If Doenitz had his 300 U-Booats after the Fall of France?

prewar Type-IX U-BOAT was ~ 5 million RM , while prewar tanks cost ~ 150,000-RM, ergo 33:1 ratio.

That's ~10,000 tanks.

However the entire prewar naval building programme during the Nazi era is about 2 billion RM not counting yard costs, Deist puts that figure at 2.5 billion RM. The personnel cost were over and above this.

The other side of the coin is that a Panzer Division cost roughly 250 million RM to raise ; staff & equip from scratch.
 
AFAIK the Brits didn't get effective at sinking Uboats by air until 1943.

Hughes & Costello 'The Battle of the Atlantic has some details on this. Including maps showing where each confirmed sinking of a sub and cargo ship occured. Coastal Command made very effective use of aircraft in 1940 & beyond. Unfortunatly they were relatively short ranged aircraft like Hudsons. By early to mid 1941 the submarines were unable to operate effectively in the Home Waters or on the Western and Northern Approaches. In the spring and summer of 1942 the same occured off the US coast. The Happy Time there ended when effective air patrols were organized. In these two cases & elsewhere the Germans were smart enough to break off the campaign when the threat of unsustainable losses became too high. The maps Hughes & Costello provide for each calendar quarter show clearly how the campaigns shifted around the Atlantic & how by the autum of 1942 the mid Atlantic was the only remaining area the submarines could still effectively fight in. Crossing the North Sea, the GIUK gap, the Denmark Strait, the Bay of Biscay was practical, but fighting anywhere in range of the B18 Bolos,

Some Uboats were sunk before then, but prior to 1943 they were primarily for spotting Uboats and forcing them to dive,

If the aircraft were not effective at sinking the submarines, then why did they bother diving?
 

hipper

Banned
AFAIK the Brits didn't get effective at sinking Uboats by air until 1943.

I think you mean 1942

1940 2 UBoats destroyed by aircraft
1941 3 uboats destroyed by aircraft
1942 30 UBoats destroyed by aircraft
1943 35 UBoats destroyed by aircraft
 

Deleted member 1487

If the aircraft were not effective at sinking the submarines, then why did they bother diving?
Diving helped prevent them get sunk. What upped the sinkings was the change in depth charge procedure that OR developed so that diving wasn't a safe space either. Later as the Germans shifted to surfacing at night to say transit out of the Bay of Biscay the Leigh Light and improved radar coupled with a variety of equipment to bomb Uboats made their losses unsustainable, hence 'Bloody Biscay'.

I think you mean 1942

1940 2 UBoats destroyed by aircraft
1941 3 uboats destroyed by aircraft
1942 30 UBoats destroyed by aircraft
1943 35 UBoats destroyed by aircraft
Thanks for the numbers, though it should be noted that the Germans called off the BotA in May 1943...which means those 35 losses happened in 5 months, rather than those 30 in 1942 in 12. Which supports the point that in 1943 they became extremely effective at sinking Uboats. Clearly though they were getting much better by 1942 relative to previous years, but AFAIK it was at the back end of the year; do you have monthly breakdowns for losses to aircraft?
 
About 2 months ago I read a book about British operations research as applied to the BotA and how and when aircraft became effective at sinking Uboats....which was in 1943 when they got the right techniques and equipment for the job. (Blackett's War is the book).


Some time I read, in Black May, that British bomber crews erred by aiming their bombs forward of the conning tower. When asked why, they said the u-boat moves forward when it dives. Actually it couldn't move forward much in the short time of an air attack. Afterward air crews aimed their bombs dead on to the conning tower, and kills increased. The point is that it took a while to learn the right techniques; we can't expect great effectiveness in killing boats c 1940.
 
Thanks for the numbers, though it should be noted that the Germans called off the BotA in May 1943...which means those 35 losses happened in 5 months,

A number of u-boats were hit by aircraft in the second half of 1943. Soon after the boats were recalled in May they went to South American waters, where US aircraft, forewarned by ULTRA, were waiting for them. A u-boat radioed "Air like Biscay!"
 

Deleted member 1487

Some time I read, in Black May, that British bomber crews erred by aiming their bombs forward of the conning tower. When asked why, they said the u-boat moves forward when it dives. Actually it couldn't move forward much in the short time of an air attack. Afterward air crews aimed their bombs dead on to the conning tower, and kills increased. The point is that it took a while to learn the right techniques; we can't expect great effectiveness in killing boats c 1940.
Agreed, but reducing the effectiveness of Uboats by forcing dives is probably nearly as good in overall terms of getting convoys through with low losses.

A number of u-boats were hit by aircraft in the second half of 1943. Soon after the boats were recalled in May they went to South American waters, where US aircraft, forewarned by ULTRA, were waiting for them. A u-boat radioed "Air like Biscay!"
Got some numbers?
 
If the aircraft were not effective at sinking the submarines, then why did they bother diving?

116 Coastal Command aircraft were shot down by U-boats which did not dive. The weapons and tactics employed by aircraft, and the weapons and tactics employed by U-boats changed during the course of the war.
 

Deleted member 1487

116 Coastal Command aircraft were shot down by U-boats which did not dive. The weapons and tactics employed by aircraft, and the weapons and tactics employed by U-boats changed during the course of the war.
That was a remarkably rare situation. The FLAK Uboat experiment was a disaster:
http://uboat.net/types/u-flak.htm
Early war with lightly armed CC aircraft it was much easier to pull that off but by 1941-42 that was a death sentence to even try.
 

hipper

Banned
Diving helped prevent them get sunk. What upped the sinkings was the change in depth charge procedure that OR developed so that diving wasn't a safe space either. Later as the Germans shifted to surfacing at night to say transit out of the Bay of Biscay the Leigh Light and improved radar coupled with a variety of equipment to bomb Uboats made their losses unsustainable, hence 'Bloody Biscay'.


Thanks for the numbers, though it should be noted that the Germans called off the BotA in May 1943...which means those 35 losses happened in 5 months, rather than those 30 in 1942 in 12. Which supports the point that in 1943 they became extremely effective at sinking Uboats. Clearly though they were getting much better by 1942 relative to previous years, but AFAIK it was at the back end of the year; do you have monthly breakdowns for losses to aircraft?

http://www.ibiblio.org/pha/USN/Defeat-of-Enemy-Attack-on-Shipping.pdf

Tables of uboat losses about page 27o
 
Some time I read, in Black May, that British bomber crews erred by aiming their bombs forward of the conning tower. When asked why, they said the u-boat moves forward when it dives. Actually it couldn't move forward much in the short time of an air attack. Afterward air crews aimed their bombs dead on to the conning tower, and kills increased. The point is that it took a while to learn the right techniques; we can't expect great effectiveness in killing boats c 1940.

And with more targets they may well learn quicker. Frankly this seems to shaping up to be another scenario where for no particular reason the Germans change their plans to improve their performance while the British just sit around looking bemused at it all...
 
Agreed, but reducing the effectiveness of Uboats by forcing dives is probably nearly as good in overall terms of getting convoys through with low losses.

Consider another scenario. Say Germany eschews plans to build Bismarck/Scharnhorst class ships and has 100 U-boats at the start of the war. Britain assigns more bombers to coastal command. But just before the start, the Germans send their u-boats to the central Atlantic, and rely on still neutral Italy and Spain to keep them supplied for extended periods, by means of supply ships in secret locations, a few in the Canary islands. If RAF bombers can't reach the central Atlantic, where many more boats are prowling, what would shipping losses amount to compared to those incurred historically?
 
It would've been better to invest the metal and labor wasted on Bismarck and Tirpitz on more subs. Had 300 been available by July 1940, without sacrificing army or Luftwaffe strength, they might've forced Britain to give up in 6-12 months.
Or maybe the Graf Zeppelin? The battleships after all did prove to be of at least some use.
 

nbcman

Donor
Or maybe the Graf Zeppelin? The battleships after all did prove to be of at least some use.

Also if the Germans could gain more materials if they didn't lay down the Lutzow or the Seydlitz heavy cruisers that they never completed IOTL.
 
In the late 1950s a research paper was published in Germany that examined what type of fleet the KM could have built instead of the historical fleet. It was written by officers who were part of the war time KM design office, and vetted by one of the top wartime designer.

They focused on the resources funding and ship yards involved in the construction of the 4 battleships and 5 heavy cruisers [Bismarck ; Tirpitz ;Scharnhorst ; Gneisenau plus 5 Hipper/Prince Eugen cruisers] . They concluded they could either build 21 Deutschland raiders OR 375 Type VII U-Boats....and completed before the war began.
 
In the late 1950s a research paper was published in Germany that examined what type of fleet the KM could have built instead of the historical fleet. It was written by officers who were part of the war time KM design office, and vetted by one of the top wartime designer.

They focused on the resources funding and ship yards involved in the construction of the 4 battleships and 5 heavy cruisers [Bismarck ; Tirpitz ;Scharnhorst ; Gneisenau plus 5 Hipper/Prince Eugen cruisers] . They concluded they could either build 21 Deutschland raiders OR 375 Type VII U-Boats....and completed before the war began.

Right, completely unbiased assessment of course....
 
This is saying that starting in 1934 or so, in five years, the German shipbuilding industry will build 375 more (75/year) submarines than they did OTL can hire enough people do this and start from a situation where no submarines have been built for 16 years so the skill base for this is greatly depleted. Prewar building a Gato class submarine in the USA took roughly 13 months from start to commissioning. Let's assume because the type VII was smaller and had less complex auxiliary machinery (like air conditioning) let us assume under peacetime conditions and also restarting submarine building from zero it would take 7 months on the slipway, the rest of the pre-commissioning fitting out is in the water. This means you need roughly 50 slipways to build 75 submarines a year, as well as the space and equipment needed to fit out the submarines.

I will assume that not building those 9 large ships will give you enough steel, copper, and whatever other RAW materials you need to build the 375 submarines. But this gives you hulls. You need the optics for all those periscopes, which means many, many more optics than for the rangefinders aboard those 9 ships. You need one or two radio sets for each submarine, even if you have 10 radios per large ship (you don't) this means 660 more radios. 375 submarines will require more precision gauges than 9 large ships. 375 U-boats mean 375 deck guns, yes smaller than the main guns on the big ships but it is still 375 "extra"guns" The list goes on and on - it is not just a question of steel.

Germany will need, beginning in 1934, to build all those slipways they don't have. This means that in order to build 375 submarines by September 1939 you'll be building at a rate of 100/year at some point because you won't be building 75/year from the get-go. remember this is on top of small coastal and training submarines Germany must build.

Having a stack of steel, copper, cables, and so forth does not a submarine build. Having foundries and plants does not an armaments industry make - you need to retool and build new production lines. Without the large surface ships, Germany certainly could have built many more submarines, although not 375. As I have previously posted, you need to train a large number of sailors and build a shore establishment to manage this - a nontrivial exercise. Others have pointed out how a massive U-boat building campaign would have resulted in a British response. Finally, if the Germans do not have a significant surface fleet (nothing larger than destroyers) the RN basically has complete freedom to use their capital ships where they want to (no fleet in being) and in the run up to the war will be building more destroyers/escorts.
 
Consider another scenario. Say Germany eschews plans to build Bismarck/Scharnhorst class ships and has 100 U-boats at the start of the war. Britain assigns more bombers to coastal command. But just before the start, the Germans send their u-boats to the central Atlantic, and rely on still neutral Italy and Spain to keep them supplied for extended periods, by means of supply ships in secret locations, a few in the Canary islands. If RAF bombers can't reach the central Atlantic, where many more boats are prowling, what would shipping losses amount to compared to those incurred historically?

Sounds like Italy and Spain are not really neutral in this case, and the Royal Navy is able and would have devoted more pre-war production to escorts. Spain suffers from the lack of food imports, and Italy faces a larger Royal Navy surface fleet, both apologise and remain neutral afterwards.

Convoys are adopted sooner and the US is upset by the 'accidental' sinking of its ships, American involvement in the war is accelerated.

Meanwhile the Royal Navy prevents the German landings in Norway and the battle for France suffers from the losses sustained in Norway, although close the French just manage to hold out and it all ends in tears for Germany.
 
Consider another scenario. Say Germany eschews plans to build Bismarck/Scharnhorst class ships and has 100 U-boats at the start of the war. Britain assigns more bombers to coastal command. But just before the start, the Germans send their u-boats to the central Atlantic, and rely on still neutral Italy and Spain to keep them supplied for extended periods, by means of supply ships in secret locations, a few in the Canary islands. If RAF bombers can't reach the central Atlantic, where many more boats are prowling, what would shipping losses amount to compared to those incurred historically?

If the Spanish are involved then the rule is that you cannot use the word 'secret' ;)
 
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