BoB Mathematical Modeling of Alternative Outcomes

The original post is interesting. Didn't Dowding know that he just had keep Fighter Command a Force in Being until the end of September, after which the weather would end any threat of an invasion until the following Spring.

pinehilljoe said:

The original post is interesting. Didn't Dowding know that he just had keep Fighter Command a Force in Being until the end of September, after which the weather would end any threat of an invasion until the following Spring.

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It is or was common knowledge, not only weather but daylight. However this is just statistical probability of bad weather. Four years later at D-Day the invasion was postponed because of bad weather in June while a later storm completely swept away one of the Mulberry harbours on June 19th which should be the very height of summer. The Mulberry harbours had a design life of 3 months which takes them up to September, the remaining harbour was actually strengthened and lasted for 8 months in use.

Koopernic said:

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Dealing with the Royal Navy:
1 The invasion corridor would be cordoned off with a dense mine field from the Royal Navy.
2a Coastal Artillery, based in France, would also cordon of the invasion corridor from the Royal Navy out to much of the distance. The 8.8cm FLAK 37 is a deadly anti shipping weapon due to its fire control and ability to FLAK burst. I imagine 105mm, 6 inch, 8 inch and 11 inch coastal artillery would be set up by the German Navy (who had troops and division for harbour defence). That should protect the invasion fleet half way if not the whole way across the channel in some areas
2b Luftwaffe FLAK 37, FLAK 38 and FLAK 39 8.8 cm, 10.5 com and 12.8 cm guns would be highly effective against shipping and craft.
3 Luftwaffe would have had time to reassess its performance at Dunkirk and change its anti shipping attack methods. We KNOW they became effective. Briefings, notes to crew and a little bit of practice against towed targets. They will learn quickly and they will also be undistracted by campaigns elsewhere.

4 One thing I need to research more is the state of German radar in mid 1940. Seetakt Shipborne radar was definitely available on anything from destroyer up plus a few of the larger torpedo boats. SeeArt (See Artillery) is essentially Seetakt converted for coastal anti shipping use, FuMo 1 Calais A and B and FuMO 2 Calais.

The shore based Seetakt peformed better than ship based because it had a larger antenna, more powerful transmitter and could afford more complicated circuitry that didnt require the same lever of minurisation, marinisation and shock resistance.

This means that a few radar equipped Kriegsmarine ships half way across the channel can detect the Royal Navy and either open fire using night vision optics or illuminate with star shell or search lights while smaller craft attack. The shore based artillery would take care of the rest.
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Now, do you really think that the RN would have just sit and watch if the KM had begun to laid those dense minefields? Or might the RN and RAF attack those minelayers?

On coastal arty, maybe it is better to check what those German coastal guns achieved between 1940 and 1944,
Dover Strait coastal guns - Wikipedia
British coastal convoys had to pass through the bottleneck of the Dover strait ... Although the German guns regularly fired on these slow moving convoys from 1940 to 1944, with an interlude in 1943, they only sank two ships (both in 1944) and damaged several others.

On Siebel ferries, for their effectiveness or lack of it in real life, even only on a big lake, see the links in my message #85 Sukho Island, they were rather ineffective even against Soviet auxiliary gunboats.

The Channel guns were pretty rubbish. In 4 years of shooting they hit two ships sinking one and damaging the other so she had to be beached as her cargo of 2800 tons of petrol in cans was on fire

Here's the alternative outcome that, IMO stands the best chance of success over Britain for Germany, and puts Hitler in the best position to successfully invade Russia. 22 June 1940, France surrenders. 23 June 1940, Hitler announces a unilateral armistice and end of hostilities with Britain. Churchill refuses, says Britain will fight on, but to what end? Churchill is now under pressure from the Opposition parties and his own MPs to accept. Now what? One wildcard is the Italians, they've already invaded France and commenced offensives against Britain in North Africa. Mussolini must be forced to stand down.

nuuumannn said:

Just a wee example of how difficult it was for the Luftwaffe to sink shipping in 1940. On the afternoon of 10 July Dornier Do 17s of KG 2, escorted by Bf 110s of III/ZG 76, with Bf 109s from JG 51 high above the formation were sent to destroy a convoy sailing through the Channel, which had been spotted earlier in the day by a Dornier recon aircraft escorted by Bf 109s of I/JG 51, which had been attacked by six Spitfires of 74 Sqn, but managed to return damaged for two Spits damaged by the escorts. At 1pm, the German formation of Do 17s and Bf 110s were detected at 60 plus aircraft by the defences and Flights from three squadrons were sent up to meet them. Attacked from head on, the Do 17 formation was split up and in disarray. By the end of the afternoon, three Bf 110s and three Do 17s were lost and one Bf 109 and pilot lost and one damaged, for the loss of one Hurricane and pilot to the RAF, although four aircraft were damaged. On that afternoon, the RAF achieved a six to one kill ratio, worst of all for the Germans, only one ship in the convoy was hit, despite KG 2 dropping some 160 bombs and even then, the 700 t sloop that sank was empty. Not a good day for the Luftwaffe.

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Shortround6 said:

One of the British 'Boats"
View attachment 606657

During the war (but not by the summer of 1940) about 800 trawlers were taken into RN service from the Hull and Dovercourt Fisheries. Other areas of The UK also had substantial numbers join the RN

See Trawlers – World War 2 | Harwich & Dovercourt | History, Facts & Photos of Harwich

Not all had 4 in guns.

It was the hundreds of these "boats" available that made Sealion such an impossibility. They were available for minesweeping, mine laying (not very well, anti sub use, and as small gun boats. The Germans did have similar but not in anywhere near the numbers the British did. Much like the larger ships , the Germans are outnumbered by very large amounts.

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Opperation SeaLion required Air Dominance, the term used in German documents. If they had of achieved that, which I contend they could have with Drop tanks on all Me 109/Me 110 and 50% of the Me 110 repplaced by equal numbers of Fw 187 they could have. All these fighters would need to be fitted with the approprate REVI and altimeter alarms to allow slide bombing. That would substantially increase the Lufwaffe's anti shipping capability.

Your example above of the Luftwaffe suffering losses trying to sink a convoy shows them being thwarted by RAF land based fighters. It doesn't really count in the even of Luftwaffe total air superiority.

The slow but seaworthy trawler isnt a great military ship but would tend to overwhelm. It looks very vulnerable to Me 110 strafing and could be dealt with by sufficient e-boats. The Siebel Ferrys would provide a basic perimeter defence, allowing e-boats or trawlers to detach to intercept RN small craft.

RCAFson said:

German attempts for a seaborne invasion of Crete didn't succeed despite the complete absence of RAF or FAA fighters. RN casualties due to shipborne weapons was minimal.

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And the German Navy and Military are rather over extended and they went with a paratroop based invasion that was compromised by ENIGMA decrypts revealing the drop zones.
These conditions dont apply near Calais.

pbehn said:

The discussion starts to go wrong when statements like this are made. If you believe the Channel is just a wide river the statement will not be challenged. I would like to see a few hundred unpowered barges being marshalled on a shingle beach for 2 or more days in September with a tidal drop of 5 to 7 meters. Repeatedly stating that an aircraft that wasn't built would win the day isn't a convincing argument.

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Maybe read the plan, I think they'd be moored and to a degree the barges are semi disposable.

Juha3 said:

Now, do you really think that the RN would have just sit and watch if the KM had begun to laid those dense minefields? Or might the RN and RAF attack those minelayers?

On coastal arty, maybe it is better to check what those German coastal guns achieved between 1940 and 1944,
Dover Strait coastal guns - Wikipedia
British coastal convoys had to pass through the bottleneck of the Dover strait ... Although the German guns regularly fired on these slow moving convoys from 1940 to 1944, with an interlude in 1943, they only sank two ships (both in 1944) and damaged several others.

On Siebel ferries, for their effectiveness or lack of it in real life, even only on a big lake, see the links in my message #85 Sukho Island, they were rather ineffective even against Soviet auxiliary gunboats.

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Coastal artillery works maybe half way through the channel not on the English side of it. Its being assesed

The ferry's had their limitations. They were slow and couldn't position themselves rapidly to gain surprise, disengage or intercept. What they could so is escort a slow convoy and provide FLAK and firepower at its perimeter. e-boats would need to take care of the interception. It's no surprise they were vulnerable to faster gun boats but emplyed properly as perimeter guards supported by faster boats i think it would be a different story.

fastmongrel said:

The Channel guns were pretty rubbish. In 4 years of shooting they hit two ships sinking one and damaging the other so she had to be beached as her cargo of 2800 tons of petrol in cans was on fire

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The RN without air cover would be severely compromised in its mine laying and mine sweeping operations. The RN would be severely compromised when within range of German coastal artillery

Most of the coastal artillery didn't have the range to hit near the English coast so evading German coastal artillery was merely a matter of skirting the coast on the English side outside of accurate range of German Coastal Artillery in appropriate weather conditions or at night or when jamming worked, which it tended to at the fringes. The convoys are not going straight through the middle. If they sailed within 15000 yards of the French coast it would be different story.

Clearly coastal artillery can protect the German invasion fleet to maybe 1/3rd of the way out. More or less depending on target size and speed. The rule of thumb is that artillery is accurate to 1/3rd of the distance it could shoot when shot at 45 degrees.

That means the Luftwaffe, Kriegsmarine and the Barges only need to take care of the final half of the journey across the channel. German destroyers, with radar, would need to detect British small craft and then illuminate them for other craft.

Koopernic said:

I think the discussion is going a little wrong. It's worth reading Wikipedia on this.

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we will see.

Some facts about the modified barges to invasion barges and river ships (powered barges).
1 They were to be modified by cutting of the bow and attaching a ramp to drive trucks, tanks etc on and off. They also were to have concrete poured in to strengthen floors to handle tanks. Its a fairly daunting amount of work.
2 Square bottoms roll less in heavy seas than round. This is not a problem for barges.
3 Unpowered barges after landing tanks were to be marshalled and escorted back to France after 2 days.
4 Unpowered barges could be towed or pushed by either a river ship or the 400 tugs collected for operation sea lion.

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1. How many were converted in the time available?
2. True but square bottoms will still roll, and pitch and yaw. It is a question of degree, square bottoms do not grant immunity from rolling. Riding high (low weight of cargo) means the roll a bit more than when riding low.
3. shows that a lot of towing was going on and the "invasion" was not a one or two day deal but was going to need well over a week to get the desired number of men on shore.
4. As above, but speed of river barge when towing unpowered barge is????

5 Over 260 Panzer III and Panzer IV tanks were converted to 'tauchpanzers' or diving tanks. They were sealed and could drive along the ocean floor to a depth of 15m by way of a 16m air intake hose with an radio aerial. Apart from sealing the tanks had bilge pumps and rebreather escape systems for the crew as well as a gyrocompass and navigation system. I don't think these would have been dropped into water that deep, maybe 5m but they would be impervious to fire till they surfaced. They were actually used during operation Barbarossa.
6 The smaller Panzer II modified as a schwimmpanzer (with 20mm canon) would float via way of caissons and fire their gun during their swim ashore.

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How many were actually ready in Sept of 1940 (one source says the MK III production continued into October) and how well trained were the crews of either the tanks or the landing craft/vessels. A few trial runs does not equal large numbers of trained crews.
[/QUOTE]
Dealing with the Royal Navy
1 The invasion corridor would be cordoned off with a dense mine field from the Royal Navy.
2a Coastal Artillery, based in France, would also cordon of the invasion corridor from the Royal Navy out to much of the distance. The 8.8cm FLAK 37 is a deadly anti shipping weapon due to its fire control and ability to FLAK burst. I imagine 105mm, 6 inch, 8 inch and 11 inch coastal artillery would be set up by the German Navy (who had troops and division for harbour defence). That should protect the invasion fleet half way if not the whole way across the channel.
2b Luftwaffe FLAK 37, FLAK 38 and FLAK 39 8.8, 10.5 and 12.8cm guns would be highly effective against shipping and craft.
3 Luftwaffe would have had time to reassess its performance at Dunkirk and change its anti shipping attack methods. We KNOW they became effective. Briefings, notes to crew and a little bit of practice against towed targets. They will learn quickly and they will also be undistracted by campaigns elsewhere.[/QUOTE]

1.Where do the mines come from???
What ships are going to lay the mines????
Both ends of the proposed invasion corridor need to be mined.
British have hundreds of minesweepers. British can also lay mines to tie up German ships/minesweepers so they can't be laying mines at the same time.

2. German superguns????
German 8.8cm FLAK 37 is near useless. It is 20-21 (33.8km?) miles across the channel at the narrowest point. The 8.8cm FLAK 37 had a max range against land targets of about 14,800 meters or just a bit under half way. This involves fring at around 40 degrees of elevation with a decent angle over 50 degrees. Flak burst is an illusion against ground targets at this range.
Standard German time fuse had a max 30 second run time. If time of flight exceeds 30 seconds to the intended target the shell won't reach it. Nose percussion fuses were standard fuses against surface targets.

Ranges of German guns from "German Artillery of World War Two (Ian Hogg)
37mm AA. 6565 meters
88mm AA....14,800 meters
10.5cm AA...17600 meters
12.8cm AA...20475 meters.

A few notes, The 10.5cm was only finalized for production in 1939, numbers available in fall of 1940 are???????
The 12.8cm AA gun was only placed in mass production in 1942 although prototypes and trial did exist in the late 30s. The 12.8cm gun may never have been used in the surface role?

German divisional guns include the Schwere 10cm Kanone 18 with a range of 19075 meters. every other divisional gun in service in 1940 was much shorter ranged.
German heavy artillery units did have 15cm guns which could range to 24700 meters for the best of them (ex turkish guns).

Even the German rail road guns would be hard pressed. The 28cm Cannon 'Kurz Bruno' had a max range of29500 meters and had the problem of only 1 degree of traverse on the carriage. Only eight were built, Only eight of K 5 28cm guns were in service at the start of the French campaign. a few suffered split barrels.

GO to google maps and see the distances for other parts of the Channel other than the Dover straits. German shore batteries would be useless.

More later.

Admiral Beez said:

Here's the alternative outcome that, IMO stands the best chance of success over Britain for Germany, and puts Hitler in the best position to successfully invade Russia. 22 June 1940, France surrenders. 23 June 1940, Hitler announces a unilateral armistice and end of hostilities with Britain. Churchill refuses, says Britain will fight on, but to what end? Churchill is now under pressure from the Opposition parties and his own MPs to accept. Now what? One wildcard is the Italians, they've already invaded France and commenced offensives against Britain in North Africa. Mussolini must be forced to stand down.

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What opposition parties? Churchill was the head of a coalition government.

We should start a Sealion bingo game. One point for every use of a weapon that didn't exist wasn't available.

I did think of a Sealion drinking game one drink for every use of a weapon that didn't exist but I don't want to kill off half the forum and put the rest in hospital.

Returning

="Koopernic, post: 1606638, member: 60966"]
3 Luftwaffe would have had time to reassess its performance at Dunkirk and change its anti shipping attack methods. We KNOW they became effective. Briefings, notes to crew and a little bit of practice against towed targets. They will learn quickly and they will also be undistracted by campaigns elsewhere.

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Yes they did become effective. But not in 3 months and not while distracted by fighting the Battle of Britain.

4 One thing I need to research more is the state of German radar in mid 1940. Seetakt Shipborne radar was definitely available on anything from destroyer up plus a few of the larger torpedo boats. SeeArt (See Artillery) is essentially Seetakt converted for coastal anti shipping use, FuMo 1 Calais A and B and FuMO 2 Calais.

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Just about ALL of the "destroyer up" ships were in German ports. No, they don't have to be used in a doubtful diversion scheme but they do have to get to the invasion sites, SOme will, some won't.

This means that a few radar equipped Kriegsmarine ships half way across the channel can detect the Royal Navy and either open fire using night vision optics or illuminate with star shell or search lights while smaller craft attack. The shore based artillery would take care of the rest.

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Night vision optics??????
OK German binoculars may have been better than British ones but not that magnitude of better. German ships are out numbered by about 10 to 1. British have star shells, British have some radar even if not as good. British stay about 15 kilometers from the German held shore and the shore based artillery is pretty much useless.

Achieving Air Superiority.

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requires separate posts or thread. fictitious planes are not a matter of strategy and tactics.

That Siebel barge was quite stable and used not only as an armed barge but a landing craft. It was improvised using Army Pontoon Bridge Pontoons and this made it transportable by road an rail, hence it was used in inland lakes and seas and could be used for a river crossing before a pontoon bridge was set up. It could get tiger tanks across a water crossing.


View attachment 606661View attachment 606662View attachment 606663

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Top photo shows ferry well after the BoB, The quad 20mm was not in service. While the lower "gunboat" is interesting it has some serious flaws in the Channel.
The Siebel ferries (12-20??) available at the time of Sealion had one 88mm and two 20mm guns plus their prime movers (half tracks).

Noe also the Kommandogeret 40 FLAK predictor. This computed a continuous firing solution so long as the men: the trainer, the layer(elvation) and range finder operator tracked the the targeted enemy ship. If the ship moved the solution would instantly update and the guns would repoint viag their guages If the 'ferry' moved due to swells so long as the layer/trainer maintained track and the fire order was given right it would hit. A RN MTB could be directly targeted by 30-45 rounds per minute of 8.8 cm fire either bursting above them or inside them.

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Bolded part was the hard part, even on land. This is why later war ships got RPC (remote powered control) so that the accuracy of fire was NOT dependent on two or more men trying to spin hand cranks one each and every gun connected to the predictor. This is also why some AA guns, which turned out to be successful, had short/low performing barrels. The long barrels have too much inertia and are hard to get moving, hard to stop and very hard to reverse direction on. Even local power control guns were harder to coordinate than the RPC guns, Manual guns were a whole different catagory. [/QUOTE]

A Mine corridor and coastal artillery based in France greatly simplifies the problems the German Navy and Luftwaffe would face.

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Isn't the Luftwaffe immaterial in a matter of speaking? The Royal Navy just has to pounce on the invasion / resupply craft at night.

Greyman said:

Isn't the Luftwaffe immaterial in a matter of speaking? The Royal Navy just has to pounce on the invasion / resupply craft at night.

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You cant do that, they have those crosses on the side.

Greyman said:

Isn't the Luftwaffe immaterial in a matter of speaking? The Royal Navy just has to pounce on the invasion / resupply craft at night.

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Won't work.

The Luftwaffe has better night vision.
The RN ships are too slow to steam 50-100 miles each way under the cover of darkness.
The Luftwaffe can sink the ships in port using very few bombs because they aren't moving.
eight German destroyers can fight off 50-60 British destroyers using their radar and better night vision.

RCAFson said:

What opposition parties? Churchill was the head of a coalition government.

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As Thatcher and May found out, in Westminster every MP is a potential opposition, and in Churchill's case, especially in a coalition. In May 1945, for example Labour left the coalition, forcing an election and Churchill's defeat.

Shortround6 said:

Won't work.

The Luftwaffe has better night vision.
The RN ships are too slow to steam 50-100 miles each way under the cover of darkness.
The Luftwaffe can sink the ships in port using very few bombs because they aren't moving.
eight German destroyers can fight off 50-60 British destroyers using their radar and better night vision.

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(this too: )
A Mine corridor and coastal artillery based in France greatly simplifies the problems the German Navy and Luftwaffe would face.

That's all true, you naysayer. BTW - I have the Brooklyn bridge on sale, real cheap.

In 1943 not all German Destroyers had radar, particularly the Torpedo Boat coastal vessels which were small versions of a Destroyer. In 1940 I doubt anything smaller than a large fleet Destroyer had radar.

Nothing so far has persuaded me that if Sealion went ahead it would not be like Omaha beach with the Germans controlling the air and Tirpitz sitting off shore.

pbehn said:

Nothing so far has persuaded me that if Sealion went ahead it would not be like Omaha beach with the Germans controlling the air and Tirpitz sitting off shore.

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What? No chance, Tirpitz isn't in service yet, but if she was she'd sunk PDQ. There's no chance for the Germans - you're facing off against the largest navy on his home coastline, covered by one of the largest air forces.

Surely you're just exasperated by the fantasies and denialism thus far posted and pulling our leg.

Admiral Beez said:

What? No chance, Tirpitz isn't in service yet, but if she was she'd sunk PDQ. There's no chance for the Germans - you're facing off against the largest navy on his home coastline, covered by one of the largest air forces.

Surely you're just exasperated by the fantasies and denialism thus far posted and pulling our leg.

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The Tirpitz was in service in 1944 when the allies landed in Normandy, Omaha was close to a disaster with the Allies completely in control of the air and the sea. The landing beaches in Kent and Sussex had many more obstacles, booby traps, mines and other defences than Normandy had. The idea of landing with towed barges when you don't control either air or sea is fantasy. Any ship with a gun heavier than a light machine gun can take out a barge or a tug which is most of the German invasion fleet. If there are any British ships in the Channel then they have to be eliminated before any support can be given to the landing. The whole thing is fantasy based on weapons that didn't exist working 100% while those opposing have what was historically there taken from them and what is left doesn't work at all.

The barges were hardly seaworthy and had to be towed. I read somewhere that it would take the barges 1.5 days at least to cross the Channel. The Royal Navy only had to send a couple of destroyers to sail through the formation at full speed in order to sink a substantial amount of German barges.
I the end, to say the Germans were ill prepared to conquer the UK is an understatement. The BoB while impressive in it's own right was a mere sideshow and a nice propaganda victory for the the British. It was t device for the invasion whatsoever as the Germans had defeated themselves in this regard so to speak, long before they reached Dunkirk.