The "other" Z-plan

[Kyle Holgate]

Suppose in 1938 instead of deciding on a fleet of battleships, cruisers, carriers and DD's that Hitler had instead chosen the alternative raiding navy that was proposed? So instead of 1939 arriving with only a few u-boats (IIRC about 10 were long range and deployed to the Atlantic) there were already several dozen ready to go? Further instead of having a Bismarck and Tirpitz building there are "O" or "P" class armored cruisers (for lack of a better name for them) in progress and/or near ready for sea?
The RN was sure that their Asdic was the answer to the U-boat problem, something clearly untrue as it turned out. Even with only a few boats to start with they worried Churchill. Now picture a head start of sorts - where the Germans start with quite a few more and get to their 300 (the level Dönitz believed they needed to win) perhaps a year earlier.

Wanted to talk about Hitler in the Battleship thread? Move the discussion here (though do try to keep it as non-political as you can of course).

[Smiffy]

British Intelligence was pretty good at that time. Once it was realised that a large submarine fleet was being built, more ASW vessels would have been laid down. As the fall of Norway and France could not been foreseen, I expect more fast minelayers and minelaying subs would have been built too, in order to blockade the German U-boat bases. Greater priority would have been put on ASW development, so RDF and HF/DF would have been ready sooner and maybe even the RAF would have targeted U-boat bases and building yards from Day One of the war.

[Kyle Holgate]

British Intelligence was pretty good at that time. Once it was realised that a large submarine fleet was being built, more ASW vessels would have been laid down. As the fall of Norway and France could not been foreseen, I expect more fast minelayers and minelaying subs would have been built too, in order to blockade the German U-boat bases. Greater priority would have been put on ASW development, so RDF and HF/DF would have been ready sooner and maybe even the RAF would have targeted U-boat bases and building yards from Day One of the war.

Of course the changes would have been responded to by the French and the British. Of course the RN had to be aware of other nations too, not just Germany so they'd still be "forced" to build the KGV class and the Invincible carriers and follow on ships. Unfortunatley they couldn't afford to "just" bottle up the Germans.
More ASW ships would have been a great idea, but as it turned out the catch-up of learning to use them took a while. How much mischief could the U-boats have gotten into in the mean time? The HFDF and other countermeasures were also learned for the most part and more of a reaction to the subs than a pre-planned ASW strategy.
That's my main point here - the RN took a while to spin up on ASW - longer than it took for the U-boats to get their sea legs. With dozens more submarines at war start - things would likely be quite gloomy for a while before the RN got up to speed. Even then it took until 1943 to gain the upper hand - with a 50 or so boat head start, would England had been able to manage until the 1943"ish" turn in the battle of the Atlantic?

The raiders would have been a bit interesting too. Imagine a Graf Spee that would be able to out run many patrol cruisers AND outfight them too. Of course we know that the convoys with BB escorts took care of the Atlantic routes for the most part, but a faster version of the Graf Spee at large and too fast for the BC's such as Hood or Dunkerque to chase down could have caused considerable havoc - morale wise if not in actual tonnage sunk.

[JMS]

It would be more cost effective to have disguised merchant cruisers rather than "pocket battleships" roaming around. And to debug the torpedoes.

[Ed Rotondaro]

Of course the changes would have been responded to by the French and the British. Of course the RN had to be aware of other nations too, not just Germany so they'd still be "forced" to build the KGV class and the Invincible carriers and follow on ships. Unfortunatley they couldn't afford to "just" bottle up the Germans.
More ASW ships would have been a great idea, but as it turned out the catch-up of learning to use them took a while. How much mischief could the U-boats have gotten into in the mean time? The HFDF and other countermeasures were also learned for the most part and more of a reaction to the subs than a pre-planned ASW strategy.
That's my main point here - the RN took a while to spin up on ASW - longer than it took for the U-boats to get their sea legs. With dozens more submarines at war start - things would likely be quite gloomy for a while before the RN got up to speed. Even then it took until 1943 to gain the upper hand - with a 50 or so boat head start, would England had been able to manage until the 1943"ish" turn in the battle of the Atlantic?

The raiders would have been a bit interesting too. Imagine a Graf Spee that would be able to out run many patrol cruisers AND outfight them too. Of course we know that the convoys with BB escorts took care of the Atlantic routes for the most part, but a faster version of the Graf Spee at large and too fast for the BC's such as Hood or Dunkerque to chase down could have caused considerable havoc - morale wise if not in actual tonnage sunk.

Kyle:

Along with a lack of subs, the other problem facing Germany in the opening stages of the war was unreliable torpedoes. They solved the problem faster than we did, but there were many lost opportunities as a result.

[Kyle Holgate]

Kyle:

Along with a lack of subs, the other problem facing Germany in the opening stages of the war was unreliable torpedoes. They solved the problem faster than we did, but there were many lost opportunities as a result.

Most of their torpedo issues were due to the magnetic exploder causing them problems. If you really look into it you'll find that their torpedoes worked fairly well south in the Atlantic convoy lanes, and had problems in the North sea, Scapa flow and further up toward Norway. The subs that got into the convoy lanes between Ireland and the states/Canada had a much better time and apparently more reliable "fish". Certainly they could have been better - but even with the few subs they had they did pretty well - so just quadruple the number of subs - should be 4x the mischief too in theory, torpedo troubles or no

[Mike Malanaphy]

British Intelligence was pretty good at that time. Once it was realised that a large submarine fleet was being built, more ASW vessels would have been laid down. As the fall of Norway and France could not been foreseen, I expect more fast minelayers and minelaying subs would have been built too, in order to blockade the German U-boat bases. Greater priority would have been put on ASW development, so RDF and HF/DF would have been ready sooner and maybe even the RAF would have targeted U-boat bases and building yards from Day One of the war.

Hi guys,

A lot of variables in this equation. Had the British detected the U boat build up, they had a finite umber of slips capable of turning out escort sized ships with addtional limitations of gun mountings and turbine machinery production. The corvette suited this increase because it could utitlize shorter slips that couldn't build warships and used simpler, more plentiful reciprocating engines. Between the wars, the British tried to design an escort suitable for mass production but were unsuccessful.

A note on the effect of strategic bombing on U boats lost:

Bomber Command destroyed 19 U boats, 4 of them on building slips.

8th Air Force destroyed 50 of which 6 were on building slips.

15th Air Force destroyed 15 U boats.

A total of 1,167 U boats were commissioned, but only 859 sailed.

[Mike Malanaphy]

Most of their torpedo issues were due to the magnetic exploder causing them problems. If you really look into it you'll find that their torpedoes worked fairly well south in the Atlantic convoy lanes, and had problems in the North sea, Scapa flow and further up toward Norway. The subs that got into the convoy lanes between Ireland and the states/Canada had a much better time and apparently more reliable "fish". Certainly they could have been better - but even with the few subs they had they did pretty well - so just quadruple the number of subs - should be 4x the mischief too in theory, torpedo troubles or no

Hi Kyle,

There is an interesting German perspective to this. Jak P. Mallmann Showell, a U Boat historian talks about some of the problems facing the Germans at sea. German U boats had a difficult time locating the enemy at sea. Lacking any real air recon, no sensors beyond their passive sonar, it was extremely difficult to locate convoys. He also mentions the severe Atlantic winters of 40, 41, and 42 which limited visibility. B Dienst, the German naval code service, read a British naval cypher till August of 1940, but not enough boats were available to exploit the information. That cypher was later recovered again and read from mid 42 to mid 43. Even with the U boat force at it's peak, the Germans never made an effective dent in convoys.

He hints at crew quality as being the problem. Ships sunk per U boat peaked in November, 1940 at 5.5 with 10 boats at see. By May, 1942 with 61 boats at sea, sinkings per boat were down to two ships. By the climatic Feb-Mar 1943 convoy battles, there were 116 boats at sea, but sinkings were down to .5 ships per boat. 859 boats made war patrols , but only 321 actually sank a ship and only 25 boats sank or damaged more than 20 Allied ships. This is reinforced by the fact that 2% of the skippers sank 30% of the ships. U baot skippers were much like fighter pilots. He also faults the design as essentially being updated WW I designs with little thought to habitability on long patrols.

The RN, RCN, and the USN had their hands full with U boats for quite a time. Centimeter radar and VLR Liberators were the bane of U boats. The effectiveness of this combination is shown by the fact that of the 648 boats lost in front line service, land based air accounted for 204 boats unassisted and carrier aircraft sank 39 unassisted. Though losses to aircraft were few until the latter months of 1942. Of those 648 boats lost, 215 were lost on their first patrols.


I couldn't find it, but the German historian Jurgen Rohwer made an estimate of the effect of bad torpedoes on the sinking rate and it was impressive.

300 boats in 1939 makes for an impressive number, but could it have gotten the job done?

[asnrobert]

From what I've read, crew quality was a big problem, especially by 1941. Usually, U-boat crewmen were sent to new construction so that new U-boats coming into service would have some experienced crew. By 1941, new submarines were turned out in large numbers, but, mnay of the 'aces' had been lost, along with their experience crews, so the cadre of experienced sailors simply wasn't there. When the U-570 went on her first patrol, only 5 of her crew had ever been to sea. As a result, they came unglued when they experienced their first air attack, and surrendered, allowing their sub to be captured.

[Kyle Holgate]

Hi Kyle,

There is an interesting German perspective to this. Jak P. Mallmann Showell, a U Boat historian talks about some of the problems facing the Germans at sea. German U boats had a difficult time locating the enemy at sea. Lacking any real air recon, no sensors beyond their passive sonar, it was extremely difficult to locate convoys. He also mentions the severe Atlantic winters of 40, 41, and 42 which limited visibility. B Dienst, the German naval code service, read a British naval cypher till August of 1940, but not enough boats were available to exploit the information. That cypher was later recovered again and read from mid 42 to mid 43. Even with the U boat force at it's peak, the Germans never made an effective dent in convoys.

He hints at crew quality as being the problem. Ships sunk per U boat peaked in November, 1940 at 5.5 with 10 boats at see. By May, 1942 with 61 boats at sea, sinkings per boat were down to two ships. By the climatic Feb-Mar 1943 convoy battles, there were 116 boats at sea, but sinkings were down to .5 ships per boat. 859 boats made war patrols , but only 321 actually sank a ship and only 25 boats sank or damaged more than 20 Allied ships. This is reinforced by the fact that 2% of the skippers sank 30% of the ships. U baot skippers were much like fighter pilots. He also faults the design as essentially being updated WW I designs with little thought to habitability on long patrols.

The RN, RCN, and the USN had their hands full with U boats for quite a time. Centimeter radar and VLR Liberators were the bane of U boats. The effectiveness of this combination is shown by the fact that of the 648 boats lost in front line service, land based air accounted for 204 boats unassisted and carrier aircraft sank 39 unassisted. Though losses to aircraft were few until the latter months of 1942. Of those 648 boats lost, 215 were lost on their first patrols.


I couldn't find it, but the German historian Jurgen Rohwer made an estimate of the effect of bad torpedoes on the sinking rate and it was impressive.

300 boats in 1939 makes for an impressive number, but could it have gotten the job done?


I don't think that Germany could have had 300 boats ready in 1939 under my "alternate Z plan". I'm too lazy to look it up right now - but I think the Z plan was decided on (the actual BB based one) in 1937-38, too late to get 300 seagoing boats built by the start of the war. My suggestion is that they could have had several dozen more than they did. You're right though, even if we assume they had 300 right off the bat - would that have brought England down? The Brits were and are a tough people, so I'm not so sure - still we have only to look at Germany in 1918 to see what a real blockade can do to food supplies and morale. I Often wonder at the motivations for making war that they had - and that really they were not under any direct threat (yet) from Hitler and he'd likely have let them go "easy" if they wanted out of the war. Of course Churchill wouldn't do that but a different PM might such as lord Halifax. If the U-boat war went too sour in 1939-40 would the oust Churchill? Don't know.

[Mike Malanaphy]

From what I've read, crew quality was a big problem, especially by 1941. Usually, U-boat crewmen were sent to new construction so that new U-boats coming into service would have some experienced crew. By 1941, new submarines were turned out in large numbers, but, mnay of the 'aces' had been lost, along with their experience crews, so the cadre of experienced sailors simply wasn't there. When the U-570 went on her first patrol, only 5 of her crew had ever been to sea. As a result, they came unglued when they experienced their first air attack, and surrendered, allowing their sub to be captured.

Hi Robert,

Yes, the expanison of the U boat service definitely diluted the quality of crews. Losses didn't really start to climb until late 1942 and by 1944, the chance of being sunk were very high. It's amazing that the boats continued to sail in the face of that casualty rate.

[Mike Malanaphy]

I don't think that Germany could have had 300 boats ready in 1939 under my "alternate Z plan". I'm too lazy to look it up right now - but I think the Z plan was decided on (the actual BB based one) in 1937-38, too late to get 300 seagoing boats built by the start of the war. My suggestion is that they could have had several dozen more than they did. You're right though, even if we assume they had 300 right off the bat - would that have brought England down? The Brits were and are a tough people, so I'm not so sure - still we have only to look at Germany in 1918 to see what a real blockade can do to food supplies and morale. I Often wonder at the motivations for making war that they had - and that really they were not under any direct threat (yet) from Hitler and he'd likely have let them go "easy" if they wanted out of the war. Of course Churchill wouldn't do that but a different PM might such as lord Halifax. If the U-boat war went too sour in 1939-40 would the oust Churchill? Don't know.

Hi Kyle,

I would agree. I don't think German industrial capacity was up to the taks of producing 300 boats by that time. But I believe that the numbers of boats available to Doenitz could have benn larger. Of the 57 boats he had, half were the Type IIs limited to the North Sea and the Channel. A force of of 75-100 coulkd have had a greater impact early in the war. Thouh in convoys, escorts were pathetically weak and convoys dispersed in home waters to sail indepentdently to port. The diversion of U boats to the Norwegian campaign produced little and hampered attacks on convoys for months. Not to mention the torpedo issue.

Doenitz only could muster 10 boats at sea in the fall of 1940, the first "Happy Time". The weight of another 30-40 Type VIIs with pre war quality crews could have been considerable. Not enough to tip the balance perhaps, but make the British war effort very difficult. The British merchant fleet had actually grown after a year of war due to the lack of boats to concentrate on the North Atlantic sea lanes. Centimeter radar on planes and ships in number were almost 2 years away.