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What if the Germans used u-boats as a supply vessels in Sealion

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  • Originally posted by leopold View Post
    Admiral Scheer could have been prepared in time if given enough prioirity.
    Bismark and Prinz Eugene as well.
    If the British could send Prinz of Wales on mission with workers still fitting her up than the same could be done for the above ships by the Germans.
    The timeline of preparing a major surface unit is long and complex. Germany did not have the large existing pool of already trained men that the RN had. The first day that Bismarck left Hamburg was Sept 15. The inexperience of the crew showed when the ship collided with a tugboat on the Elbe. Then when they were attacked by air, it failed to achieve a single hit with its guns.

    The Bismarck's batteries were not even calibrated until about Sept 21. The 10.5 m rangefinders were still being sorted out during Oct-Nov, and their anti-aircraft battery was still imcomplete. The Bismarck was not able to undertake their first artillery practice until mid-November.

    The Bismarck was not even ready to steam at top speed until Oct.23. As of Mar 8, the crew was still inexperienced enough to run aground. The ship did not even received its first two aircraft until Mar 15, even then, its equipment and roster were still not complete.
    Last edited by Salinator; 27 Nov 06, 22:35.
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    • Robocraufurd...thanks for the link & book title.

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      • Originally posted by leopold View Post
        Admiral Scheer could have been prepared in time if given enough prioirity.
        Bismark and Prinz Eugene as well.
        If the British could send Prinz of Wales on mission with workers still fitting her up than the same could be done for the above ships by the Germans.
        As Salinator has already explained, it takes a lot to prepare a warship for sea service. Bismarck was clearly not ready, and nor was Prinz Eugen. The Prinz Eugen only started TRAINING excercises in August, so would not be ready for a September cruise.

        Admiral Scheer was in the Baltic and sufferred minor engine problems that were quickly rectified allowing her to depart for a cruise in LATE October.

        Therefore, only 1 heavy cruiser and 2 light cruisers were available.

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        • Originally posted by salinator View Post
          The timeline of preparing a major surface unit is long and complex. Germany did not have the large existing pool of already trained men that the RN had. The first day that Bismarck left Hamburg was Sept 15. The inexperience of the crew showed when the ship collided with a tugboat on the Elbe. Then when they were attacked by air, it failed to achieve a single hit with its guns.

          The Bismarck's batteries were not even calibrated until about Sept 21. The 10.5 m rangefinders were still being sorted out during Oct-Nov, and their anti-aircraft battery was still imcomplete. The Bismarck was not able to undertake their first artillery practice until mid-November.

          The Bismarck was not even ready to steam at top speed until Oct.23. As of Mar 8, the crew was still inexperienced enough to run aground. The ship did not even received its first two aircraft until Mar 15, even then, its equipment and roster were still not complete.
          If we assume theoretically that for the sake of the Sealion operation the Kriegsmarine sends them (Bismark and Prinz Eugene+ accompanying heavy cruiser 2 light cruisers) to Norwegian fijords and they make a circle in the general direction of Denmark straits and back using radar to avoid any contact - how much of the RN forces could that engage?
          Would the risk of being intercepted and sunk be too high??
          If you believe, you receive.
          If you doubt, you go without.

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          • Originally posted by robcraufurd View Post
            On the 15th September, while still fitting out, Bismarck is buzzed by British aircraft. Her AA guns fire over 300 shots without registering a single hit. Ironically, if you chose to send her out before she's finished, like the Prince of Wales, she may well have suffered the same fate.
            .
            Since it was sunk anyway not much after that, my interest lies in wheather it could have provided a long enough distraction to ease the invasion.

            Originally posted by robcraufurd View Post
            There's quite a big difference between blitzkrieg warfare and assaults against beaches and fixed defences.
            True, however the numbers I presented were minimal. I have the general feeling that more than 15 guys can be stuffed in VII type u-boat at least for a short trip across the channel.
            (Proportionaly more on the II type)
            Originally posted by robcraufurd View Post
            Don't underestimate the power of people fighting for their homes. The Russian militias in Stalingrad impose a heavy toll on the Germans, albeit at a high price to themselves.
            That's a valid point.
            However let's not forget that the Dutch, Belgian and French didn't put up too much of a fight.
            Obviously british would be tougher than that, considering their national character and all, but I'm somewhat sceptical that the comparison with the Russians is valid.
            The reasons are these:
            1) The Russians initially didn't put up much of a fight either - it took more than an year for the partisan movement to start seriously bugging the Germans.
            2) The russian militias in Stalingrad , Leningrad etc. were mostly motivated by ruthless fanatics called political officers - those were true nutcakes! They were brainwashed for years and had kamikadze mentality to say the least.
            (I have personaly met some of those and can vouch for them)
            While there was obviously a strong patriotism in the russian soldiers and citizens, their main motivation was FEAR (by the hands of nkvd and the likes) - The british didn't have nor totalitarian society nor such skeleton of fanatics (Churchil aside).
            3) The british were not attacked on their home land for hundreds of years - there surely would have been some serious shock and desire to 'make peace' - look at the german ocupation of the channel islands - there wasn't any resistance there at all, not a single shot.


            Originally posted by robcraufurd View Post
            Nice to see that your U-Boats are able to land so much artillery that the invasion force can not only out-shoot the British defenders, but also have spare guns to defend the Channel.
            After the initial landings the artilery would have to be behind the front anyway - so it can shoot in both directions. Latter when the invasion starts advancing inland part of the artillery that was supplied meanwhile will have to be kept to protect a 10 km of shore from sea attacks - it should have only enough power to drive enemy off the coast and score occasional trawler sink.

            Originally posted by robcraufurd View Post
            Nice also to see that the Luftwaffe, which is roughly numerically equal to the RAF, is able to fly air support for the pocket AND have time to perform anti-ship patrols in the Channel.
            Don't forget that those things would happen in succession - first land force captures some airfields, then those are used for refueling 109E for shifting the balance of the air battle - and only then the LW starts more massively to fly JU 52 and to disperse unprotected bomber attacks to the RN in the channel.
            The same general principle as the Allies used when capturing Sicily - air superiority is achieved by capturing local airfields.

            Originally posted by robcraufurd View Post
            It's a good job the British haven't got any forces who might be able to sabotage airfields and equipment, isn't it? Otherwise, your flow of supplies might be disrupted. Also, it's interesting to note that airborne resupply for Crete only works because the RAF have decamped to Alexandria- the equivalent of them retreating from Kent to Glasgow.
            These are interesting questions, but before moving to them I would like to know - do you still consider the submarine supply line impossible? (And if so then why?)
            If you believe, you receive.
            If you doubt, you go without.

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            • Originally posted by leopold View Post
              If we assume theoretically that for the sake of the Sealion operation the Kriegsmarine sends them (Bismark and Prinz Eugene+ accompanying heavy cruiser 2 light cruisers) to Norwegian fijords and they make a circle in the general direction of Denmark straits and back using radar to avoid any contact - how much of the RN forces could that engage?
              Would the risk of being intercepted and sunk be too high??
              Well, at my count there are 4 battleships and a battlecruiser available by September 1940: Revenge, Nelson, Rodney, and of course the ill-fated Hood. Other ships that might have been available are Renown, Repulse and Royal Sovereign- I'm not sure whether they're on convoy duty or not. If there was an urgent need, the French battleship Paris and various other training ships might have been able to sail out, although with wildly varying degrees of efficiency. King George V would also probably have been accelerated- as it is, she commissions in December.

              Had the Germans dispatched their entire force of capital ships to Norway, the British probably would have left a force to match it- let's say for argument four capital ships, with attending cruisers. That still leaves a large number of cruisers and a single capital ship to clear the Channel, where the Germans have nothing stronger than destroyers.

              As for the risks of being sunk: it's debateable. A short cruise up and down the Axis side of the North sea isn't beyond the realms of possibility: it might have given the crew some sea experience. Since they're only sailing to Norway and back, rather than trying to break out into the Atlantic or support the invasion, nothing much would have happened. Unless, of course the British tried a submarine attack against which the Germans would have been poorly protected, since all their destroyers are protecting the invasion.
              Fere libenter homines id quod volunt credunt

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              • Originally posted by leopold View Post
                Since it was sunk anyway not much after that, my interest lies in wheather it could have provided a long enough distraction to ease the invasion.
                No. The British simply have too many capital ships. Besides, cruisers and destroyers alone would have massively out-numbered the German naval forces in the Channel.

                True, however the numbers I presented were minimal. I have the general feeling that more than 15 guys can be stuffed in VII type u-boat at least for a short trip across the channel.
                (Proportionaly more on the II type)
                You still have the problem that it's not a regular flow of reinforcements. If the U-Boats are scattered in the Channel, or if they're forced to divert to another beach, you simply can't guarantee that the reinforcements will get to where they're needed. Furthermore, if these reinforcements are the same men rowing in to the beach, then I'm even more sceptical about their ability to deliver the cargo. Rowing isn't as easy as it looks, especially in heavy seas.

                That's a valid point.
                However let's not forget that the Dutch, Belgian and French didn't put up too much of a fight.
                The continental countries are essentially overwhelmed by the speed of blitzkrieg- that's the whole point of the strategy. The British public have been deluged with instructions on what to do when the invasion comes: pamphlets, posters, everything. Furthermore, the British would have had plenty of warning that the invasion had been launched, provided by the 200 motor boats stationed off the coast of France every night.

                They were brainwashed for years and had kamikadze mentality to say the least.
                (I have personaly met some of those and can vouch for them)
                Had the invasion been launched, Churchill was planning to use the slogan "You can always take one with you."

                While there was obviously a strong patriotism in the russian soldiers and citizens, their main motivation was FEAR (by the hands of nkvd and the likes) - The british didn't have nor totalitarian society nor such skeleton of fanatics (Churchil aside).
                3) The british were not attacked on their home land for hundreds of years - there surely would have been some serious shock and desire to 'make peace' - look at the german ocupation of the channel islands - there wasn't any resistance there at all, not a single shot.
                It probably hasn't occurred to you, but people fighting to protect their liberties from a totalitarian state may be capable of just as much as those who are forced into the firing line by fear. We all remember the Spartan defence at Thermopylae: what we forget is that the Athenians evacuate their entire city just to defeat the Persians. The fact that Britain hasn't been invaded for years is irrelevant- between 35 and 50 per cent of the Home Guard are veterans of WWII, so no shortage of combat experience there. Furthermore, I'd imagine nations who are frequently invaded- the Russians, for example- to become relatively tolerant of such events, especially in the border areas. For nations who have no such history, an invasion would be even more of an outrage.

                The reason there isn't a shot fired in the invasion of the Channel Islands is that the British have already decided they're not strategically important. They evacuate those who want to leave, and leave them for the Germans. The result is that the Germans station thousands of troops there, as well as diverting 10% of the steel and concrete from the Atlantic Wall to help defend islands that the Allies simply bypass on D-Day.

                After the initial landings the artilery would have to be behind the front anyway - so it can shoot in both directions. Latter when the invasion starts advancing inland part of the artillery that was supplied meanwhile will have to be kept to protect a 10 km of shore from sea attacks - it should have only enough power to drive enemy off the coast and score occasional trawler sink.
                But it can't shoot at both directions at the same time, can it? Or would the Germans abort their attack so the artillery that's shelling British defences can wheel around and take pot-shots at a single destroyer that's cruising down the South Coast? You've now committed yourself to stationing a proportion of your artillery where it can do absolutely no good to the invasion- not a good idea when you're facing strong defences. Imagine if the British on the Somme had been forced to keep 10% of their artillery behind the lines and out of action. I'm also sceptical about the ability of forward observers to calculate ranges well enough to hit a moving target at distance- Spike Milligan recounts a story where one of his officers managed to land a shell on a German tank, although apparently it wasn't the one he was aiming at.

                Don't forget that those things would happen in succession - first land force captures some airfields, then those are used for refueling 109E for shifting the balance of the air battle - and only then the LW starts more massively to fly JU 52 and to disperse unprotected bomber attacks to the RN in the channel.
                The same general principle as the Allies used when capturing Sicily - air superiority is achieved by capturing local airfields.
                The Royal Navy isn't going to be waiting patiently for the Germans to win the air war before they start sinking U-Boats, shelling the beachheads and swamping reinforcement barges. Either you split your resources, giving the RAF the chance to defeat you in the skies over the pocket, or you accept that the Royal Navy are going to cause havoc in the Channel. If you are using the airfields for fighter missions, that means you haven't got a massive reinforcement effort going immediately: how do you hope to push inland? In Sicily, meanwhile, the commander of Luftflotte 2 has shifted most of his resources to defend Sardinia, thanks to the success of Operation Mincemeat. The task facing the Germans in 1940 will be much more difficult.

                These are interesting questions, but before moving to them I would like to know - do you still consider the submarine supply line impossible? (And if so then why?)
                Yes, the submarine supply line is impossible. Not only are submarines not designed for mass resupply, but the submarine supply suffers from exactly the same problem as the rest of Operation Sealion. The Germans are simply too weak navally to invade Britain, and air superiority alone is not enough to make up for that fact. If you can't guarantee that the initial wave of invasion will be protected, let alone the resupply effort, then there's absolutely no chance of success. Submarine resupply is a perfectly good idea for small commando forces, but not for a main theatre of war.

                It's tempting to underestimate Overlord, but it really is an incredible effort. Initial planning for an invasion starts in 1942; the Allies have both naval and air superiority; they land in an area the Germans aren't expecting, at a time when they're hard pressed on the Eastern Front; they have specially designed tanks, ships and mobile harbours. However, the fact that Eisenhower's still so unsure about its success that he prepares two speeches should show you that Sealion belongs far too much to the "cross your fingers and hope for the best" school of warfare to be redeemed by a single improvement to the resupply system.
                Fere libenter homines id quod volunt credunt

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                • "After the initial landings the artilery would have to be behind the front anyway - so it can shoot in both directions. Latter when the invasion starts advancing inland part of the artillery that was supplied meanwhile will have to be kept to protect a 10 km of shore from sea attacks - it should have only enough power to drive enemy off the coast and score occasional trawler sink."

                  From a career in the artillery I can judge this to be utterly impractical. A great way to make the battle easier for the British and make the German artillery less effective.

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                  • Ok, here I have an improvement to the initial proposal, which will remove the
                    need for rope dragging in the final stages of the container delivery.

                    The tidal level difference in the channel is ~6 meter.
                    The u-boat draft - 4.5 meter.

                    Therefore if the u-boat captain gets familiar with the coast depth he can deliver the cargo during high tide close enough to the coast then drop it's anchor and swim back.
                    After several hours during low tide the cargo will lie on the beach, approachable by foot - no need for ropes nor dragging.
                    The navigational precision can be improved by placing lights at predetermined places on the english and french side of the channel. (by simple triangulation)
                    If doable this improvement finilizes the cargo delivery sequence by making it almost completely undetectable until the very last moment when cargo is allready on the other side.

                    There are 2 additional thoughts:
                    1)- could a destroyer use it's hydrophones properly, while the water around it is being shelled? From the resources I found this seems like a serious problem.
                    2) What happens to the asdic readings if the sub lies on the seabed at 45 meter and switches off engines?
                    If I understand the 1940 asdic workings correctly they were not very good at distinguishing metal from rock.
                    3) What happend to the asdic when the sub was submerged to minimal periscope level? (just bellow the surface) From what I understend the sonar was useles in such situation.
                    If you believe, you receive.
                    If you doubt, you go without.

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                    • Originally posted by robcraufurd View Post
                      Well, at my count there are 4 battleships and a battlecruiser available by September 1940: Revenge, Nelson, Rodney, and of course the ill-fated Hood. Other ships that might have been available are Renown, Repulse and Royal Sovereign- I'm not sure whether they're on convoy duty or not.

                      Don't forget the Royal Oak as U47 is practicing dropping off cargo containers and familiarizing it's self with the English channel!
                      Wolster

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                      • Originally posted by Wolster View Post
                        Don't forget the Royal Oak as U47 is practicing dropping off cargo containers and familiarizing it's self with the English channel!
                        Are you joking? Or can't you distinguish 1939 from 1940?!?
                        If you believe, you receive.
                        If you doubt, you go without.

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                        • Originally posted by leopold View Post
                          Are you joking? Or can't you distinguish 1939 from 1940?!?
                          No, no joke. Do you presume this whole plan is going to be thought up on the day before the invasion??

                          Surely it will need to be planned, practiced and the U-boats readied for towing the containers? The containers themselves need to be constructed, transported to the French sea ports. The U-Boat commanders will need to become familiar with the English channel and how the containers affect the handling. Ditching drills need to be practiced. Gunther Prien would have certainly been involved as an experienced skipper.

                          How long are you giving them for this? September '39 to September '40 seems reasonable, maybe a little tight even.

                          Therefore an operation such as sneaking into Scapa Flow would never have happened and the Royal Oak is ready to repel the invasion.
                          Wolster

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                          • Originally posted by Wolster View Post
                            Therefore an operation such as sneaking into Scapa Flow would never have happened and the Royal Oak is ready to repel the invasion.
                            To be honest, Royal Oak would probably have gone to the Mediterranean or ended up on convoy duty. She's just a little bit too slow to be a front-line ship any more, although she might have freed up a quicker ship to be stationed with the Home Fleet.

                            Originally posted by leopold View Post
                            Therefore if the u-boat captain gets familiar with the coast depth he can deliver the cargo during high tide close enough to the coast then drop it's anchor and swim back.
                            And rip out his bottom on any rocks that might be there: Type IIs, after all, don't have any watertight compartments. Of course, since it's so shallow, at least his crew might survive. You've also just restricted your timings even more: as soon as the British have word from the French Resistance that the Germans are using U-Boats as supply vessels, and the first reconnaissance plane notices Germans unloading cargo in this way, they'll be able to predict with startling accuracy when the U-Boats will be present.

                            The navigational precision can be improved by placing lights at predetermined places on the english and french side of the channel. (by simple triangulation)
                            If doable this improvement finilizes the cargo delivery sequence by making it almost completely undetectable until the very last moment when cargo is allready on the other side.
                            Completely undetectable? You're putting lights on both sides of the Channel, lights which will have to be distinguishable from ordinary lights through a periscope from some distance. May as well hoist a giant flag saying "Cargo being dropped here, please don't investigate."

                            1)- could a destroyer use it's hydrophones properly, while the water around it is being shelled? From the resources I found this seems like a serious problem.
                            It also sounds like a serious problem for the sub, especially in the relatively shallow water that you propose they unload in.

                            2) What happens to the asdic readings if the sub lies on the seabed at 45 meter and switches off engines?
                            If I understand the 1940 asdic workings correctly they were not very good at distinguishing metal from rock.
                            The British estimate the position of the submarine and use depth-charges, hoping either to score a lucky hit or force the submarine into fleeing. If you're planning on stopping every time the British detect you, however, considering that the detection range of ASDIC is 2km, you're not going to go very far.

                            3) What happend to the asdic when the sub was submerged to minimal periscope level? (just bellow the surface) From what I understend the sonar was useles in such situation.
                            Well, since the range of the Type II is about 70km submerged, and the speed drops to 4 knots, it means you're going to double the time of your trip and vastly increase the time spent refilling air tanks and recharging batteries. If you only submerge when you see something that could be an ASW vessel, you run the risk of being shelled- if not by the British, then by stray German artillery shots.
                            Last edited by robcraufurd; 29 Nov 06, 16:12.
                            Fere libenter homines id quod volunt credunt

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                            • Originally posted by Wolster View Post
                              No, no joke. Do you presume this whole plan is going to be thought up on the day before the invasion??

                              Surely it will need to be planned, practiced and the U-boats readied for towing the containers? The containers themselves need to be constructed, transported to the French sea ports. The U-Boat commanders will need to become familiar with the English channel and how the containers affect the handling. Ditching drills need to be practiced. Gunther Prien would have certainly been involved as an experienced skipper.

                              How long are you giving them for this? September '39 to September '40 seems reasonable, maybe a little tight even.

                              Therefore an operation such as sneaking into Scapa Flow would never have happened and the Royal Oak is ready to repel the invasion.
                              Ok, so you're not joking.

                              1) For the most part the containers will consist of allready available 20x1meter metal pipes. The process of construction will be very simple: - get pipe, smash one of it's sides closed, put a lid with bolts on the other side - container ready. Five of this clustered together will consist a sub's load.
                              2) As to the handling of the sub with the container drag - considering that the
                              u-boat commanders were the elite of the kriegsmarine, 2 months would be sufficient - besides they did know the channel -many of the submarine officers were WWI veterans.
                              If you believe, you receive.
                              If you doubt, you go without.

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                              • Do you realize what even STD schedule pipe weighs per foot?. You do not just "smash" metal pipe together it has to be "tapered" and forged that way. The other end then need a flange welded to the end and a blind bolted to it about 1000 lbs in weight. The 65' of pipe will need to be welded together from three 20' pieces and then the whole thing needs to be hydro-tested to see if the welds leak at various pressures.

                                Here is the specs for "STD" pipe, 38" diameter:
                                wall thickness - 0.375"
                                weight per foot - 150.69 lbs or 224.26 kg per metre.

                                20 meters (65') of pipe would weigh:

                                9800 lbs or just under 5 tons.
                                4485.2 kg or about 4.5 metric tonnes.

                                It's weight per volume far exceeds its diplacement capacity so this cylinder will simply,...sink.

                                Neutral bouyancy with this design is not possible.
                                The Purist

                                Words ought to be a little wild, for they are the assault of thoughts on the unthinking - John Maynard Keynes.

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