Seelöwe: British Defensive Measures - Naval and Air Ops

[David Floyd]

I know that Operation Sea Lion has been discussed before, however, I think this is a new twist on the discussion. This is my first post here, by the way

Anyway, let's assume that Germany is able to gain air superiority over the Channel and Southern England in summer/autumn of 1940, and that Germany goes ahead with Operation Sea Lion, involving the use of virtually all of the fallschirmjaeger and glider forces, backed up by amphibious landings using every craft Germany could scrape up - let's say all told a couple of division-equivalents of airborne troops and a couple more divisions of infantry as an initial landing force in the Dover area, with obviously more to come, both shipped in and flown in.

My question is this: Would the Royal Navy have been able to, even in the face of the Luftwaffe, disrupt the landings to such an extent the invasion had to be abandoned?

I think that it could, and I'm envisioning something along the following lines:
The Home Fleet sorties from Scapa Flow, and sails down the coast of England under friendly air cover. The operation is timed such that the RN does not enter German aircover in the daylight, and much of the voyage to the Channel can be done under cover of darkness when the Luftwaffe cannot operate against it. The RAF sorties every last fighter in its inventory to put an air umbrella over the fleet in the Channel, forcing the Luftwaffe to first deal with the remainder of the RAF, while the Royal Navy, with something like 6 BBs and several dozen cruisers and destroyers mops up the Kriegsmarine and especially any large transports in the Channel. While obviously a suicide operation, it would only have to succeed in wiping out a good chunk of Germany's sea transport capability, which was extremely limited already, in order to force Sea Lion to be abandoned (along with the troops already landed in England).

Would that have been feasible? I'm certain it would at least have been attempted, and it seems to me that the RN was large enough to at least have some chance at destroying the invasion.

[Tiornu]

I don't believe the RN intended to use its major units against an invasion. Instead you'd see sloops, patrol vessels, trawlers, motor launches, and the like. If you look at Crete, the RN was able to do its job in the face of enemy air superiority, and I have no doubt they'd manage in the defense of their home.

[Gungnir]

IRRC, Operation Sealion would only be launched when the Royal Navy was destroyed. Operation Sealion was the invasion of Britain... what prevented the Germans from launching their navy (To land on British shores) was the British RAF and Royal Navy.

Luftwaffe takes out RAF. Gains air dominance. Luftwaffe takes out Royal Navy. Kriegsmarine gains naval-sea dominance. INVASION!

but this didn't happen

that was the idea, was it not?

so the Royal Navy could not exactly have disrupted Operation Sealion. because the idea was to destroy that.

or are you asking, if RAF was destroyed and it was the Royal Navy against Luftwaffe and Kriegsmarine. Without air cover and dominace, the British would have a difficult time. Even though the British navy outmatched and outgunned the Kriegsmarine without the RAF, the Luftwaffe would have somewhat easy targets.

[David Floyd]

Operation Sea Lion relied on having local air superiority over the Channel and Southeastern England in order to shuttle troops across using Germany's very limited sealift capability, IIRC.

Destroying the RN was certainly unrealistic - if that was ever the goal, then why sortie the Kriegsmarine's capital ships a couple at a time at the convoy routes? Why not attempt to concentrate the Kriegsmarine surface fleet and try to force an engagement with the Royal Navy? Preferably this would be done a little at a time - the strategy would be the same as the Imperial Navy's strategy in WW1, that is, to isolate and destroy elements of the Royal Navy. In this case, the goal would obviously be to lure the RN under Luftwaffe air cover and force and then force a fleet action, right? Of course, this is sort of moot, seeing as how the Norwegian campaign destroyed most of the operational German destroyers, as well as the heavy cruiser Blucher, and damaged numerous other major German surface units.

On the other hand, this isn't what happened, nor was it ever, as far as I know, a goal of the Germans. Hence, I can see them possibly attempting Sea Lion if the Luftwaffe gained air superiority over the Channel and southeastern England, and if enough sealift could be concentrated in the Channel. I don't view either of those things as particularly likely, but this is a WI, after all.

So, then, it seems to me that the Royal Navy would have to attempt to sortie on a virtual suicide mission in order to destroy the concentrated German sealift forces, and thus defeat the invasion. Certainly it would have had a difficult time, but the RN could have utilized darkness to move into German aircover initially, and then rely on limited RAF cover to fend off some of the Luftwaffe attack aircraft - the RN needed just enough time to shoot up the mass of underprotected German shipping, after all.

[Lkefct]

My understanding of it is that there are something like 80 destroyers set asside in addition to small combatants, and a few cruisers and other capital ships. If the RN sorites all of the ships in short order, and makes a massive run to the invasion area, I find it hard to beleive that the German Navy or Luftwaffe could deal with a high speed sotie. Also, you can almost be assured it would be at night, at 25-30 knots. They can cover a large distance. They also do not need to be there when the assualt troops hit the beach, but need only cut the supply lines by destroying the transports and barges.

Most of the German capital ships are out of action following Norway. Immediately after Norway, there where something like 3 cruisers and 4 detroyers avalible for action. There would be Uboats, but there are only a few of them (20 or so ocean going boats). Uboats are not very effective vs escorts (60 + sunk during all of WW2). Air attacks would be the chief defense of the attackers. In addition, any RAF units who run to Scotland, would be drawn into battle, and they luftwaffe would be forced to act as the heavy artillery for the ground troops until armor and heavy weapons can be landed in mass.

Dive bombers are fairly effective against ships, but most German bombers are He111 or Do 17's, which can only manage shallow dives at best, so they are effectively level bombers. Unless they come down to very low levels, they are not going to be able to hit anything, and if they do they would be very vulnerable to light flak of massed RN destroyers. All the air attacks and the German surface Navy would take their toll of course, but in the end, I don't think they would do near enough damage to even slow the RN. Using the pacific war as a model, the USN was able to destroy small, fast moving task forces the Japanese tried to use similar tactics. It lead to long running, battles, with huge # of sorties taking to sink the few ships present (my recollection is close to a thousand sorties for a 10 ship task force). Given the distances invloved, the RN is certainly going to be able to get a few ships through in even the most optimistic esitmates of German effectiveness. At worse, a lot of destroyers would make it into the area that the German supplies are coiming. The German plans all call for large minefuelds, but since the per-war stocks had all been expended during 1939, I find the idea somewhat optimisitc, and not very realistic.

The invasion fleet itself was intended to be mostly unpowered barges. A few power vessels, mostly improvised would tow the rest across the channel. The attackers would be moving very slowly, and not many ships would be doing most of the work. It almost ensures that the British are ready and waiting for them on the beach, and any RAF bombers would also be called into action, if not during the day, at night bombing french supply ports. The Rhine barges used where very unseaworthy, and any amount of heavy seas likely would cause all kinds of problems to the attackers. A few RN destroyers, if they got in, would be able to ram, shoot and swamp with their wakes a large portion of the invasion fleet very quickly. Given the vast quantities of supplies needed to supply even a single division, something like 500 tons of ammo for each division, plus fuel, food, more weapons, and replacements, it would me almost impossible to keep an invasion supplied if the RN shot up many of the barges. Air supply would be an option, but in Norway and Holland a considerable # of Ju 52 had been lost, and they cannot carry many tons of material per sortie, plus you have to carry in a large amout of the fuel to refill the tanks to fly back.

In short, while the Luftwaffe and Kriegsmarine would cause a heavy losses to the RN, it was simply beyond Germany's means to carry out a cross channel invasion. This is especially true that the luftwaffe never was able to actually defeat the RAF, but drive them to near the breaking point. It would have easily been possible for the RN to force the channel and shoot up any armada of supply barges bring over an attacking force or the follow up supplies.

[Tiornu]

"Dive bombers are fairly effective against ships, but most German bombers are He111 or Do 17's, which can only manage shallow dives at best, so they are effectively level bombers."
The LW had done rather poorly at Dunkerque. The anti-ship capability we associate with Stukas in the Med had not yet developed.

"The German plans all call for large minefuelds, but since the per-war stocks had all been expended during 1939, I find the idea somewhat optimisitc, and not very realistic."
Yes, definitely, the mine factor would way heavily in favor of the British, not the Germans.

"Why not attempt to concentrate the Kriegsmarine surface fleet and try to force an engagement with the Royal Navy?"
Exactly. You don't normally want to make it easier for the enemy to destroy you.

[Walter_Warlimont]

(1) Let's assume that Germany is able to gain air superiority over the Channel and Southern England in summer/autumn of 1940.

(How would the Luftwaffe manage to do this & not stop their bombing campaign of London?)

(2) Germany goes ahead with Operation Sea Lion, involving the use of virtually all of the fallschirmjaeger and glider forces, backed up by amphibious landings using every craft Germany could scrape up - let's say all told a couple of division-equivalents of airborne troops and a couple more divisions of infantry as an initial landing force in the Dover area, with obviously more to come, both shipped in and flown in.

(How do you propose to do this without ports to use & airfields to land your planes on?)

(3) Would the Royal Navy have been able to, even in the face of the Luftwaffe, disrupt the landings to such an extent the invasion had to be abandoned?

(Probably within 3 days, if not less.)

(4) I think that it could, and I'm envisioning something along the following lines:
The Home Fleet sorties from Scapa Flow, and sails down the coast of England under friendly air cover.

(The only problem is, the Home Fleet based @ Scapa Flow will not be involved unless the Germans put capital ships of their own into the fray.)

(5) The operation is timed such that the RN does not enter German aircover in the daylight, and much of the voyage to the Channel can be done under cover of darkness when the Luftwaffe cannot operate against it.

(Upon learning of any incursion by the Royal Navy from Scapa Flow, Luftflotte 5 from Norway would have been dispatched to attack them even if it was at night & they would have continued harassing them all the way to the channel causing them to burn much needed fuel & to waste much needed ammo that they would need later, whereby causing them to return to a port somewhere to replinish their stores before comitting to any incursion in the channel.

Also, there would no doubt be various intercepts of the Scapa Flow Fleet by German Torpedo Boats, Schnell-Boats & U-Boats using hit & run tactics.)

(6) The RAF sorties every last fighter in its inventory to put an air umbrella over the fleet in the Channel.

(If Dowing would even allow such a thing to happen, then that would leave London unprotected during the German bombing missions that have yet to be lifted.)

(7) forcing the Luftwaffe to first deal with the remainder of the RAF, while the Royal Navy, with something like 6 BBs and several dozen cruisers and destroyers mops up the Kriegsmarine and especially any large transports in the Channel.

(Again, British Capital Ships will not get involved unless there is an appearance made up of German Capital Ships in the area.)

(8) While obviously a suicide operation, it would only have to succeed in wiping out a good chunk of Germany's sea transport capability, which was extremely limited already, in order to force Sea Lion to be abandoned (along with the troops already landed in England).

(A suicide mission for who?)

(9) Would that have been feasible?

(Anything is feasible given the right type of planning & time to implement those plans.)

(10) I'm certain it would at least have been attempted, and it seems to me that the RN was large enough to at least have some chance at destroying the invasion.

(The Royal Navy could have stopped the invasion using only their Destroyer forces that were in the area.)

[Walter_Warlimont]

I don't believe the RN intended to use its major units against an invasion. Instead you'd see sloops, patrol vessels, trawlers, motor launches, and the like.

For the most part this is true, even though there would be several Destroyers & a few Light Cruisers to contend with as well.

[Walter_Warlimont]

IRRC, Operation Sealion would only be launched when the Royal Navy was destroyed.

Unfortunately, this simply was not the case at all, as it would have been impossible for Germany at any time during World War II to completely destroy the Royal Navy.

Operation Sealion was the invasion of Britain... what prevented the Germans from launching their navy (To land on British shores) was the British RAF and Royal Navy.

Yes, according to Churchill & other authors, what prevented the Germans from commencing with Operation Sealion was the RAF.

But according to the author Derek Robinson & a few others, it was the Royal Navy.

If the Luftwaffe takes out the RAF, they Gain air dominance.

Maybe with someone else besides Goring in charge of the Luftwaffe, the complete destruction of the RAF might have been a possibility, but only under completely different circumstances such as not diverting from bombing the airfields, aerodromes, radar stations, etc, to bombing London instead.

If the Luftwaffe takes out the Royal Navy, then the Kriegsmarine gains naval-sea dominance. INVASION!

I think the Luftwaffe would have needed about 5,000 more planes to have made that a reality.

But this didn't happen, and that was the idea, was it not?

To a degree, but not so extreme as to what you are suggesting.

So the Royal Navy could not exactly have disrupted Operation Sealion, because the idea was to destroy that.

But since there was no feasible way to destroy the Royal Navy outright, an intervention on their part would have eventually been forthcoming, if not immediately to some degree on that first day.

(or) Are you asking, if RAF was destroyed and it was the Royal Navy against Luftwaffe and Kriegsmarine. Without air cover and dominace, the British would have a difficult time. Even though the British navy outmatched and outgunned the Kriegsmarine without the RAF, the Luftwaffe would have somewhat easy targets.

If the RAF was completely wiped out, it is highly likely that the Royal Navy in desperation would have comitted every available ship to stopping the Invasion & even despite being attacked by all available German Warships & Luftwaffe aircraft, the invasion would still have been defeated eventually.

[Andreas]

You are being ridiculous. This has been shown a few times already. The list of ships stationed at the responsible commands has been given as well. Defensive plans are outlined in the literature, e.g. Fleming.

All the best

Andreas

Well, I can only mirror yourself. Prove it...!!

According to the British Admiralty, to oppose SEA LION, “the action of the navy’s light forces (patrol boats, destroyers, and some cruisers) against enemy transports would be limited to the range of air cover provided by Fighter Command.” The battleships and heavy cruisers would remain out of the range of German aircraft, 24 hours away in northern ports, until the actual beach assault had commenced. (19, 148).

They are quoting Overy, Richard, The Battle of Britain: The Myth and the Reality, New York: W.W. Norton & Company, 2000, p. 148

At the beginning of September the Admiralty had disposed sixty-seven (plus six cruisers) for immediate response to an invasion alarm. The first warning of the invasion’s sailing would come, it was hoped, from RAF reconnaissance over the assembly ports. But in case – as was likely – the Germans waited until after dark before commencing their 12-hour[2] toil across to England, the Royal Navy had a pool of 700 armed patrol craft (requisitioned motor yachts and trawlers) of whom around 200 were on picket duty “off the north coast of France”[3] every night. So, owing to either the air reconnaissance or the trip-wire patrols, there was a high likelihood that the German invasion armadas would have found British destroyers[4] between them and their intended landing-beaches when they approached on the morning of D-Day. As well as torpedoes and guns, each destroyer carried 40 depth-charges filled with 600-800lbs of Amatol (depending on Mk) which could have demolished the tows of wallowing barges packed with soldiers and horses.

The second tranche of RN interventions would have been the thirty-four corvettes and sloops, and the MTBs, employed on East Coast and Channel convoy routes. Then, within twenty-four hours of the alert, the cruisers and capital units of the Home Fleet would have started to arrive from the far north and west. 165 minesweepers of varying pedigree were at hand to maintain swept channels. Finally, many of the thirty-five submarines based in home waters would have headed for the Channel to disrupt the shuttling back and forth of barges required by the German build-up for the next ten days.

Friday, 13 September

Battleship NELSON, battlecruiser HOOD, anti-aircraft cruisers NAIAD and BONAVENTURE, and destroyersKASHMIR, KIPLING, ZULU, SIKH, SOMALI (D.6), and ESKIMO were ordered from Scapa Flow at 0700 to Rosyth for anti invasion duties.

These ships departed Scapa Flow on the 13th and were joined at sea by destroyers JACKAL and ELECTRA, after refuelling at Scapa Flow.

Anti-aircraft cruiser CAIRO joined off Noss Head.

The British force arrived at Rosyth that same day.

This force joined battleship RODNEY, which had arrived at Rosyth on 25 August. Destroyers COSSACK and MAORI had also arrived at Rosyth on 25 August from other duties.

Destroyers MATABELE, ASHANTI, TARTAR, and PUNJABI had arrived on the 11th.

Destroyer BEDOUIN was undocked from the Scapa Flow floating dock at 1600/15th and proceeded to Rosyth at 1945 on the 15th.

On 16 September, anti-aircraft cruiser CAIRO returned to Scapa Flow for convoy anti-aircraft protection duties.

Saturday, 14 September

Battleship REVENGE and light cruiser EMERALD departed the Clyde to come under the command of Western Approaches.

The ships were escorted from the Clyde by destroyers MACKAY, WESTCOTT, SCIMITAR, and SKATE.

Battleship REVENGE arrived at Plymouth on the 15th.

All of this has been posted before I believe.

All the best

Andreas

[Andreas]

Andy H has helpfully posted the Dover and Portsmouth Command lists for 15 September 1940:

Dover Command

Portsmouth Command

Some information on the defense of the south-east can be found here:

http://forum.axishistory.com/viewtopic.php?t=84742

All the best

Andreas

[Jon G.]

A number of off-topic posts were removed by me.

Everybody, please try sticking to the topic and refrain from making personal comments about other forum members simply because you disagree with them. Also, try keeping this discussion on the high level it started at - use data and not insults to dispute points made by other posters.

Please file complaints over other posters by PM. Do not post your complaints here. Thank you.

Jon, moderator.

[Gooner1]

From Dover Command War Diary

14/09/40 'Boom Defence Vessel "Falconet" and two drifters laid one mile of "Sausage net" to Eastward of Dungeness. This being the commencement of a second line of this form of obstruction between that point and Folkestone.

By 30th September this second line was almost complete but bad weather had caused some breaks in the first. The booms were between 1/2 mile and a mile offshore.

[Gooner1]

Found some details for the Counter Invasion Methods in Dover Command.
This is dated 30th June 1940.

NAVAL MEASURES.

2. - The detailed measures are laid down in Dover Operation "Napoleon".
These are broadly:-

(a) Destroyer patrols in the Channel, to intercept and engage the enemy at sea, and to support the small craft (b) and (c) below;

(b) Listening patrols of asdic trawlers about 4 miles off-shore to detect the approach of the enemy, to report and attack him;

(c) Inshore patrols of drifters and motor-boats to report and attack the enemy.


3. The methods of reporting the enemy, both by simple firework signal to our forces ashore, and by R/T or W/T to the Flag Officer Commanding Dover.



As of 21st September 1940 to meet the possibility of invasion Dover forces consisted of three Divisions of 4 AntiSubmarine and MineSweeping Trawlers, one Division of 5 "LL" Trawlers, three Divisions of 4 Auxiliary Patrol Drifters and one Division of 3 Auxiliary Patrol Drifters.

In addition one or two Divisions of 4 Destroyers would normally be on patrol.

[RichTO90]

Thank You Andreas, those are some very impressive lists. I'm glad you took the time to provide the links. I must say, that there are a LOT of ships of various sizes in both Dover & Portsmouth Command.

I am curious though, if it would be possible to find out where all of those ships were 10 days later on September 25th, 1940?

Actually the small craft dispositions did not appear to vary much over time once established at the ports. The major changes over time were to strength of the harbor flotillas and their armament. At this time most of the patrol craft (harbor launches and drifters) were armed with .303 Lewis guns and the occasional .50 machine gun. The larger patrol trawlers were armed with machineguns and very occasionally a 2-pdr single-mount 'Pom-Pom' and rarely a 3-inch 12 cwt gun. The ASW and minesweeping trawlers were somewhat more heavily armed, but throughout this period coastal forces were being heavily augmented as new craft and weapons became available, eventually all the older harbor craft were replaced by the purpose-built HDML (Harbor Defence Motor Launch) armed with .303 and .50 caliber machineguns and a 20mm Polsten and the existing trawlers were more heavily armed with 20mm and 40mm guns as well as some 3-inch as well ass augmented by the American-built BYMS (British Yard Minesweeper). Having looked at some of the strength committed to NEPTUNE from Coastal Forces I can attest that certainly by 1944 Coastal Forces was very powerful indeed.

So you can more or less treat these strengths as a starting point and assume they increased from there. For the larger vessels there was considerable movement from port to port and flotilla strengths constantly were changing as new builds went into commission and other vessles were lost or damaged. The Admiralty Red List was compiled from the movement orders and station changes and seems to have been published roughly fortnightly?