Quote:
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Originally Posted by Khayman
Quote:
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Originally Posted by Magua
By Contact Reports of Convoys, and then the old trusty Eyeballs for others.
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But where did the contact reports come from? |
Two sources: Sightings by other u-boats, and signals intelligence from B-Dienst.
Also, to a lesser extent information from aerial reconaissance by the Luftwaffe, but that was fairly rare, and even when it was available it was often useless.
And I beg to differ with you again Magua, but BdU did send information about individual ships, at least on occasion. An example from "Operation Drumbeat" by Micheal Gannon is given in the chapter titled "Waiting for Hardegen", and this is the text of the message as intercepted and translated by Bletchley Park:
OFFICER. TO HARDEGEN U-123. ON 1 JANUARY EVENING IN SQUARE
WRANGELSTRASSE 1587 GREEK SHIP DIMITRIOS INGLESSIS REQUESTED
TUG ASSISTANCE OWING TO DAMAGED RUDDER. YOU MAY ATTACK
IF NOT FARTHER THAN 150 MILES FROM POSITION GIVEN. BDU OPS.
The only possible source for this information would have been from B-Dienst. The position given (near Longitude 48 degrees West) was too far for aerial recon.
That report is confirmed by the Eastern Sea Frontier war diary (a US document) found here:
http://www.uboatarchive.net/ESFWarDiaryJan42APP3.htm. relevent quote:
January 1, 1942
ENEMY ACTION DIARY
1030: Relieved Lt-Cdr., P.P. Bassett, USNR. 1200: Received message from ComBostDist CG that unidentified ship, no position given, has lost rudder - requires assistance. No record call sign given in dispatch. Called Moran Transportation Co. in attempt identify. Not their ship. Received additional dispatches, still without identity or position until 4:04 p.m.
1615: Dispatch from Com 1 - ship in distress is Dimitrios Inglessis - posit. Lat. 48-13N and 47-45W. Additional confirming despatches received until 6:04 p.m. OPNav and CinCLant know about this. Captain Stapler directed "No further action"
0930: Turned over to Lt-Cdr., Osburn. Submitted.
R. H. Braue, Lieut (jg), USNR
According to
http://www.theshipslist.com/ships/li..._Dempster.html (scroll down to Burutu(2)), that ship was only 5,275 tons, so it wasn't an exceptionally large and attractive target.
As the war went on, position reports from both signals intelligence and from u-boat sightings would have dried up. The British changed their codes because they knew from reading intercepted u-boat traffic that the Germans were reading their codes That progressively locked out the B-Dienst, from mid 1943 to early 1944. After that, very little information came from intercepted communications. They could still use direction finding and traffic analysis to 'guess' at the position of a convoy, but that information is less precise (at the ranges involved, a 100 mile error in position would have been normal, and a 50 mile error in DF would have been exceptionally good).