How Did the U-Boats Find Targets

[bill clarke]

Ok guys this may sound silly, but in the game we get a red icon to signify a enemy contact, but in reality how did the u-baots fins their victims ?

[Khayman]

Patrol lines of U-Boats along presumed Convoy courses. First one to spot a convoy would home in other boats. Codebreaking and other intelligence. Guesswork. Sometimes the Luftwaffe, but their position reports were frequently found to be so inaccurate as to be virtually useless.

[tbarak]

I read too that they used a kind of dragnet technique, where the boats spread out abreast with maybe 50 miles between them and they "swept" the sea. Much like how fowl hunters walk abreast through the bushes to flush game birds. Only problem was I think maximum visibility is maybe 15 miles so there were always holes in their line of sight. It was in all reality a pathetically hit and miss operation with too few boats and ineffective tactics.

[runyan99]

In short, they picked a good spot, and then got lucky.

[Heibges]

The S.O.P for a patrol would be to stay on the surface and conserve as much fuel as possible. Soundchecks were conducted at dawn and dusk, so the uboat wouldn't be surprised in the rapidly changing visibility conditions.

I heavy fog, and conditions of extremely poor visibility, uboats stayed submerged because the danger of being rammed was greatly iincreased.

Airborne radar caused the the uboats to have to recharge batteries at night and attack submerged during the day. Their great successes had been mostly based on the highly mobile nighttime surface attack.

After Black May, uboats were increasingly forced to stay submerged for up to and including the entire patrol. This was accomplished through use of the snorkel. Due to its low underwater speed, the only way a uboat could intercept a target now, was if it steamed right over it. Also, by this time, uboats spent much more of their time going to and from port rather than patrolling for the same reason.

During the good years, to intercept a convoy they would set up a patrol line in the convoys path. They would move toward the convoy at low speed. If they got to a point where they should have intecepted the convoy, but hadn't, they turn around and follow a reverse course at hight speed, then start the process again. The first uboat to spot the convoy became the contact holder and would broadcast updates every hour. If a contact holder stopped broadcasting, another boat was expected to take over as contact holder. Keep in mind, uboats did not conduct "coordinated attacks" on convoys in the tradional military sense in the word.

Originally Posted by runyan99

In short, they picked a good spot, and then got lucky.

Bingo!!!

[Khayman]

Originally Posted by runyan99

In short, they picked a good spot, and then got lucky.

I think that's underestimating the German code-breaking efforts. A lot is said of the breaking of Enigma, but the Germans had their successes as well. Frequently the patrol line was placed on a known route rather than one that was guessed at. You could say it would then be very unlucky if no U-Boat made contact.

[Puster Bill]

Originally Posted by Khayman

I think that's underestimating the German code-breaking efforts. A lot is said of the breaking of Enigma, but the Germans had their successes as well. Frequently the patrol line was placed on a known route rather than one that was guessed at. You could say it would then be very unlucky if no U-Boat made contact.

This is true. During early 1942, when the British were reading the 3 rotor Naval Enigma fairly well, they were able to route their convoys such that only 1 in 10 convoys were discovered by u-boats. When the 4 rotor Enigma came in, the Germans found 1 in 3 convoys. That is because they had been reading the British codes. In fact, Wilhelm Tranow's Beobachtungsdienst ("Observation Service", usually shortened to B-Dienst) had been reading British Naval and Merchant Marine codes since the beginning of the War. They were able to read the two main English systems up until about mid 1943 - early 1944. The Allies changed their codes due to definite proof from intercepts of messages to the U-Boats that the Germans had cracked their codes and were routing them to intercept convoys and individual ships.

The British actually knew, or at least suspected, that this was the case for quite some time (in fact, some of the highest level users of the British 'Naval Cypher', which was really a codebook, got the only unbreakable system to superencipher it, the one time pad), but it takes time to compile and distribute a system. You need everyone to start using it at the same time, otherwise you will compromise the new system by having similar or identical messages in both the old and new systems.

The final word must go to Karl Doenitz on the effectiveness of B-Dienst: He said they supplied fully half of the intelligence used by the Kriegsmarine.

By Contact Reports of Convoys, and then the old trusty Eyeballs for others.

[Khayman]

Originally Posted by Magua

By Contact Reports of Convoys, and then the old trusty Eyeballs for others.

But where did the contact reports come from?

Originally Posted by Khayman

But where did the contact reports come from?

Convoy Contact Reports came from BDU. From Reports by other U-Boats or by Intel. If a Single Ship was spotted by a U-Boat the only report would be "Ship Sunk". End of Single Contact.

There is one case of a Single Ship Being reported by BDU. But in all of the other instances Single Ships were a result of good eyes on the Bridge. That's from the personal accounts and reports I've read.

[Khayman]

Originally Posted by Magua

Convoy Contact Reports came from BDU. From Reports by other U-Boats or by Intel.

Ah so what has already been said in this thread basically. I was just wondering if you were in a loop of "How do U-Boats find targets" being answered by "Other U-Boats" which begs the question of "How did that U-Boat find targets" answer being "Other U-Boats" and so on. Would lead to a circular mess, furrowed brows and screams of confusion.

Originally Posted by Magua

There is one case of a Single Ship Being reported by BDU. But in all of the other instances Single Ships were a result of good eyes on the Bridge. That's from the personal accounts and reports I've read.

I'd have to disagree. U-Boats on the coast of the US at first found that ships were broadcasting in the clear, with no encryption at all. Their sailing times and routes were easily heard. Also I'd be very wary of making such a strong statement, unless you have access to complete BdU records.

Sorry, I'm nit picking. I got up the wrong side of the bed I think. I should be more

[Puster Bill]

Originally Posted by Khayman

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).

Originally Posted by Khayman

Ah so what has already been said in this thread basically. I was just wondering if you were in a loop of "How do U-Boats find targets" being answered by "Other U-Boats" which begs the question of "How did that U-Boat find targets" answer being "Other U-Boats" and so on. Would lead to a circular mess, furrowed brows and screams of confusion.

I'd have to disagree. U-Boats on the coast of the US at first found that ships were broadcasting in the clear, with no encryption at all. Their sailing times and routes were easily heard. Also I'd be very wary of making such a strong statement, unless you have access to complete BdU records.

Sorry, I'm nit picking. I got up the wrong side of the bed I think. I should be more

Okay, let me rephrase it....instead of "all the other instances", I'll change that to "from the instances I have read about.."

Originally Posted by Puster Bill

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).

Yep, I've read that one documented case of Hardegans... That one instance...1......But you must admit that there are vastly more readings that describe the other view???