Naval gunnery 1890 to 1945 and lessons drawn


Naval gunnery was in a dismal shape during the last decade of the 19th century. The old extremely smoke-producing blackpowder (not really a "powder" any more at that time) propellants had recently been replaced by smokeless propellants (such as the hazardous cordite in the Royal Navy) and breech-loaded guns were being adopted for good, but the gunnery and artillery ship design was in a horrible state of affairs.

Expected useful firing ranges were short (less than 4 km against ships), as optical range-finding was in its infancy and there was no central fire control yet. The coal-fired boilers produced terrible amounts of smoke and many guns were placed so low even on battleships that fairly normal rough seas made them temporarily unusable as waves crashed into them.

The typical armament of an armoured ship of the time consisted of two or four large calibre guns (8"...13.5" calibre), with a substantial secondary battery of  usually 4...6" calibre and soon some smaller guns specifically to shoot at the small (about 200 tons) and nimble torpedo boats.

There was a break in rate of fire between 6" guns and heavier guns because 6" has the heaviest shells that can be loaded by hand throughout a long battle by the non-roided men of the 1890...1945 period. The heavier guns used more machinery to load shell and propellant and this was slower, not faster (and still is, though it's faster than manual loading for the modern naval guns of up to 130 mm).

This huge drop in rate of fire from about 5...15 rpm for 5...6" guns to 1.5...3 rpm for most heavier guns was in part cushioned by the reality of long-range gunnery post-1910, but this rate of fire and the huge cost, size and mass increase past 6" calibre led to a curious situation at first:

Ever since the 1860's there were many warships with a primary artillery of few impressive big turret guns and many more smaller and somewhat hidden casemate guns up to 6". The public perceived the primary guns as the defining firepower. Those guns may have penetrated heavy armour protection on other ships, while the smaller guns did not. The reality was almost certainly known to most warship-commanding naval officers and naval gunnery officers: The secondary guns were the main armament and the big guns were for show and possibly useful in coastal bombardment, or as a deterrence.

The small guns fired so much more often that they were bound to score about tenfold as many hits at the then-relevant combat ranges. The heavy guns fired so rarely that corrections after observation of fall of shot by the gunner were obsolete by the time the heavy guns were ready to fire again.

Smaller than 8" shells were also less likely to be duds when they hit some unarmoured part of a ship where a very large calibre shell fuses often failed to trigger even as late as during the Second World War.

Royal Sovereign (1891) 13.5" twin barbette
A most egregious example was the Royal Sovereign class, which had four 13.5" guns in twin barbette mounts. Those were unarmoured to save mass high up on the ship, to improve rolling behaviour and general seakeeping. (The ships of this class still rolled badly when introduced.)

These 13.5" guns fired one broadside salvo every 135 seconds only, (0.44 rpm), as they could only be reloaded in fore-and-aft position. They might not have fired more than four or five shots per barrel in a battle, for the unprotected crew would likely have been cut down by fragmentation and even shrapnel (that was still a thing in navies at the time and has recently kind of returned with the 35 mm Millennium gun and its AHEAD munition) by many small calibre hits at that point. Meanwhile, the Royal Sovereign's protected 6" gun crews could have continued the fight with 25 or more rpm in total (port or starboard).

You may think that those 6" shells wouldn't do much damage, but most parts of any warship were unprotected or at most protected against fragments and shrapnel. Fires could be started (there was still much flammable material and even oil lamps in use) and the heat and smoke could render the burning ship combat ineffective (secondary fires could even doom it).

Most direct damage done - even by hits of the heaviest calibres -  would still usually be superficial, as the shells up to the First World War period usually used impact fuses without the delay required for explosions where they hurt the most (boiler rooms, turbine rooms, magazines deep inside the  hull). Secondary explosions were rather flash fires in turrets or where turrets and their munition hoists if not magazines were very close to the side of the hull. The extremely delicate boiler rooms with all their pressurized containers and pipes were so rarely harmed that even badly-hurt ships could make it to home port if not finished off by a magazine explosion or torpedo hit.

A bit more about rate of fires; by the Second World War, these had been improved to maximum slightly more than 3 rpm for (German) 15" guns, about 15 rpm for some (American) 6" guns, about 20 rpm for (American) 5" guns and also for 4" guns. Army 3" guns had reached about 30 rpm before 1900 already, but many early naval 3" mounts fell well short of such  rate of fire. The practical rates of fire on a warship in a gunfight were mostly MUCH slower.

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Let's pause with this military technology history wonkery and look at a still-relevant lesson:

The public was very much fascinated by and interested in its battlefleet (at least the middle and upper classes, especially in urban areas). Such huge armoured ships did cost a fortune each, and were a heavy fiscal burden even to the richest countries. Yet all this attention did not reveal the terrible flaws of the capital ships of the period, much less lead to civilian oversight pressure to work on those deficiencies. That push came largely from some high-ranking officers who especially in the Royal Navy thought the time was due to become an actual fighting force again. (The newcomer German navy had been in technology catchup and modernisation mode anyway and no such awakening experience.)

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Thus improvements were made after the Royal Sovereigns; later capital ship primary artillery always had properly-protected turrets (many gun crews in the 4"...6" gun range especially on cruisers remained inadequately protected even against fragmentation), and a long time after (after the First World War) the last navies adopted proper and high-enough mounted secondary artillery turrets instead of casemates. There were also experiments with really high-mounted casemates in the superstructure. 

The biggest change happened with regard to fire control and quantity of the primary artillery guns. The individual aiming was hopeless at long ranges, and thus fire control became centralized with gunners in turrets merely following orders about elevation and training as well as shooting the guns.

It was understood that simply giving more gunnery practise did not suffice; you needed to observe the fall of shot and correct accordingly. This required salvo fire and all guns aiming the same (or, if spaced much, at least using the same gun elevation). A mast top-located observer would see whether the water fountains were too far left, right, long or short and issue corrections. Eventually, the salvoes would straddle the target (shells impacting on or around the target) and the salvoes would continue without further corrections at highest possible rate of fire until the salvoes were observed to be off again or the target turned.

Mechanical fire control computing aids were introduced, communication devices were needed between fire control and turrets and optical rangefinders were introduced and improved until they could in theory measure distances to the horizon. Such (except the computers) was the art of gunnery by the First World War. This centralised aiming and firing depended so much on observation of the fall of salvoes that a rule of thumb began to dominate warship design; it took a salvo of at least six shots for a proper observation, and the guns better not be spaced very much (this led to a few capital ships with all primary artillery on the forecastle; Nelson, Rodney, Strasbourg, Dunkerque, Richelieu, Jean Bart). Some capital ships had 12 primary artillery guns and were able to shoot at two different targets with full fire control process simultaneously. This helped alleviate the issue of long spacing between turrets. Many dreadnoughts and super dreadnoughts were on the other hand unable to fire with a full 6 shell salvo in (nearly) all directions, although this had already been achieved with HMS Dreadnought (and the prototype battlecruiser HMS Invincible shortly after). They were thus rather a kind of ship of the line, optimised for broadsides only.

The so-called Pre-Dreadnought battleships with their mere two or four primary artillery guns were thus obsolete with the rise of centralised aiming and firing, and the appearance of HMS Dreadnought in 1906 is commonly considered to be the signal for this paradigm change. 

Finally, by about 1910 there was no reasonable doubt any more that the primary artillery was actually the main armament of battleships. The other guns turned into self-defence weapons until battleships were turned into heavy (anti-air) escorts by the rise of the aircraft carrier in 1942 (then the secondary or even tertiary guns in the 40 mm...133 mm range became the main weapons).

Now back to why large calibre gun rates of fire weren't THAT terrible during the World Wars as it seemed (despite shooting even more slowly in practice than nominally able to): The cycle of flight of shot, observing, reporting, calculating, transmitting directions to turrets, turrets training and elevating according to directions and finally firing a salvo together took longer than the reload even of a 16" gun. Practical rates of fire were even much worse than nominal ones. The Bismarck was capable of shooting its 38 cm (~15") guns in 18 second intervals. That should have sufficed for about 45 salvoes in its battle with HMS Hood and HMS Prince of Wales. It fired off 13 salvoes only.

The nominal rate of fire was really only important at short ranges that required no observation and corrections, such as night combat at ranges of less than 4 km. Such ranges also devalued armour very much; horizontal armour would not be tested and vertical (belt) armour would be more easily penetrated as it was meant to protect at a greater distance only. This quick fire superiority scenario of a short range night battle allowed the really quick-firing American 6" guns to shine in the Guadalcanal campaign. Even the Japanese battlecruisers were inadequately protected against 6" shells due to their narrow belt armour.

(Now keep in mind that a ship such as the HMS Royal Sovereign of the 1890's would have made full use of its rate of fire, for it would not have the shoot-observe-correct fire control cycle. It would have made full use of 2 rpm rate of fire if it had had such a rate of fire. Its 0.44 rpm broadside rate of fire was thus exactly as bad as it sounds. The 2 rpm of some First World War-era main guns was not as bad, as the fire control process slowed them to less than 2 rpm during most of the battle anyway.)

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Fast forward to the Second World War period: What was the peak of warship gun duel gunnery then?

The peak in daytime would have been like this: An aircraft or small and nimble escorting destroyers would lay a smoke concealment to blind the enemy fire controllers (see excellent collection of photos here). 

The own ship would use its radar and fire control computer for a first salvo or set of bracket salvoes, and a spotter (float)plane would issue the corrections by radio instead of the ship's own observers in mast tops. Top quality radars could even detect the impact slashes of big shells and shells had dyes of different colours so fire controllers could tell which salvo had been fired by which ship. Depth charge throwers ("K-guns") could be used to deceive enemy spotters to believe that the target was straddled when it was not (this was greatly complicated by the use of dyes and dependent on seeing the salvo being fired). It was also possible to group the artillery of one calibre into two or three groups that shoot at different elevations in order to quickly find the correct elevation by observing which impact group was more close to the target (bracket fire). Knowing the correct distance to the target and even the two ships' movement vectors accurately and doing all calculations correctly (including coriolis force correction) would not necessarily suffice to get the elevation right on first try: The temperature of the propellant, barrel temperature, air temperature, air humidity, how much the barrels were worn and wind also had an effect. A radar-only fire control without impact splash observation would have failed at medium and long ranges with the state of the art of even 1945.

Secondary artillery could use the same sophisticated fire control process as primary artillery.

The targeted ship would make evasive manoeuvres when straddled, degrading or resetting both the fire control process against itself and its own fire control process (if it has any and isn't completely blinded).

This combination of fire control and countermeasures rarely if ever happened in perfection. Smokelaying is tricky in windy conditions and some navies had good-enough radars only late in the war (Japan) or never (Italy). The battle in the Java Sea saw Japanese cruisers using the smoke+spotter plane combination, though. Radar-controlled fires were used as well, albeit sometimes with surprisingly bad results (the Bismarck was very poor at getting the elevation right, for example).

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An aircraft carrier as a mere support ship without any torpedo bomber or (dive) bomber could still have had decisive impact on a battlefleet engagements of the 1930's by providing smoke, spotters (replacing the more fair weather-dependent floatplanes and flying boats) and fighters to chase off or down enemy spotter planes. This begs the question why some navies (Germany, Italy and mostly also France) neglected the aircraft carrier so very much. It was already a decisive asset without high performance aircraft (Morse radios/wireless telegraphs were already tested in aircraft during the First World War).

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Yet again, I saw no trace of public pressure on navies to correct such a deficiency during the 1920's and 1930's. The naval discussion in Germany was about the expenditure for the Deutschland class (the later so-called pocket battleships*) until dictatorship took over and public discourse was muted. A similar excuse can be given for Italy, albeit as far as I know their dictatorship would have tolerated pro-carrier enthusiasm  while censoring negative critique. Their navy was barred from having aircraft in favour of their air force, so I suspect their naval top brass simply passed on a critical naval asset because it wouldn't have been fully theirs (the carrier aircraft would not have been navy-operated). I see no excuse whatsoever for France, which had a carrier arm that badly stagnated with the Béarn**.

So why were such severe shortcomings not corrected under public pressure in general? It wasn't just the dysfunctionality of dictatorships. The story of anti-air artillery during the 1920's and 1930's was a farce all around the world. The ridiculously poor quality and also ridiculously poor quantity of anti-air guns in that period was in stark contrast to the known threat of torpedo bombers of the Interwar Years. Their heavy and still very short ranged (low muzzle velocities) medium anti-air artillery was even too weak to protect their own spotter planes from enemy planes even only overhead themselves. Even ships such as heavy cruisers were often only equipped with four weak heavy anti-air guns and a couple machineguns. Moreover, several exercises thoroughly embarrassed navies, as they failed to hit the aerial target for extended times.

It's a general problem with (relatively) highly technicized armed forces in peacetime. Warfare against peer or better opposition may reveal their deficiencies, but most of the time armed services can hide their shortcomings behind the veil of secrecy.

It's a cautionary tale regarding how much top brass can be trusted by the public.


 In kind you want yet more video about naval gunfire control:

*: The Spanish España class deserves this title much, much more.

**: Which also had poor quality aircraft during the 1930's.  


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