Could Operation Sealion really have succeeded?

CHL was RAF operated while the CD sets were British Army. It's the usual inter service rivalry. CD sets were developed from the Army's GL (Gun laying) radar sets for directing coast defense batteries rather than general search sets. They could function as the later however. So, CD was usually found near coast defense sites.
CHL was developed from the same basic technology to fill gaps in CH's coverage, particularly at low altitudes. Organizationally, CHL tied into the air defense system while CD operated locally with Royal Artillery coast defense guns. In addition, the Army had mobile RDF radars as well as the mobile GL sets.

The main point is that Britain had considerable numbers of radar sets in service in 1940 that could have and would have discovered a German invasion fleet well before it arrived.

It's interesting to note that many of the British sets were really pretty crude constructions. CHL and CD radars were usually mounted on wooden platforms using a wood and chicken wire antenna with simple dipoles. They lacked automatic switching to allow the antenna to be both a receiver and transmitter and instead used separate portions for that purpose, of like CH used entirely separate antennas. CHL was rotated using bicycle chain and sprockets, and in early versions rotated by hand.

 

Sorry, yes that is what I meant. The CHL system used the Army CD radar sets Mark I; it was the basis for the first 24 CHL stations. So it wasn't really a rivalry thing, it was a serendipity thing. The Army was developing radar for gun laying and the RAF for air warning.

In any case, yes, they would have likely discovered the German fleet at least 30-40 miles out.

 

Really? 2 years later, they didn't detect a large german surface in the channel force for half a day. With much better radar equipment.

The germans didn't detect the allied invasion fleet before it was visible from the beaches. In 1944!

In 1940, german submarines used to attack at night on surface, where they were nearly invisible. Skilled commanders could stay in between a convoy for hours with burning ships around. So i don't think they would have been useless.

 

The "channel dash" stuck pretty close to the French coast and even if they had Doppler would have been moving more or less perpendicular to the radar so not much discrimination from the clutter of the French coast. It also likely didn't come with 40 miles until getting close to Dieppe. So that's not really much of a counter example. Consider that the invasion fleet would be approaching from more or less open water. There would be sea clutter but as many vessels as we're talking about would make a considerable chance of detecting them. Then there's the top speed of the barges to consider. I've never gotten a good number for it but it's unlikely that it would have been above 6 knots and may have been as low as 2 or 3 knots. The current would have effectively cut this some as well so even if detected at say 30 miles it's going to take them at least 6 hours to reach the coast and could take them as much as 15 or more!

Did the Germans have sea search radar in place and looking in 44? I doubt it. For one thing the allies would have detected and attacked such installations. So that's not all that relevant either.

Subs had a pretty hard time targeting warships at full speed. Hanging around the shallow Channel area in daylight wouldn't be all that safe either. Operating in the Channel even at night would have left them subject to attacks by Coastal command as well. I'm not sure what phase of the moon they were going for but it could be a critical consideration. The Germans also didn't really have all that many subs at that point and calling most or all of them back to get ready for SeaLion would be noticed and allow the British more flexibility in regards to how they used their DDs and other escorts.

 

During Cerberus (the channel dash), even the constant air-patrol was undetected. And when they approached Cherbourg, they were pretty close to the british coast.

Yes, surface night operations would have been very risky, but not hopeless, There was no surface radar on the ships back then and in a few years of surface operations in the convoy warfare, only very few subs were sunk because of detection at night. U-Boat commanders reported that escorting vessels passed them in close distance without detecting them and they were on the hunt!
And there was a Luftwaffe too, ships in the channel would have been an ideal target for the later almost useless Ju 87. And the Me 109 didn't struggle with range problems in the Channel.

But I agree, the real invasion force of autumn 1940 was not suited for the task. The later Admiral of the Bundesmarine Friedrich Ruge assumed that 100 fast and big Marinefährprahme would have been enough to establish a beachhead in Summer 1940 short time after the Fall of France. https://en.wikipedia.org/wiki/Marinef%C3%A4hrprahm
Not impossible, german shipyards built nonsense like the both aircraft carriers or the KdF-Liners, so the had the materials and the capacity to built it.

 

The big difference however is that Britain was expecting the invasion and doing every thing possible to see it comming, the Dash caught them by surprise because it was unexpected.

 

Cerberus was expected, the RN expected it only the other way round. Start at daylight, passing Calais at night.

 

U-boats in 1940 attacked convoys which had few escorts and which often didn't know they were under attack until the first torpedos hit. That was a key advantage that's often overlooked. People think of it like a war game where both sides know they're playing, but the escorts had no way of knowing which of a hundred long, dull, nights on convoy duty would be the one. Even at the height of the U-boats' success, most convoys got through without even being spotted, let alone attacked. U-boats, or submarines in general, practiced something akin to guerilla warfare, able to strike anywhere over a vast area of ocean, against defenders stretched thin and never knowing where or when they might be attacked.

Fighting in a restricted area against concentrations of enemy ships and aircraft primed for battle is a completely different story. Even heavily escorted troop convoys and the like suffered minimal losses to submarines. In a Sealion scenario, the U-boats' opposition would be warships, fully alert, operating at high speed, nothing like a plodding convoy on a North Atlantic night.

 

??? From what I read the unusal air activity was one of the first things detected. It just wasn't associated with the dash at the time. From the maps I've seen they were well over 40 miles from the English coast at Cherbourg and pretty close to the French coast which means they were a pretty poor radar target.

It's not that the surface night action with the uboats would have been that risky just that they wouldn't have been that effective. The uboats would have had to have been spread out pretty thinly and the RN formations would have been penetrating the line (if they had to penetrate the line) in fairly concentrated groups moving at considerable speed. That's not a good engagement profile for the uboats. The risk to the uboats would have been getting into position and staying there.

They needed to do more than establish a bridge head and to say the resources and capacity was available is kind of meaningless. They needed the vision to see that it was necessary and also would have had to decide what to give up to build these instead. Then of course there's the fact that until fairly close to the start of the war Hitler thought of the British as more of an ally or at worse a neutral rather than an opponent. Building an invasion fleet wouldn't help all that much without a KM to protect it either and Norway saw the KM surface fleet gutted.

 

I would say apple's to orange's, but it is not even that close.

Cerberus was anticipated not expected. the RN had to plan for 4 possible options, with the Channel Dash being only one of these. They could try to return to Germany by the traditional route around the west and north coast's of Ireland-Great Britain, or they might break out into the Atlantic in search of convoy's, or they might remain in Brest as a fleet in being.

It's hard to credit that the actual movement was Expected since the primary surface force, 6 Destroyer's, who should have been on high alert (4 hours notice) were not, and all the smaller ships are likely to do is die gloriously for King and Country. Nor does having only one submarine, who was off recharging it's batteries, watching for a movement out of port, was indication any sense of urgency.

Cerberus, or any kind of movement, could take place at anytime, but the invasion of Britain had a very restricted clock running on it. That being the difference between anticipated and expected.

 

And Cerberus was almost two years later.
So: They couldn't discover an invasion fleet at distances over 40 miles.

Juergen Oesten, commander of U-61 (knights cross), reported that he sunk 20 ships during his career, 19 at night on surface. His attacks were performed similar to speedboat tactics. He reported that the small tower of his boat seemed invisible to surface ships, especially at short distances below 3000m.
So, successes were likely, but for sure not enough to defend an invasion fleet.

 

Again, Cerberus is a flawed comparison.

Cerberus was a group of 50 German warships, moving at high speed. Seelowe would involve thousands of craft, the vast majority of which would be small, slow moving auxiliaries, like barges, their tugs and merchant ships.

Nor is Herr Oesten's war record terribly credible in this context, I find that none of his kills were warships, though he did damage 1 (HMS Malaya, WWI dreadnought). What he did sink were slow moving merchantmen, a far cry from what he would face attempting to stop a German invasion. On the surface he was faster than most of his targets, and many of the escorts for that matter, but against MTB's and even second class Destroyers he would be a sitting duck on the surface.

 

Your argument does not really support your conclusion. I wouldn't expect radar in the UK to detect an invasion fleet composed mostly of barges at over 40 miles in most cases anyway. Unless it was mounted well up a cliff they would be over the radar horizon. Other means of detecting them were possible and utilized. Note that one of the things that delayed the reaction to Cerberus was the fact that the first RAF planes to spot the German ships were under orders to maintain radio silence and didn't report them until they returned to base. An invasion fleet is a whole different matter. There's also the fact that the preparations for the invasion would be much more visible in the hours and days leading up to the launching than was the case for Cerberus. The use of multiple ports with significantly different distances from the invasion beaches would also mean that some portions of the invasion fleet would be at sea longer than others making detection of the invasion in a timely manor even more likely especially considering the speed of the barges.

As for the subs first of all how do they get to their patrol location? Many aren't based in France yet. Their absence in the North Atlantic is going to be a bit of a red flag isn't it? Much of the area in the channel and around it are a bit shallow to hide in during the day and having a bunch of (already over taxed) fighters orbiting over an area with nothing on the surface is a bit of red flag as well isn't it? The subs might get a ship or two but they certainly wouldn't be capable of stopping the RN from hitting the invasion fleet and they would take significant losses trying to.

Looking at WWII ship losses I see only 8 RN cruisers sunk by Uboats and from what I can see most if not all were cruising and not at full speed or expecting immediate action like they would be in the case of a run in against the invasion fleet(s). Similarly I see only 24 DDs sunk by Uboats which is about 20% of RN DD losses. Especially since the Uboats won't be able to mass against the RN forces I simply don't see them doing all that much. Note that the RN could easily use small craft to flood the areas where the naval combatants would pass through giving them a very good chance to detect and engage or avoid the Uboats.

 

Cerberus is a poor example. The Germans in preparation for that operation set up multiple jamming stations along the French coast specifically to degrade British radar. This is something that doesn't exist in 1940 and something the Germans have zero experience with. The Channel Dash also took less than a day to accomplish, at least for the part going through the narrowest sections.

For Seelöwe you have a huge fleet of ships and boats moving at just a few knots taking as much as 72 hours (3 days) to make the crossing and assemble off the intended landing beaches over another 48 (2 days) hours or so. If the British can't figure out that there is an invasion occurring in the nearly a week it takes for it to arrive and land itself on Britain, I'd say the British deserve to be invaded.

 

Let's just drive a stake through this thread right now. Let's give the Germans 1000 MFP, 500 Siebel ferries, and 250 decent merchant ships. That's more than enough landing craft and shipping to put their first wave on the beaches. The Royal Navy will still demolish the landings in nothing flat. Seelöwe will fail and the Germans can't stop that because they lack a navy to do so.
Submarines won't substitute for surface combatants. The Luftwaffe is no substitute. The Germans lose because they don't have a navy and aren't getting one anytime soon.

 

In my humble opinion, SEA LION would have been a 100% disaster for our peace loving German tourists in 1940.

The RN Home Fleet had very roughly, including ships on patrol etc, as at 23/5/1940

13x BBs and BCs

7x CVs

14x CAs

29x Cls

184x DDs

73x SSs

18x MTBs. (all via a very tedious Google search)

All based in British ports from Scapa Flow, to Scottish ports , to the North Sea ports, to Southern Counties and Western Counties.

The Kreigsmarine had a couple of major ships and TEN DDs, to oppose them and protect the barges. One out of every 3 was UNpowered and had to be towed by the powered one. The barges were still water things more at home on the Rhine than the English Channel. The Luftwaffe had NIL torpedo bombers at that time. The dive bombers were good at stationary targets but NOT moving ships, as they proved at 'Dynamo'. The barges were capable of about 5 knots at most, and the trip across the channel could take best part of a day, or night.

SO!

ALL of those barges are very vulnerable to the bow wave of a BB or even a DD etc etc etc. all the RN had to do was charge up and down and the channel would have been like a German vegetable soup!

With not a shot being fired!

Agree?

 

Sorry John...im not trying to trip you up...
"Luftwaffe had NIL torpedo bombers" - Which may be true however, there were are couple of squadrons of Stukas that were "meant" to go onto the new aircraft carrier the Germans were building...they were sent to "normal" unit instead as the carrier wasn't ready...They even still had their anchor emblem painted on them...I don't think it would have taken much to sling a fish under one of these?

 

The Luftwaffe eventually used several aircraft types as torpedo bombers, the He111, Ju88, and even the He115 seaplane, but they hadn't given much thought to it in 1940, even though they had several units (KG-26, 30, 40) assigned to maritime operations. For an analogy, the Italians established their first torpedo bomber unit on July 25, 1940, and it carried out its first (unsuccessful) mission on August 15; the Germans could probably have done something similar had they made the commitment.

The Stukas in their dive bombing role were highly effective against ships, so they would probably stick to that.

 

CAC, Carronade.

At 'Dynamo', the allies lost i think a total of SIX DDs, all I think to dive bombing, again I think, ALL were stationary at the time.

The Stuka was great aircraft to destroy a bridge, or even a tank, but the key is that they are stationary!

JMO


John

1164
1182

 

Havant was underway, Grenade and Basilisk stationary, Keith probably also, Grafton was torpedoed by a U-boat and Wakeful by an S-boat.

In the Norwegian campaign, Afridi, Gurkha, the Polish Grom, and the French Bison were sunk by German aircraft while maneuvering at speed in open ocean. Heavy cruiser Suffolk was badly bombed and barely survived. AA cruiser Curlew was sunk by Ju-88s while steaming at high speed, although in a fiord. We can't just cling to one example; there is a long list of destroyers and other warships sunk by Ju-87s, -88s, and other German aircraft which were available for Sealion had it happened.

This does not mean that the Luftwaffe could defeat the Royal Navy. The key point about operations like Norway, Dunkirk, or Crete is that the navy accomplished its assigned missions despite painful losses.