Groundhog Thread v. 2.0 - The most important battle of WW2

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1943 saw a large number of new weapons/technologies either introduced or much wider distribution.
Hedgehog scored first kill in Nov 1942. It had taken a while for it to get sorted out.
Squid was introduced in 1943 but only scored first kill in 1944.
The Fido air dropped homing torpedo was first used in March 1943.

More escorts became available in 1943, British may have used larger depth charge patterns.
AS the war progressed the British introduced weighted depth charges to increase the sink rate and introduced more powerful explosives to increase the lethal radius.

Better Sonars,
better radars.
Escort carriers in large numbers.
More long range land based aircraft.

more that I have forgotten.

perhaps the Germans lost more U-Boats because they sent more but it took until 1943 to develop the weapons/sensors/experience to kill the increased number of U-Boats.
 
It was marginal gains all over the various fields of technology. For example I found this, just on the subject of air dropped depth charges.

NavWeaps Forums-Aerial Depth Charges of WWII

Does anybody know a good website that has the specifications of aerial depth charges, i.e. model number/type, year used, weight, explosive chage, etc.
www.tapatalk.com
Experience showed that it required some 170 man-hours by maintenance and ground staff to produce one hour of operational flying and more than 200 hours of flying to produce one attack on a surfaced U-boat. Hence over 34,000 man-hours of effort were necessary just to attack a U-boat.
In early 1941 the attack kill probability was 2% to 3% (i.e. between 1.1 million and 1.7 million man-hours were needed by Coastal Command to destroy one U-boat).

It is in this area that the greatest contribution was made by OR in Coastal Command and so we shall examine it in more detail. (Note here that we ignore the question of the U-boat being attacked and damaged, but not killed. To include this merely complicates the discussion).

Plainly in the above calculation the "weak link" is the low attack kill probability and it is this that really needs to be improved.

The main weapon of attack against a surfaced (when spotted) U-boat was depth charges dropped in a stick (typically six 250lb (110kg) depth charges) in a more or less straight line along the direction of flight of the attacking aircraft. After hitting the water a depth charge sinks whilst at the same time being carried forward by its own momentum. After a pre-set time delay, or upon reaching a certain depth, it explodes and any U-boat within a certain distance (the lethal radius) is fatally damaged. Six variables were considered as influencing the kill probability:

1) Depth (time) setting for depth charge explosion
In the first two years of the war depth charges were mainly set for explosion at a depth of 30/45 metres [this figure having being set years ago and never altered since]. Analysis of pilot reports by ORS showed that in 40% of attacks the U-boat was either still visible or had been submerged less than 15 seconds (these are the U-boats that we would expect to have most chance of killing as we have a good idea of their position). Since the lethal radius of a depth charge was around 5-6 metres it was clear that a shallower setting was necessary.

Explosion at a depth of 15 metres was initiated and as new fuses became available at 10 metres and then 8 metres.

2) Lethal radius - As mentioned above the standard 250lb depth charge was believed to have a lethal radius of only 5-6 metres. Plainly to increase this radius (within the 250lb limit) the chemical explosive inside the depth charge should be more powerful (e.g. increasing the lethal radius by just 20% increases the lethal volume (sphere) around the depth charge by 72.8%). The best chemical explosive currently available was therefore introduced. Note here that it could be argued (and was) that since a 250lb depth charge had too small a lethal radius a bigger charge (600lb (270kg) was prescribed by the Air Staff) was needed. ORS suggested 100lb (45kg) on the basis that it would be more effective to have many small explosions rather than one large explosion. (As an analogy would you prefer to throw many small balls at a small target or one large ball?). In fact neither alternative ever really preceded past the trial stage due to increasing success with the 250lb depth charge.

This illustrates the concept of "tradeoff" which often appears in OR in that, for a given total bomb load we have to make a choice (tradeoff) between bomb size and number of bombs (from one big bomb to many small ones).

3) Aiming errors in dropping the stick - By the end of 1942 it had become clear that too many pilots were reporting having had "straddled" a target U-boat with a stick of depth charges without sinking it. Either their claims were unduly optimistic (the ORS view) or the lethal radius of a depth charge was much less than currently believed (the Air Staff view). To settle the issue cameras were installed for recording U-boat attacks. Analysis of 16 attacks indicated that ORS were right. This analysis also showed that pilots were following tactical instructions and "aiming off" (aiming ahead of the U-boat to allow for its forward travel during fall of the depth charges). However analysis also revealed that had they not aimed off 50% more kills would have been recorded. Pilots were therefore instructed not to aim off.

4) Orientation of the stick with respect to the U-boat
Here the question was whether to attack from the beam, quarter or along the U-boat track. No definite answer was really reached until 1944 when it was concluded that track attacks were more accurate (probably due to the pilot using the U-boat wake to help him line the plane up).

5) Spacing between successive depth charges in a stick In the early part of the war this spacing was specified at 12 metres. ORS calculated that increasing this to 33 metres would increase kills by 35% and this was done.



6) Low level bombsights - For much of the war all low level attacks on U-boats were by the pilot acting as bomb aimer/release. Although pilots (and Air Staff) believed they were accurate photographic evidence did not support this belief and ORS pressed for bombsights to be provided. By late 1943 a low level (Mk.III) sight came into use increasing kills per attack by 35%.
 
But, there is still the point that there is no proof that redirecting convoys was saving shipping and that not redirecting convoys was causing losses .See the example of May 1940/November 1939 : there is no proof that the low shipping losses of November were caused by the fact that the B Dienst was decoding messages of the RN and that Bletchley Park was decoding the messages of Doenitz. And there is no proof that the high losses of May 1940 were caused because the B Dienst decoded the messages of the RN,but that BP failed to decode the messages of Doenitz .
Every day the RN was transmitting hundreds,or thousands of messages. The B Dienst decoded a small part of them ,most were useless for the Germans and most of those that arrived at the HQ of Doenitz ( Lorient ) were obsolete .And for most of the others, Doenitz had not the means to react on them, to use them .
It was the same for Ultra .
In the second half of 1941 Ultra decoded daily 1000 messages, most of them worthless because it took a long time, too much time to read them and to transmit some of them to RN HQ and to the US : messages that remained at BP were worthless .
 
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But you recently said the code-breaking was a myth.
So once again changed your tune...

False page/book references, fantastic claims, skewed numbers and flip-flopping stances - interesting.

So what are your thoughts on the Bell P-39?
 
Do some research and you will find that the Germans couldn't understand why their U Boat search lines often couldn't find the convoy's they knew were in the area. It was because the British were often able to redirect the convoys away from the known danger area.
You forget that you don't need to know what a message says, just knowing where the message has been sent from will tell you roughly where the U Boats are.

If you need a clue to help with your research, look up Rodger Winn and his work with the Tracking Team which he headed from the end of 1939.

PS still waiting for your tactical insight into how you select the tankers given the tactical situation at the time to explain why Donitz was such a fool and not a good U Boat Commander

PPS In case your wondering why I'm not letting this go its because my Grandfather was in the Merchant Navy and was sunk once in WW1 and twice in WW2. He had a grudging respect for the German submarine service despite having more reason than most to hate them
 
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This is wrong. Do some more reading instead of just guessing. Messages from U Boats and concerning U Boats were known to be so and given priority. Submarine commanders did not chit chat and gossip.
 
To know roughly where the U Boats were, or to know roughly where the the convoy was, was totally worthless . You had to know where they were precisely .The U Boat search lines could mostly not find the convoys they knew were in the area, not because of Ultra, but because the only thing the U Boats knew was that a convoy was in the area .And the area was too big .
About Doenitz :
he knew where the convoys started : NY,etc, but could not attack them there , he also knew where they were going (Liverpool ) ,but did not attack them there. He attacked them where he could not find them : in the Atlantic .
Not an intelligent strategy .
He knew that if he did not find them,he could not attack them,but still refused to change his strategy .
And , then, he had the ''brilliant ''( haha ) idea to attack the stronger one (US ) by sending his U Boats to the eastern/southern coasts of the US (Drumbeat ),knowing very well that going and returning would consume most of their fuel, meaning that they could operate only a short time .And he knew very well that the oil tankers that were lost had as destination,not Britain, but the eastern states of the US and Canada : Britain did not import ONE ton less of oil because of Drumbeat, thus, Drumbeat was nothing more than a wast .
Oil was Britain's Achilles Heel, most of the other products could be made in Britain .Attacking Britain's coastal shipping could have obtained better results,but he failed to do it .
Why ?
Because he was obsessed by the idea that the only thing that could force Britain to capitulate,was to sink more,while the truth is that it was not a question of quantity, but of quality .Not : how much, but what .
 
pbehn said:
This is wrong. Do some more reading instead of just guessing. Messages from U Boats and concerning U Boats were known to be so and given priority. Submarine commanders did not chit chat and gossip.
Click to expand...
Most messages about convoys by U Boat commanders and by the B Dienst could be thrown away : they were useless the moment they were written, they were useless the moment Doenitz received them .And, even if they gave precise information about a convoy ( speed, direction, escort ) most of them remained useless ,for the very simple reason that to attack a convoy , you need submarines that had sufficient fuel and ammunition and that were not too far from the point where they could attack a convoy : and messages from the B Dienst did not give Doenitz these submarines.
 
Notwithstanding these difficulties,oil tankers were attacked and were lost .The question is : why were not more oil tankers sunk .
 
Of course most messages are useless, thats why Bletchley park had 5,000 people.
 
I see that I have to be the first to cite C.Blair ( a must, although I do not agree about everything he is saying ) :
from The Hunters P 425 and 426
''Doenitz erred in his insistence that the KM stake almost all on the overtouted medium Type VIIC U-Boat .''
'' Doenitz also erred by greatly overestimating the ability of single U-Boats to find,shadow and attack convoys ''.
'' In the absence of good intelligence on convoy locations, Doenitz was compelled to convoy-hunting ''patrol lines ''
Here Blair is saying that Doenitz had no good intelligence on convoy locations,, this means that the Ultra messages had not much importance and that it was it most cases not needed to redirect convoys.
''German U-Boats were at the close of 1941, nowhere close to isolating and strangling Britain .''
''Wolf pack tactics were on the whole a failure ''.
''Nonetheless ,the myth of U-Boat prowess and invincibility had taken firm root in the public mind for the second time in this century .''
But ( what Blair is not mentioning ) the biggest mistake ( not that Germany would have won without this mistake ) was the total absence of a concentration ( Schwerpunkt ) in the strategy of Doenitz : what was he doing ? He was sending his U-Boats on the seven oceans to search for ships to be sunk ,and when a big number was sunk, the submarines went to an other ocean to do the same .
Doenitz wanted to have decisive strategic results,but failed to elaborate and to follow a strategic plan .
 
You simply cannot be serious, read it to yourself. You are ascribing the efforts of the allies to thwart U Boat activity to Doenitz being foolish. When Doenitz did make a massed attack in 1943 he faced massed losses, between air and sea assets a U Boat could be found and attacked on the surface or submerged anywhere near a convoy by day or night, and travelling on the surface could be found by day or night too, but they couldnt travel far under water.
 
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