U-Boat Counterfactuals, Klasse XXI and Secondary Armaments

[MKSheppard]

On another forum, someone mentioned that the recources spent on the larger ships of the German surface fleet, would have been more usefull when spent on building more U-boats instead.

While I certainly agree with the first part, wouldn't it have been more usefull to divert those recources in the Luftwaffe and/or Wehrmach rather than building more U-Boats?

As far as I know, U-boats were only efficient for a short period during the war but I might be mistaken.

So, which would give the most bang for buck? More U-boats or more land/airforce?

Keep in mind that this kind of production isn't infinitely fungible: you might be able to take the steel you would have spent building a battleship and use it to make a few dozen U-boats, but you certainly can't make it into a few thousand planes. Different weapons use different parts of the country's industrial capacity, so building less of X doesn't always mean being able to build more of Y. Even if it does, that doesn't mean the same equation will work the other way around.

That leads to a general question:

Might there have been logistics issues with building more U-boats, because of building slip availability or the U-boats needing materials that were vitally needed for programs other than capital ship construction? Stuart's recent posts on heavy tank production have got me wondering about that sort of issue...

Certainly are. Surface ships are ton for ton cheaper then submarines, and submarines drew off what was mostly a different, more specialist industrial base which usually involved completely separate building yards, and higher ratios of certain key mineral resources like copper for all the electric motors and batteries.

So converting surface ship tonnage into submarines will not produce particularly impressive results.
Germany had limitations on raw materials even before WW2 broke out (because they had to pay to import them and Hitler was spending every dime already) that affected production of weapons as much as a lack of sufficient industry did. So steel for ships doesn’t turn into aluminum for planes. Gneisenau accomplished the impressive feat of TWICE donating her entire main armament for shore batteries.

You could have turn the surface ship tonnage into more tanks and land artillery with perhaps better results. A plant that makes armor for battleships can also turn around and make armor for tanks, and gun factories tend to be pretty adaptable. Tank production was already held back by lack of steel.

As it was Germany got a pretty good value using surplus warship guns from all the projects it canceled and ships it disarmed for coastal defense. Germany had actual slim hope of winning a land war too, the naval situation was pretty hopeless when even France alone was building or planning a fleet on par with the German program.

That said, I am not sure how effective Dönitz' planned 300 boat navy was going to be, even if they were to be finished all before 1939.

The kind of investment needed to support that kind of U-Boat fleet is another matter, too. Even disregarding notorious problems with copper Germany had to import and even outright rob from Allied freighters during the war, you'd need more dry docks to service the boats, more bunkers to shelter them from aircraft, more torpedoes (Wasn't there only one plant making torpedo batteries in the entire third reich? I'm not sure where I read this, though), optics, hydrophones, officers, etc.

Donitz certainly thought he'd have been able to accomplish much, much more if he had 300 boats to play with, and it makes sense: the question is, though, would he have been able to do enough to actually starve Britain? The British Isles were never in actual danger of starving or even running out of vital resources to supply their industry throughout the war. And if Germany can't force them to their knees by early 1943, they uboat fleet is f---d.

One thing to remember as well is that most of the German surface fleet was built or very near completion during the late '30s. Scrapping or not building that fleet then isn't going to help much if the production is switched to building Mk1 Panzers.

Do you have any specific examples of how Churchill exaggerated the effect of the U-boats?

There's mentions of it in Hitler's U-Boat War, but I will have to dig through the book, so it will take some time

I'll post citations as soon as I get them.

IIRC, this was the nadir of the sub; when detection technologies made them easier to spot and kill while they still labored under the same old problems of being submersibles more than truly submarine vessels, unable to travel at high speeds underwater due to not being able to run their main engines and having a limited amount of time when they could be submerged.

The funny thing is that all the technologies used for the Type XXI subs (the first "real" SSKs) existed well before the war: hell, it even used Type IX batteries! The "revolutionary" solutions on the Type XXI were basically: a hydrodynamic hull optimized for underwater performance, large battery compartment and snorkels. Some other cool kit it had was pretty much optional to those three: the streamlined hull alone allowed the Type XXI to move faster underwater than most convoy escorts could without losing the ability to use their sonar.

The funny thing is that all the technologies used for the Type XXI subs (the first "real" SSKs) existed well before the war: hell, it even used Type IX batteries! The "revolutionary" solutions on the Type XXI were basically: a hydrodynamic hull optimized for underwater performance, large battery compartment and snorkels. Some other cool kit it had was pretty much optional to those three: the streamlined hull alone allowed the Type XXI to move faster underwater than most convoy escorts could without losing the ability to use their sonar.

It's worse that that; the streamlined hull idea went back to the British R class submarines that were being built at the end of WW1 (in fact, when the technical details of the Type XXI submarines became available to the allies in 1943, the first thing the RN did was to pull the design cover for the R class). However, the design wasn't original even then, the basic idea of a submarine being streamlined for underwater speed went back to the first days of submarine warfare. Then, submarines were seen as being for coastal (and in particular harbor) defense. They would stay in port, then when an enemy blockading fleet appeared, go out, attack and return. Very much as the Hunley did in fact. What they needed was underwater speed so the boats were built relatively streamlined. When subs turned into commerce destroyers, they needed the paraphenalia associated with that mission and that took priority over underwater speed.

The underwater speed of the Klasse XXI is also misleading. Yes, the type could do around 16 knots underwater but in doing so she would run her batteries flat in around 45 minutes. That's true today by the way; a modern diesel-electric SSK running at top speed underwater will deplete her batteries in about the same length of time. Also, a surface ship trying to keep track of her will indeed be outrunning her own ability to use sonar but that doesn't actually mean too much. Surface ships worked in teams with some ships drifting to keep sonar contact, others moving at high speed into new tactical positions. This was - and is - called "sprint and drift". The interesting bit is that of the Klasse XXI has the same shortcoming; if she ran flat-out she would be sonar-blind also so her situational awareness drops to zero. The true importance of the Klasse XXIs underwater speed isn't that she can outrun surface ships, she can't. What she can do is use her speed to slide between the beams of the sonars being used to track her, in other words evade rather than outrun. This was countered by a modified sonar system that used three beams rather than one.

What the Klasse XXI fans don't tell you is that by 1944 the Allies knew all about the design, what it was capable of doing and how to counter it. They'd had the design specs for the Klasse XXI and had modified two British S-class submarines to simulate Klasse XXIs (in fact, ironically enough, the British were operating submarines with Klasse XXI performance before the Germans). They learned a lot from those experimental boats. One lesson was that, in fact, Klasse XXI was a pretty bad design. Amongst other things, it was extremely sensitive to depth control. A combination of high underwater speed and that sensitivity meant she could dive out of control without warning and go through her maximum safe depth before the crew could correct the dive. Another was that the "figure of eight" hull design was unnecessarily complex and hard to build. Finally, the Allies learned that the standard Allied submarines, the Balao/Tench class for the US and the T/A class for the UK, could be modified to equal or exceed Klasse XXI performance at relatively little cost. That gave rise to the post-war Guppy programs.

In terms of countermeasures, the plans for what to do in the event of a major Klasse XXI offensive were in place. Perfectly adequate weapons already existed; the Hedgehog and Squid ahead-throwing ASW launchers were already in service and perfectly adequate. The next-generation UK Limbo and US Weapon Able were already advanced in development (Weapon Able became Weapon Alpha and was disappointing; Limbo in contrast was a truly deadly submarine-killer. As to platforms, what Klasse XXI did was make obsolete the slow escorts, the British Flower class corvettes and the US 19-knot DEs. Note how quickly they all went postwar. However, the US had already shifted production to the 24-knot DE and the British to new classes of frigates. In addition, the plans were for the mass conversion of older destroyers to ASW configuration. Essentially, the US Navy planned to convert all of its destroyers (up to and including the Fletcher Class) to ASW configuration with three Hedgehogs per ship (A big trainable one in place of B gun and two smaller fixed mounts in the waist). The British planned to mount two Squids per destroyer.

Most of this stuff can be found in Norman Friedman's "Illustrated Design Histories" of US Navy destroyers and submarines. It doesn't set out to do so but as a side-efefct , the books destroy the myth of the Klasse XXI quite effectively.

The underwater speed of the Klasse XXI is also misleading. Yes, the type could do around 16 knots underwater but in doing so she would run her batteries flat in around 45 minutes. That's true today by the way; a modern diesel-electric SSK running at top speed underwater will deplete her batteries in about the same length of time.

Well, yes. The XXI's capabilities would only be decisive in combat during the early war, when ASW tactics were in their infancy and sonar-equipped escorts were few and far between. They were marginal by the time when the XXI was actually introduced and would have to face heavily escorted convoys with experienced crews.

Also, a surface ship trying to keep track of her will indeed be outrunning her own ability to use sonar but that doesn't actually mean too much. Surface ships worked in teams with some ships drifting to keep sonar contact, others moving at high speed into new tactical positions.

That started inning its way into operations after a couple of years, though.

What the Klasse XXI fans don't tell you is that by 1944 the Allies knew all about the design, what it was capable of doing and how to counter it. They'd had the design specs for the Klasse XXI and had modified two British S-class submarines to simulate Klasse XXIs (in fact, ironically enough, the British were operating submarines with Klasse XXI performance before the Germans).

Well, that I didn't know.

One lesson was that, in fact, Klasse XXI was a pretty bad design. Amongst other things, it was extremely sensitive to depth control. A combination of high underwater speed and that sensitivity meant she could dive out of control without warning and go through her maximum safe depth before the crew could correct the dive. Another was that the "figure of eight" hull design was unnecessarily complex and hard to build. Finally, the Allies learned that the standard Allied submarines, the Balao/Tench class for the US and the T/A class for the UK, could be modified to equal or exceed Klasse XXI performance at relatively little cost. That gave rise to the post-war Guppy programs.

Blair also mentions in his book it had other deficiencies: one, the snorkel had a faulty floater blocking the air intakes from taking in sea water. It had a tendency to get stuck in the "closed" position, and there was no cutoff for the diesels, so, uh, you can see the problem

There were also problems with ball bearings and the modular construction done by companies that never built ships before, but those were not endemic to the design.

In terms of countermeasures, the plans for what to do in the event of a major Klasse XXI offensive were in place. Perfectly adequate weapons already existed; the Hedgehog and Squid ahead-throwing ASW launchers were already in service and perfectly adequate. The next-generation UK Limbo and US Weapon Able were already advanced in development (Weapon Able became Weapon Alpha and was disappointing; Limbo in contrast was a truly deadly submarine-killer.

Wasn't one of the only two Type XXIs sent to Norway to begin combat operations sank by an airplane while snorkeling? That alone proved it was far from invincible, especially in light of swarms of Allied ASW airplanes.

Most of this stuff can be found in Norman Friedman's "Illustrated Design Histories" of US Navy destroyers and submarines. It doesn;t set out to do so but as a side-efefct , the books destroy the myth of the Klasse XXI quite effectively.

Blair's "Hitler's U-Boat War" does that, too, especially with anecdotes about the Type XXI trying to kill its own crews in various creative ways

All right. With all that established: why weren't those submarine technologies introduced sooner by someone, given that most of them seem to have been around well before 1943? Was it simply a case of "we can't design and prototype this thing fast enough to get it into service when it will do some good," or something more subtle?

^At the start of the war, the decision was made to focus on mass production of existing types, considering how few submarines Germany had available. There were months where less than ten submarines in total were on patrol, so the decision made sense then.

All right. With all that established: why weren't those submarine technologies introduced sooner by someone, given that most of them seem to have been around well before 1943? Was it simply a case of "we can't design and prototype this thing fast enough to get it into service when it will do some good," or something more subtle?

The simple answer is that they weren't needed. From about 1915 onwards, the submarine was seen as a commerce destroyer. That meant it needed to have radios so that it could communicate with home base (to get the latest data on convoy routings etc and to report results), the ability to search wide areas to locate targets - implying relatively tall masts and spots for lookouts, a pentiful supply of torpedoes to kill said merchant ships and a gun (or more) to finish off targets not worth a(nother) torpedo. The target was a fleet of merchant ships that thumped along at 6 - 8 knots tops. Subs had to run on the surface to find their targets (and, later that exposed them to aircraft requiring more guns to fight off said aircraft) so the design stressed surface speed and surface seakindliness. Long underwater endurance, high underwater speed etc simply weren't needed anb that meant those characteristics could be sacrificed to get the other requirements.

It's not often realized the extent to which submarines - up to 1945 at least - fought on the surface. Typically they would run into a convoy at night, on the surface, make their attack on the surface and run on the surface. Diving was pretty much a last resort. Once they were down, they were very slow, and had a limited life. After 1943 there were so many allied escorts that they could afford to detach some to sit on each submarine until its batteries went flat (which is still a viable tactic by the way, it's called hold-down). The Klasse XXI was an effort to design a submarine that could evade the air patrols and escorts to make its attacks. That was a desperation resort and represented a sacrifice of commerce destroyer characteristics in favor of survival. In other words, Klasse XXI represented the decision that it was better to have a poor commerce destroyer that could survive rather than an excellent commerce destroyer that couldn't.

The Type XXI's abilities were pretty much moot in every way once it entered service. It didn't matter if Germany could build another 300 of them. By 1944 most German submarines were being sunk before they could even leave port. Even if they could, Allied Radar sensitivity and roaming hunter killer groups made performing so much as a sortie an act of suicide. The Type XXI's snorkel could actually be detected on radar, defeating the purpose of the whole system! Also, what PeZook said did most likely happen. Submarines traveling at periscope depth can be seen by aircraft in calm waters. Conveniently the only time during which the snorkel could even operate. The Type XXI just never really stood a chance in the Atlantic. Once 1943 was over Allied shipping was more or less untouchable. The only thing the Kriegsmarine could hope to do by that point was harass any Allied ship that strayed too close to Germany's coastline.

That's overstating things a little bit. Pre 1943 and pre-snort (by the way, the snort was a Dutch invention; pre-war Dutch submarines serving in the DEI had snorts, the Germans copied the idea from a captured Dutch O-boat) a submarine running on the surface could be spotted from literally hundreds of miles away. So, once there were enough MPAs to cover the Atlantic, teh U-boats were history. What the snort did was cut down that radius of search from around 200 miles to about 20. In other words the huge area search capability of MPAs had gone. That gave the U-boats the ability to go back into the Atlantic provided they didn't actually do anything. If the captain was so ill-advised as to want to do something, he would have to give his position away to do it. That's the beauty of convoys by the way, they eliminate the step of finding the enemy. They force the enemy to find you and tell you he's around. So, a Klasse XXI out in the Atlantic was probably quite safe as long as he stayed away from convoys. Or anything else. But, as soon as the boat made an attack, its a target (the sinking merchant ship is called a flaming datum). This is where the other characteristic of the Klasse XXI comes in, it's fast enough to get away from the flaming datum. This process is called Clearing Datum. Something nuke boats are very good at, diesel-electrics not so much. So, given a flaming datum, a Klasse VII or Klasse IX boat is dead meat, a Klasse XXI has some chance of getting clear. The improvement is there but its incremental rather than revolutionary. And, of course, like every other incremental improvement, teh advantages it brings are transient.

MPA: Something Patrol Aircraft?

Sorry, MPA. Maritime Patrol Aircraft.

Stuart, would you then say that the Klasse XXI was a step down in commerce raiding effectiveness compared to the VII and IX, with that sacrifice being accepted for greater evasive ability?

That's a bit black and white. It's important to remember that the Klasse XXI was quite a bit bigger than the VII and IX and size has its virtues. However, under ideal circumstances, the especial characteristics of the Klasse XXI (underwater speed and endurance) weren't worth very much so ton-for-ton under ideal circumstances, the VI and IX were better commerce destroyers. However, under the circumstances that prevailed in 1944-45, the Klasse XXI was the better commerce destroyer because it could survive (not would survive) while the VII and IX could not.

The best way to think about it is that to survive in 1944/45 meant paying a price and that price came out of commerce destroyer capability. If that price wasn't paid, the submarine didn't survive.

I believe, although this may just be my incorrect opinion, that the main problem with the Japanese submarine forces was not equipment or numbers but tactics. That is, they persued the wrong targets for a fleet of WW2 subs, going out to hunt for warships instead of things they could actually catch like transports and tankers. Their doctrine was in in fact, hugely deficent in many areas when it came to submarines.

The (Submarine) force often operated helter-skelter during the war, being constantly obligated to commit submarines in unanticipated and ever increasing and dangerous crises. Submarines undertook a wide variety of assignments; for example, they were deployed along picket lines in an attempt to ambush and pursue enemy naval forces, only to be ordered and sometimes reordered to dash elsewhere when enemy forces were discovered beyond the original picket lines. Submarines were assigned to reconnoiter heavily guarded enemy ports and advance anchorages. There they sometimes launched midget submarines, human-piloted torpedoes, and aircraft, with minimal results. Submarine aircraft also dropped a few incendiary bombs on Oregon forests, and submarine deck guns fired on other minor targets on the American mainland and various islands. In addition to supply and evacuation operations with bypassed Japanese island garrisons, submarines transported highly explosive gasoline for refueling seaplanes. Moreover, the Japanese undertook other dangerous submarine transport operations with their German allies on the other side of the globe, with whom they exchanged personnel and small amounts of strategic goods, such as quinine and tungsten, and blueprints and prototypes of war machinery. There were also various forays into the Indian Ocean, but crises in the Pacific often forced the boats to concentrate there against strong and rapidly advancing Allied forces. These highly dispersed operations characterized much of Japanese submarine strategic and operational activity throughout the war. The occasional entreaty advocating concentration against enemy sea communications and extended U.S. supply lines, particularly to the South Pacific and Australia, was always played down and usually rejected.

Further explanation for the failure of the submarine force has its roots in the shortcomings of Japanese naval doctrine. The Imperial Navy's neglect of antisubmarine warfare (ASW) before the war proved deadly to the wartime Japanese merchant marine, but the Japanese submarine force was also adversely affected. Japanese submarines were poorly prepared to cope with U.S. Navy ASW operations.

During months of work against German U-boats in the Atlantic before the attack on Pearl Harbor, the U.S. Navy had the experience of escorting convoys, experience that sharpened ASW skills. The Japanese navy had no such wartime experience. When war came, Japanese submariners were unaware that they could be so effectively and systematically pursued on the surface by enemy radar and beneath the sea by sonar. Japanese submarines made little deliberate effort to avoid detection by such sophisticated sensors; moreover, Japanese submarine-borne radar and active sonar used later in the war were primitive by U.S. Navy standards and of little consequence. With no significant ASW doctrine, Japanese submariners, unlike their American and German counterparts, had little understanding of the theories of sound promulgation in relation to temperature layers or water stratification. Careful maneuvering while submerged could reduce the chance of detection, but deeply submerged Japanese submarines usually ascended directly to periscope depth to reconnoiter in a quick 360-degree sweep and then surfaced, fearing only the possibility of being spotted directly and visually by an enemy patrol. Japanese submarines were usually large, powerfully armed, and fast on the surface, but once detected they made good targets because of their slow submerged speed, poor maneuverability, and limited diving depth. Finally, a lack of concern about ASW manifested itself in submarine designs that failed until late in the war to emphasize noise-reduction features.

On the other hand NOT having the uboats would've vastly eased the strain on the allies.

Actually, that's an interesting argument but not quite the way you intend it. Let's imagine a timeline (impossible I know but bear with me) in which the German Navy doesn't build any submarines at all. Zilch, nada. Instead they put all their energy into building up a surface fleet (the building slips and infrastructure required magically materializing when needed). Doing some quick mathematics based on the 1939 issue of Janes Fighting Ships the German navy can build two additional Bismarck Class battleships plus some supporting ships. That means they have roughly double the fleet they had in reality (again, I know that's impossible but let's just see where this goes).

So the British respond. They have no submarine threat to worry about but they do have a more powerful surface fleet as an enemy. So, they build the Lion class battleships and keep Vanguard building at top speed. They don't build the sloops and corvettes, at least not in the same numbers (remember, they can't know that the Germans will not be building submarines at some time). Given that the Germans are building a surface fleet, the British have to take the Z-plan seriously and design (and build) follow-ons to the Lions.

All that requires a lot of resources. Now, we know that the German submarine offensive was actually pretty ineffectual except for a few special circumstances (drumbeat being one) so the question is, will the resources absorbed by building up an enhanced battlefleet be greater than the resources freed by not building the corvette fleet and not suffering the U-boat losses. I'd suggest that is an issue over which a long debate could be held and I wouldn't like to argue it either way.

How much better would have say German technology and better numbers have helped the Japanese hypothetically?

To some extent, the Germans did but as Vehrec pointed out, the issues with the Japanese submarine fleet were conceptual and operational rather than technical. The Germans could make a difference in things like messing standards and deployment but the truth is the operational conditions in the Pacific were such that German experiences weren't really transferable. In technical terms, the Japanese certainly weren't behind the Germans, arguably they were ahead of them in some areas. One hears a lot about the Klasse XXI and Klasse XXIII U-boats but the fact that the equivalent Japanese designs (the I-201 and Ha-201) were more effective boats goes unnoticed. They weren't German y'see.

So, all in all, probably no difference.

I don't think the surface fleet strategy you describe is all that impossible, Stuart. If the Germans reoriented their submarine resources to building more battleships and finishing their real carrier and a few converts, their Navy might have been a far more formidable threat in a surface engagement. And then yeah, the British would have to take the Z-plan more seriously. Whether that would have actually forced their hand to answer with a similar naval buildup, that's not a given though. Action-reaction does not always work.

I don't think the surface fleet strategy you describe is all that impossible, Stuart. If the Germans reoriented their submarine resources to building more battleships and finishing their real carrier and a few converts, their Navy might have been a far more formidable threat in a surface engagement. And then yeah, the British would have to take the Z-plan more seriously. Whether that would have actually forced their hand to answer with a similar naval buildup, that's not a given though. Action-reaction does not always work.

Actually, action-reaction very rarely works. 8) The idea has caused more trouble than most things I can think of. However. . . .

It's a good question what the British would have done if they had seen a serious German surface fleet build-up. We know the Lions would have been built; the primary reason for their cancellation was to clear the slips for ASW work - the cruiser fleet took a big hit for the same reason as did the carriers. So, absent the German submarines, we can assume that the pre-war package of battleships, armored carriers, cruisers and destroyers goes through. However, where we go from there could be a very good question. I can see Sir Arthur Harris claiming his bombers could destroy the German ships in port (well, actually, knowing Sir Arthur, he would claim that the ships would be sunk while he was burning the ports down). The submarine community would claim they could keep the German ships bottled up using mines and torpedo attacks and the carrier fraternity would claim their carriers were the ideal way of nailing the German battleships. So, the actual course the British would have adopted post-Lion class is up in the air. However, all of the options would involve heavy resource expenditure one way or another.

Equally, on the German side, it's interesting to argue what might have happened if the Germans had scrubbed submarine construction AND surface ship production. A lot of those resources could have been transferred to Army use giving them a lot more really heavy artillery and a substantive improvement in their vehicle production (and optics; the U-boats were a massive sink-hole for first-line optical equipment. Give that kit to German tank destroyers and things might have gotten tricky. A German navy consisting entirely of S-boats and minesweepers wouldn't have done any worse than the German Navy did historically and it would have freed up a lot of resources.

On the other hand, a non-Navy Germany wouldn't help the allies that much. Both the British and Americans needed their navies for duties other than a war with Germany so they'd still have massive naval construction programs. just the balance within those programs would change.

Would you mind expanding on that for people who've read less strategy literature? I'm curious.

Action-reaction is a theory about the dynamics of international relations in which the process is driven by actions and the reactions of others to those actions. Each reaction, in turn, becomes an action that generates its own set of reactions and so on ad infinitum. So, as a supposed example, pre-WW1, the British switch from 13.5 inch guns to 15 inch guns for their battleships so the Germans react by shifting from 12.2 inch to 15 inch while the US shifts from 14 inch to 16 inch. The British see the Germans and Americans shifting to 15/16 inch so they then plan a shift to 18 inch. Another example is supposed to be people, especially the U.S. are developing anti-ballistic missile systems so that decision drives people to install MIRVs on their missiles so that they can swamp the ABM system with warheads. There's a lot more examples we can give here and they affect nearly every area of military technology.

So far, that all sounds very good but, as always, the devil is in the details. Taking the battleship example first; when the archives were studied, it became apparent that the German decision to shift from 12.2 inch to 15 inch was nothing whatseoever to do with the British decision and that the British decisions were nothing to do with anybody elses. In each case, all the nations involved were following a strategic logic of their own that had very little to do with waht other nations were doing. There was a "battleship environment" certainly but it determined things in only a very simple, generic sense. Each nation was really committed to building the most powerful battleships they could for the requirements of their own national strategies and that was what determined gun caliber. Nobody was responding to anybody else.

The ABM/MIRV case was even more emphatic on the issue. MIRV was introduced for reasons that had nothing to do with ABM. Put briefly, what drove ABM was the realization that a land-based missile force is a very expensive way of deploying a strategic nuclear deterrent. It doesn't look it at first, but it is because the missile is actually the least expensive part of the system. Typically, the missile itself costs around 10 percent of the cost of the system built around it. So, if we want to double the number of nuclear warheads delivered to the target, sticking to one warhead per missile means we have to double the number of missiles in the whole system and that doubles the cost of the whole system. If, however, we double the number of warheads on the same missile, we only have to buy the new missiles and we can put them in the same silos. That means we only have to spend 10 percent of the cost needed to double the number of missiles. There was a problem of course; a MIRV system with multiple warheads per missile can be easily countered by shooting down the MIRV bus before it discharges its missiles. 20 single-warhead missiles are actually significantly more "penetrative" than 10 double-warhead missiles. Taking it to extremes, 20 single-warhead missiles are vastly more penetrative than two ten-warhead missiles. Only, two ten-warhead missiles are vastly less expensive than twenty single-warhead missiles. So, people wanted to go to MIRV to reduce costs, MIRV was only viable in the absence of ABM and that's why there was such pressure to destroy ABM in the 1970s.

The lesson here is that things are always much more complex than they seem and the very simplistic action-reaction theory falls apart once we start to look deeply at what was going on. This phenomenum where what appears to be a reaction to something in reality turns out not to be is almost universal to the point where it is very hard to find an example of action-reaction actually taking place. They do exist but they are very rare indeed (this isn't helped by the fact that sometimes X is described as being "an answer to Y" for public consumption whereas in fact the truth is "nevertheless, we were going to do X anyway".)

It gets even worse because the naive and innocent (or evil and malicious) then use action-reaction to try and kill off things they don't like - which is usually everything. Their argument goes "if we do X, they will do Y. We don't want them to do Y so we mustn't do X." This argument gets used against every defense program; "if we build a new fighter, the other side will build a better one. We don't want them to do that so we mustn't buy a new fighter."

The truth is that all nations have their own strategic outlook and build the weapons and systems needed to execute the strategies determined by that outlook. What other nations are doing only figures into that in a very general sense.

^However, without a surface fleet, what is to prevent the British from taking Norway and cutting off ore transports?

The invasion could have been done with only cruisers and destroyers. No surface fleet at all is not realistic because of the threat of the Soviets and even the lesser fleets in the Baltic.

The Lions would certainly be built as they are adequate to deal with Bismark klasse vessels but I'm not so sure that Vanguard would get any priority in that situation. The KGVs of course would deal with the twins and a properly sorted KGV would be an enemy worthy of respect to the Bismarks. Particularly with more Tribals and Colonies for escort. Maybe there would also be a more universal program of modernisation so you don't end up with the contrast, for example, between Repulse and Reknown or between Barham and Warspite.

A KGV in good working condition was perfectly adequate to blow seven kinds of hell out of the Bismarck and the RN knew it. The problem really was that it took a long time to get the KGVs up to full working condition. The Lions were an example of British strategic considerations in view and really were what the Royal Navy wanted to build. Vanguard was a curious ship; she was originally intended as a sort of battlecruiser for the Far east fleet and if built as intended she would probably have spent most of her life in Singapore. She was actually additional to the fleet plan in that she didn't use battleship bottlenecks (which was why she kept being built while all the other heavies were cancelled). The intriguing question is whether, as Lions replaced the Rs, would the guns from the Rs be used to build more Vanguards? One suspects they might well have been. That gives rise to another intriguing question, what would the effect have been if the UK had a pair of Vanguards in Singapore instead of PoW and Repulse? Wouldn't have stopped the Japanese trying something of course, but might have given them a much harder fight in Malaya.

Another intriguing question; what would have happened once the Lions were under way. They were basically (IIRC) 38 and 39 programs. That leaves us with the 1940 and 41 battleship programs. One might suspect a repeat Lion with perhaps a bit more armor.

I suspect we would have seen a British building program that went like this (36, 37 and 38 all historical except completions were delayed in OTL)

1936 program 3 KGVs commissioning 1940
1937 program 2 KGVs commissioning 1941
1938 program 2 Lions, one Vanguard, commissioning 1942 (Lions), 1941 (Vanguard)
1939 program 2 Lions (completing 1943)
1940 program 2 repeat Lions, one repeat Vanguard, completing 1944 (Lions), 1943 (Repeat Vanguard)
1941 program 3 repeat Lions, completing 1945

So, if the Z-plan had been completed (made possible by not building submarines), teh German battleline would ahve been

6 H class
2 Bismarck
2 Scharnhorst (with 15 inch guns)

for 48 16 inch guns and 28 15 inch

And the British battle line (assuming the Vanguards are out in Singapore)

10 Lions
5 KGV
2 Nelson
3 modernized QE
1 Hood
2 Renown

for 108 16 inch guns, 44 15 inch guns and 50 14 inch guns.

I'd also guess that Hood and Repulse would be modernized to Renown standards.

[ That gives rise to another intriguing question, what would the effect have been if the UK had a pair of Vanguards in Singapore instead of PoW and Repulse? Wouldn't have stopped the Japanese trying something of course, but might have given them a much harder fight in Malaya.

I guess this counterfactual boils down to AA armament. Vanguard certainly had a much better AA suite than PoW and Repulse, but much of the equipment she had would not have been available in 1941. The 5.25" dual purpose guns themselves would have been a major advantage, of course, but the light AA gun suite probably would not have been nearly as impressive in 1941. Do you have access to sources which would give an idea of the original planned AA armament of Vanguard?

[ That gives rise to another intriguing question, what would the effect have been if the UK had a pair of Vanguards in Singapore instead of PoW and Repulse? Wouldn't have stopped the Japanese trying something of course, but might have given them a much harder fight in Malaya.

I guess this counterfactual boils down to AA armament. Vanguard certainly had a much better AA suite than PoW and Repulse, but much of the equipment she had would not have been available in 1941. The 5.25" dual purpose guns themselves would have been a major advantage, of course, but the light AA gun suite probably would not have been nearly as impressive in 1941. Do you have access to sources which would give an idea of the original planned AA armament of Vanguard?

PoW had the same number of 5.25'' guns, Vanguard had the advantage of an improved mount (roomier and stronger turning motors?) that might not have been available had she been finished before the war. Design 15E (the final one) had an AA-armament of 16 5.25'' guns, 6x 2-pdr mk VI (octuples) and 4 UP-launchers, comparable to what was present on a KGV as built (December 1940: four Mk VI and four UP-launchers, the four 12.7mm MG originally specified were never fitted). All based on Raven/Roberts British battleships of WWII, german edition

The difference wouldn’t come from the different anti aircraft armaments as much as two Vanguards are simply bigger ships, better protected and with homogenous ship handling characteristics in speed and turning circles. That means they can maneuver together rather then being split apart under an air attack. They also had better detail design with actual emergency generators, and while that was the result of war experience, other navies had realized the need for such generators prewar anyway.

The difference wouldn’t come from the different anti aircraft armaments as much as two Vanguards are simply bigger ships, better protected and with homogenous ship handling characteristics in speed and turning circles. That means they can maneuver together rather then being split apart under an air attack. They also had better detail design with actual emergency generators, and while that was the result of war experience, other navies had realized the need for such generators prewar anyway.

I suppose the better torpedo protection would help, although how much it would help would depend mostly on sheer luck (i.e. the actual location of torpedo hits). Emergency generators certainly would, but I don't know about the maneuvering. The Japanese torpedo bomber crews were very well trained and conducted a nearly text book attacks historically, which were spesifically designed to minimize the efficiency of evasive maneuvers.

All in all I estimate that without significant improvement to AA armament the effective results would be the same. Perhaps only one ship is sunk or both even manage to stay afloat, but probably so badly damaged that they would not be able to carry on with their mission to seek out Japanese invasion forces. Not that the mission made much sense anyway, since two capital ships with a small number of destroyers was clearly not enough for the task.

Maneuver can still help against a torpedo attack. As I recall, Repulse managed to dodge... somewhere between 15 and 20 torpedoes before the Japanese managed to get a synchronized attack in and nail her. It's not enough, but it can help improve the effectiveness of other features like AA defenses and torpedo protection.

PoW had the same number of 5.25'' guns, Vanguard had the advantage of an improved mount (roomier and stronger turning motors?) that might not have been available had she been finished before the war. Design 15E (the final one) had an AA-armament of 16 5.25'' guns, 6x 2-pdr mk VI (octuples) and 4 UP-launchers, comparable to what was present on a KGV as built (December 1940: four Mk VI and four UP-launchers, the four 12.7mm MG originally specified were never fitted). All based on Raven/Roberts British battleships of WWII, german edition

I think its reasonable that a non-slowed-down Vanguard would have had the same AA armament as a KGV; the improved turrets wouldn't have shown up until later (probably on the Repeat Lions). That still gives the two battleships a lot more AA firepower than they had historically though; Repulse's AA firepower was very weak.

The real problem is that none of this will save one of the battleships if they take a hit in the same place as did for PoW. Statistically, that isn't unlikely. There's one chance in six that a torpedo will go into the screws and shafting. That'll do for any battleship.

The impact of two Vanguards in Singapore would be more political than anything else. They are a demonstration of a serious attempt to defend the place.

.

The real problem is that none of this will save one of the battleships if they take a hit in the same place as did for PoW. Statistically, that isn't unlikely. There's one chance in six that a torpedo will go into the screws and shafting. That'll do for any battleship.

The odds are a lot less then one in six that damage in that area would cause such catastrophic flooding and such extensive loss of power. A direct hit on the shaft bracket is more like a 1/200 chance. USS Intrepid took a deep running torpedo hit in-between her rudder and her screw, not a very large space, and this did not lead to the loss of use of any shaft for example. The rudder was ruined.

The odds are a lot less then one in six that damage in that area would cause such catastrophic flooding and such extensive loss of power. A direct hit on the shaft bracket is more like a 1/200 chance. USS Intrepid took a deep running torpedo hit in-between her rudder and her screw, not a very large space, and this did not lead to the loss of use of any shaft for example. The rudder was ruined.

A massive, immediate ship-killing flood like the one that got PoW is unlikely I agree; in that sense PoW was very unlucky (but then she was a very unlucky ship). However, the vulnerable area of the shafts and screws run for over a hundred plus feet and a hit anywhere in that area is going to cause a mass of grief. It only needs a very slight bend in the shaftline for the propshaft to start reaming the guts of the ship out. The damage tends to escalate from there. Even although immediate massive flooding might not take place, progressive flooding throughout the entire powertrain in inevitable. If the ship gets back to port before she sinks (progressive flooding is virtually unstoppable with the resources available at sea) she'll be in drydock for months plus before getting fixed. Even then, she'll never be quite the same again.

Intrepid was very lucky indeed; that torpedo must have been just outside the area where shaft deformation occurs.

By the way, shaft deformation was why many of the post-war DEs were single-shaft. The argument was that in a hull of that size, any blow big enough to cause shaft deformation on once side of a twin-screw would take out the other side as well. A single shaft being buried in the hull structure would have a better chance of escaping damage.

[...]

A modernised Reknown class with 4.5" AA as opposed to early 5.25" AA on KGVs would have been useful.

I can't find the reference, but some KGV-concepts (and also studies for Hood-rebuilds) had 20x 4.5'' instead of the 16x 5.25'' guns.
For AA, the 4.5'' would have been preferred, but the RN considered them too light to be useful defending against destroyers performing torpedo attacks. They requested at least 13cm guns for dual purpose artillery. An early 1930s study for a battleship was similar to the german and italian practise of using 6'' against destroyers and ~10cm as heavy AAA.

I would think that the mass and space used mounting two types of secondary armament, even if either is ideal for their respective jobs, would completely outweigh the gains in efficiency. I know I'd much rather have 20 guns that aren't perfect for either job but will work than 10 of each that are ideal.

That said and speaking as someone who is far from an expert on naval operations, isn't screening against torpedo boats and destroyers what the escorts are for anyway?

That said and speaking as someone who is far from an expert on naval operations, isn't screening against torpedo boats and destroyers what the escorts are for anyway?

You cannot always count on escorts so you need secondary armament. With it, for example, even a single heavy ship can defend itself against 6-12 destroyers, as the Battle of the Dogger Bank showed. Without, it is a big huge target just begging for a torpedo attack.

I would think that the mass and space used mounting two types of secondary armament, even if either is ideal for their respective jobs, would completely outweigh the gains in efficiency. I know I'd much rather have 20 guns that aren't perfect for either job but will work than 10 of each that are ideal.

That said and speaking as someone who is far from an expert on naval operations, isn't screening against torpedo boats and destroyers what the escorts are for anyway?

You are right. Mixed secondaries by WW2 were woefully wasteful of space. Look at the deck plans of the Twins, the Bismark klasse and the Yamato class. In fact Yamato later had some 6" guns removed to make space for more 5" guns. IMHO the US 5"/38 setups were the best but bear in mind that before that gun's developement in the mid '30s US capital ships could have two different 5" guns - a low elevation for anti-surface work and a high angle elevation gun for AA work. One was 25 calibre and the other, from memory, 52 calibre. The dual purpose gun, as noted above, was 38 calibre.

The 5"/38 was not the best for surface work, though adequate but it was good for AA with a relatively high rate of fire. so you have the standard US fast battleship fitout of 20 5"/38s (except South Dakota - she had 16, two turrets removed to make space for flag facilities). Standard later US cruisers such as the Baltimores and Clevelands had 12, 2 fore, two aft and 4 on each beam amidship, all in the standard US navy twin turret.

(One calibre = the muzzle diameter so calibres are used as shorthand for the length of the barrel)

I agree with the second point. Capital ships are too expensive to not be escorted by smaller, faster craft. The RN even had classes of cruisers and destroyers that were designed specifically for fleet work, such as Arethusa and her sisters.

You are right. Mixed secondaries by WW2 were woefully wasteful of space. Look at the deck plans of the Twins, the Bismark klasse and the Yamato class. In fact Yamato later had some 6" guns removed to make space for more 5" guns.

One has to remember, however, that the AA optimized secondaries could be used against surface targets as well. They were not exclusive AA guns but dual purpose guns. The Italian 90 mm guns were admittedly marginal against surface targets larger than a gunship or torpedo boat, but the French 100 mm, German 105 mm and the Japanese 127 mm "AA" guns certainly were powerful enough to seriously damage destroyers even if the sub-127 mm guns were far from ideal for the task. So the mixed secondaries were only a problem for AA defense, not really for defense against destroyers, especially since the 150-155 mm weapons were more effective than 127 mm guns would have been.

I am not saying that mixed secondaries were a good idea, but in the 1930s only the US Navy and to somewhat lesser degree the Royal Navy and the French Navy correctly estimated the relative threats presented by aircraft and destroyers. The US Navy ended up sacrificing some anti-destroyers firepower for better anti-aircraft firepower, which was ultimately the right decisions. The Royal Navy and the French Navy wanted to have the best of both worlds. The 5.25" DP was a only partially successful until the improved RP10 mountings for the Anson and Vanguard. The French 152 mm DP gun on the other hand were almost a complete failure for AA work and in fact the French had to replace some of them with 100 mm guns. Even after the war the French were unable to fix them completely. So it's not like uniform DP secondary guns were not attempted but only the US 5"/38 really hit the spot.

I am not saying that mixed secondaries were a good idea, but in the 1930s only the US Navy and to somewhat lesser degree the Royal Navy and the French Navy correctly estimated the relative threats presented by aircraft and destroyers. The US Navy ended up sacrificing some anti-destroyers firepower for better anti-aircraft firepower, which was ultimately the right decisions. The Royal Navy and the French Navy wanted to have the best of both worlds. The 5.25" DP was a only partially successful until the improved RP10 mountings for the Anson and Vanguard. The French 152 mm DP gun on the other hand were almost a complete failure for AA work and in fact the French had to replace some of them with 100 mm guns. Even after the war the French were unable to fix them completely. So it's not like uniform DP secondary guns were not attempted but only the US 5"/38 really hit the spot.

There's another aspect to this as well. During the era when secondary batteries were regarded as a defense against torpedo craft, the caliber of secondaries used for that purpose was related directly to the size of those targets. The guns were selected for their ability to do a lot of damage to said craft quickly, before the latter could fire their torpedoes. In the early days (up to Dreadnought) the 12 pounder and its equivalents were considered perfectly adequate for this role. This is disguised because the pre-Dreadnoughts carried heavy "secondary" batteries of 6 inch and 9.2 inch guns or their equivalents. These were not anti-destroyer guns but were intended to be part of the ship's anti-capital ship armament, providing smothering fire with HE while the big guns provided penetrating and crushing power. That was the theory anyway. I put the secondary in quotation marks because those batteries of smaller guns were often regarded as the ship's primary armament and the quartette or so of big guns were secondary to them. The "anti-destroyer" (actually anti-torpedo-boat) guns were the 12 pounders and 3 inch weapons and their equivalents.

Now, several things happened in the early years of the 20th century. One was that battle ranges went up and experience showed that the heavy batteries of 6 inch and 9.2 inch class weapons really weren't worth the weight they absorbed. In fact, they were a liability because they meant that magazines for them were dispersed all over the ship. So battleships simplified their armament by concentrating on heavy anti-ship guns and anti-torpedo boat guns. So, we have Dreadnought with 12 inch and 12 pounders. The US did the same with its first class of Dreadnoughts that carried 12 inch and 3 inch guns. The French, Germans and Japanese kept the 6 inch and their equivalents in the ship layout but these were not anti-torpedo boat guns (note that the same ships also carried the 12 pounder equivalents for that role). Those 5.9 inch, 5.5 inch et al weapons were still part of the main battery and were intended for anti-capital ship work. The inclusion of those guns was a highly retrograde feature that showed the Germans, Japanese and French had completely missed the point. The Germans and French could be forgiven, in naval terms they were bungling amateurs. The Japanese had no such excuse; it was their great naval victory off Tsushima that had highlighted the uselessness of the medium-caliber batteries.

Another thing that happened was that torpedo boats started getting bigger. From 1905 onwards this process was fast as torpedo-boat destroyers were evolved to sink torpedo boats and then took over the latter's role. They weren't just getting bigger, they were getting faster and the torpedoes they carried were also getting larger, faster and longer-ranged. It was very quickly apparent that the 12 pounder, 3 inch and 3.4 inch guns used for anti-torpedo boat work were outclassed and inadequate. The requirement was changing; the new destroyers could fire from further out and make their attacks with less warning. This decreased the window of opportunity to sink said destroyers and that needed guns with longer range and heavier shells. Have a look at a 1914 JFS and the surge in size, speed and fighting power of torpedo boats as they evolved into destroyers is very obvious. So, the British went from 12 pounder to 4 inch, the US went to 5 inch. Note that on these ships, there remained only two types of gun, the heavy anti-capital ship guns and the light anti-destroyer guns. There was no secondary armament per se. Once again, the Germans managed to miss the point completely; they held to the intermediate-caliber guns and left the anti-destroyer task to the inadequate 3.4 inch gun. The Japanese and French wised up and they eliminated their light anti-destroyer guns completely. They introduced new caliber guns (5.5 inch) for the secondary battery and use dthem for anti-destroyer work.

By 1912, even the four inch and its equivalents were becoming regarded as ineffective. There was a lot of pressure to make the next jump up to six-inch weapons. The French and Japanese weren't worried; they were ahead of the curve with their 5.5s anyway. The Americans were quite happy with their 5 inch gun and the Germans were happy with their 3.4 inch. In Britain, there was a big debate over the anti-destroyer battery with one side claiming the six-inch was essential due to its range and weight of shell while the other claimed that the four inch with its high rate of fire was the better choice. The six-inch crew won that battle temporarily although they lost it later and the UK reverted to the four inch, then changed its mind again and went back to the six inch as destroyers continued to grow.

OK, now we can jump forward and we can look at the situation in the 1930s. Destroyers had grown a lot bigger, a lot faster and a lot better armed. Eight or even ten torpedoes were standard, guns were 4.7 inch or 5 inch while their speed had jumped from the high twenties to mid-thirties. Even the six-inch gun wasn't going to cut it as an anti-torpedo defense. So what were navies to do? The obvious "answer" to the big new destroyers was a heavier anti-destroyer gun. Was that going to be eight inch? Or 9.2 inch? Or 12 inch? Once again, the obvious answer was the wrong one; the fact was that no battleship of reasonable dimensions could carry an effective anti-destroyer battery. In fact, an effective anti-destroyer gun for battleships couldn't be designed at all. A gun that fired a shell heavy enough to cripple a destroyer quickly couldn't be fired fast enough to guarantee scoring a hit in the time available.

So, the anti-destroyer mission had more or less gone away. That's why "dual purpose" guns were adopted by the British and U.S.; they realized that with the anti-capital ship and anti-destroyer functions both gone, there was no point in looking for anti-surface capability. On the other hand, aircraft were growing threats and that was the new primary role for the secondary battery. Again, there was a fight over that (these things never happen quickly or cleanly) but the upshoot of the debate was the US 5 inch L38 and the British 5.25 L50. In fact, the row continued well after that point, the obvious results being the 4.5 inch secondary batteries on the modernized battleships and battlecruisers. The Germans (of course) completely missed the point and retained the 5.9 inch as a classical anti-capital ship secondary battery while replaced the old 3.4 inch with a 4.1 inch gun for anti-torpedocraft work - except that anti-torpedo craft role now included anti-aircraft.

So, the argument over whether Bismarck et al should have had dual-purpose "secondary" armaments or not misses the point. As the British and Americans defined things, she had a modern dual-purpose secondary battery, her 4.1 inch guns. The catch was that she had a traditional secondary battery as well - and therein lay the problem. A British or American design team in the German's shoes would almost certainly have thrown that battery of 5.9 inch guns away and installed additional 4.1 inch guns. After all, the 4.1 inch fired faster, was easier and faster to swing and train, wasn't weighed down with an armored turret and, to a 1941 destroyer, the difference between getting him by a 4.1 inch shell and a 5.9 inch shell wasn't really consequential. In either case, she'd live long enough to get her torpedoes off.

Imagine Bismarck with no 5.9s but 16 twin 4.1s instead of eight. She would have had a lot better AA firepower - and that might have saved her - and her anti-destroyer capability wouldn't have been any worse. What she would have lost was her anti-capital ship secondary battery - and that had been obsolete since 1905.

PS It should be noted that the above refers to why design choices were made; how the guns actually got used is entirely another matter.

NOTE: There was a lot more discussion by others regarding AA/Secondary Armaments; but my primary objective is to try and save Stuartisms, as I'm older myself, and I only have "N" amount of time to do this project.