implies the first wave is more likely 1000-2000 vessels.

Suddenly, 80 ships sunk looks like rather a lot like 5-10% of the first wave killed before they hit the beach... We're talking units literally decimated before making it ashore.

As the warships come up, the first things they are encountering are not the barges. They're running into minelayers, minesweepers, warships, aux. escorts, Siebel Ferries, motor boats, submarines, and of course, the Luftwaffe. The barges are further back towards the French shore. The warships have to push these aside, then sail onwards to the barges. Once they reach the barges - assuming they do - then they can start sinking them. As each barge is targeted and hit, the men on it will jump in the water, the barge will sink, the destroyer will move on, and other ships will pick up the men in the water. Here, in the "1st Convoy",

http://niehorster.org/019_italy/41-05-20/convoys.html

is a data point on how many men per barge will be killed or wounded. "At least" 10 out of 25 caiques were sunk. 297 casualties out of 2,300 embarked on 25 of them. That's roughly 92 men per boat sunk with about 30 casualties per boat. Of those casualties, many were lost because the SAR was not quick. In the Channel SAR is on the spot. Figure somewhere north of a 70% survival rate per barge sunk.

 

[DaveBC]

If anyone wants to understand just how wrong things can go on the first day, read up on the early exercises of Amphibious Forces Atlantic Fleet in 1941. These drew on 20+ years of tests, experiments, and exercises by the USN. Inexperience on the part of the staff and crew of newly organized landing craft flotillas were a reoccurring problem. Each exercise revealed why training has to be through, frequent, and tough. As late as March 1942 a exercise off the Carolina coast saw the bulk of the 9th ID assault force landed eight miles off target. The new landing craft group assigned to the 9thID were unable to deal with a combination of shore line haze and a stronger than expected coastal wind. Combined with poorly chosen land marks and the usual coastal water current & the navigation boats were completely lost within minutes after they departed the embarkation area several miles offshore. One finds the same occurrences over and over with newly formed amphib boat units. Navigation errors were routine, & the ability to maintain formation and landing sequence poor or non existence. The highly disciplined beach assaults of the USN Amphib Forces or the US 6th Army in the PTO were the result of frequent training exercises, and harsh experience.

Thanks again for this insight.

This is precisely what I was curious about with my earlier question to you and I think people, people meaning Glenn really, need to pause before continuing with the wild speculation about who sinks what.

Quite apart from how many ships do or don't get sunk per wave, what force exists to reunite the barge fleet and get it back on schedule once it gets partially disrupted, delayed, drawn off course, etc., etc., etc. in wave 1?

I watched cadets marching in formation the other day. You have to actually practice in order to do that kind of thing, but maybe that's only a land thing. I'm sure when you're on a barge speeding along at 4 knots and trying to coordinate via loud-hailer, it's easier. I confess I have never served in the navy or worked on a boat, so maybe I'm dramatically overestimating the difficulty of coordinating precisely timed maneuvers by thousands of boats spread over hundreds of square miles of open ocean.

 

[Zincwarrior]

I stated 80 RN warships sink targets at a hypothetical tempo of 80 ships per 2 hours. The tempo, or rate, at which ships are sunk will decrease with the size and scale of the forces engaged. That is to say, it will take 100 ships much longer to sink 100 targets than it will 1 ship to sink 1 target.

You just restated what you said before, so I’ll restate, you think the Prince of Wales will take two hours to sink a barge?

So, if the RN engages the invasion in daylight, it's in a battle of tempo with the Luftwaffe, with the RAF also attempting to disrupt the Luftwaffe's tempo.

No. The RAF will be very happily shooting down skads of LW aircraft. At this point, they’ve gotten very good at it.

On a related note, from well provisioned and prepared base, and for a short number of days, a Stuka could fly up to 10 attacks per day.

Please revisit the Stuka casualty rates against the British in BoB. You’ve effectively sentenced the Stuka crews to death. The Soviets will be very very happy about this.

Where do you think Sealion is taking place, in the Thames River? The RAF goes after the LW like in the Battle of Dunkirk, not like the Battle of Britain.

First they have to get into the Channel. Ships entering the Channel will be hit by the British BBs and heavy cruisers. There may be no KM ships larger than an E boat that survives to escort the barge fleets. Its something they are good at. Ask the Bismark’s crew.

https://www.worldatlas.com/aatlas/infopage/englishc.gif

Put them in the North Sea and off Brest. Having the British carrier groups further off shore. Nothing goes in. Nothing goes out.

So if the British react energetically they can contain a beachhead and if they fuck it up they are in trouble? Yes, that is correct. But what I find "madness" is that you'd assume it would be one and could not be the other. Oh wait, it's 79 years after the fact - you can type whatever you want.

I’m sorry, are you not familiar with methods to block an amphibious invasion or any kessel? A blocking force to contain the beach head then heavier formations to fill in and squeeze until the pocket is liquidated.

 

[Glenn239]

This is maybe a sensible proposition if the only defensive asset the British have is the RN, but they also have the RAF. Tempo will cut both ways. The Luftwaffe proved incapable of defeating the RAF, in a superiority battle. During this battle both airforces proved capable of striking enemy shipping.

Neither air force is stopping the other. The LW is blowing straight through the RAF to ruthlessly bomb and strafe the RN - posters here think being strafed by 20mm was some sort of tickle parade. It was not. The RAF is blowing straight through the LW to bomb and strafe the invasion fleet - the LW can't stop them, (I don't think the RAF had cannons though, just MG's). The big difference is that one side is bombing 80 warships and the other side is going after 4,000.

Even if one accepts your “80 naval vessels sink 80 invasion hulls in 2 hours” assumption, which to me seems ‘light’ - this means this attack can be repeated at least one more time in the Channel crossing. Also, it should be noted that invasion hulls can be sunk returning to Europe unladen which will still hurt the Operation

In the link above Force D with maybe 7 warships versus only 1 escort providing cover fire sank 10 invasion barques in about 2 hours. Even with radar directed gunfire, that was a tempo of about 1.5 targets sunk per warship per two hours. Correcting for more escorts, heavy air attacks, and no gunnery radar I thought 80 per 2 hours was actually pretty aggressive.

 

[alfredtuomi]

the "plan" called for initial landing of the first echelon of the first wave on the beaches shortly after dawn and high tide.so the dance begins at night.apparently the trawlers are out every night and the destroyers can move at other than full speed and considering the number of potential targets there will be a running "battle".....until of course the transport ships anchor to unload.

 

[DaveBC]

You just restated what you said before, so I’ll restate, you think the Prince of Wales will take two hours to sink a barge?

Perhaps even more! Prince of Wales will be engaging at maximum range to steer clear of the German guns and unlike when it fought Bismarck there won't be a big fat bow fuel tank to puncture.

First they have to get into the Channel. Ships entering the Channel will be hit by the British BBs and heavy cruisers. There may be no KM ships larger than an E boat that survives to escort the barge fleets. Its something they are good at. Ask the Bismark’s crew.

The Bismarck didn't go through the Channel. The Channel Dash in contrast worked perfectly.

 

[Zincwarrior]

No problem. Just issue each landing ship with a large trampoline.

Put the 88s on the trampoline. When the barge gets near the coast they bounce it inland - instant deployment. While on the ocean the trampolines will act as shock absorbers for the deck rolling. Advantage...Germany!

 

[RodentRevolution]

The Bismarck didn't go through the Channel. The Channel Dash in contrast worked perfectly.

Well except for Gneisenau hitting that mine and then that wreck...but it'll be fine after a spell in drydock, nothing can happen to it there.

 

[RodentRevolution]

In the link above Force D with maybe 7 warships versus only 1 escort providing cover fire sank 10 invasion barques in about 2 hours. Even with radar directed gunfire, that was a tempo of about 1.5 targets sunk per warship per two hours. Correcting for more escorts, heavy air attacks, and no gunnery radar I thought 80 per 2 hours was actually pretty aggressive.

Given your figure of 80 warships and the likely length of an anti-Sealion engagement you realise your maths have just supported the 1000 plus invasion craft sunk figure you have spent so much time arguing against?

 

[alfredtuomi]

hmmmm...the channel dash put the scharnhorst in drydock for a year and gniesenau into drydock for the remainder of the war.they both hit mines and one precipetated a chain of events that removed her from the war.

and of course they went from being a significant threat to shipping to not very much.

success dash for who?

 

[RodentRevolution]

success dash for who?

Goebbels, always think of der Goebbels

 

[jsb]

As the warships come up, the first things they are encountering are not the barges. They're running into minelayers, minesweepers, warships, aux. escorts, Siebel Ferries, motor boats, submarines, and of course, the Luftwaffe. The barges are further back towards the French shore. The warships have to push these aside, then sail onwards to the barges. ........Of those casualties, many were lost because the SAR was not quick. In the Channel SAR is on the spot. Figure somewhere north of a 70% survival rate per barge sunk.

I have to ask,
1- Why do we think RN warships need to bother with escorts that are to slow to catch them and not in position?
2- What will happen to SAR on this scale? Just what ships (because LW cant possibly do it at that scale) are doing SAR on thousands of casualties in the water at once?

Your own web page says, "That the losses were so small was owing to the very efficient German Seenotdienst (Air Sea Rescue Service) cooperating with Italian torpedo boats immediately despatched to the scene."