Seelöwe - German & British mining operations

[Bronsky]

Split from viewtopic.php?t=69066 by the moderator - Andreas

A good point was made by Rich at some earlier point on this thread, to the effect that the Axis simply didn't have the capability to lay the kind of minefields that the Sealion plan called for, even if it had had the mines.

Apologies if this has been covered before, and/or if this isn't the right sub-thread, here are some data points on the topic.

During WWI, Britain and France had decided to block the Dover straits by laying a minefield. The field included 4,000 British and 1,000 French mines.

For WWII, they decided to repeat the performance: between September 1939 and April 1940, the British alone laid some 8,000 mines. These successfully deterred U-boats from using the Channel after the losses of 3 subs in October.

Mine-laying speed: as part of their contribution to that field, three French minelayers (Pollux, Infatigable, Sioux) laid 1,095 mines between 5 and 27 September 1939, so 365 per ship over a period of 3 weeks. Pollux came back to add another 255 during February 1940.

Part of the German mine-laying effort has been covered in these threads (searching "Minesperren" should help): it seems that German minelayers could lay 200 mines per night and per ship (though it's unclear how often they could do that).

Air-dropped mines require specialized training: bombers found it difficult to find their targets over land, finding the right location on an expanse of otherwise unremarkable sea is very hard. So the Luftwaffe would scatter mines all over the place, including in the path of the Seelowe convoys. According to Ruge' "Der Seekrieg", the Luftwaffe had preferred to develop its own model of sea mine rather than go with the Kriegsmarine design. That model had the advantage that it could be dropped without a parachute, at the cost of a largely worthless fuse. British minesweepers had no problems with it. Still according to Ruge, planned production of air-dropped sea mines was 50,000 pieces per year, though I'd be surprised if that target had been achieved.

Some rates of laying air-dropped mines: 11/39 (first month): 68. 12/39: 0 (bad weather). 8/40: 600. 9/40 & 10/40: 1,300. 11/40: 2,400 in November. 12/40: 800 (? not sure about that one). Sources: Ruge for 1939, either Hooton or the 1948 RAF history of the Luftwaffe for the 1940 figures.

In "Germany in the Second World War", vol 5 p.637 (I forget if I took this from the German edition or the English translation, so page number might be off), German fleet strength as of 1 May 1940 is listed as having 43 minesweepers 2,985 torpedoes and 12,663 mines & booms.

Regarding planned German mine barriers, the largest fields were B2 and B3, located in mid-Channel between Dieppe and Beachy Head. They were to include 2,400 EMG moored contact mines. Compare this to the almost 10,000 mines in the Allied minefield between Dover and Calais (a shorter distance).

Total of all planned German minefields was about 5,600 mines. The total German stockpile of mines included roughly 4,000 EMGs, a smaller number of EMC and EMD mines (similar characteristics), and some 4,000 UMA submarine-laid anti-submarine contact mines. No fields using the latter mines were planned.

Source for the German mines: Schenck, pp.330ish.

[Walter_Warlimont]

The LW had done rather poorly at Dunkerque. The anti-ship capability we associate with Stukas in the Med had not yet developed.

This is of course an opinion which I do not agree with. I think that the Luftwaffe, with their Stukas performed quite well, as is evidenced by the stories told by those who were at Dunkirk.

(The Miracle of Dunkirk, By: Walter Lord)

Yes, definitely, the mine factor would way heavily in favor of the British, not the Germans.

The Mine Barriers would have assisted the German Invasion Forces, but while not stopping the Royal Navy completely, those same Mine Barriers would have prevented them from entering en masse, the lanes that were being used by the Invasion Craft, until they could have been cleared away.

(No Source is Available, as That is Just Common Sense)

[LWD]

...

Yes, definitely, the mine factor would way heavily in favor of the British, not the Germans.

The Mine Barriers would have assisted the German Invasion Forces, but while not stopping the Royal Navy completely, those same Mine Barriers would have prevented them from entering en masse, the lanes that were being used by the Invasion Craft, until they could have been cleared away.

(No Source is Available, as That is Just Common Sense)

There are a number of things to consider here.
1) The who can lay the mines the fastest? The impression I get from the discussion above is that it is the British.

2) If the Germans put up mine barriers the British can concentrate their mining effort between these barriers. If the RN gets inside them they also restrict the ability of the Germans to disengage.

3) If the British can figure out where to lay their mines or already have mines layed then these can be a real problem to the Germans.

4) AT least some of the British fields such as those around Dover or for that matter along most of the southern coast of interest may be covered by shore batteries.

5) Who can clear the mines the fastest? In the abscence of opposition this looks to be the British. The Germans are going to face shore batteries, the RN and the RAF while for the most part the British mine layers will face the LW with perhaps some KM opposition. If you will look through the following referance: http://www.maxwell.af.mil/au/afhra/numb ... 468155.pdf (it seams to be difficult to get to at times and may take considerable time to come up) there is a quote where the KM stating that they were behind schedule in their mine sweeping efforts due to a lack of LW support.

All in all it looks to me like mine warfare may not be all that much to the German's advantage. I think on one of these threads there were some numbers posted on the quantity of British mines on hand during this period and something about how they were being held for use vs Sea Lion but I'm not sure that was sourced.

[Walter_Warlimont]

You guys really have no clue as to the use of the "Mine Barriers". do you?

There were to have been "Mine Fields" layed at each end of the approaches to the channel granted, but these "Mine Barriers" were to form the lanes in which the Invasion Craft were to "Drive Through" for lack of a better term & if I remember correctly (Man I Hate Abbreviations) the mines in the "Mine Barriers" were to be placed at 10 meter intervals. (Wish I knew what that distance is in feet).

There were to be if I remember correctly 2 rows of mines in the "Mine Barriers" that formed the lanes on each side of each lane.

2 rows of mines..................................................................

Invasion Craft in the middle.................................................

2 rows of mines.................................................................

Invasion Craft in the middle................................................

2 rows of mines................................................................

Invasion Craft in the middle...............................................

2 rows of mines..............................................................

Etc,..............................................................................

[RichTO90]

You guys really have no clue as to the use of the "Mine Barriers". do you?

Yeah, I gotta say that's what it looks like. Of course you just proved you either have a lousy memory or are just making this up as you go along. Effectively the plan was to isolate the eastern entrance of the Channel between Dover and Calais, place a barrier Beachy Head to Fecamp, neatly isolating the two halves of the German invasion fleet from each other , and then placing two 'traplines' off Portsmouth and Darmouth. There was no effort to close off the western end of the Channel.

The barriers were:

SW 1, 2, 3, and 0 all laid in August and not really part of the Seelöwe plan, but usually counted as part of the plan. They were all laid parrallel to the French and Belgian coast running essentially from SW to NE, sequentially beginning with SW 3, mid-Channel, due east of the Thames estuary.

Planned barriers:
A1 and A2, two short parallel lines southeast of the Isle of Wight, running SW to NNE, roughly 15 and 30 kilometers long.

B1, 2, 3, and S were to be laid as a nearly continuous but somewhat overlapping line from Beachy Head S and then running SSE towards the French coast near Fecamp, roughly 100 kilometers in length. As such it would have neatly cut off all vessels from Cherbourg and Le Havre that were engaged in landing ops west of Beachy Head from being supported by friendly forces east of the barrier and vice versa.

C1, 1a, 2, 3, and S filling the space between Dover-Calais and SW 3. C1 ran roughly WSW to ENE for about 25 kilometers, starting about 15 kilometers NE of Dover. C1a apparently was planned as three parallel rows between Dover and Calais from nearly shore to shore, roughly 40 kilometers. C2 ran the same direction and length as an extension of C1 starting a few kilometers N of the E end of C1. And C3 was a 15 kilometer link between the end of C2 and SW3. CS was two parallel rows running E from Ramsgate about 20 kilometers. There were also a series of four 'V' fields with each leg about 5 kilometers long running parallel to the coast between Dunkirk and Ostend, apparently designed to keep the British from approaching those ports to closely.

D1 and D2 which were similar to A1 and 2, but running NNW to SSE offshore from Dartmouth.

All told, roughly 450 kilometers of mines. Now, given that they could lay perhaps 4,000 at most at a time (the T-Boot, V-Boot, and other such would lay theirs at the last moment during the assault close to the coast), then the density either would be miniscule 11-12 per kilometer or it would require a long time run-up to lay them....and even with the 12,000-odd actually available, including air-dropped the density at best would be perhaps 26 per kilometer. That isn't insignificant, but it means that basically only the Dover-Calais field was really close to a 'barrier' - if it could be laid and maintained.

Rohwer addresses the question, I translated a part of this a while ago, but am not going to again.

Die Lage der geplanten Sperren sind aus der Abbildung (oben) zu ersehen. Alle Sperren sollten in mehreren Reihen geworfen werden. Zusätzlich sollten Gebiete dicht unter der englischen Küste durch Schnellboote mit Minen verseucht werden. Auch die Verminung aus der Luft durch Flugzeuge der 9. Fliegerdivision wurde genau geplant.

Die Sperren SW1, SW2, SW3 und SW0, die im August geworfen wurden, standen in keinem direkten Zusammenhang mit »Seelöwe«, waren aber in die Planungen mit einbezogen. Am 31. August gingen auf der Sperre SW1 die britischen Zerstörer Esk und Ivanhoe verloren, der Zerstörer Express wurde schwer beschädigt. Die Wirkung dieses Verlustes auf britischer Seite war kaum zu unterschätzen. Allerdings nicht nur in demoralisierender Hinsicht. Die britschen Einheiten hatten nämlich ebenfalls den Auftrag, Minen zu werfen, um den Aufmarsch der Invasionsflotte zu stören. Es darf davon ausgegangen werden, dass mit Beginn der »Seelöwe«-Operation das Landungsgebiet innerhalb kürzester Zeit von englischer Seite vermint worden wäre, und dass deutsche Minensuch- und räumeinheiten dagegen nichts mehr hätten unternehmen können.

Im Gegensatz zu den anderen Teilstreitkräften bewertete das OKM den Wert der Minensperren daher überaus kritisch. Man wandte ein, dass die Sperren nur wirksam blieben, wenn eine Räumung von britischer Seite her verhindert werden konnte. Für diese Aufgabe konnten die eigenen Kräfte nur über einen langen Zeitraum hin verstärkt werden. Im Nachhinein ist festzustellen, dass die Räumung von Minensperren auf britischer wie auf deutscher Seite keine konkreten Planungen gab.

http://www.wlb-stuttgart.de/seekrieg/ks ... frames.htm

[RichTO90]

Rich, it's times like this you remind me so much of Leandros.

I can't read German.

What the heck are you doing in Germany then? Rear detachment for people in the sandbox?

Actually I translated part of this in an earlier thread. Basically it says that it was planned that all the barriers should be in multiple rows of mines....so multiply the 450-odd kilometers of barrier by X number of rows. Thats a LOT of mines and a lot of time to lay them.

It goes on to say that the mines in the SW barriers laid in August did sink two British destroyers and damge a third, which was great. But they suddenly realized that the British could just as easily lay mines to obstruct the German invasion fleet - if not more easily considering they could lay them close to a protected shore and that they had a heck of a lot more minelaying capability than the Germans did. The loss also alerted the British to the threat and the began to apply their not to insignificant minesweeping capability to the problem (that's my aside BTW). Rohwer then basically that was typical for the plan....they came up with an idea and suddenly realized they simply didn't have the assets the Britsih had to counter it so their threat wasn't really credible.

Or you could search out my original translation and read it.

Now I gotta go copy & paste 17 pictures of maps to support my position about the "Mine Barriers"

Why? The link I provided includes a map of the barrier plan and I also provided a rather nice summary of them? Your description was incorrect, either your memory or your source was badly flawed. Or maybe both?

It's days like this, I wish I had never left my mother's womb.

Thanks Rich, Thanks.

TANSTAAFL dude.

[Walter_Warlimont]

Rich, it's times like this you remind me so much of Leandros.

I can't read German.

What the heck are you doing in Germany then? Rear detachment for people in the sandbox?

Actually I translated part of this in an earlier thread. Basically it says that it was planned that all the barriers should be in multiple rows of mines....so multiply the 450-odd kilometers of barrier by X number of rows. Thats a LOT of mines and a lot of time to lay them.

It goes on to say that the mines in the SW barriers laid in August did sink two British destroyers and damge a third, which was great. But they suddenly realized that the British could just as easily lay mines to obstruct the German invasion fleet - if not more easily considering they could lay them close to a protected shore and that they had a heck of a lot more minelaying capability than the Germans did. The loss also alerted the British to the threat and the began to apply their not to insignificant minesweeping capability to the problem (that's my aside BTW). Rohwer then basically that was typical for the plan....they came up with an idea and suddenly realized they simply didn't have the assets the Britsih had to counter it so their threat wasn't really credible.

Or you could search out my original translation and read it.

Now I gotta go copy & paste 17 pictures of maps to support my position about the "Mine Barriers"

Why? The link I provided includes a map of the barrier plan and I also provided a rather nice summary of them? Your description was incorrect, either your memory or your source was badly flawed. Or maybe both?

It's days like this, I wish I had never left my mother's womb.

Thanks Rich, Thanks.

TANSTAAFL dude.

Actually, the British DID in fact lay a Mine barrier of their own along the beachline in front of the very beaches where the invasion craft were to approach.

It's effectiveness however would have been anyones guess.

TANSTAAFL????????

No Comprende Mon Ami.

[Bronsky]

You guys really have no clue as to the use of the "Mine Barriers". do you?

I believe we do.

The difference is that you seem to consider only what they were meant to do, whereas we consider what they were likely to achieve.

There were to have been "Mine Fields" layed at each end of the approaches to the channel granted, but these "Mine Barriers" were to form the lanes in which the Invasion Craft were to "Drive Through" for lack of a better term & if I remember correctly (Man I Hate Abbreviations) the mines in the "Mine Barriers" were to be placed at 10 meter intervals. (Wish I knew what that distance is in feet).

My problem isn't your being metric (which is fine with me), it is with your assumptions.

1. Your recollection of the German plan isn't quite correct (see the map in the site linked to by Rich, you want to click on " Minensperren" on the left of the screen),

2. The proposed invasion route i.e. roughly Calais to Dover would run directly across the main Allied minefield, which the Germans hadn't had time to clear and wouldn't have time to clear if they wanted to lay their own fields

3. The Germans didn't have enough mines to make a decent obstacle. A single line with 1 mine every 10 meters is very little, given how some mines will be laid in wrong positions (leading to gaps), others will break their moorings, and the Allies only have to clear 10-20 mines before they have a safe channel.

4. Taking the series of "B" fields. Dieppe to Newhaven is 64 nautical miles, let's call it 50. That's 9,260 mines at 10m intervals. In other words, almost the entire German stockpile will be absorbed to do just that very flimsy line.


I question the German ability to lay mines fast enough, as well as replenish the mine field. I question the German ability to prevent the British from clearing mines, particularly near their own coast. The Luftwaffe can help lay harrassment minefields but given the known inaccuracy of air-dropped mines you don't want to use them anywhere near the invasion channels.

Then of course there is the question of British minefields, which I haven't seen addressed in these threads so far.

[LWD]

...
Then of course there is the question of British minefields, which I haven't seen addressed in these threads so far.

It has been brought up a couple of times but not recently. One note of interest is that from what I've seen a lot of the German mine laying ships were double duty types that also did mine sweeping. That means they would have been in demand for both functions during the invasion. Note that these are also both high risk functions that will result in losses even in the abscence of strong British opposition. Since some of both operations would be taking place in range of British shore batteries even without the RN and RAF one could expect substantial losses to these boats.

[RichTO90]

Actually, the British DID in fact lay a Mine barrier of their own along the beachline in front of the very beaches where the invasion craft were to approach.

It's effectiveness however would have been anyones guess.

Uh-huh, just as for the German mine barriers. The difference was that the British coastal mine barriers could be laid by small craft from the ports and could be covered by shore batteries and local patrol craft.

What is that old military adage? Something to the effect that any obstacle or barrier not covered by fire is useless?

TANSTAAFL????????

No Comprende Mon Ami.

There Ain't No Such Thing As A Free Lunch.

If you want to play you have to pay.

[RichTO90]

...
Then of course there is the question of British minefields, which I haven't seen addressed in these threads so far.

It has been brought up a couple of times but not recently. One note of interest is that from what I've seen a lot of the German mine laying ships were double duty types that also did mine sweeping. That means they would have been in demand for both functions during the invasion. Note that these are also both high risk functions that will result in losses even in the abscence of strong British opposition. Since some of both operations would be taking place in range of British shore batteries even without the RN and RAF one could expect substantial losses to these boats.

The British had the 1st Mine-laying Squadron based at Scapa, with five merchants converted to lay mines. They were fairly large ships and could carry 500 to 600 mines each. In addition, many of the British light cruisers and destroyers could be fitted as fast minelayers at the start of the war, typically carrying 0 to 40 mines each (they were to be replaced by the Abdiel class fast minelayer 'cruisers' after 1942).

And yes, just about any ship could be adapted as a minelayer, all of the German T-Boot and Z-Boot could carry mines IIRC, and V-Boot and S-Boot were also routinely used as such. The problem is - as I continue to harp on - they can't do everything at once. A R-Boot cannot simultaneously be an assault troop carrier with the Vorasuabteilungen, be a minelayer, be a minesweeper, and be an escort vessel. It just doesn't work and something has to give. In the same vein, the 7-8 Z-Boot and 17 T-Boot cannot simultaneously guard the minelayers, escort the invasion barges, engage Royal Navy warships and minesweepers, and line mines themselves. There are simply too many tasks for two few vessels and experienced crews.

[RichTO90]

[4. Taking the series of "B" fields. Dieppe to Newhaven is 64 nautical miles, let's call it 50. That's 9,260 mines at 10m intervals. In other words, almost the entire German stockpile will be absorbed to do just that very flimsy line.

Yep. Take my rough count of 450 kilometers in total.

As one row that equals 45,000 mines.
As two rows that equals 90,000 mines.
As three rows that equals 135,000 mines.

Divide by the number and capacity of dedicated minelaying ships, be generous and call it 5,000. Assume that it takes a night to lay them, that the vessels can be restocked with mines during the day so that they can turnaround immediately, and that none suffer damage or breakdowns interupting their mission.

That means that laying a single row as a minimum will take 9 days.
Two rows will take 18 days.
Three rows will take 27 days.

You must further assume that the British will not notice this operation and thus will take no countermeasures, such as sending their considerable fleet assets to disrupt these missions or their considerable mineclearing assets (over 20 fleet minesweepers and 250 minesweeping trawlers in home waters, plus about 20 destroyers rigged for sweeping) to clear the barriers simultaneously with the Germans attempting to lay them.

You must also assume that all the barriers will be laid and plotted accurately, so that they will not be as great a threat to the Germans as to the British (blue-on-blue mine losses were actually failry common, mostly due to mislaid fields or to 'drifters' coming loose from their moorings).

In other words, this is pie in the sky silliness.

[leandros]

And yes, just about any ship could be adapted as a minelayer, all of the German T-Boot and Z-Boot could carry mines IIRC, and V-Boot and S-Boot were also routinely used as such. The problem is - as I continue to harp on - they can't do everything at once. A R-Boot cannot simultaneously be an assault troop carrier with the Vorasuabteilungen, be a minelayer, be a minesweeper, and be an escort vessel. It just doesn't work and something has to give. In the same vein, the 7-8 Z-Boot and 17 T-Boot cannot simultaneously guard the minelayers, escort the invasion barges, engage Royal Navy warships and minesweepers, and line mines themselves. There are simply too many tasks for two few vessels and experienced crews.

Of course you are correct about this. But, as with the Luftwaffe, not all KM units would necessarily have to perform all tasks simultaneously. When the vorausabteilungs were ashore the vessels carrying them would be free to perform othe missions. When the minefields were laid these vessels would be free to perform other missions. When the minesweepers had cleared the way for the invasion fleet they would be free to perform other missions, etc. etc. (as Yul Brunner said...... ...)

As for mining - Klee writes:

"For flank protection of the crossing routes there were planned laying tactical minefields. The average distance between mines within the various fields would be 30-55 meters. It was planned to integrate the French-British minefields in the area Dover-Calais and Dunkirk into the total German mine planning. By Sept. 4th 6.800 mines (among them 800 fakes) and the necessary equipment had been made ready. Delivery to departure ports to be ready by Sept. 19th. The mining operation should take place in the period S-8 to S-2".

Looking in at Rohwer and Hümmelchen one can see that mining was going all the time, also before the period mentioned above:

http://www.wlb-stuttgart.de/seekrieg/40-09.htm

1.– 2.9.1940
Kanal
Der F.d.M. Kpt.z.S. Bentlage wirft mit den Minenschiffen Tannenberg, Roland und Cobra von Rotterdam aus in der südwestlichen Nordsee die offensive Minensperre »SW 3« mit ca. 600 Minen. Sicherung durch die 5. Z-Fl. (FKpt. F. Berger) mit den Zerstörern Erich Steinbrinck, Paul Jacobi und Karl Galster, der 2. T-Fl. (KKpt. Riede) mit T 8, T 5, T 6 und T 7 sowie der 5. T-Fl. (KKpt. Henne) mit Falke, Iltis, Jaguar und Greif.

1.– 30.9.1940
Gewässer um Großbritannien
Die dt. 9. Flieger-Division wirft Luftminen in der Themsemündung, in Scapa Flow, im Moray-Firth und vor Aberdeen, Newcastle und Middlesborough. Weitere Einsätze gegen andere brit. Häfen folgen. Verseuchung der Themsemündung am 14.9., 15.9., 17.9., 18.9., 23.9. und 30.9. Insgesamt werden im September 184 Luftminen abgeworfen. –– Durch Minentreffer verloren gehen gehen am 1.9. vor Penzance der Minensuchtrawler Royalo, am 9. und 12.9. vor dem Humber der Fischdampfer Dervish (346 BRT) bzw. der Tanker Gothic (2444 BRT) und am 22.9. vor Harwich der Minensuchtrawler Loch Inver (356 BRT).

5.– 6.9.1940
Nordsee / Kanal
Dt. Minenschiffe, gesichert durch die 2. T-Flottille (KKpt. Riede) mit T 5, T 6, T 7 und T 8 führen in der Straße von Dover das Minenunternehmen »Walter« durch.

6.– 7.9.1940
Kanal
Offensives dt. Minenunternehmen SW.0 nördlich von Terschelling. Die Minenleger Togo (Kpt.z.S Böhmer) und Kaiser mit 405 EMB-Minen und die 5. T-Flottille (KKpt. Henne) mit Greif, Falke, Iltis und Jaguar mit 1000 Sprengbojen an Bord, werden von dem Zerstörer Karl Galster und der 1. T-Flottille (KKpt. von Rennenkampff) mit Kondor, T 1, T 2 und T 3 gesichert. Nach dem Werfen der Sperre kehrt der Verband nach Den Helder zurück.

8.– 9.9.1940
Nordsee / Kanal
Offensive Minenunternehmung »Hannelore« der 2. T-Flottille (KKpt. Riede) mit T 5, T 6, T 7 und T 8 in der Straße von Dover.

8.– 11.9.1940
Kanal
Verlegung dt. Minenlegerverbände für das Unternehmen »Seelöwe«. Am 8.9. laufen Schiff 23 / Stier (Kpt.z.S. Bentlage), Königin Luise, Schwerin, Preussen, Hansestadt Danzig und Grille, begleitet von 4 Torpedobooten, von dt. Nordseehäfen aus; am 9.9. vereinigen sie sich vor Rotterdam mit Tannenberg, Cobra, Kaiser, Roland, Togo und 2 Torpedobooten. Hansestadt Danzig und Kaiser laufen in Antwerpen ein. Grille, Königin Luise, Preussen und Roland werden beim Einlaufen in Ostende von Flugzeugen angegriffen, erleiden aber nur Splitterschäden. Die Westgruppe mit Schiff 23, Tannenberg, Cobra, Togo und Schwerin setzt die Fahrt am 10.9. von Calais aus fort, Sicherung übernehmen dazu die Zerstörer Hans Lody (Kpt.z.S. Bey), Karl Galster, Theodor Riedel, Friedrich Eckholdt und Friedrich Ihn, die am 9.9. aus Wilhelmshaven auslaufen. Sie erreichen am 11.9. Cherbourg.

12.– 14.9.1940
Kanal
Weitere Minenleger, Stralsund (Kpt.z.S. Brinkmeier), Skagerrak und Brummer, verlegen unter Sicherung von 4 T-Booten von deutschen Häfen in den Westraum. Brummer geht nach Antwerpen, die zwei anderen nach Le Havre, nachdem sie vor Zeebrügge einen Luftangriff abgewehrt haben.

19.– 20.9.1940
Kanal
Der B.d.Z., Kpt.z.S. Bey, läuft mit den Zerstörern Hans Lody, Friedrich Eckholdt, Karl Galster, Theodor Riedel und Friedrich Ihn von Cherbourg zu einem Vorstoß in das Gebiet zwischen Lizard und Start Point aus, doch wegen der Wetterlage wird das Unternehmen abgeblasen. –– Die Minenleger der Westgruppe, Schiff 23, Tannenberg, Schwerin, Togo und Cobra, verlegen unter Sicherungsgeleit der 5. T-Flottille von Cherbourg nach St. Nazaire.

30.9.– 1.10.1940
Kanal
Offensive Minenunternehmung »Werner« der 5. T-Flottille (KKpt. Henne) mit Greif, Kondor, Falke und Seeadler vor Dover.

Planned minefields:

[LWD]

...
Of course you are correct about this. But, as with the Luftwaffe, not all KM units would necessarily have to perform all tasks simultaneously.

If any significant number have to do 2 or more tasks at the same time you have a problem.

....
As for mining - Klee writes:

"For flank protection of the crossing routes there were planned laying tactical minefields. The average distance between mines within the various fields would be 30-55 meters. It was planned to integrate the French-British minefields in the area Dover-Calais and Dunkirk into the total German mine planning. By Sept. 4th 6.800 mines (among them 800 fakes) and the necessary equipment had been made ready. Delivery to departure ports to be ready by Sept. 19th. The mining operation should take place in the period S-8 to S-2".

Looking in at Rohwer and Hümmelchen one can see that mining was going all the time, also before the period mentioned above:...

Indeed but if you look through http://www.maxwell.af.mil/au/afhra/numb ... 468155.pdf
You will see that in September the KM was already behind in it's mine sweeping duties. Now when the Germans start laying these additional mine fields they are going to need to use many of the mines weepers to lay mines. They are also very likely to encounter British opposition which will have the following impacts:
1) Some of the newly fields will be swept. Note that the British will know where they have been swept the Germans may not.
2) German mine layers will be sunk and damaged. Anything that takes significant damage will not be available for futher mine laying, sweeping, escort, or transportation duties.
3) An effort of this magnatude is very likely to set off some warning bells in British intellignece agencies. Not only does this telegraph Sea Lion to some extent but it also suggest some British counter measures. For instance laying mine fields perpendicular to the German ones. This may catch some of the mine layers if done before the German fields are complete and adds more duties for the German mine sweepers.

[leandros]

They are also very likely to encounter British opposition which will have the following impacts:
1) Some of the newly fields will be swept. Note that the British will know where they have been swept the Germans may not.
2) German mine layers will be sunk and damaged. Anything that takes significant damage will not be available for futher mine laying, sweeping, escort, or transportation duties.
3) An effort of this magnatude is very likely to set off some warning bells in British intellignece agencies. Not only does this telegraph Sea Lion to some extent but it also suggest some British counter measures. For instance laying mine fields perpendicular to the German ones. This may catch some of the mine layers if done before the German fields are complete and adds more duties for the German mine sweepers.

Sure, but if you read through Rohwer's of this period the KM minelaying operations met very little opposition from the RN. As for bells ringing I don't think they needed the minelaying to understand what was going on....