Operation Sea Lion (1974 Sandhurst Wargame)

[Garrison]

Sealion was ready to execute, (ie, commence the countdown) in mid-September 1940, the required transport had been assembled or would be there on the required date. It was not ordered to proceed for a variety of reasons, primarily because air superiority had not been established.

Air superiority provided a great excuse for the Heer and the Kriegsmarine to refuse to execute an operation they knew was never going to work. The only way the hastily thrown together assembly of barges and tugs was going to affect the British is if the mere threat of invasion forced them to negotiate peace. The half assed Sealion invasion force had about the same effective combat power as FUSAG in 1944. If somehow some part of the Sealion force did reach the beaches the outcome would make Dieppe look like a strategic masterpiece.

 

[Zheng He]

Air superiority provided a great excuse for the Heer and the Kriegsmarine to refuse to execute an operation they knew was never going to work. The only way the hastily thrown together assembly of barges and tugs was going to affect the British is if the mere threat of invasion forced them to negotiate peace. The half assed Sealion invasion force had about the same effective combat power as FUSAG in 1944. If somehow some part of the Sealion force did reach the beaches the outcome would make Dieppe look like a strategic masterpiece.

Reader said in July 1940 that the KM could not execute Sea Lion.

 

[Grognard49]

Your source confirms my estimate. I said that over 500 yards the barges would be next to useless - I estimated 1 hit in 200 shots at 1,000 yards. Your source from five years ago says that at 600-1000 yards they scored 3 near misses in 100 shots. I'm dead nuts on with the estimate.

Your estimate is not even in the ballpark of reality, especially in the sea conditions found in the Channel.

Any barge is going to have a very high metacentric height. Their construction determines that. A large metacentric height will cause a vessel to be too stiff. A stiff vessel quickly responds to the sea as it attempts to assume the slope of the wave. An overly stiff vessel rolls with a short period and high amplitude which results in high angular acceleration. Successful naval gunnery depends on continuous aim on the target. All naval gunners have practiced this technique since the early 20th century. The gunners on the barges would not be trained in this and the high amplitude and acceleration of the roll would cause extreme difficulty to aim any weapon on target due to the inertia of the barrel and mount. An automatic weapon might make an occasional hit in passing but any continuous aimed fire would be impossible in these circumstances. Hits would be rare.

The RN gunners, on the other hand, on their warships with a lower metacentric height, had been practicing this technique since the time of Percy Scott. They will be the ones doing the hitting.

 

[DaveBC]

Air superiority provided a great excuse for the Heer and the Kriegsmarine to refuse to execute an operation they knew was never going to work. The only way the hastily thrown together assembly of barges and tugs was going to affect the British is if the mere threat of invasion forced them to negotiate peace. The half assed Sealion invasion force had about the same effective combat power as FUSAG in 1944. If somehow some part of the Sealion force did reach the beaches the outcome would make Dieppe look like a strategic masterpiece.

Now here you have hit the nail on the head and it is something I have wondered about for years. The excuse is just too convenient.

"If only super-duper Air Marshall Goering had delivered us the promised air superiority, why yes, Fuhrer, we were certainly ready to set sail! Such a shame we won't be going after well! Oh, well. Drinks?"

The only thing holding me back on this is whether German interservice rivalry was really strong enough that the navy would leave the air force twisting in the proverbial wind that badly, but if the alternative was annihilation in the Channel, maybe they would.

 

[DaveBC]

Your estimate is not even in the ballpark of reality, especially in the sea conditions found in the Channel.

Any barge is going to have a very high metacentric height. Their construction determines that. A large metacentric height will cause a vessel to be too stiff. A stiff vessel quickly responds to the sea as it attempts to assume the slope of the wave. An overly stiff vessel rolls with a short period and high amplitude which results in high angular acceleration. Successful naval gunnery depends on continuous aim on the target. All naval gunners have practiced this technique since the early 20th century. The gunners on the barges would not be trained in this and the high amplitude and acceleration of the roll would cause extreme difficulty to aim any weapon on target due to the inertia of the barrel and mount. An automatic weapon might make an occasional hit in passing but any continuous aimed fire would be impossible in these circumstances. Hits would be rare.

The RN gunners, on the other hand, on their warships with a lower metacentric height, had been practicing this technique since the time of Percy Scott. They will be the ones doing the hitting.

I feel like this is significant but do you mind breaking it down for me so I understand the point properly.

Are you saying that combat-worthy vessels are intentionally designed to improve aim by minimizing the ship's movement with the waves, or are you saying that naval gunners -- as opposed to army artillerymen -- train specifically in ways to counteract that motion? If so, what does that training look like, because surely the barge gunners could do the same?

Perhaps the answer is both but I just want to understand this.

This isn't really a "Sea Lion" question per se because I agree the whole thing is a delusion, but I'm curious about the naval gunnery aspect.

 

[soothsayer]

Your estimate is not even in the ballpark of reality, especially in the sea conditions found in the Channel.

Any barge is going to have a very high metacentric height. Their construction determines that. A large metacentric height will cause a vessel to be too stiff. A stiff vessel quickly responds to the sea as it attempts to assume the slope of the wave. An overly stiff vessel rolls with a short period and high amplitude which results in high angular acceleration. Successful naval gunnery depends on continuous aim on the target. All naval gunners have practiced this technique since the early 20th century. The gunners on the barges would not be trained in this and the high amplitude and acceleration of the roll would cause extreme difficulty to aim any weapon on target due to the inertia of the barrel and mount. An automatic weapon might make an occasional hit in passing but any continuous aimed fire would be impossible in these circumstances. Hits would be rare.

The RN gunners, on the other hand, on their warships with a lower metacentric height, had been practicing this technique since the time of Percy Scott. They will be the ones doing the hitting.

What is the metacentric height of the RN mine trawlers that make up the majority of small fleet in the channel?

 

[Grognard49]

I feel like this is significant but do you mind breaking it down for me so I understand the point properly.

Are you saying that combat-worthy vessels are intentionally designed to improve aim by minimizing the ship's movement with the waves, or are you saying that naval gunners -- as opposed to army artillerymen -- train specifically in ways to counteract that motion?

Perhaps the answer is both but I just want to understand this.

Naval warships are a compromise of many different factors. Increasing topweight on a ship decreases the metecentric height which gives a slower, more gentle roll which makes for easier aiming of it's weapons. However, this will also decrease the stability if the ship is damaged below the waterline. How much compromising do you want to do?

Naval gunners at that time were extensively trained for this type aim. It takes skill and practice to achieve success at this. In the army, field artillery personnel were generally not trained for direct fire at moving targets. Anti-tank gunners were trained for this from a stationary firing position, not one which was moving in two axes.

I did a quick search and found a good introduction to the history of continuous aim in the RN and USN if you are interested. http://denninginstitute.com/pjd/TT/Sims/Sims.pdf

 

[Grognard49]

What is the metacentric height of the RN mine trawlers that make up the majority of small fleet in the channel?

Since there were many different designs of trawlers used by the RN for minesweeping, it isn't possible to know without performing an inclining experiment on each type, and each member of of the type since any modifications to installed equipment will change the metacentric height (GM).

Generally speaking a trawler will have a relatively low GM since a slower, gentler roll makes for more comfort and safety for the crew working on deck.

 

[sloreck]

By WWII you also had plotting computers which assisted by doing things like calculating lead based on the targets speed/direction (as entered by observers before radar gunlaying), also accounted for ship movement, and for the big guns, they also calculated things like temperature and barometric pressure which will affect the flight of even 16" shells. At longer ranges, you also need to compensate for the fact that the eath's surface is curved, not flat - at 25 miles this matters. You also had gun mounts/turrets that had relatively rapid slew rates in both azimuth and elevation - some smaller ones were manually operated, like land based artillery, but larger were powered. Naval gunnery, except for AA, generally operated at ranges where you needed optics to see the target, unlike anti-tank gunners who always operated using the Mark I eyeball, and naval gunners had to deal with a gun platform that was moving in roll, pitch, and yaw simultaneously. Land based artillery had a fixed firing point, whether or not the target was moving. An improvised artillery mount on a barge hitting a target at other than point blank range is like winning the lottery - it happens but don't count on it paying your mortgage. Oh, and btw, naval guns tended to have elaborate mechanical systems for bringing ammunition to the guns that exceeded the rate of fire of land based artillery, let alone "strap on a barge" artillery.

 

[Grand Admiral Thrawn]

@Glenn239 what about Cape Matapan? If Espero is the norm for the RN, then Matapan should have missed most of their shots, and expended almost all of the ammo. But if it is the norm for facing a stationary (or near stationary if the currents are against the Germans) target, it seems Sealion will lose badly, as everyone has tried pointing out to you. Not the same? Slow targets, tank and 88 gunners don't train for naval night battle, no escorts to first alert and then defend the convoy, and British intelligence finding out early enough to position all their pieces.

And Espero shows the weakness of the Germans. Allowing for easy math, 10 German DD versus 80 RN DD, if the RN showed up at once, in one location (instead of swarming), they likely leave some destroyers to screen the KM and the rest steam off to cause havoc. Say, 20? Give the German 50 min to sink all with no losses- but now the Germans are in a stern chase, getting 7% hits yet using all ammo. See how contrived your scenario is?

 

[fourthmaninaboat]

@Glenn239 what about Cape Matapan? If Espero is the norm for the RN, then Matapan should have missed most of their shots, and expended almost all of the ammo. But if it is the norm for facing a stationary (or near stationary if the currents are against the Germans) target, it seems Sealion will lose badly, as everyone has tried pointing out to you. Not the same? Slow targets, tank and 88 gunners don't train for naval night battle, no escorts to first alert and then defend the convoy, and British intelligence finding out early enough to position all their pieces.

And Espero shows the weakness of the Germans. Allowing for easy math, 10 German DD versus 80 RN DD, if the RN showed up at once, in one location (instead of swarming), they likely leave some destroyers to screen the KM and the rest steam off to cause havoc. Say, 20? Give the German 50 min to sink all with no losses- but now the Germans are in a stern chase, getting 7% hits yet using all ammo. See how contrived your scenario is?

And just so Glenn doesn't try to argue that Matapan was only done with radar, only Valiant had radar for the battle; one RN officer commented that it wasn't a good example for the advantages of radar as Barham and Warspite, both without it, were equally accurate as Valiant, scoring hits on their first salvoes.

 

[hipper]

Not at all. More like that, if it takes 80 RN warships 2 hours to sink 80 invasion hulls because of the difficulties presented in the armaments on those hulls, then that's 3920 invasion units left and the Luftwaffe has landed, rearmed, and returned. Do you understand the concept of tempo? The German tempo is the Luftwaffe - how fast can it attack, rearm, and attack again? The British tempo is their fleet - how many ships can each warship sink per hour?

think about it a moment Glen your concept relies on a complete lack of friction, and ignores the concept of relative speeds, a barge train confronted by a light cruiser, could scatter and perhaps some barge units would escape, or stay together and be sunk. however any scattered barge train is not going to contribute to an invasion attempt.

 

[steamboy]

And just so Glenn doesn't try to argue that Matapan was only done with radar, only Valiant had radar for the battle; one RN officer commented that it wasn't a good example for the advantages of radar as Barham and Warspite, both without it, were equally accurate as Valiant, scoring hits on their first salvoes.

True but don't forget, these are the Italians, not the Notzi's that Glenn speaks so highly of. So of course they would do FAR better than the Italians. Its in the Ubermensch genes.

 

[Ian Hathaway]

Ian gave me a heads up on those numbers.

The information I provided came from the attached file.

 

[steamboy]

inb4 someone suggests using the Deutschland class battleship with the escort fleet.

 

[SealTheRealDeal]

inb4 someone suggests using the Deutschland class battleship with the escort fleet.

Why even escort it? The barges will be sent right to London via giant trebuchet.

 

[Deleted member 94680]

I feel like this is significant but do you mind breaking it down for me so I understand the point properly.

Are you saying that combat-worthy vessels are intentionally designed to improve aim by minimizing the ship's movement with the waves, or are you saying that naval gunners -- as opposed to army artillerymen -- train specifically in ways to counteract that motion? If so, what does that training look like, because surely the barge gunners could do the same?

Perhaps the answer is both but I just want to understand this.

It’s a bit of both if I understand it correctly. Warships are designed to be the best “gunnery platform” they can be, whilst Naval gunners train to fire from moving vessels. Crazy, I know, but Naval gunners train on naval vessels to perfect the art of naval gunnery, whilst army artillerymen don't.

 

[Finbarr the Fair]

It’s a bit of both if I understand it correctly. Warships are designed to be the best “gunnery platform” they can be, whilst Naval gunners train to fire from moving vessels. Crazy, I know, but Naval gunners train on naval vessels to perfect the art of naval gunnery, whilst army artillerymen don't.

This of course leads to an obvious "solution". The Germans should draft the gunnery crews from The Twins and other naval vessels in the repair shop. Possibly those from Bismarck also

As trained KM gunners they will clearly be so much better than their RN peers that even on small, unseaworthy, boats they will drive off RN destroyers and armed auxiliary craft.

End sarcasm.

 

[hipper]

This of course leads to an obvious "solution". The Germans should draft the gunnery crews from The Twins and other naval vessels in the repair shop. Possibly those from Bismarck also

As trained KM gunners they will clearly be so much better than their RN peers that even on small, unseaworthy, boats they will drive off RN destroyers and armed auxiliary craft.

End sarcasm.

the KM was using most of their seamen as crews for the very large number of auxiliary vessels required for the invasion. I dont think they had the manpower to man army guns on barges.

 

[vizzer]

I don't see why anyone is concerned about hit rates as, from previous practice c.f. Bismarck & Graf Spee, as soon as the RN turn up the Germans either flee or scuttle themselves. (Exaggerating slightly)