Could Operation Sealion really have succeeded?

Against a nation with a neglible Airforce, only partially mobilised, unmodern army (25,000 men), and small navy, yet they still managed to inflict losses inspite of the total surprise achieved by the Germans and their audacious plan. The Germans were not going to get anything free like that against the UK.

The KM lost ships at an alarming rate, and these were armed vessels, not barges. At the end of the campaign, the KM had in service one Heavy Cruiser (Hipper), two light cruisers, and 4 destroyers. They lost three cruisers and ten destroyers. Most of their surface fleet was put out of action for months.

 

The RN definitely were better than kriegsmarine ships, the battle in narvik fjord shows that in my opinion. However, once the Luftwaffe got a chance, the numbers soon were evened...

Norweigian campagn:

Carriers: RN ->one

Cruisers: RN 2, German Navy 3

Destroyers: RN 7, Kriegsmarine 10

http://www.naval-history.net/WW2RN05-194006.htm

 

Not sure I would call that the Luftwaffe evening the numbers. The carrier and five destroyers were sunk by German surface ships, and the cruiser Effingham ran aground.

The key point in all these confrontations of Luftwaffe and Royal Navy - Norway, Dunkirk, Crete - is that the Luftwaffe never prevented the navy accomplishing its assigned missions. Even when the Germans had total control of the air - which they wouldn't in any Sealion scenario - the Navy did what it was tasked to do.

 

For instance:

Thanks to these continual updates streaming into X Fliegerkorps headquarters, on the afternoon of 9 April over 100 sorties were launched (See Table 1) against the inbound British Fleet. The raid was made up of Ju 88s from KG. 30, He 111s from KG. 26 and Stukas from StG. 1. Unable to make the distance to the target and return, the Stukas instead bombed and sank a Norwegian destroyer off the Norwegian coast. Yet the interception had come too late as earlier in the day the destroyer had caught the German supply ship Roda in open waters and sunk her.
While the Stukas were at work on the Norwegian destroyer, the main force of German bombers had been able to locate the British fleet. Attacking through a withering barrage of anti-aircraft fire the bombers attacked and were able to sink the destroyer HMS Gurkha. In addition to this the battleship HMS Rodney, and the cruisers HMS Southampton, Devonshire, Sheffield, Glasgow and Galatea were all damaged to varying degrees. To supplement the damage that had been wrought, the attack had forced many of the British vessels to withdraw from their positions and return to Scotland for resupply. In most cases the resupply was for anti-aircraft ammunition as the prodigious use of such ammunition during the defence of the Fleet had meant that some ship’s lockers were up to 40 percent empty after the last wave of bombers had departed the scene. Considering the size of the attacking force, which numbered some 88 aircraft, the results that had been achieved, were considerable.
http://www.wiki.luftwaffedata.co.uk/wiki/index.php?title=Wesertag_-_Anti-Shipping_Operations

Table 4: Royal Navy Vessels Lost To Aircraft during Weserübung
09/04/40 Destroyer GURKHA (1,870t) Sunk by aircraft bombs, off Stavanger, Norway
20/04/40 Trawler RUTLANDSHIRE (458t) Attacked by aircraft and grounded, Namsos, Norway
25/04/40 Trawler BRADMAN (452t) Sunk by aircraft, West Coast of Norway.
25/04/40 Trawler HAMMOND (452t) Sunk by aircraft, Aandalsnes. Norway.
25/04/40 Trawler LARWOOD (453t) Sunk by aircraft, West Coast of Norway
28/04/40 Trawler CAPE SIRETOKO (590t) Sunk by aircraft, West Coast of Norway
29/04/40 Trawler CAPE CHELYUSKIN (550t) Sunk by aircraft bombs, off Norway
30/04/40 Sloop BITTERN (1,190t) German bombers off Namsos, Norway
30/04/40 Trawler JARDINE (452t) Sunk by own forces after damage by aircraft, West Coast of Norway.
30/04/40 Trawler WARWICKSHIRE (466t) Sunk by aircraft, Trondheim area, Norway.
3/05/40 Destroyer AFRIDI (1,870t) Sunk by aircraft bombs, off Norway
3/05/40 Trawler ASTON VILLA (546t) Sunk by aircraft off Norway.
3/05/40 Trawler GAUL (550t) Sunk by aircraft off Norway.
3/05/40 Trawler ST. GORAN (565t) Sunk by aircraft, Namsos, Norway
21/05/40 Trawler CAPE PASSARO (590t) Sunk by aircraft, Narvik area, Norway
22/05/40 Trawler MELBOURNE (466t) Sunk by aircraft, Narvik area, Norway
25/05/40 Special service vessel MASHOBRA (8,324t) Damaged by aircraft, and beached at Narvik
26/05/40 Boom defence vessel LOCH SHIN (255t) Capsized at Harstad, Norway, after being damaged by aircraft and beached.
26/05/40 Cruiser CURLEW (4,290t) Sunk by aircraft, bombs, off Ofotfiord, Norway
10/06/40 Armed boarding vessel VAN DYCK (13,241t) Lost in convoy probably by German air attack, Narvik area, Norway

 

...which is widening the goalposts unnecessarily; the point of the Norway reference is that in an operation FAR more improvised and worse "carried" than Sealion would have been, the GErmans managed to get ashore, develop their beachheads and their hold on landing areas etc. without the "advantage" of disembarking over beaches, forcing them to utilise Norwegian harbour facilities....and yet were ashore in strength and consolidated enough in one day to proceed successfully against the British - who landed along the coast one day after them.

In Sealion - against some quite thin shore defences in reality - there were places where main force was going to get them ashore and consolidate initial beachheads very rapidly. Romney Marsh for example would in effect be wholly ceded to them BY the prompt, planned demolition of all crossings across the Royal Military Canal....which was why, in the Napoleonic Era, the RMC was dug after all - to cede the Marsh to an invader and pin him there...

But that was an era BEFORE ampibious tanks, combat engineers....and airborne forces dropping BEHIND the RMC The planned fast motorised dash once off the beaches and across the RMC towards Folkestone and Dover...planned for the early afternoon of S-Day IIRC...was for example going to be proceeding north just west of Hythe them immediately east behind the town through a carpet of FJ dropped that morning at 6am....

One mistake that's often made when looking at BOTH sides' invasion and counterinvasion preparations is to look at them TOO closely - look at each individual pillbox and coastal battery in the landscape, for instance, as that's what's been studied most in the last couple of decades...and not to step back to a more holistic view of the battlefield; hence people easily miss the importance of the British armour's "hurry up and wait" order in Sussex...the impassable terrain behind the initial beachheads between Rye and Hythe...the FJ's role not just in taking RAF Lympne, etc., etc. -

...but also people tend to miss that the FJ were to be used in a new-for-them, "purist" blocking role, carpeting the long tapering open valley running from Ashford down to Hythe/Folkestone, hemmed in by the coastal escarpment on one side and the Kentish Downs on the other. It took me literally years to think of looking at a relief map of the area, and working out why MILFORCE's orders were so very specific about routes to be taken to the coast on S-Day depending on what option in their orders they were directed to carry out; they're the ONLY routes to the coast that they could have used...and the Germans seem to have worked this out too, from their pretty comprehensive photo recce, and tasked the FJ with blocking or at least slowing the transit of counterattacking forces to the beachheads.

This looks strange to people who look at Sealion and bits of Sealion out of context - given that after it didn't take place, the Germans "returned" to using the FJ for seizing point targets - airfields in the USSR and Poland in Barbarossa, the Corinth bridges, the three Crete airfields etc. - a purist blocking role was certainly atypical for the FJ apart from the Dombas operation in Norway...but it's exactly what Allied theorists on the use of airborne forces were writing about mid-war, and what we did in Normandy on D-Day.

 

Except that same geography that was blocking MILFORCE, would have have just as much a hindrance to the Germans; with the added benefit of them not receiving sufficient further supplies, .

It was doomed. There were two reasons it never occured; the RAF, and RN.

The best summary I saw of it was on another board:

"Germany spent 7 years preparing for a land war with France and to a lessor extent Poland, Britain spent 7 years preparing for air war with Germany."

No one in Germany in March 1940, was seriously anticipating invading the UK in July 1940. In the UK, during March, people were considering how to best defend UK airspace.



Hardly the vision of a nation in defeat. Especially when we look at the status for LW operational crew over the same critical period:



Much ado is made about the strain on the UK pilot force pool; It was worse for the Germans; they were attacking, and seeing little to no gain, for weeks on end. Their propaganda machine was talkng about the RAF being finished, and yet when they crossed over the channel; there were the fighters. No wonder they got Channel Fever.

 

If torpedoes would have worked in Norway (very likely in the Channel), the german U-Boats would have inflicted losses which would have been hard to justify by the RN. Norway showed the German High Command, that air superiority was more important than control of the sea. That is way Raeder convinced Goering that total control of the air was needed for an invasion.

 

-First of all Norway was further removed from the RN's home bases than the English coast would be, the ability to react past the initial dispositions shortened.

-There were a number of instances that the Norwegians failed to engage the Germans because of uncertainty as to what they should do. There would not be the same issue with a German invasion of England. There were cases where the Germans used English recognitian signals to prevent the Norwegians from engaging.

-No one doubts that the Germans could have gotten some troops ashore, it's their ability to land reinforcements and supply them once the element of surprise was past.

-The Germans in Norway did not try to land large bodies of troops across the beach. It's a whole different ballgame. They used surprise to quickly land across port facilities.

-In Norway the Germans counted upon minimal resistance and a quick capitulation. They got that. Britain would resist, Britain would not capitulate.

-German logistics during the Norwegian campaign were inadequate and they for a period had to rely on aerial resupply. The numbers and amount of supplies they would need to fly into Britain to support the force are not sustainable. They would have to seize and hold airfields, the British would be targeting the vunerable supply aircraft, and would simply use airstrikes or artillery to make the seized airfields inoperable.

-The FJ may initially have been able to block some British response but in the days before Panzerfausts would they have the ability to hold long once armor came up? The British would respond with combined arms, in their own backyard, it isn't Crete. Air, artillery, infantry and armor. The success of the FJ would depend on if, the heavier forces could break out and relieve them with sufficient heavy units and those heavy units would need to be adequately supplied.

-In Norway, despite having air superiority the Luftwaffe struggled to supply Dietl's forces at Narvik, despite an anemic British ground campaign. This is important because had the British pushed harder, Dietl's resistance would have expended larger quantities of supplies and ammunition. He already judged his position untenable and had decided to fight a delaying action, or even move into Sweden and request his troops be interned. In Sea Lion Britain would not cede air superiority. It would be German ships subjected to allied air attacks with non-existant/inadequate friendly air cover, a virtual complete reversal of the situation the British faced in Norway.

"Dietl was entirely dependent on the Luftwaffe for ammunition, reinforcements, and most types of supplies, all of which had to be delivered by air drop or sea plane. Dietl was so desperate for heavy weapons that 10 Ju-52s brought in a battery of mountain artillery, landing on an improvised air strip on Hartvig Lake (14 April). These aircraft had only enough fuel to make it to Narvik and were to be abandoned and allowed to sink into the lake when the ice thawed......pp. 9-13. Ziemke (p. 88) provides information on support received through Sweden via rail, to include rations, medical supplies, ski equipment, clothing, but not ammunition. Also 230 German “specialists” arrived via Sweden during the course of the campaign."
One of the big lessons learned about amphibious operations against opposition, during the 20's and 30's by the British and Americans was the need to build combat power quickly so that the forces could not be contained in their beachead. Part of this was to get sufficient supplies ashore as rapidly as possible in order for the landing forces to be able to sustain combat effectiveness. Reinforcements needed to be landed rapidly to sustain the buildup and breakout.

-One of the ways the Germans got around the supply issue during Operation Weserubung was:
"Supply ships camouflaged as merchant vessels actually preceded the assault ships and lay in wait in Norwegian harbors."
Not likely to be an option for Sea Lion.

-The reason for the seizure of Denmark was to provide a land bridge for resupply and reinforcement, and to provide airbasing for aviation assets to support the Norway operation. Britain had no Denmark.

-The area the RN had to cover in order to intercept KM and merchant shipping was immense. The channel would be a much more confined and limited area.

-The initial German landings put only a total of 8,700 troops ashore, at Narvik, Trondheim, Bergen, Oslo, Kristiansand and Arendal. This is a drop in the bucket compared to what would be needed to invade Britain.

There are plenty of other aspects that make this operation different from what one considers a classic amphibious assault, this was more like a raid where they stayed instead of withdrawing. Had the Norwegians been able to mobilize and/or had realized what was actually happening before the Germans seized the mechanisms necessary for them to mount any type of organized defense, it would have been a disaster for the Germans. However, it was during the period known as the "Phoney War" and they got sucker punched.

 

Norway was a completely different challenge for both sides, i agree. But what it showed: Allied organization and tactics at land and in the air were far away from german standards. Their landings - Namsos, Andalsnes - were chaotic and achieved nothing. Even the small forces at Narvik, half of them were sailors from the destroyers, weren't forced to disappear.

Narvik is closer to Scapa Flow than to Wilhelmshafen.

 

I probably wasn't clear in my reply. I was referring to the RN's ability to react to events in the Channel vs it's ability to react to events in Norway. To be honest I never looked at the distances and reaction times for the Norway campaign.

 

They were limited due to lack of foreign exchange due in part to an over valued Mark and a significant amount of debt. Essentially no one outside of Germany wanted Marks at least a face value.

Over on the axis history fourm there are a fair few number of sea lion threads (including the BoB what if thread) that go into considerable detail on the ships available. For the KM during the September through October period they had one panzershiffe, a heavy cruiser that was briefily available until it had an engineering failure shortly after it came of of repair status, and 3 light cruisers. I forget how many DDs but not many.

My understanding was that each tug would tow 2 or 3 barges ideally at least one of the barges would be powered. I've yet to see anything definitive on how fast they would be though. "Reasonable" estimates varry between 3 and 6 knots with some suggesting as high as 8 or as low as 2.

As stated earlier the channel was not a good operating environment for U-boats. Night raids by British subs may have been even more important than the U-boats in part due to the very limited number of cargo ships available to the Germans and their critical import.

 

Probably already stated...but the bulk of the attack on invading boats and ships would be the RAF...one wouldnt put bulk ships into a small area...that would be a Stuka's wet dream...i would send squadron after squadron day and night and straff and bomb the crap out of them...Not to mention the build up of land based artillery around the two or so landing areas available...

 

From what I recall of previous discussions this is not the case. RAF fighters were not even planned for use vs the invasion fleet. Bombers would have been but the RN especially at night would likely have done the most damage to the invasion fleet. Coastal battereries may actuallly have done more damage than aircraft.

 

Even the first wave is problematic. The Germans need about three days (72 hours) just to move their invasion fleet to the landing beaches. This is due to several reasons, the primary one being the utterly slow speed of advance of many of the ships and barges involved. The next is that they planned on launching the invasion from a few larger ports. That would mean that the shipping would have to stream out of the port and assemble into convoys at sea further slowing the movement.
The Allied planning for D-Day had to take into account this sort of thing and which port ships would move from, in what order, and not overload any one port with shipping to prevent a bottleneck.

So, once the invasion fleet arrives, it would have to land the forces brought. This could be done in one of two ways:
Piecemeal as they arrive in whatever order they arrive or the fleet could stage off shore and organize waves to land together.

Then comes the next problem. Many of the landing barges are unpowered and the Germans have limited tugboats and other ships for handling these. Pushing them ashore in a surf is going to be a real challenge. If the tug were to ground or strike or suffer damage in doing this it limits further landings slowing things down again. There is also a very real problem with these barges simply cluttering up the beach making it difficult or impossible for following ones to even beach at all. The barges were also poorly equipped to maintain a steady position on the beach. That is, they are likely to be tossed about by the surf and shift position.
Lacking retraction gear, most are going to be a one-way trip in. That is, once they land their cargo they are finished and can't be used again. So, most of the landing force's capacity is lost with the first wave ashore, even without enemy interference.

Any barge that is unpowered and loses tow on the way across becomes a problem. First, until the tow is recovered it's adrift and not going to end up at the landing at all. Second, it's a hazard to navigation for all the other convoy ships and barges. Recovering a tow is going to be difficult since most unpowered barges would be in tow as a group of 4 to 6 behind a single tug. One loses it's tow, the tug really can't go to it's rescue.

As for U-boats. These would be nearly worthless against RN fleet units. They couldn't operate on the surface against them at all. That would be near suicidal for them. All an RN DD or other ship with ASW weapons need do is drive the U-boat down where it can't launch a torpedo attack to make it worthless. Offensively, unless the RN's ship(s) literally run over the U-boat they are all but immune to attack while it is submerged.
Here you have a submarine with a realistic 4 to 6,000 yard range of view and hearing submerged that can make maybe 6 knots at most trying to position against a ship making 15 to 20 knots, zig zagging, and possibly using ASDIC while doing so.
While it is possible for a U-boat to attack a combatant, it's almost pure luck that they will be able to do so.

If anything, the British will have better luck with their subs against the invasion. The Germans have poor ASW capacity. They have a large near stationary fleet of ships and barges as potential targets. This is what WW 2 subs excel at sinking.... Poorly defended, slow, vulnerable merchant ships.

As previously noted, I'd expect the RN to hit the Germans in transit at night. After all, they have three plus nights to do it. Flares, radar, star shell, and ships with real fire controls are going to tear the German invasion fleet a new one. Look at the German invasion attempt at Crete. The Germans were using a convoy of impressed trawlers and small freighters to move a battalion of the 6th Mountain Division to Crete by sea. The Italian Navy provided two DD as escort. The RN showed up at night with a cruiser - destroyer surface action group, sank the two Italian escorts and then proceeded to sink the entire convoy in short order.
No difference with Seelöwe. Same thing's going to happen.

Worse, with many of the German barges and such armed with improvised gun mounts and such, once the shooting starts the Germans are very likely to fire on friendly as enemy in the confusion. Any unpowered barge that loses tow is finished as an invasion vessel. The question then becomes how much of what the Germans left port with actually makes it to the invasion beach in some condition to permit it to land? I'd guess that casualties could run as high as 50% or more of the invasion fleet not making it or showing up days late after struggling to cross the Channel.

What does show up is likely to be disorganized and landed without vital equipment and supplies. So, while the first wave might get ashore and even make a beachhead, there isn't going to be much of a second wave to reinforce them and what does show up takes a week or more to arrive. The German plan is pretty much nearly self-defeating.

 

The Germans don't have a bad a track record on amphibious landings, Norway, Crete (ok the amphibious leg failed but they still kicked the allies out), or operation Albion in WW1, the sort of chaotic situation that would develop is also very well suited to their low level initiative tactics. The reaction to Torch is probably also significant, the Allies had both naval and air superiority by 1943 but the Germans still got a lot of troops across unscathed.

Having said that the British advantages are huge, a totally hostile country with high morale and significant depth, even if short of fully formed and equipped units is an almost impossible nut to crack if operating at the end of a tenuous supply line.

What was the chances of Bletchley decrypting some critical message in September 1940 ? it could be decisive.

BTW your recollection if the Crete naval ops is wrong, there were two German convoys, each escorted by an Italian torpedo boat (small destroyer if you like but at 700t not in the same class of the more common > 1000t contemporary fleet destroyers), the first was destroyed despite the efforts of the TB that survived, the second mostly successfully retreated to the mainland as the TB and the Luftwaffe discouraged the RN squadron from closing in. There also was an Italian convoy from the Dodecannese that made it to Crete with no opposition (the RN got no info from ULTRA on that one as it was a fully Italian operation). So if we imagine a no ULTRA setup even such slow convoys could have a chance.

Does anyone know what were the capabilities of the radar chain against surface forces ?

 

The chances of Bletchley decrypting the specific operational order in September 1940 is pretty low. While they had some successes, chiefly against the Luftwaffe, it was hit or miss, fragmentary, and not always timely.

The Chain Home Low system was in place and was capable of picking up an invasion fleet...roughly at 30-40 miles from the coast IIRC (have to look it up).

This is just one of those what ifs that never dies.

 

To be fair in the first case Germany landed on a largely undefended target initially and in the other if 2/3rds of the landing force is driven off statistically they are going to fail more often than not. It's true Allied forces operated with profound advantages in Amphib operations, but Germany also operated with profound advantages over her targets, Norway was at peace, effectively no standing military and had scant hours to effect any form of defense. In Crete the defenders were the remains of a army hastily withdrawn from the Greek mainland ( and recently savaged in battle), with little time to reform into effective force. It would be as if Sealion was launched say 2 weeks after Operation Dynamo.

In both cases these operations were executed on a shoestring and they were damn lucky.

 

Britain had two radar chains that would have been effective in detecting an invasion fleet. The first is CHL or Chain Home Low. It was primarily for detecting low flying aircraft that would be below the detection limits of CH. The second is CD or Coast Defense operated by the Army not the RAF. The later was specifically for detection of ships with about a 25 mile range on a 10,000 ton vessel. That varies some depending on the set's height above sea level.

 

And there were 4000 horses planed for the first wave alone. Good luck trying to get any surviving ones harnessed up in the middle of a battle.

 

Terry, as I understand it, the CHL system was the CD radar sets. 24 such sets were ordered in August 1939 and emplaced at CH sites and were known as the CHL system.