A case for underwater torpedoes on capital ships.

[BobRoss0902]

While many mock pre-dreadnoughts and dreadnoughts for having torpedo tubes there is actually a very good reason as to why they had them. Often times the gun technology was not up to date with the protection during this period, if two pre-dreadnoughts were to find each other and engage in 1v1 combat, neither would really be able to do much damage due to the emphasis on secondary arms rather than the all big gun design dreadnoughts are known for, as well as the fact that the armor on both ships would usually be enough to deflect any shells that came their way.

This is the reason why at the battle of Tsushima most of the capital ships of the 2nd pacific squad were lost due to fire and shrapnel rather than the penetrating catastrophic hits you would see in battles like the Battle Of The Denmark Straight. Guns simply did not have the penetrating power to get through hostile armor. The same issue was seen with ironclads, where an ironclad couldn't sink another ironclad, but anything other than an ironclad was pretty much dead if they ran into on 1v1.

However the torpedo acted as an equaliser of sorts, now smaller ships would have a fighting chance against a capital ship if they played their cards right. But now we go back to the issue of an ironclad not being able to sink another ironclad, the torpedo was able to effectively ignore armor, so when you have an issue of your conventional weapons not being able to penetrate enemy armor and instead having to rely on crew casualties, and things that are more based around chance rather than skill such as fires, and ammo detonations. You can start to see why it would be very tempting to put torpedoes on capital ships.

They already fought at close ranges, within torpedo distance due to lack of gun tech, the guns themselves were unable to actually do damage to the ship itself outside of fires, spalling, etc... and there was this new weapon that was going to change everything, now your capital ships wouldn't just be resigned to fighting smaller ships, now they could actually threaten each other. And while hindsight is 2020 about the usefulness of fixed underwater torpedo tubes on a battleship, it makes significantly more sense if you think about it from the eyes of the time period.

EDIT: The reason why dreadnoughts continued to keep them was there was still leftovers from the mentality of "Capital ships will get in close and form a line of battle" for quite some time even after the launch of HMS Dreadnought. It is also part of why it took so long for many navies to dump the idea of casemates entirely and switch to the more practical less but more useful and with wider arcs of fire turret secondaries.

Thanks for coming to my TED talk.

Edited June 2, 2020 by BobRoss0902

[TBRSIM]

From around 1880 to the dreadnought age capital ships had 3 (later 4) different weapon "systems", the main gun battery ("battery" meaning the entirety of the guns and all directly supporting subsystems, components and expendables like rangefinders, ammunition handling infrastructure, ammunition etc.) , the secondary gun battery (later with QF guns), the torpedo battery and (later) the anti-torpedo-boat batteries (tertiary and sometimes quarternary).

The "original" 3 weapon systems were in a mutual balance with the defensive system, the ship's armor. The main gun could pierce the armor if a hit was gained at close enough range. But rate of fire vs. the combined probabilies of hit and penetration, especially under anything but point-blank conditions, meant that the "all big gun ship" was not really viable until advances in firecontrol, rangefinding and munitions handling (and design for such) advanced in time for HMS Dreadnought. So the roughly 320-400 main gun rounds (assuming four barrels) were not enough to ensure sufficient destructive effect on even one peer target at expected (if not hoped for) engagement ranges. The secondary battery pitched in. At close to point blank range even it could pierce much (enough) of a peer adversary's armor, and that at a higher rate of fire from far more barrels. That piercing range however was less than that of the main battery, so only both together would have hat sufficient probability of effect within the expected engagement range basket. In any case the torpedo battery was the most dangerous of the weapon systems. It could hole a ships hull under the armor belt and sink it. Essentially, this danger created a "minimum acceptable combat range" in capital ship peer-peer combat that was sufficiently large as to render penetration of (main) armor by the secondary battery firing AP moot. Then there was the theory the IJN subscribed to that the secondary battery could serve to engender a cumulative secondary damage effect even without piercing (main) armor and the attendant choice for HE only ammunition there. And the secondary battery would also have been the weapon system of choice against any non-peer adversaries.  

The curious thing is that between ca. 1880 and 1905 the advances in main gun, secondary gun and torpedo batteries (with their attendant techologies such as range finding, shell design, fire control etc.) essentially cancelled themselves out and the three-way balance was maintained while the engagement range basket grew somewhat, argually all three were co-equal weapon systems, none was primary. The torpedo boat was a potential spoiler for which the anti-torpedo-boat battery was added. Only with the technological advances, especially in fire control, that made main guns viable weapon systems with effective ranges (at acceptable phit and ppen) of more than 5kyd (i.e. well beyond torpedo range and beyond the range at which an AP shell from a secondary battery gun could penetrate capital armor, even in secondary locations) this balance was finally broken and the "all big gun" ship became viable where the "main guns" finally were the undisputed primary weapon system. Nevertheless the German Navy remained intellectually invested in the secondary battery (the "Mittelartillerie"), even when Bismarck was designed, while the RN eliminated it entirely quite early (even though the proponents for 6inch guns on battleships kept piping up their dissent) and the USN eventually merged secondary battery and anti-torpedo-boat battery with the(new) heavy anti-air battery into the dual purpose gun battery without expecting it to contribute to peer combat beyond starshells.

[DougToss]

Please tell me we are not going down the road of people thinking secondary guns were more effective than they were again. Just look at the British firing tables comparing 12" and 6" guns and read about the myriad problems they had with secondaries of all types, but especially large ones. 

[TBRSIM]

No, they were not "more effective", but they were considered, at the time, a co-equal weapon system due to their ROF/PEN/Range combination closing a capability gap of main guns in the 1880-1905 timeframe. This however was NOT true anymore beyond that, even though some navies did take about 4 decades to realize this...

[DougToss]

Anytime after the Canet gun was superseded by modern designs, secondary guns were obsolete. Nobody really knew that until the Russo-Japanese War, but once the rate of fire of a 12" gun climbed above a round every few minutes, the course of naval warfare was decided. 

What I'm saying specifically here, as has been mentioned over and over again, supported by historical accounts, gunnery tables, and formulae, is that people here are expecting far too much from secondary guns.