Seelöwe - German & British mining operations

[Knouterer]

I certainly am, and the more so because my opinions are based on careful consideration of the available facts and figures, rather than airy assertions like "I'm sure the Germans would have thought of that".

[fredleander]

I certainly am, and the more so because my opinions are based on careful consideration of the available facts and figures, rather than airy assertions like "I'm sure the Germans would have thought of that".

.....like I said.... ...

Fred

[Knouterer]

Just like the Germans, the British were using aircraft (Hampdens and Beauforts of Bomber and Coastal Command) to lay magnetic mines near enemy ports.
According to Roy Conyers Nesbit in his history of 217 Squadron Coastal Command (http://www.amazon.co.uk/Expendable-Squa ... e+squadron ), along the French coast these mines sank one vessel in August 1940, four in September, and two in October. These included two cargo vessels, two tugs, one Vorpostenboot, one minesweeper and one fishing vessel. Three of the seven sinkings took place off Lorient, perhaps indicating that the RAF was concentrating efforts there in the hope of bagging U-boats operating from that port.

[Knouterer]

A further thought on the German minelaying program for Seelöwe: assuming, for the sake of argument, that S-Day had been set for 24, 25 or 26 September, the minelaying would have started right in the period of the full moon (15-17 Sept.). Admittedly the program had some flexibility, as the table shows there were a couple of "spare days" which could have been used to catch up if the minelaying had been delayed because of the weather or for any other reason. However, it would not have been possible to avoid moonlit nights altogether.

People who believe that even then the minelaying formations would somehow have escaped the notice of the destroyer patrols, the many vessels of the auxiliary patrol, the watchers on the coast, and the regular patrols by Coastal Command aircraft, are of course fully entitled to their opinion.

[Knouterer]

In that context, as the map on the preceding page shows, the first fields to be laid, D1 and D2, were just a (very) few miles from Dartmouth (where by the way the Royal Naval College was and is). According to Philson's OOB for the Royal Navy as of 30.9.1940, at that small port the following were based:

1 base ship (Britannia II)
5 anti-submarine trawlers
1 anti-submarine guardship
8 auxiliary patrol trawlers (plus 5 under repair)
1 examination service vessel
2 submarine chasseurs (French vessels with Polish crews)
5 auxiliary patrol motor boats
2 RAF rescue launches

[Knouterer]

The submarine chasers, by the way, CH.11 and CH.15, were of this type. This is CH.14 Dielette, the 20 mm Oerlikon guns on the bridge would not have been there yet in 1940. CH.6 and CH.7 of the same class (French-manned) were sunk by the German Torpedoboote Greif, Kondor, Falke, Seeadler and Wolf on 12 Oct. 1940 - one of the few occasions when the Germans DID engage, because they had overwhelming firepower.

[Knouterer]

To get back to Smith's book for a second, on page 120 he writes about minelaying operation Hannelore on the night of 8-9 September by the 2nd Torpedo Boat Flotilla (T-5, T-6, T-7 and T-8):

"This time they were extremely fortunate to escape both detection and annihilation; only more bad weather saved them." (because strong RN destroyer forces were out that night)

That would suggest that if the weather had been better, and if they had been escorting much bigger and slower Minenschiffe, detection and annihilation would have been almost certain.

[Knouterer]

Minenschiff Tannenberg, with two of the three 15 cm guns clearly visible, and the Königin Luise in happier days:

[Knouterer]

Apparently, it wasn't just the mines properly speaking that broke free in some numbers, but the Sprengbojen as well, according to this extract from the War Diary of 1st London Brigade (WO 166/1040), which was responsible for guarding a stretch of the northern coast of Kent:

[Knouterer]

And while I'm at it, a couple of interesting tables from the same WD, showing the times of high and low tides, sunrise and sunset in Sept. and Oct. 1940. It will be seen that the high tides on the north coast of Kent (between Whitstable and Herne Bay) were/are very different from those at Dover.
Unfortunately, the page for the last days of Sept. has gone missing, but the tables show that at that time sunrise would have been at shortly before seven (British Summer Time, or perhaps British Standard Time, whichever you prefer), which was just before eight German time.
Of course there always is some predawn light, but if the invasion forces had hit the beach at 0600 German time, and the Fallschirmjäger had been dropped at the same time as the plan was according to Schenk and others, it would still have been seriously dark IMHO, apart from any moonlight of course.

[Knouterer]

One obvious problem with the German moored mines in the Channel was that with a tidal range of 18 feet or so, mines that were a few feet below the surface at low water on spring tide would at certain other times be so far under water that destroyers with a draught of about 13 feet (full load), and perhaps even cruisers with a draught of 20 feet or so, could sail right over them unharmed.

To solve this problem the Germans developed a "tidal mine" or Gezeitenmine (EMG). According to Schenk, this had slight negative buoyancy (leichter Untertrieb) and was held up, at a constant depth below the surface, by a small inconspicuous buoy. However, it appears that in fact the mine itself had positive buoyancy and by itself would come up to the surface, but was held down by a 100 kg weight - see drawing. Of course there may have been different experimental versions.

According to Schenk, 4,000 mines of this type "would be produced", and the table above includes 2,700, but it is not clear how many were actually available in the autumn of 1940. According to Campbell, Naval Weapons of WWII, it was "... introduced in 1941 but later withdrawn as it was impossible to render it absolutely safe" (?). On the other hand, forum contributor "Bergedorf" has found evidence in the German records that at least some were available in Sept. 1940.

According to this American report from 1946 (page 22) the EMG was "designed in 1940" but no data on production as far as I can see: http://www.ibiblio.org/hyperwar/USN/ref ... -Mines.pdf

[Juha Tompuri]

According to this American report from 1946 (page 22) the EMG was "designed in 1940" but no data on production as far as I can see: http://www.ibiblio.org/hyperwar/USN/ref ... -Mines.pdf

EMG
Moored surface mine developed from EMC and introduced in 1941.

http://www.navweaps.com/Weapons/WAMGER_Mines.htm

Regards, Juha

[Knouterer]

The Westgruppe (Schiff 23, Tannenberg, Cobra, Togo and Schwerin) arrived at Cherbourg on the late evening of 10 sept. From then on they stayed in harbour (at 6 hours' readiness to move). Schiff 23 was hit by a bomb on the 18th, minor damage. Cobra sustained some splinter damage. In view of the threat from the air unloading the mines had already started the day before. On the 19th the last mines were unshipped and the ships began the move to St. Nazaire where they arrived on the 21st.

British reconnaissance apparently spotted this movement of "Gruppe West" (escorted by the 5th T.-Flottille). From an intelligence summary in the War Diary of the 45th Inf. Division (WO 166/536):

"Two convoys of merchant vessels, numbering 10 in all and accompanied by 1 destroyer and 9 escort vessels, were seen about noon on 20 Sept. some 20 miles S.W. of BREST steering South. They had been located earlier steering west off MORLAIN and then passing USHANT.

Comment. This is the first time such a convoy has been seen to leave the CHANNEL and go South. It is still too soon to say what is the purpose of the move, but the ships may have left LE HAVRE or CHERBOURG because these ports are so vulnerable to air attack."

[Knouterer]

To further illustrate the point that at any time in 1940 there were a lot of "floaters" - hundreds in all probability - bobbing up and down in the Channel, regardless of the weather on the preceding days and regardless of what the Kriegsmarine did or did not do with regard to Seelöwe, a few extracts from the War Diary of the "Kent" Battery of the Royal Marines (Mobile Naval Base Defence Organisation), which installed a coast defence battery of three 6" guns at Dungeness Point in September 1940 (ADM 202/168):

"1 Oct. 0930. British mine washed ashore near No 1 S/L – attempts to explode while approaching shore with rifles & Lewis Gun unsuccessful. When washed up on beach it was found to be pierced by numerous bullets."

"3 Oct. Various mines washed ashore near Battery & detonated or rendered safe by Naval Personnel."

"5 Oct. 0150. Especially violent explosion thought to be mine washed ashore between Battery & Lighthouse."

In that context, fishermen repeatedly complained to the Admiralty about RN ships sinking floating mines by piercing the air chamber(s) with rifle fire without detonating them; there were a number of cases were trawlers were blown sky high when they dragged up such sunken mines.

To further illustrate that point, some quotes from the WD of the 340th Coast Battery at Hythe (WO 166/1827), some 8 miles to the NE:

2 Sept.: "Four steam trawlers fired at and sank two drifting mines 2,000 yards off shore."

3 Sept.: "Two steam trawlers fired at and sank a drifting mine 7,000 yards off shore."

4 Oct.: "Unexploded British mine washed up 25 yards South of NO. 1 S/L."
(Naval personnel removed detonator)

29 Oct.: "Two mines washed up. One 200 yards East of No. 2 Gun and one 200 yards West of No. 1 gun. Both mines rendered harmless."

30 Oct.: "One mine washed up 500 yards East of No. 1 S/L. One observed floating 50 yards off shore, 300 yards East of No. 1 S/L."

[fredleander]

The submarine chasers, by the way, CH.11 and CH.15, were of this type. This is CH.14 Dielette, the 20 mm Oerlikon guns on the bridge would not have been there yet in 1940. CH.6 and CH.7 of the same class (French-manned) were sunk by the German Torpedoboote Greif, Kondor, Falke, Seeadler and Wolf on 12 Oct. 1940 - one of the few occasions when the Germans DID engage, because they had overwhelming firepower.

Or maybe because it was one of the few occasions at the time that the RN were actually there. It is only fitting to note that earlier that night the German force also sunk the RN armed trawlers Listrac and Warwick Deeping. They also took the time to stop and rescue 40 sailors from the French sub-chasers. According to Smith they were French/Polish-manned.

Low on ammunition the German ships high-tailed home when five much stronger British destroyers arrived in the area. By superior maneuvering the German force was able to escape.

Fred