If the RAF had been defeated in the Battle of Britain

[Shortround6]

For the British, adopt constant speed propellers when the rest of the world did.
Learn to navigate at night (or develop navigation aids).
Don't go sub hunting with carriers with only few destroyers for escorts and planes that have ineffective anti-sub weapons.
There are a lot more.

 

[parsifal]

Opinions will vary of course, but for the RN the greatest single failure was the under estimation of the uboat threat. it was the campaign in which the Germans came the closest to actually defeating Britain. A few more escorts instead of building more BBs, the setting up of a proper ASW command prewar would have been a great help.

The reason thre is a far greater fascination with German what ifs is that the failures in the german camp are so much more obvious. in reality both sides fought a pretty competent war. Applying our wisdom after the fact is unrealistic in my opinion. Being there with incomplete information, or even wrong information under the pressure of combat makes it much harder than it looks

 

[Koopernic]

In regards to the German Navy's "Torpedo Crisis". Had the Torpedoes kept proper depth, the magnetic proximity pistols not detonated prematurely and had the contact pistols triggered reliably dozens of Royal Navy Ships would have been sunk and dozens of German destroyers and u-boats in good working order and opperational

The u-boat hydrophone operators could hear the torpedoes detonate prematurely or hear the thud of the torpedo hit and the torpedo engines stop or hear the torpedo pass right underneath the sound of the targets propellers often launched from impossible to miss distances of 800m

It was so bad the entire u-boat fleet was relived of duty by Raeder and all the German u-boat aces that never came back without a tally came back with nothing for the only time.

1. The early years of the U-boat force were doomed by faulty torpedoes. In 1939-40 the torpedoes suffered from the following problems:
   
   Premature detonations due to faulty magnetic proximity detonator. This giving away the U-boat's presence and approximate position.
   Failure of contact detonator at certain angles of attack - torpedo doesn't explode.
   Running well under the required depth and running underneath the target without exploding.
   Exploding at the end of their runs when fuel expended - also giving away the presence of the U-boat.
   
   Here are details of the most important torpedo failures of the Germany U-boat Service.
   
   14 September 1939:
   U-39 sights HMS Ark Royal. Approaches undetected to 800 meters, and fires 2 torpedoes. Both explode 80 metres short of Ark Royal's hull - giving away U-39's position. The escorting destroyers pounce on U-39 so fast that she doesn't have time to dive deep and is and sunk - the first U-boat to be sunk in WWII.
   
   20 September 1939:
   U-27 sights 2 British destroyers. Approaches undetected to firing position and fires 3 torpedoes. All three explode before reaching their targets. U-27 is sunk.
   
   27 October 1939:
   U-46 attacks a British convoy, escorted by a cruiser. Attacks twice and fires 8 torpedoes against a wall of overlapping merchant ships. Only one hits. Reloaded. Cruiser stopped on surface rescuing survivors. U-46 fires 2 torpedoes at close range. Both explode before reaching the target.
   
   30 October 1939:
   U-56 encounters the flagship of the British Home Fleet - battleship HMS Nelson, in company with Rodney, Hood and 12 destroyers. Approaches undetected. Fires three torpedoes. Two are heard (two metallic clangs) to strike the hull of HMS Nelson - but both fail to explode. Third torpedo runs too deep, passes underneath the battleship without exploding, and finally explodes at the end of its run.
   
   Sep 1939 - June 1940 - Many other failures against merchant shipping.
   
   April - June 1940 - Norwegian Campaign - an utter failure of the U-boat Service.
   
   10 April 1940, 2210 hours:
   U-48 encounters Cumberland class cruiser and fires 3 torpedoes. Two explode prematurely before reaching the target, last one misses and explodes at end of its run.
   
   10 April 1940, 2115 hours:
   U-48 encounters York class cruiser and fires 3 torpedoes. All three explode prematurely before reaching the target.
   
   10 April 1940, 2210 hours:
   U-51 encounters 2 destroyers and fires 2 torpedoes. One torpedo explodes prematurely after reaching arming distance, the other explodes 300 feet from destroyer's hull.
   
   14 April 1940:
   U-48 encounters HMS Warspite and 2 destroyers. Fires 4 torpedoes with contact detonators at battleship - 2 impact Warspite's hull, but fail to explode.
   
   15 April 1940:
   U-65 fires 2 torpedoes at a troop transport. No success.
   
   16 April 1940
   U-47 attacks 4 troop transports at anchor in Bygdenfjord. Range 750-1500 yds. Ships in a solid wall ahead of U-boat. Fired 4 torpedoesl - all torpedoes failed to explode. Enemy not alerted. Reloaded. All torpedoes thorughly checked. Surfaced after midnight and attacked again. Precise fire control data - torpedo running depth set at 12-15 feet. 4 more torpedoes fired. Result nil. 1 torpedo off course, exploded against the cliff. Enemy alerted - U-47 withdraws. Runs aground, refloated. Pursued with depth charges - engines damaged. Escaped. Summary: 8 torpedoes fired at stationary targets at close range, no hits.
   
   19 April 1940
   U-47 encounters HMS Warspite (again) and 2 destroyers. Attacked battleship at 900 yards, firing 2 torpedoes. No success.
   
   So, had the torpedoes been working reliably in the period Sep 1939 - June 1940, the Germans would almost certainly have sunk:
   
   1 x Carrier Ark Royal
   2 x Battleships Nelson and Warspite
   3 x Cruisers
   7 x Destroyers
   5 x Troop Transports (1 loaded, 4 empty)
   
   The loss of these ships would have considerably affected the balance of sea power in the Mediterranean. For example, at the Battle of Calabria in early July 1940, HMS Warspite was the only fully modernised Queen Elizabeth class battleship present that could match the firing range of the Italian battleships Cavour and Cesare. An early hit by Warspite at very long range surprised the Italians, and as a result they withdrew from the battle almost before it had started. Without Warspite, the other old, unmodernised British battleships would have been considerably outranged by the 2 Italian battleships, and the battle would have been much more hard-fought as a result.
   
   The next fully modernised Queen Elizabeth class battleship was HMS Valiant, and she wasn't available to enter the Mediterranean until the end of August 1940. So for the first 3 months of the Mediterranean War, the Italians would have had the advantage in any battleship engagement.
   
   Also, if Ark Royal had been sunk in September 1939, the British may not have had a fast Illustrious-class carrier based at Gibraltar in May 1941, to launch the fatal torpedo attack that jammed Bismarck's rudder. If not, Bismarck would have escaped to France.
   
   (Note: The losses above would be in addition to the historical losses between Sept 1939 and June 1940 of
   1 x Carrier Courageous
   1 x Battleship Royal Oak
   3 x Cruisers
   3 x Armed Merchant Cruisers
   23 x Destroyers
   1 x Troop Transport (empty)

1. A book called "naval blanders" notes that Churchill but also a number of other high level naval personnel (i think the first lord of the admiralty as well, but i´m not sure about that). The death of Churchill alone would have large effects in the whole handling of the war by the UK. Also the effect on moral would be great.
2. The British carrier HMS Ark Royal capsized and sank 13 hours after being hit by a single torpedo from U-81. The HMS Courageous, on the other hand, sank only 17 minutes after being hit by two torpedoes from U-29.
3. HMS Barham capsized and exploded only 2 and a half minutes (!) after being hit by three torpedoes from U-331. HMS Nelson barely survived a magnetic mine explosion on 4 Dec 1939, and survived a hit by a single Italian air-launched torpedo in 1941.
4. I think it's reasonable to suggest that two torpedo hits would have been enough to sink either Ark Royal or Warspite. And three torpedo hits would almost certainly have been enough to sink Nelson - although she would have a chance of surviving two hits if one of them didn't flood an engine room.
5. Any battleship might be able to survive a single torpedo. HMS Barham survived a single torpedo hit from U-30 off the Clyde on 28 Dec 1939 but 2 is unlikely if the older type. These are the larger u-boat type.
   
   Winston Churchill was indeed on HMS Nelson when she was attacked by U-56 on 30 Oct 1939! The loss of the flagship of the Home Fleet, and Winston Churchill, the CiC of the Home Fleet, and the Admiral of the Fleet would have been a devastating blow to the RN - far greater than the loss of Hood or even the POW and Repulse. The death of Churchill would have changed history

Articles: Faulty Torpedoes - The German Crisis

https://digitalcommons.georgiasouth...ng.com/&httpsredir=1&article=1599&context=etd

More reliable torpedoes for the Uboat in 1939/40

 

[Koopernic]

The training bases could be moved, the factories not so much. At least not in a few weeks.
Deeper penetrations would also lead to higher German losses. For incoming raids Radar told the British they were coming and told them the course over the channel (which could change over land) once 100-200 miles into Britain the British would know where they are and would know what route they would have to take to get out of Britain.
Please note that a lot of the early raids were right along the coast and the Germans could be over water in minutes if not, in some cases , seconds.



I believe the carrier was the Graf Zeppelin, the Graf Spee was the Panzerschiff sunk off Montevideo. The Germans may very well have been down to 4 destroyers in June of 1940 but in the fall they were up to at least 7 with another 2-3 soon to be repaired?




The last was not going to happen. And I would note that British submarines caused a substantial amount of damage to German heavy vessels even if they did not sink them.

In order for even a remote chance of a German invasion you need the following pre conditions. These are only the realistic ones.



1. even with the best torpedoes in the world the U-boats could not have saved the Scharnhorst from getting hit by a torpedo from a destroyer unless you think the U-boats could have swept the Norwegian coast of all British surface ships. Commander of the Glorious should have shot for stupidity had he lived. Gneisenau among other misadventures was hit by a torpedo from HMS Clyde on June 20th which put here out of action for 5 months. Karlsruhe was sunk by the HMS Truant. Leipzig and Nurnberg had both missed the Norwegian campaign due to torpedo damage suffered in Dec 1939 From British subs.
U-boats weren't going to save the Blucher either unless better torpedoes could take out shore batteries.
2. covered above.
3. There was nothing wrong with flying the initial FW 187s with Jumo 210s. either 1/4 or 1/3 of the Bf 110s used in Poland used Jumo 210s due to the shortage of DB 601 engines. Perhaps the mistake was in not shifting over later, but the whole evaporative cooling system scheme also delayed development of the FW 187 . I would also note that NO service Ju 87 used a DB 601 engine so they cannot be blamed for the FW 187 not getting them.



4. most sources say the Germans had 56-57 U-boats at the start of the war. How many were ready for sea may be different. Many are the small type IIs but that is the size you want if actually trying to operate in the channel or british coastal waters. I don't know how many more they got in service in teh year leading up to Sea lion.

Stopping production of large surface ships means the British have time to change their building plans. I would also note that something under 2000 tons of steel had been assembled at the docks for the first two H class ships when construction was stopped so that doesn't get you much in the way of U-boats. Assuming of course that the steel is even suitable for U-boats and doesn't have to be sent back , melted down and reworked. Scrapping the Bismark and Tirpitz before completion means an awful lot of wasted money in already completed engines and armament (H class guns were used in shore batteries) and could very well signal to the British that they don't need five King George Vs??

more later.

I've separated out the torpedo issue.

In terms of then Focke Wulf Fw 187 "Falke" long range escort fighter. Its first flight was in May 1937. That's sufficient time to get the aircraft operational with several squadrons by the end of 1939.

Just looking at a Google map of Britain shows that an Me 109 and Me 110 with their 400 and 500 mph range respectively. will be unable to escort over the entirety of the UK even with drop tanks which might extend radius of action from 130 to 260 and 160 to 320 miles respectively.

The Fw 187 is no more going to be competitive with the Kestrel sized Jumo 210 than the Me 109 or Me 110 will be. Hurricanes, Spitfires and Defiants can't work with Kestrels nor could Me 109, Me 110 or Fw 187 be competitive with jumo 210. It's a waste of time developing and testing this aircraft with the Jumo 210. Richthofen did so because his hands were tied but wanted to throw Focke Wulf some money.

The Fw 187 excellent performance did not derive from its fashionable use of evaporation surface cooling in some models. It's excellent suitability came from having power to weight ratios, wing loading and drag to power ratios as good as or better than single engine fighters such as the Me 109.

It retained some of the advantages of 2 engine types greater internal fuel capacity and showed itself of carrying at least 1300L of fuel which is 650L/engine compared to the Me 109 400L/engine. That should give it a range of 700 miles ie radius of action of about 480 miles with drop tanks.

It could be made operational with the better performance the either the DB601 or the Jumo 211 irrespective of whether it had conventional radiators or evaporation types.

What was missing is the doctrine. When they saw its superior performance the powers kept trying to turn it into a sort of super zerstroyer with second crew members, rearward facing crew members and flexible armament all of which ruined its performance.

Such a long range escort also helps the Luftwaffe protect the u-boats over the Bay of Biscay etc.

Clearly something better than the Fw 200 needs to be ready. The Ju 89 with Jumo 211 can do it but it requires the scrafice of some He 111 to get the engines. This aircraft, likely with a 20mm tail gun will be able to deal with Hurricanes on CAM ships.

Ive tried to show that with luck (good torpedos) and the minor reallocation of resources (Drop tanks and Fw 187 instead of some Me 110) the Germans might have been in a position to guard their invasion fleet from the RN and RAF and have air superirity over the entire UK. However I don't think they'll have a suitable fleet of amphibious landing craft.

 

[wuzak]

Did the Luftwaffe ever really come close to defeating the RAF? Or were they just close to defeating 11 Group?

And if the German invasion of Britain had been launched and failed, as spectacularly as predicted, how much damage would that do to Germany's war effort?

If the invasion failed, does that force the cancellation or delay of Barbarossa? Or does Barbarossa go ahead, but leaving France poorly defended, allowing the Allies to land a year or more earlier than they did?

Who would pay for the failure? Goering? Raeder? von Brauchitsch?

 

[wuzak]

In terms of then Focke Wulf Fw 187 "Falke" long range escort fighter. Its first flight was in May 1937. That's sufficient time to get the aircraft operational with several squadrons by the end of 1939.

With Jumo 210s.

The Fw 187 was cancelled before the idea of the Battle of Britain would have entered the planners' minds.

 

[Shortround6]

The 20mm tail gun in a JU 89 (or what ever 4 engine beast the Germans come up with ) would have been the MG FF or MGFF/M with a 15 round magazine, aimed by hand.

The FW 187, with whatever engines, would have had the same 20mm guns (MG FFs or MG FF/Ms) with a single 60 round drum apiece. Radio operator/rear gunner in the BF 110 had two extra magazines/drums per gun help with multiple engagements.

Germans had no idea (or very little) that they would have the Atlantic coast of France to base subs on when the FW 187 was canceled.

 

[pbehn]

With the German codes it is a mystery to me how long the "plausible denial" ruse worked, Maybe it is an effect of a totalitarian regime, who would want to tell Adolf that the codes and system need to be changed because they have been broken for years?

 

[swampyankee]

With the German codes it is a mystery to me how long the "plausible denial" ruse worked, Maybe it is an effect of a totalitarian regime, who would want to tell Adolf that the codes and system need to be changed because they have been broken for years?

I don't think it needs to be a totalitarian regime; there are many cases in democracies where government officials -- and military officers are exactly that -- will completely ignore evidence that contradicts their personal beliefs, e.g., US torpedoes during WW2. Of course, military hierarchies are not democracies, and those in the democracies, like the US, may have be equally rigid and even less accepting of criticism from subordinates or outsiders*
than those in non-democratic regimes.

The German officials were probably told by the nazi experts on Enigma that it was unbreakable. They had probably purged the academics and civil servants who had the prestige to overcome the arguments from the second-raters that were left.



* "Outsiders" as in people from a different unit, such as submarine captains in the USN.

 

[parsifal]

If the operators had followed procedures correctly it would have been much harder to break ENIGMA,

Because the Germans assumed that procedures were being followed, and because the odds of cracking the code under those assumed conditions were just about zero, the Germans were never able to work out what was happening. I know of at lest one occasion when KTB (UBoat command) suspected that their codes had been compromised , but their enquiry always thought it more likely that there was a traitor at work.

In a way they were right, The abwehr was a compromised organisation if ever there was one.

In 1972 the British Security Service revealed the extent to which the Abwehr's agent network had come under its control after it had compromised the organization's communications. Both the Abwehr's hand and machine ciphers, codenamed ISOS and ISK, respectively, had been solved early in the war, which gave the Allies a formidable advantage in manipulating its activities. The Abwehr was also handicapped by high-level defections of staff in Lisbon, Istanbul, and Ankara, and by agents in the US and South Africa.

The Abwehr may also be said to have been disadvantaged by the political views of its personnel, fear of their Sicherheitsdienst rivals, and the inherently insecure practice of allowing case officers to recruit and run agents for long periods without the discipline of rotating handlers who could exercise independent judgment, routinely conduct rigorous integrity tests, and be confident that their own careers would not end in a posting to the Russian Front in the event that one of their recruits had been "doubled" by the enemy.

Wilhelm Canaris was a German naval officer who escaped from internment in Chile during World War II; Canaris was appointed chief of the Abwehr in January 1935. He proved an assiduous spymaster, and under his supervision extensive networks were developed in Great Britain and the United States and representatives were posted under diplomatic cover to most of the capitals of Europe. His organization grew very large, adopted the Brandenburger Grenadier regiment as a military adjunct, and trained saboteurs to disrupt industry in the United States. Although personally an anti-Nazi, Canaris employed many zealous Nazis, but some of those closest to him were to be implicated in the 20 July 1944 plot to assassinate Adolf Hitler.

Prior to the invasion of the Soviet Union in June 1941, Canaris disclosed details of the plan to his Polish mistress, Halina Szymanska, whom he knew to be in touch with Polish, and presumably therefore British, intelligence officers. Canaris was dismissed following the defection of Erich Vermehren and was arrested in the aftermath of the 20 July plot. He is believed to have been hanged at Flossenberg concentration camp in February 1945. After his death, rumors abounded about the extent of his contact with the Allies, but no credible evidence has emerged to support assertions that he held a wartime meeting with the British Secret Intelligence Service chief Stewart Menzies in Spain. In February 1940 GRU defector Walter Krivitsky claimed to MIS that Canaris has been on the Soviet payroll before the war, but again the allegation is unsubstantiated

 

[swampyankee]

The British XX (Double Cross) scheme was quite effective at turning agents. Being offered the opportunity to help the British against the nazis or being hanged and buried in an unmarked grave tended to encourage most spies and traitors to chose the first option.

 

[stona]

The poor operational procedures used by some Enigma operators, notoriously in the Luftwaffe, certainly hoped in early breakthroughs. I already said that in 1940 the British could read almost all Luftwaffe radio traffic.

Other 'myths' often repeated in true Hollywood style include that the breaking of Enigma was achieved by 'Colossus' the first electronic digital computer. It was in fact first broken with good old pen and paper and an electro-mechanical device called by the British a 'Bombe'. The Bombe was based on the earlier Polish Bomba, but operated on rather different principles.

Here's a slightly technical bit.

The Polish Bomba exploited the fact that the same message indicator was sent twice at the start of each message, a major flaw in the German cryptographic procedures. When the Germans realised this and abandoned the practice on 10th May 1940 the Polish Bomba became useless. The date will not be lost on any historian.

Turing designed the British Bombe in 1939. Compared to the Polish Bomba, it used a completely different approach. It was based on the assumption that a known (or guessed) plaintext, a so-called crib, is present at a certain position in the message. Famously weather reports and simple 'Heil Hitler' sign offs were among those used.The Bombe was further enhanced with the so-called diagonal board, an invention of fellow code breaker Gordon Welchman, that greatly reduced the number of steps needed for the code breaking effort (I've never worked out how this functioned, but it obviously did!). A second Bombe, with Welchman's diagonal board present, was installed at Bletchley Park on 8th August 1940. The first machine was soon similarly modified.

During the course of the war, over 200 Turing-Welchman Bombes were built.

Cheers

Steve

 

[pbehn]

The poor operational procedures used by some Enigma operators, notoriously in the Luftwaffe, certainly hoped in early breakthroughs. I already said that in 1940 the British could read almost all Luftwaffe radio traffic.

Other 'myths' often repeated in true Hollywood style include that the breaking of Enigma was achieved by 'Colossus' the first electronic digital computer. It was in fact first broken with good old pen and paper and an electro-mechanical device called by the British a 'Bombe'. The Bombe was based on the earlier Polish Bomba, but operated on rather different principles.

Here's a slightly technical bit.

The Polish Bomba exploited the fact that the same message indicator was sent twice at the start of each message, a major flaw in the German cryptographic procedures. When the Germans realised this and abandoned the practice on 10th May 1940 the Polish Bomba became useless. The date will not be lost on any historian.

Turing designed the British Bombe in 1939. Compared to the Polish Bomba, it used a completely different approach. It was based on the assumption that a known (or guessed) plaintext, a so-called crib, is present at a certain position in the message. Famously weather reports and simple 'Heil Hitler' sign offs were among those used.The Bombe was further enhanced with the so-called diagonal board, an invention of fellow code breaker Gordon Welchman, that greatly reduced the number of steps needed for the code breaking effort (I've never worked out how this functioned, but it obviously did!). A second Bombe, with Welchman's diagonal board present, was installed at Bletchley Park on 8th August 1940. The first machine was soon similarly modified.

During the course of the war, over 200 Turing-Welchman Bombes were built.

Cheers

Steve

They also used the fact that some raids were reported in a known short code. Sea mining "gardening" operations used this, a bomber laying mines in a known area would trigger a known response transmitted by enigma.

 

[Juha2]

On the Koopernic's torpedo failure list, that is the German view, British agreed with some cases, some were according to British wake explositions, which could happen to any torpedoes, e.g. 14 Sept 39 Ark Royal
"At 1512 ARK ROYAL was back on a south westerly course and making 26 knots to catch up with her screen who were now about two miles ahead. When Leading Signalman Joseph Ernest Hall, Official Number P/J 42557, who was on watch, observed the commencement of torpedo tracks and his very prompt and accurate report enabled the Officer of the Watch to put the helm over to port causing the torpedoes to miss astern and detonated about half a cable on the port quarter. It was noted that the tracks were very evident, much more so than those of our own torpedoes.

ARK ROYAL signaled FAULKNER informing her of the submarine attack. The FAULKNOR, FIREDRAKE and FOXHOUND then reversed course and proceeded to join the ARK ROYAL."

And some didn't happen according to the RN, e.g. in the HMS Warspite case on 14 Apr. 40 the RN didn't notice the hits. And most navies had problems with their torpedoes early in the war, the USN problems are probably the most famous besides the KM's, but as the attack on Ark's Swordfishes on HMS Sheffield instead of KMS Bismarck shows, also the RN had problems with its magnetic proximity detonators.

On intelligence, the game was more even than is usually admitted. On German successes/Allied failures see: Christos military and intelligence corner: Index

 

[stona]

They also used the fact that some raids were reported in a known short code. Sea mining "gardening" operations used this, a bomber laying mines in a known area would trigger a known response transmitted by enigma.

Also, from time to time so called 'code books', which were actually key sheets were captured. These gave the daily settings for Enigma machines within, say, the KM for several days. This would give any code breaker information such as which wheels were used, in what order, and the initial settings. Anyone with a compatible machine could read the coded messages with no need for difficult and time consuming decryption, at least for a few days or until the enemy realised the key sheets were missing/compromised.
Cheers
Steve

 

[pbehn]

Also, from time to time so called 'code books', which were actually key sheets were captured. These gave the daily settings for Enigma machines within, say, the KM for several days. This would give any code breaker information such as which wheels were used, in what order, and the initial settings. Anyone with a compatible machine could read the coded messages with no need for difficult and time consuming decryption, at least for a few days or until the enemy realised the key sheets were missing/compromised.
Cheers
Steve

Certain ship,s known to have these were targeted, I think they were weather ships that had to be issued with them in advance. You would think such a ship suddenly stopping transmitting would have set off an alarm in some departments but it didn't.

 

[Graeme]

it was the campaign in which the Germans came the closest to actually defeating Britain.

How close?

 

[Milosh]

Came across this on the U-boats (not sure where the data came from).

1939:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Sep39 48/178,621
Oct39 33/156,156
Nov39 27/72,721
Dec39 39/101,823
Tot39 147 (36.75/month)/509,321 (127,330.25/month)
British merchant ship construction capacity from 1939-1941 did not exceed 1.2 million GRT per year.
US merchant ship construction in 1939 was 0.242 million GRT.

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Aug39 19/2
Sep39 3/0
Oct39 13/3
Nov39 10/1/1
Dec39 5/1/1
Tot39 50/7/2 (an average of 10 patrols per month and 14% lost)

Thus for 1939, an average of 2.94 ships were sunk per patrol and one U-Boat was lost per 21 ships sunk (note that throughout these averages will be slightly inflated since they do not include the minor contribution of the Italian submarine fleet.)

1940:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan40 53/163,029
Feb40 50/182,369
Mar40 26/69,826
Apr40 6/30,927
May40 14/61,635
Jun40 66/375,069
Jul40 41/301,975
Aug40 56/288,180
Sep40 60/288,180
Oct40 66/363,267
Nov40 36/181,695
Dec40 46/256,310
Tot40 520 (43.33/month)/2,462,867 (205,238.91/month)
US merchant ship construction for 1940 was about 0.5 million GRT.

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan40 8/2
Feb40 10/3
Mar40 10/2
Apr40 19/3
May40 8/0/2
Jun40 18/3/1
Jul40 4/0
Aug40 16/2/1
Sep40 12/0
Oct40 13/2
Nov40 14/1
Dec40 6/0
Tot40 138/18/3 (an average of 11.5 patrols per month and 13% lost)

Thus for 1940, an average of 3.77 ships were sunk per patrol and one U-Boat was lost per 28.89 ships sunk.

1941:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan41 23/129,711
Feb41 47/254,118
Mar41 41/236,549
Apr41 41/239,719
May41 63/362,268
Jun41 66/325,817
Jul41 26/112,624
Aug41 27/85,603
Sep41 57/212,237
Oct41 28/170,786
Nov41 15/76,056
Dec41 23/93,226
Tot41 457 (38.08/month)/2,298,714 (191,559.5/month)
US merchant ship construction 1941 0.804 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan41 10/0
Feb41 18/3/2
Mar41 15/3/3
Apr41 14/2/2
May41 21/0/2
Jun41 22/2/3
Jul41 24/1/9
Aug41 42/5/9
Sep41 38/0/2
Oct41 37/0/6
Nov 41 27/5/5
Dec41 49/4/6
Tot 41 287/25/49 (an average of 23.9 patrols sailing per month and 8.7% lost)

Thus for 1941, an average of 1.59 ships were sunk per patrol and one U-Boat was lost per 18.28 ships sunk.

1942:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan42 56/310,224
Feb42 72/429,255
Mar42 93/507,514
Apr42 81/418,161
May42 129/616,835
Jun42 136/636,926
Jul42 96/467,051
Aug42 117/587,245
Sep42 96/461,794
Oct42 89/583,690
Nov42 126/802,160
Dec42 64/337,618
Tot42 1,155 (96.25/month)/6,158,473 (513,206.08/month)
British and Canadian merchant ship construction 1942 1.8 million GRT
US merchant ship construction 1942 5.433 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan42 50/2/5
Feb42 29/3/2
Mar42 32/2
Apr42 37/2/2
May42 23/3
Jun42 39/9/5
Jul42 45/7/3
Aug42 58/10/4
Sep42 52/8/8
Oct42 62/6/10
Nov42 54/8/6
Dec42 59/8/7
Tot42 540/68/57 (an average of 45 patrols sailing per month and 12.6% lost)

Thus for 1942, an average of 2.14 ships were sunk per patrol and one U-Boat was lost per 16.99 ships sunk.

1943:
Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Jan43 44/307,196
Feb43 67/362,081
Mar43 110/633,731
Apr43 50/287,137
May43 46/237,182
Jun43 17/76,090
Jul43 46/237,777
Aug43 20/92,443
Sep43 16/98,852
Oct43 20/91,295
Nov43 9/30,726
Dec43 8/55,794
Tot43 452 (37.67/month)/2,510,304 (209,192/month)
US merchant ship construction 1943 13.081 million GRT

Number of U-Boat patrols (combat patrols only, does not include tanker/resupply missions)/losses/aborts prior to contact in principle theaters (North Atlantic, South Atlantic, Indian Ocean, and the Americas)
Jan43 61/13/11
Feb43 72/8/9
Mar43 59/16/10
Apr43 95/35/18
May43 55/23/9
Jun43 46/23/9
Jul43 39/27/7 (49 total patrols of all types)
Aug43 33/12/6
Sep43 32/11/10
Oct43 62/23/9
Nov43 36/9/4
Dec43 31/10/2
Tot43 621/210/104 (an average of 51.75 patrols sailing per month and 33.8% lost)

Thus for 1943, an average of 0.73 ships were sunk per patrol and one U-Boat was lost per 2.15 ships sunk.

So, overall, the most successful year for the U-Boats was 1940, before the expansion of the force allowed for an increase of more than about a dozen patrols sailing per month, and well prior to the entry of the US and its shipbuilding capacity into the war. Worse, the performance of the U-Boat force in 1941 and 1942 never exceeded its performance in the first months of the war. And, after 1943 the U-Boat campaign became ever less relevent to the outcome of the war.

Allied and Neutral ship tonnage sunk by German and Italian submarines (#ships, GRT)
Tot44 125/663,308
Tot45 63/284,476

US merchant ship construction for 1944 was 12.257 million GRT
US merchant ship construction for 1945 (through 1 May) was 3.548 million GRT

U-Boat Fleet to 1Sep42
On 19Aug39 there were 57 U-Boats in commission, 20 sea-going U-Boats and 18 'ducks' were fully ready to put to sea
Total number U-Boats deployed to 1Sep42 275
Total number lost 94
Total number retired 10
Total number available 171

U-Boat Fleet 1Sep42 to 1May45
Total number deployed 1Sep42 to 1May45 531
Total number lost 1Sep42 to 1May45 568

British controlled merchant shipping over 1,600 GRT (number/in thousands of gross tons)
3Sep39 2,999/17,784
30Sep40 3,75721,373
30Sep41 3,608/20,552
31Dec41 3,616/20,693

Thus, despite the 'success' of the U-Boat force in 1940 (relative to its performance in 1941 and 1942) it had no appreciable effect in reducing the size of the British merchant fleet.

Numbers of ships arriving and losses in North Atlantic convoys inbound to Britain (ships arriving/losses)
1939 700/5 (7.1%)
1940 5,434/133 ((2.5%)
1941 5,923/153 (2.6%)
1942 4,798/80 (1.7%)
1943 5,667/87 (1.5%)
1944 7,410/8 (0.1%)

The operational U-Boat force from 1943-1945 never approached a "steady 400-500 boat." Rather, during 1942 the peak strength of boats assigned to combat flotillas (including those under repair for combat-damage and breakdowns, but excluding those assigned to school flotillas, experimental projects, or otherwise retired from combat) was 202, during November. The low in 1942 was 89 in January. The average monthly strength during 1942 was 143.83. The strength of the force peaked in May 1943 at 237. It had declined to a low of 159 by November. Average monthly strength during 1943 was 197.58. The peak strength during 1944 was 168 in February, the low was 146 in November. Average monthly strength in 1944 was 157.83. The peak strength in 1945 was April with 165, the low was May with 134, prior to the surrender. <http://www.onwar.com/ubb/smile.gif>

At that, these were much better than 1939 (average of 19.5 monthly), 1940 (average of 18.75 monthly) and 1941 (average of 47.5 monthly). OTOH, the 'bang for their buck' was probably highest in 1940, which was also arguably the U-Boats most 'successful' year in terms of ships sunk per patrol and U-Boats lost per ship sunk (see my previous reply).

 

[Koopernic]

With the German codes it is a mystery to me how long the "plausible denial" ruse worked, Maybe it is an effect of a totalitarian regime, who would want to tell Adolf that the codes and system need to be changed because they have been broken for years?

The plausible deniability effort was quite extensive so anyone would have had difficulty.

Nevertheless the Germans never stopped improving and modifying their system. These efforts would have sent Bletcheley Park blind but for the strange failure to distribute the modifications fully.

Doenitz himself was suspicious and some within the cryptography branches knew enigma was vulnerable if the engineering effort was put in. One officer worked out that an enigma code could be cracked with 50,000 Hollerith punch cards. The Germans had mathematical and statistical punch card machine normally used in accounting and statistics that could search, sort and collate punch cards but also accumulate statistical data and patterns. They were computers. I've seen these envelop like slips running and to process 20 cards a second is nothing for these machines. So some people knew of the danger but each time they were talked down and the seniors assured that all had been checked and was OK. The Germans however did persistently take action, such as introduce a partially rewiredable keyboard (which stopped Polish efforts) and introduce a 4th rotor to naval enigma. It just wasn't enough.

I part it was the lack of being able to appreciate the resources the allies had and could put into it.

A lot of writers like to blame the "totalitarian government" but I think that is survivors or victors bias for the most part. The reality is that the allies had vastly more resources to put into such things and a relatively modest 2500 mile flight from Newfoundland to Bristol made cooperation easy. Engineers and scientists also like to crow about their part and Historians are ideological and will try to draw such conclusions to favor their pet politics. Both the Germans and Japanese did rather well competing commercially after WW2 and having worked with older Germans, Koreans and Japanese I can say their formal respect culture hierarchical systems have a way for the different ends to communicate, in some ways far more egalitarian than the anglo cultures.

The situation with German cryptography was this:
1 The treaty of Versailles had prohibited any German code breaking efforts or organisations.
If they broke this and were discovered they could get invaded as the French did in the Rhineland, trade or banking boycotted, overseas assets seized.
2 This meant any expertise in ciphers was reduced to a few mainly engineers who informally maintained an expertise in the area as second responsibility.
3 Engineers are usually pretty good at mathematics but their tool chest of techniques is perhaps 2% of what a Professionally developed mathematician has that is operating at Phd level. Their idea of mathematics is solving a fire control problem.
4 This also meant that cipher efforts had to be split up between army, navy and Luftwaffe. Combining them would be too formal and lead to discovery by the allied commission.

This created organisational and structural problems for the Germans, it meant that career experts and departments did not develop.

The Solution, and it shows good thinking, was to use commercially derived cipher machines which were used to protect contract prices from competitors.
The Germans were AFAIKT the first to do this on a massive scale in part due to the difficult of distributing code sheets in WW1 and in part due to exercises with the new Blitzkrieg tactics that showed the amount of communication needed.

These are some of their efforts. UKWD on its own could have succeeded.

Rewirable Keyboard for 10 Characters. This sent the Polish Methods Blind. The whole keyboard should have been made so.
Naval Enigma M4 (4 rotor Engima). This famously sent Bletchely Park Blind for a long time. It was a 4th stationary rotor.

UKWD or Umkehrwalze D known as "Uncle Dick" at Belchely Park. This was formidable and would have sent Bletchely Park Blind on its own. It was the equivalent of a new rotor and if every enigma machine had of been supplied it the new rotor could not be reconstructed by following a known message from a broken code group into an unbroken code group.
UKW Dora UKWD for Naval enigma.
Lückenfüllerwalze The rotor would step in an irregular pattern. Could be ued with or indpendatly from UKWD
Enigma Uhr or 'enigma clock' A clockwork mechanism altered the 10 way rewirable keyboard.


Because all of these systems were not distributed widely enough it was posslbe to crack them as they communicated into and out of cracked code groups.

The first orders for UKWD are 222–2542/40 of 19 July 1940 for 4000 units and 222–2543/40 of 12 October 1940 for 6048 units. This confirms that 1940 was the year it was decided to equip the Wehrmacht Enigma machines with a pluggable reflector. Additionally, existing Enigma machine orders received add-on orders for UKWD. These concerned the orders 222–2515/39 for 500 units, 222–2–2501/40 for a first delivery of 480 units and again in February 1941, for the same order, a second delivery of 1200 units. Hence, in 1940 alone a total of more than 11,000 UKWDs were ordered. In addition to these orders, UKWD orders were also placed for the new naval Enigma M4. On 13 September 1940 the OKM, Inspektion der Marine, Zeugamt, Wilhelmshaven placed order no. 18824 G for 1891 UKWD wheels. The order was later amended for an additional 2218 units. On 30 April 1941 OKH placed an order, SS 222-2-6401/41, for 1200 Heeres Enigmas equipped with UKWD...


A report of the Army Security Agency [2, p. 13], written shortly after the war, states: "How close the AngloAmericans came to losing out in their solution of the German Army Enigma is a matter to give cryptanalysts pause. British and American cryptanalysts recall with a shudder how drastic an increase in difficulty resulted from the introduction by the German Air Force of the pluggable reflector ('Umkehrwalze D', called 'Uncle Dick' by the British) in the spring of 1945 [this should read: 1944]. [...] Only a trickle of solutions would have resulted if the pluggable reflector had been adopted universally; and this trickle of solutions would not have contained enough intelligence to furnish the data for cribs needed in subsequent solutions. Thus even the trickle would have eventually vanished.

 

[Koopernic]

The 20mm tail gun in a JU 89 (or what ever 4 engine beast the Germans come up with ) would have been the MG FF or MGFF/M with a 15 round magazine, aimed by hand.

The FW 187, with whatever engines, would have had the same 20mm guns (MG FFs or MG FF/Ms) with a single 60 round drum apiece. Radio operator/rear gunner in the BF 110 had two extra magazines/drums per gun help with multiple engagements.

Germans had no idea (or very little) that they would have the Atlantic coast of France to base subs on when the FW 187 was canceled.

The Oerlikon guns could use 15 round clips, 60 round drums or 100 round drums and sizes in between. The 100 round drums are quite large and wouldn't fit into a wing but as the Fw 187 used fuselage mounted guns this wouldn't be a problem. I doubt it would have made the Fw 187 any less effective and they would have been replaced by belt fed MG 151/15 or MG151/20 soon enough.

I don't think you can be sure that a hypothetical Ju 89 would have been only armed with a single MG FFM in the tail. One reason the Luftwaffe didn't have large turrets is because their aircraft were too small to carry them. That wouldn't be the case with the Ju 89.

You can see some kind of tail turret concept here on this Ju 89.

Obviously by 1940 this aircraft has Jumo 211 engines or DB601 engines of around 1100hp and its speed and armament would be more evolved. It would be much better than the Fw 200 and would almost be able to out run Fairy Fulmars and limit Hurricanes to a tail chase.

Fw 200 can not adequately support the German Navy or the U-boats.

General characteristics

• Crew: Five
• Length: 26.49 m (86 ft 11 in)
• Wingspan: 35.25 m (115 ft 8 in)
• Height: 7.60 m (24 ft 11 in)
• Wing area: 184 m² (1,979 ft²)
• Empty weight: 17,000 kg (37,480 lb)
• Loaded weight: 20,800 kg (50,266 lb)
• Max. takeoff weight: 27,800 kg (61,160 lb)
• Powerplant: 4 × Daimler-Benz DB 600A, 560 kW (750 hp) each

Performance

• Maximum speed: 386 km/h (241 mph)
• Range: 2,980 km (1,862 mi)
• Service ceiling: 7,000 m (22,960 ft)
• Wing loading: 112 kg/m² (25.4 lb/ft²)
• Power/mass: 0.06 hp/lb ()

Armament
(proposed)

• 2 × 20 mm MG FF cannons
• 2 × 7.92 mm (.312 in) MG 15 machine guns
• 1,600 kg (3,520 lb) bombload

The gunner on the He 177 could fire sitting or prone. The range of travel is 70 degree cone. His position is well armored. This is quite an aerodynamic set up.