Some questions regarding interwar battleship construction

I was reading some random ship specs, and a couple of questions popped up (well, one of them was older and resurfaced):

1) Why did Italy and Japan spend craploads of money on refurbishing ships with little no combat value?
The old Cavours and Dorias (which themselves were basically improved Cavours) were of little use, even after having their ancient 12-inchers rebored to 12.6. For the manpower and resource cost of refurbishing the four old ships (and still ending up with subpar results), they could have built two more new Littorios.
Same with Japan and the four old Fuso/Ise. Even after the rather expensive refurbishment, they were no match for treaty battleships (NorCals/SoDaks), nevermind "escalator clause" ones. To compare/contrast, the rebuilt Kongos were frail, but could keep up with carriers, while the Nagatos were quite solid (Nagato took two nuclear blasts and still remained afloat for nearly 5 days afterwards).

2) Why did so many navies insist on keeping dual-calibre secondary armament?
The only navies to have unified their secondaries into a single dual-purpose calibre were the Royal Navy and the USN. Everybody else (MN, KM, RM, IJN) used one calibre for surface (usually 6-inch or thereabouts) and another for heavy anti-air (5-inch +/-). Since the secondary surface armament usually had worse fire control than the main guns, their effectiveness was limited at best (especially on old refurbished ships like Kongo, where the guns were casemated).
 
Last edited:

Germaniac

Donor
Its very difficult for a naval officer to explain to uninformed people why their extremely expensive basically unused battle toys are totally obsolete and need to pay for NEW battletoys.
 
Germany was faced with a situation whereby their heavy ships might well have to engage in close-range night actions in the North Sea. Given that there was no such thing as radar, and that Germany's escort forces were vastly inferior to a potential rival's, then the requirement for an effective anti-destroyer/light cruiser battery was strong. But such a battery would be too heavy to also be effective against aircraft. Hence, separate secondary batteries were required.
 
I was reading some random ship specs, and a couple of questions popped up (well, one of them was older and resurfaced):

1) Why did Italy and Japan spend craploads of money on refurbishing ships with little no combat value?
The old Cavours and Dorias (which themselves were basically improved Cavours) were of little use, even after having their ancient 12-inchers rebored to 12.6. For the manpower and resource cost of refurbishing the four old ships (and still ending up with subpar results), they could have built two more new Littorios.
Same with Japan and the four old Fuso/Ise. Even after the rather expensive refurbishment, they were no match for treaty battleships (NorCals/SoDaks), nevermind "escalator clause" ones. To compare/contrast, the rebuilt Kongos were frail, but could keep up with carriers, while the Nagatos were quite solid (Nagato took two nuclear blasts and still remained afloat for nearly 5 days afterwards).
IJN could not build any new ships from WNT (1923) to 2LNT (1 Jan 1937) without starting something very bad for them.....its rebuild that you can have or nothing.
RM could have but again politics would make it disruptive and I bet the RM sold the rebuilds like Super Hornet F18/E....don't worry its just a cheap modification not much more than a simple service...
2) Why did so many navies insist on keeping dual-calibre secondary armament?
The only navies to have unified their secondaries into a single dual-purpose calibre were the Royal Navy and the USN. Everybody else (MN, KM, RM, IJN) used one calibre for surface (usually 6-inch or thereabouts) and another for heavy anti-air (5-inch +/-). Since the secondary surface armament usually had worse fire control than the main guns, their effectiveness was limited at best (especially on old refurbished ships like Kongo, where the guns were casemated).
Most of the old ships had been built with casement before aircraft where really a threat and its really hard and expensive to refit turrets compared to just adding deck AA guns.

The DP guns are late 30s and cost a lot so only a few got finished in time for mass use in WWII (ie USN 5/38 who had time and money to spare) look at what happens to people who tried it too early on http://www.navweaps.com/Weapons/WNFR_51-45_m1932.php!

Also remember that the DP guns that are actually good at AA are mostly lighter (max 5.25" and even then that's to big you want 55lb) than the good anti DD guns (any old 6" 100+lb) so its a trade off and as the relative threats change from night DDs to aircraft due to aircraft and radar improving the best gun changes.... and all heavy AA is very much weaker before US VT shells in 43+ anyway. That and the good or not so good fire control is one of the most expensive and hardest to make things to buy in 30s/40s.
 
Germany was faced with a situation whereby their heavy ships might well have to engage in close-range night actions in the North Sea. Given that there was no such thing as radar, and that Germany's escort forces were vastly inferior to a potential rival's, then the requirement for an effective anti-destroyer/light cruiser battery was strong. But such a battery would be too heavy to also be effective against aircraft. Hence, separate secondary batteries were required.
Germans had radar. It wasn't exceptionally good, because it was decimetric (Hitler's 1939 Directive cut funding for centimetric radar), but suitable enough for tracking (though ironically it still had a lower CEP compared to the guns of some ships it was installed on). As for anti-destroyer work, The US had shown that quick-firing 5-inch tier weaponry is more than a match for unarmoured/lightly armoured ships. A 6-inch gun is slower firing than a 5-incher, even if the latter's ammo is two-piece, while 3.9-inch tier guns are a bit too light for surface work. Another thing is that, with a single unified calibre, you only need one set of directors/calculators (since there's only one set of ballistic specs).
Most of the old ships had been built with casement before aircraft where really a threat and its really hard and expensive to refit turrets compared to just adding deck AA guns.

The DP guns are late 30s and cost a lot so only a few got finished in time for mass use in WWII (ie USN 5/38 who had time and money to spare) look at what happens to people who tried it too early on http://www.navweaps.com/Weapons/WNFR_51-45_m1932.php!

Also remember that the DP guns that are actually good at AA are mostly lighter (max 5.25" and even then that's to big you want 55lb) than the good anti DD guns (any old 6" 100+lb) so its a trade off and as the relative threats change from night DDs to aircraft due to aircraft and radar improving the best gun changes.... and all heavy AA is very much weaker before US VT shells in 43+ anyway. That and the good or not so good fire control is one of the most expensive and hardest to make things to buy in 30s/40s.
The problem was that, on casemated ships, the secondary artillery was very limited in value. Poor angles and no real centralized direction meant they were mostly good for near misses, rather than actually sinking a modern ship. Laffey was crippled by a hit from Hiei's main, rather than secondary guns (after shredding the superstructure with its quick-firing 5-inchers). Samuel B. Roberts and Johnston were similarly mauled primarily by 14-inch shells.
The early DP guns (5.25'' KGV, 130 mm Dunkerque) had some performance issues not least because they still weighed towards the anti-surface side of the DP balance (too heavy and slow for AA work). The 130 mm's main problem was the heavy single-piece ammo (generally unworkable above 120 mm) although the quad mounts were very unreliable (owing to overly optimistic designers). Again, by the mid-30s the threat of nighttime DD torp runs had considerably decreased once radars were adopted (admittedly, the French, Italians and Japanese lagged badly in adoption). And, as I've noted, quick-firing lighter-calibre (4.7'' +/-) RPC guns were proven to be just as effective at opposing lightly armored ships as slower-firing higher calibre ones. As for VT fuzes, yes, that was the greatest single improvement to heavy AA, however linking an automatic fuze setter to a predictive target data calculator (who automatically updated based on radar returns) could provide relatively adequate results (well, as long as there was electricity) when combined with turret RPC.
IJN could not build any new ships from WNT (1923) to 2LNT (1 Jan 1937) without starting something very bad for them.....its rebuild that you can have or nothing.
RM could have but again politics would make it disruptive and I bet the RM sold the rebuilds like Super Hornet F18/E....don't worry its just a cheap modification not much more than a simple service...
The IJN got outplayed at Washington because the US had broken their cypher. Had they managed to keep a semblance of secrecy, I think they could have pushed for 'grandfathering' ships that were already around (or close to) 50% completed (IIRC the two Tosas and about half the Amagis), in exchange for accepting 'downgrades': the two Fusos and the oldest two Kongos would be decommissioned (maybe convert a couple to carriers instead of scrapping), the Tosas would have the same number of turrets as the Nagatos (sneakily keeping the 5th mount concealed under redesigned superstructure), the Amagis would use the 14'' guns from the decommissioned ships and have only 4 turrets (again, keeping the 5th mount concealed under light superstructure, and having the mounts capable of accepting 16''). Had they had the presence of mind to poison the conference by bringing up the difference between light and heavy cruisers (which happened anyway at 1st London), they might've been able to get away with their tricks in the resulting debate between US and UK representatives. On the other hand, the IJN itself was shattered into factions who displayed enormous mutual hatred, and it's hard to say whether the plan would've been digestible by some of the loonier admirals (though it would have landed them in the same 6-4 situation as post-WNT, except with newer ships).
The RM... I really don't get it. 12'' were already outmatched by the end of the First World War (even the French had switched to 13.4'' guns on the Bretagne). By the 1930s they were completely obsolescent. Slightly reboring them to 12.6'' was pointless; while on paper they were close to the calibre of the Dunkerques, the actual ballistics were inferior. And Italy could ill afford subpar ships, which the Cavours and Dorias definitely were, compared to the Littorios.
 
Last edited:
Germans had radar. It wasn't exceptionally good, because it was decimetric (Hitler's 1939 Directive cut funding for centimetric radar), but suitable enough for tracking (though ironically it still had a lower CEP compared to the guns of some ships it was installed on). As for anti-destroyer work, The US had shown that quick-firing 5-inch tier weaponry is more than a match for unarmoured/lightly armoured ships. A 6-inch gun is slower firing than a 5-incher, even if the latter's ammo is two-piece, while 3.9-inch tier guns are a bit too light for surface work. Another thing is that, with a single unified calibre, you only need one set of directors/calculators (since there's only one set of ballistic specs).

Sorry, I should have been clearer. There was no such thing as radar when these ships were being designed, and the US had taught no lessons about gun calibre.
 
Germans had radar. It wasn't exceptionally good, because it was decimetric (Hitler's 1939 Directive cut funding for centimetric radar), but suitable enough for tracking (though ironically it still had a lower CEP compared to the guns of some ships it was installed on). As for anti-destroyer work, The US had shown that quick-firing 5-inch tier weaponry is more than a match for unarmoured/lightly armoured ships. A 6-inch gun is slower firing than a 5-incher, even if the latter's ammo is two-piece, while 3.9-inch tier guns are a bit too light for surface work. Another thing is that, with a single unified calibre, you only need one set of directors/calculators (since there's only one set of ballistic specs)

The problem was that, on casemated ships, the secondary artillery was very limited in value. Poor angles and no real centralized direction meant they were mostly good for near misses, rather than actually sinking a modern ship. Laffey was crippled by a hit from Hiei's main, rather than secondary guns (after shredding the superstructure with its quick-firing 5-inchers). Samuel B. Roberts and Johnston were similarly mauled primarily by 14-inch shells.
The early DP guns (5.25'' KGV, 130 mm Dunkerque) had some performance issues not least because they still weighed towards the anti-surface side of the DP balance (too heavy and slow for AA work). The 130 mm's main problem was the heavy single-piece ammo (generally unworkable above 120 mm) although the quad mounts were very unreliable (owing to overly optimistic designers). Again, by the mid-30s the threat of nighttime DD torp runs had considerably decreased once radars were adopted (admittedly, the French, Italians and Japanese lagged badly in adoption). And, as I've noted, quick-firing lighter-calibre (4.7'' +/-) RPC guns were proven to be just as effective at opposing lightly armored ships as slower-firing higher calibre ones. As for VT fuzes, yes, that was the greatest single improvement to heavy AA, however linking an automatic fuze setter to a predictive target data calculator (who automatically updated based on radar returns) could provide relatively adequate results (well, as long as there was electricity) when combined with turret RPC.

The IJN got outplayed at Washington because the US had broken their cypher. Had they managed to keep a semblance of secrecy, I think they could have pushed for 'grandfathering' ships that were already around (or close to) 50% completed (IIRC the two Tosas and about half the Amagis), in exchange for accepting 'downgrades': the two Fusos and the oldest two Kongos would be decommissioned (maybe convert a couple to carriers instead of scrapping), the Tosas would have the same number of turrets as the Nagatos (sneakily keeping the 5th mount concealed under redesigned superstructure), the Amagis would use the 14'' guns from the decommissioned ships and have only 4 turrets (again, keeping the 5th mount concealed under light superstructure, and having the mounts capable of accepting 16''). Had they had the presence of mind to poison the conference by bringing up the difference between light and heavy cruisers (which happened anyway at 1st London), they might've been able to get away with their tricks in the resulting debate between US and UK representatives. On the other hand, the IJN itself was shattered into factions who displayed enormous mutual hatred, and it's hard to say whether the plan would've been digestible by some of the loonier admirals (though it would have landed them in the same 6-4 situation as post-WNT, except with newer ships).
The RM... I really don't get it. 12'' were already outmatched by the end of the First World War (even the French had switched to 13.4'' guns on the Bretagne). By the 1930s they were completely obsolescent. Slightly reboring them to 12.6'' was pointless; while on paper they were close to the calibre of the Dunkerques, the actual ballistics were inferior. And Italy could ill afford subpar ships, which the Cavours and Dorias definitely were, compared to the Littorios.
In 1931-1936 when these ships were designed nobody was certain about radar being effective. Likewise nobody knows the value of 6" relative to 5" from experience, but everybody knows that Destroyers have gotten bigger since WWI, torpedo ranges longer and that smaller guns had issues dealing with destroyers then

Casemates were of limited value, this was known, but the ships existed and rebuilds extensive enough to get rid of them cost serious money

In 1931-36, when the ships with Single Purpose secondaries were designed, the threat of DD's at night was still very real. Radar in 1936 was known to have military implications but exactly how it would perform, when it would be available shipboard and what the tactical implications were were not

There was more to the WNT than that. For one thing there was a balanced ratio of Post Jutland ships, 3 US, 3 UK, 2 Japan, Japan getting 4 more throws that off. Not to mention Tosa and Amagi being overweight for the Treaty, Hood got away with it because she was built and only 1. Those sorts of changes you propose are essentially impossible to hide in a peacetime environment. In 1921 any arguments on Light/Heavy distinction are fairly theoretical, only the Hawkins really exist as what we think of as heavy cruisers, though the US classifies its old ACR and some PCR as Heavy cruisers, and thus its only minor, not like LNT when there are a bunch with a bunch more building and funds are tight again

Italy laid down 4 15" Battleships in WWI, but didn't have the money to finish them after the war. Re-boring the 12" guns got some more firepower for their stopgap ships. The point of those rebuilds was that while inferior to the Littorios they were supposed to be ready faster, in order to have something that can be of some use if war broke out before the Littorios were ready. With hindsight we know these cost/time estimates were hilariously wrong, but they had no hindsight
 
Germans had radar. It wasn't exceptionally good, because it was decimetric (Hitler's 1939 Directive cut funding for centimetric radar), but suitable enough for tracking (though ironically it still had a lower CEP compared to the guns of some ships it was installed on). As for anti-destroyer work, The US had shown that quick-firing 5-inch tier weaponry is more than a match for unarmoured/lightly armoured ships. A 6-inch gun is slower firing than a 5-incher, even if the latter's ammo is two-piece, while 3.9-inch tier guns are a bit too light for surface work. Another thing is that, with a single unified calibre, you only need one set of directors/calculators (since there's only one set of ballistic specs).

The problem was that, on casemated ships, the secondary artillery was very limited in value. Poor angles and no real centralized direction meant they were mostly good for near misses, rather than actually sinking a modern ship. Laffey was crippled by a hit from Hiei's main, rather than secondary guns (after shredding the superstructure with its quick-firing 5-inchers). Samuel B. Roberts and Johnston were similarly mauled primarily by 14-inch shells.
The early DP guns (5.25'' KGV, 130 mm Dunkerque) had some performance issues not least because they still weighed towards the anti-surface side of the DP balance (too heavy and slow for AA work). The 130 mm's main problem was the heavy single-piece ammo (generally unworkable above 120 mm) although the quad mounts were very unreliable (owing to overly optimistic designers). Again, by the mid-30s the threat of nighttime DD torp runs had considerably decreased once radars were adopted (admittedly, the French, Italians and Japanese lagged badly in adoption). And, as I've noted, quick-firing lighter-calibre (4.7'' +/-) RPC guns were proven to be just as effective at opposing lightly armored ships as slower-firing higher calibre ones. As for VT fuzes, yes, that was the greatest single improvement to heavy AA, however linking an automatic fuze setter to a predictive target data calculator (who automatically updated based on radar returns) could provide relatively adequate results (well, as long as there was electricity) when combined with turret RPC.
1- All of the above is irrelevant for why ships where designed without DP turrets..... just how many battleships where designed after 1939! Vanguard maybe but even thats copied due to wartime pressure of the Lions/KVG.

2- 5.25" isn't really early its Date In Service is 1940

3- Mid-30s isn't really full of radars...... January 1939, USN first on a battleship prototype system, the 200-MHz (1.5-m) XAF, was tested at sea?
From NAVweps, "Trenckle says that Admiral Graf Spee had an experimental FuMO 22, and Prager that Deutschland had a Seetakt set in the autumn 1937"

4- That's all very advanced tech (and still mostly not tested) when the decisions need to be made abut the new BBs that where built with SP guns.

The IJN got outplayed at Washington because the US had broken their cypher. Had they managed to keep a semblance of secrecy, I think they could have pushed for 'grandfathering' ships that were already around (or close to) 50% completed (IIRC the two Tosas and about half the Amagis), in exchange for accepting 'downgrades': the two Fusos and the oldest two Kongos would be decommissioned (maybe convert a couple to carriers instead of scrapping), the Tosas would have the same number of turrets as the Nagatos (sneakily keeping the 5th mount concealed under redesigned superstructure), the Amagis would use the 14'' guns from the decommissioned ships and have only 4 turrets (again, keeping the 5th mount concealed under light superstructure, and having the mounts capable of accepting 16''). Had they had the presence of mind to poison the conference by bringing up the difference between light and heavy cruisers (which happened anyway at 1st London), they might've been able to get away with their tricks in the resulting debate between US and UK representatives. On the other hand, the IJN itself was shattered into factions who displayed enormous mutual hatred, and it's hard to say whether the plan would've been digestible by some of the loonier admirals (though it would have landed them in the same 6-4 situation as post-WNT, except with newer ships).
The RM... I really don't get it. 12'' were already outmatched by the end of the First World War (even the French had switched to 13.4'' guns on the Bretagne). By the 1930s they were completely obsolescent. Slightly reboring them to 12.6'' was pointless; while on paper they were close to the calibre of the Dunkerques, the actual ballistics were inferior. And Italy could ill afford subpar ships, which the Cavours and Dorias definitely were, compared to the Littorios.
5- IJN got outplayed as the US is far larger so will win any building race its willing to pay for and wants to win.
6- The USN would say that its spare Colorado and 6 SD and 6Lex are alll "close to completion and deserve to be built".....RN would say its laid the first rivet of its 4G3 and 4N3 and thus they should also be completed.....
7- WNT didn't limit Cruisers except that they all need to be under 10,000 and >8" guns so no CLs......
8- Any USN RN build race will swamp the IJN so why risk it.....
9- Rebuild make sense if they are cheap and you cant start new (or at least don't want to due to money or politics or risking a international building race starting) with hindsight they (especially the last two) are bad value but at the time they are not bad and at least they are reasonably fast.
 
Last edited:
Also - the USN regarded the surprise night encounter seriously enough to arm the Lexingtons not with 5" guns, but with 8" guns...
Not just them the IJN (7.9" guns) and RN (4.5" belt) both protected carriers with massively more guns and or protection than we would now with hindsight favour.
 
Turrets are complicated, difficult to design, often cramped inside, expensive to build, weigh rather a lot, and require significant supporting equipment and structure directly beneath.

Casemate guns were a lot simpler solution, and allowed greater flexibilty on the location of the ammunition hoists and magazines.

As to DP guns, even the USN partially got lucky on that. The fleet it had under WNT featured 5"/50 anti-surface guns and 5"/25 anti-aircraft guns. The 5"/38 is a vastly more logical outcome as a universal DP gun from that starting point than it would have been if the USN had started instead with the planned 6" secondaries on the Lexington and South Dakota designs of 1918, hard to convince that a smaller gun is an upgrade.
 
I was reading some random ship specs, and a couple of questions popped up (well, one of them was older and resurfaced):

1) Why did Italy and Japan spend craploads of money on refurbishing ships with little no combat value?
The old Cavours and Dorias (which themselves were basically improved Cavours) were of little use, even after having their ancient 12-inchers rebored to 12.6. For the manpower and resource cost of refurbishing the four old ships (and still ending up with subpar results), they could have built two more new Littorios.
Same with Japan and the four old Fuso/Ise. Even after the rather expensive refurbishment, they were no match for treaty battleships (NorCals/SoDaks), nevermind "escalator clause" ones. To compare/contrast, the rebuilt Kongos were frail, but could keep up with carriers, while the Nagatos were quite solid (Nagato took two nuclear blasts and still remained afloat for nearly 5 days afterwards).

2) Why did so many navies insist on keeping dual-calibre secondary armament?
The only navies to have unified their secondaries into a single dual-purpose calibre were the Royal Navy and the USN. Everybody else (MN, KM, RM, IJN) used one calibre for surface (usually 6-inch or thereabouts) and another for heavy anti-air (5-inch +/-). Since the secondary surface armament usually had worse fire control than the main guns, their effectiveness was limited at best (especially on old refurbished ships like Kongo, where the guns were casemated).
To the first question, Japan rebuilt the Fuso and Ise classes because they didn't really have a choice. Even under Washington Treaty limits, they wouldn't be able to lay down a replacement for Fuso until 1935; the rest would have to wait until 1937. Also consider the timing; the reconstructions of the Fuso class began in 1930, well before anyone else's modernizations and a decade before any treaty battleships were actually completed. Granted, it took forever and that pushed the Ise-class reconstructions to the 1934/1935 timeframe... Anyway, they also weren't intended to stand up to treaty battleships: they were intended to stand up to the Standards, and they would've done much better against those ships.

The Italian rebuilds were conducted under similar circumstances. While Italy could have built new battleships in the 1920s and 1930s, a combination of factors (money, vacillation over what design to build, and a desire to not provoke the French into outbuilding them) put that idea out to pasture. Then, by 1932, the Italians were designing the Vittorio Venetos but had no prospect of completing them anytime soon and the French had just laid down the Dunkerques, so the Italians kind of panicked and rebuilt their older ships as a faster stopgap measure.

With hindsight, while I think the Cavour rebuilds were justifiable, the Doria rebuilds were not. Those only got started in 1937 and didn't complete until right around when the first pair of Vittorio Venetos hit the water. Italy would've probably been better off chucking the last pair of rebuilds and just shoving the old ships into reserve.

To the second, dual-purpose guns are not easy to build and they come with penalties. DP guns are not as good in either AA or antisurface roles as dedicated guns, and the larger caliber compared to most dedicated heavy AA meant that it was difficult to design a mount with enough training and elevation speed to do the job. So if you're really worried about mass destroyer attacks, a 6" gun is desirable due to the superior range and hitting power. There's also the fact that swatting destroyers isn't really a matter of fire control, and more a matter of volume. WWII-era fire control systems were simply not designed to cope with the kind of wild maneuvers destroyers could and did perform.

Of the powers that did go to DP guns, France tried a 6" DP gun and failed, the Royal Navy emphasized surface firepower in its 5.25" and suffered according penalties in AA, and the US essentially offloaded the destroyer-shooting mission to its big light cruisers. Something other countries couldn't really do for cost reasons.
 
What everyone else has said. That is, it was rebuilds or nothing because of the 1st London Naval Treaty.

In the case of Italy (and has been stated already) the Doria rebuilds (1937-40) are harder to justify than the Cavour rebuilds (1933-37).

However, if there was no 1st WNT did Italy have the industrial capacity to lay down 2 Littorios in 1933 and complete them in 1937 and another 2 in 1937 and complete them in 1940, without delaying the 2 Littorios that were laid down in 1934 and the two that were laid down in 1938? For example did they have enough slipways of the required length?

Does anyone know the monetary cost of the rebuilt Italian battleships compared to a Littorio?

Warspite's 1934-37 modernisation was about 30% of the estimated cost of a new 35,000 ton battleship, Renown's 1936-30 modernisation was about 40%, I don't have the costs of the rebuilds of Queen Elisabeth and Valiant, but my guess is that they would have been similar to the cost of Renown's modernisation. I've read that the projected cost of the planned modernisation of Hood was £4.5 million, which would have been 60% of the cost of a new ship.

For what it's worth this is the Washington Treaty's replacement schedule for Italy. Had there been no First LNT they could have laid down 5 capital ships by the end of 1936. However, it might not have done them any good because the same treaty allowed France to lay down its 5 replacement ships by the end of 1933 as well, while the British were allowed to lay down 10 replacement ships between 1931 and the end of 1936. Having written that the French and British might not have laid down all the ships that they were allowed to.

WNT Italy Mk 2.png
 
Last edited:
This is the WNT's replacement schedule for Japan. It shows that they could have laid down 6 capital ships by the end of 1936.

However, as the same treaty allowed the British and Americans to lay down 10 capital ships "each" between 1931 and 1936, building new ships instead of rebuilding existing ships might have been to the disadvantage of the Japanese.

Washington Treaty Japanese Capital Ships.png
 
....Of the powers that did go to DP guns, France tried a 6" DP gun and failed, the Royal Navy emphasized surface firepower in its 5.25" and suffered according penalties in AA, and the US essentially offloaded the destroyer-shooting mission to its big light cruisers. Something other countries couldn't really do for cost reasons.
I agree with all of the above but thought I should add,
That the RN could show how hard it was to build a good DP gun even when you are one of the rich large navy's, it built many, many different types in the 20/30/40s searching for what it actually wanted at different stages...

They started with in service in 1920,
6"/45 (15.2 cm) BL Mark XII and Mark XX - as standard low angle,

5.5"/50 (14 cm) BL Mark I - but it was a heavy shell so they tried something else lighter and still low angle

4.7" (12 cm) BL Mark I for DDs LA only

4"/45 (10.2 cm) QF Mark V Main AA gun to light for DP

So they worked on,
1926 4.7"/40 (12 cm) QF Mark VIII 1926 Yay high angle AA but not good for LA so not DP :-(

1930 4.7"/45 (12 cm) QF Mark IX- low angle only sorry...

1930 5.1"/50 (13 cm) QF Mark I - a experimental try in 30s 108 lbs. (49 kg) an incredibly heavy round to load!

1931 4"/45 (10.2 cm) QF Mark XV - to light for DP and low firing weight first between decks (BD) twin mounting so probably helped later DP guns development.

1936 4"/45 (10.2 cm) QF Mark XVI and Mark XVI* 4"/45 (10.2 cm) QF Mark XVII 4"/45 (10.2 cm) QF Mark XVIII 4"/45 (10.2 cm) QF Mark XXI - good AA but to light for true DP

1938 4.5"/45 (11.4 cm) QF Marks I, III and IV - great all great apart from why go with fixed ammo at 87 lbs. (39.5 kg) when split would be 55 lbs. (24.95 kg) ( v USN 5/38 at 55.18 lbs. (25.0 kg))

1939 4"/40 (10.2 cm) QF Mark XIX why not make another lighter guns?

1940 4.7"/50 (12 cm) QF Mark XI why not try again, and lets try and be cheap on the mount to make it even more heavy...?

1940 5.25"/50 (13.4 cm) QF Mark I for BB secondary and DP Cruisers

1940 4.7" (12 cm) BL Mark II - I mean why not its build a completely new gun or we would have to change the DDs ammo shelf's....?

1934(1941RN) 5"/38 (12.7 cm) Mark 12 - might as well try somebody else's DP gun as well on at least one ship?


1947 4.5"/45 (11.4 cm) QF Mark V - YAYYYYY DP finally, if a bit late and still the twin is a bit heavy for a now secondary wepon on post war missile ships coming....

* note this is only guns that made it onto ships from new others do exist if you want to keep reading http://www.navweaps.com/Weapons/WNBR_4-40_mk7.php etc......:'(:'(:'(:'(

With hindsight a 1936 4.5"/45 MKI with split ammo or a 1930 4.7"/45QF MKIX with a real HA mount would have solved everything.
 
Top