First dual-purpose armament

That would imply that Musashi never had any 5" (127mm) guns at all?? I really would suggest some double-checking. I'll pull out Conway's All the World's Fighting Ships 1922-46 and Jenschura et. al. Warships of the Imperial Japanese Navy and see what else I have around the house. We also have a couple of references from combinedfleet.com:

Yamato-class Battleship | Nihon Kaigun
Best Battleship: Secondary Batteries

Here's another quickie from http://www.scharnhorst-class.dk/scharnhorst/history/scharncerberus.html:

"the complements of the two battleships had been augmented by detachments of naval coastal gunners - sailors who normally never went to sea, but whose 20 mm quadruple-mounted guns were intended to strengthen the anti-aircraft defences."

Since the quad 20mm was fired manually/optically by a gunner on-mount, it could just be bolted or welded to the deck and be ready for action. Heavy flak guns, to be worthwhile, would have to be integrated with a director system and stable element. There were cases like Yamato or HMS Malaya when additional guns of the same type already carried (5", 4") were added, but these were permanent installations.

Which reminds me, the suggested interpretation of Breyer would also imply that Yamato as built did not have those four Type 94 AA directors, and that they too were worked in when the midships 6.1" turrets were removed?

 

Well now, I may have to stand corrected. Breyer contradicts himself. In another section he DOES mention twelve 127mm guns in the "final design of 1937". However, he omitted them in his main discussion of armament for both Yamato and Musashi. Hmmm. He also said that Shinano (not sure if in original BB version or the final carrier form) was to have100mm dual-purpose guns but no 127s.

 

AFAIK, all of the Yamato A-140 designs specified twelve 127mm, with the A-140-I having sixteen 127mm. Light AA was to be composed of 24 25mm guns.

It is also worth noting that the twelve 155mm guns were to have been dual-purpose guns, capable of both HA and LA fire. However, due to several factors the guns proved very inefficient as AA weapons and were rarely, if ever, used in this role.

The Hull #110(the Shinano as a battleship) was to have had the 100mm guns( Japanese 10 cm/65 (3.9") Type 98 ), as were the other two Yamatos(#111 & #797), as well as, the "Super Yamatos"(#798 & #799). The 100mm Type 98 was to have replaced the 127mm as the main AA gun of the Japanese, however, production problems, as well as, the demand far out-striping supply, prevented this from happening.

 

I think one thing that hasn't been stressed enough is that what made the 5"/38 such a great DP weapon wasn't just the gun but the entire weapons system. The gun, plus the Mk 37 director, plus the stable element, plus good ammunition, and later on the VT fuse. The integral shell hoist in most 5"/38 base ring mounts had a great influence on the guns high rate of fire. (5"/38 mounts lacking integral hoists were rated at 12-15 rounds per minute, with the hoists 15-22 rpm) Many of the round types were DP also, incorporating a nose and base fuse.

Where the 5"/25 was really lacking was in range. From Navweapons.com; "during gunnery trials in 1941, USS North Carolina (BB-55) was able to repeatedly shoot down drone aircraft at altitudes of 12,000 to 13,000 feet (3,700 to 4,000 m), about double the range of the 5"/25 (12.7 cm) AA Mark 10 used on older ships." The 5"/38 had a max range with AAC ammunition of 18,200 yards and max ceiling of 37,200 feet, the 5"/25 had a max range of 14,500 yards and max ceiling of 27,400 feet.

 

Excellent point USMCPrice! Fire control is just as important as number and caliber of guns, but hardly ever gets the same attention.

For one example, the British early in the war mounted old 3" or 4" guns on many of their destroyers, in lieu of the after torpedo tubes. These proved almost completely useless and were soon removed.

 

I knew about the different ceiling and range but didn´t think it was important as it was de facto impossible to hit a moving ship with a level bomber unless the level bomber flew at masttop altitude. That the actual ceiling/range was that much lower and that different had escaped me. It must had had something to do with the different MV. The higher the better for hitting fast and/or distant targets as the plane moves less far away in the time between the shell fired and the shell´s arrival in the target area. However I think the Mk.37 FCS also had an effect and the the ships with the older 5"/25 also had older FCS like Mk.33.

A few words about Dual-Purpose guns in general: Having them was helpful but I think only small warships like destroyers and so on actually needed them. Bigger warships had the space to mount seperate anti-ship and anti-air batteries and they were also screened by smaller ones.

 

I don't know that that is true. Topweight was a critical factor in cruisers in particular. With all the additional electronics sensors and their associated equipment the weight of additional mounts was critical. Then you have deck space, as the war progressed AA suites became heavier and heavier. If you had a seperate 5"/51's for surface and 5"/25's for AA and combined the roles into a single mount you freed up space for an additional twin or quad bofors mount. While the big boys may have been screened by the destroyers it did not alleviate the need for a substantial AA suite nor the need for the ability to engage smaller surface threats than the main battery could easily engage. In fact the ability to engage in both types of mission made the ships more valuable. In the U.S. navy at least, providing additional AA support for the carriers was as, if not more important than the need to provide naval gunfire support or the ability to engage in surface actions. Also, if it were true that there was no advantage in a single DP mount vs seperate surface/AA mounts, why did the U.S., based upon combat experience, redo so many of it's capital ships with the DP mounts?

 

Dual purpose also means you have more guns to fire in either mode and a simpler fire control set up.

 

I think we should also look at the 8" mounts of the Kent class,they came earlier than most guns mentioned here and the 80 degrees elevation was intended for AA fire though in practice the slow turret traverse made then not very effective in the role.

 

In the WWII era, the concept of separate low-angle and high-angle secondary armaments mainly pertained to capital ships. Cruisers had their main armament and one secondary battery, mainly for AA work, although it could engage surface targets.

The "dual-purpose question" for cruisers was combining the main armament in light cruisers with the AA, as in the Dido or Atlanta classes. The main armament in a light cruiser was comparable to the low-angle secondary in a battleship.

The Deutschland class "pocket battleships" are a curious case. Legally they were replacements for the early 1900s Deutshland class battleships which Germany was allowed to retain under Versailles. Their configuration of main, low-angle secondary, and heavy AA batteries was consistent with battleship practice; no contemporary cruiser had low-angle secondaries. The 11" main armament was in the capital ship class as defined by the naval treaties, the closest thing to an authoritative definition of "what is a cruiser/battleship?" But they were ultimately redesignated heavy cruisers and are considered as such in many references.

Getting back to "real" battleships, DP armament had one other virtue in that it freed up space for massive heavy automatic weapons batteries. US BBs had up to 80 40mm and the British KGV class 96 2pdr/40mm (or 114 in HMS Howe, which replaced all 20mm with 18 single 40mm). The only European battleship to approach this was Richelieu, whose 152mm secondaries had originally been intended for DP operation. She would have had only two main and five secondary turrets; even with two of the latter replaced by 100mm AA she still had room for fourteen quad 40mm.

 

As capital ships operate well outside the range of 4" to 5" guns, I was mainly thinking about cruisers. They got their 6" or 8" guns for the anti-ship work. DP-guns might be a nice extra but on how many and what occasions are the used against ships? In a night battle for example ranges are extremenly short. 4"-AA, 5"-AA and 5"-DP would all be able to engage the enemy.

Like I said: Its nice to have them but its not an absolute must. And the US 5"/38 was no doubt a much better AA-gun than the 5"/25. I guess that´s why they installed them. Not because it was DP but superior AA.

 

The secondary armaments on capital ships originally came from the need to engage fast moving torpedo boats and destroyers. This need did not go away. A smaller caliber, rapid fire weapon was optimal. Generally speaking the larger the caliber the slower it is to train and the lower the rate of fire, not as good for engaging smaller, faster ships trying to close the range.
Ships also seldom operate on their own but in task groups with screens of these smaller ships. So yes, a secondary battery is important. Lastly, a capital ship cannot always dictate when and where it does battle. At night or in inclement weather visibility and therefore engagement ranges are reduced. The secondary battery was also quite usefull at shooting up the enemys upperwords which were only lightly armored if armored at all. Destroying your opponents command, control, communications, sensors and fire direction is one way to give yourself an advantage while the main battery works on the more heavily armored areas.

 

Right but only if we refer to the time before WW1. In WW1 destroyers failed to get within striking distance. After WW1 the capital ships got faster, while destroyers didn´t, destroyers got bigger(=bigger targets) and ranges increased.

Ranges were reduced to machine gun range in case of one night battle near GC. In that case a 5"/25 would have scored just as easily as the 5"/38.

That is right but again only if we refer to 1905 or so. At Tushima much damage to the Russian ships was done that way but it was also noticed that this damage had not been lethal, that only the 12" guns inflicted that kind of damage. Hence the "all big gun ships" with improved FCS that allowed battle to be fought outside the range of the secondaries.

 

How does the capital ship getting faster have anything to do with speed of tracking and rate of fire for the main battery? If the torpedo attack by destroyers was no longer a threat, why did nations continue to mount torpedos on destroyers? Why did nations continue to teach it as a tactic and still employ destroyers as screening forces? Why did the U.S. Sumner and Gearing class destroyers all of which were designed and built during the war and their designs incorporating lessons learned in actual combat still mount 10 torpedo tubes?
Where is the evidence that secondaries were only important for engaging small, fast vessels, prior to WWI? Let's look at the US battleship Wyoming laid down in 1910, commissioned 1912. Her secondary armament consisted of 21x5"/51's, she's pre-WWI. Let's then look at the Nevada commissioned in 1919, basically a pre-WWI design with alterations based upon war experience, secondary battery 20x5"/51's. Or how about the USS Tennessee, the first US battleship designed and built post-Jutland, commissioned 1920, secondary armament 25x5"/51's. If anything it would appear that there was a slight increase in the secondary battery. Not something you'd expect for a threat that the war proved was non-existant. Is this just a US thing, well let's look at the HMS Hood, commissioned in 1920 and incorporating the lessons from Jutland. Secondary armament as built, 12x5.5" and 4xQF 4" for AA defense.

What does that prove?

 

When battleship design stabilized in the 1890s, it included a secondary armament of guns around 6" for engaging the "soft" parts of hostile battleships and an anti-torpedo battery around 3", which was adequate against the small torpedo boats of the time. In the early 1900s the secondary armament was supplemented or replaced with 8-10" guns in turrets, retroactively termed the "semi-dreadnought" configuration. Ultimately secondary or intermediate guns were done away with entirely in the dreadnought, which at first (HMS Dreadnought, USS South Carolina) had only 12" main guns and 3" anti-destroyer weapons which, in the absence of the former secondary armament, picked up the name despite its different function. The increase from 3" to 4, 5, or 6" in subsequent dreadnoughts reflected the increase in size and power of destroyers; the 5 or 6" guns of WWI battleships were the functional equivalent of the 3" of the 1890s.

While a battleship might fire its lighter guns at another if they happened to meet at close range, the design trend was towards longer-range combat, exemplified by the all-big-gun armament, director control (usually located atop tall masts), increased elevation, and eventually air spotting.

Longer range meant that in some cases like Dogger Bank, destroyers were less likely to be able to engage, but that was also a factor of good visibility and the tactical situation, one side fleeing. The one big battle of WWI, Jutland, saw considerable action by destroyers; although there were few hits, torpedo attack and the threat of same constrained Jellicoe's actions, while the British battle line was disrupted at times by ships taking evasive action. Destroyer torpedos also featured in WWII battles like Surigao Strait or Samar, again reflecting the tactical situation more than speed differences or maximum ranges.

Battleships like our "standard type" were designed to engage their counterparts at long range and carried secondary guns for torpedo defense. Friedman's US Battleships Illustrated Design History even mentions debate comparing the merits of 5" guns vs. improved underwater protection. US designs included as many as 22 5"; the reduction to 12-14 was because hull-mounted guns proved impractical in heavy seas (I've also seen the 25 figure for the Tennessee but that is incorrect, maybe a typo). Late WWI era designs like South Dakota or Hood put all secondary guns above the main or forecastle deck.

The standard type were basically "post-Jutland" ships although the "all or nothing" concept originated with the Nevada design of 1911. Subsequent classes through the Colorado and even South Dakota were incremental improvements including steady growth in size.

 

Planners between the wars could not rule out a Jutland type engagement, actually it was the main scenario they designed battleships for, and that means a fleet made up of a battleship main line and multiple destroyer/torpedoboat squadrons that would try to get in torpedo range and would deal critical damage if successful. Due to the size increase of destroyers navies believed a 6" secondary, like on the latest generation of ww1 battleships was required to stop them and as attempts to produce a DP 6" or larger were unsuccessful the secondary/tertiary arrangement came into being with separate 6" LA and lighter HA weapons.
As the air threat increased allied navies, that could generally rely on having large destroyer screens decided they could afford to have a lighter than 6" DP gun as the screen would reduce the torpedo boat threat, axis navies couldn't and kept a 6" secondary.

 

The smaller the speed advantage of the DD, the smaller the chance to get the capital ship within torpedo range. Even the famous Japanese Long Lance that combined a very high speed and a very long range was a failure in daylight battles. So I guess navies expected too much from DD or mounted the tubes for night battles. Under these circumstances torps were a success.

Well, in WW1 DD either didn´t get within range or when they did(Jutland) the slow capital ships easily evaded the torps. IMO that shows the threat was overrated.

 

IIRC ALL dreadnoughts combat losses in WW1 were due to torpedoes, though none were from destroyers, and none dreadnoughts were lost to big guns. Little evidence there to dismiss the threat as "overrated".

 

I assume by dreadnoughts you mean dreadnought battleships only.

HMS Audacious: Ran on a mine in 1914
SMS Szent István: Sank by MAS with torpedoes in a night battle in 1918

Who else lost a DN battleship? Noone as far as I can tell. Unless I overlooked something only one battleship was lost to a torpedo launched from a surface ship and that happened at night.

 

Well, the three British battle cruisers at Jutland were done in by gunfire, though it was largely due to their own deficient ammunition handling practices. More to the point the very well protected Lutzow was on the verge of sinking entirely from gun hits - she had settled to the point where her A turret was completely under water - although a destroyer did scuttle her by torpedo. The crucial damage was a pair of 12" hits from Invincible in the forward submerged torpedo room.