On the hypothetical duel between the armored cruisers Nissin and Bayan
When designing the Garibaldi-class cruisers, the Italians deliberately sacrificed their performance in favor of increased armament and armor. But, of course, too much couldn't be expected from a ship with a displacement of approximately 7700 tons.
Comparing the armor masses of the Nissin and Bayan is very difficult, as their weight lists were compiled using different methods. The Bayan was protected by 1449 tons of armor, while the Nissin and Kasuga are listed at 1343,8 tons. However, the weights listed for the Japanese cruisers do not include at least the two armored decks and armored grates (grates?), which together weigh 651 tons, as well as a section of the lower deck, which may also have been armored (86,5 tons).
At the same time, calculating the Nissin's armor by adding these figures together and comparing the resulting 1994,8 tons with the Bayan's armor mass may also be incorrect. This is because the armor deck was typically laid on a substrate of standard shipbuilding steel. Thus, the Bayan's 30mm armor rested on 20mm of steel, and the latter was apparently included in the hull weight, not the armor itself. Meanwhile, the Nissin and Kasuga's deck weights included both the armor and the substrate, if any.
And finally, it cannot be ruled out that the Nissin and Kasuga did not have any deck armor at all, but used ordinary shipbuilding steel instead—which is why, in fact, the “armored” decks were taken into account in the hull weights, and not the armor.
Be that as it may, it must be assumed that the combined weight of the Kasuga and Nissin armor (as well as the structural steel used for armor, if any) exceeded that of the Bayan and was inferior to the Izumo. As for the quality of the cemented armor, as usual, the sources are divided. It is reliably known that the armor plates were produced at the Terni plant, but by what technology? Although some sources cite Krupp armor, this is likely incorrect, as the Italians mastered this armor later. Most likely, the Nissin and Kasuga received armor roughly equivalent in quality to an improved version of Harvey's cemented armor.
Main armor belt
The armor scheme of the Japanese armored cruisers Kasuga and Nissin is relatively simple, although it cannot be called straightforward.
The comparatively short citadel is striking. Unfortunately, I haven't yet found the length of the 150 mm belt that formed it: the 55 meters cited by V. L. Kofman don't align at all with existing diagrams, which place the citadel length at under 50 meters. Overall, however, it was certainly significantly shorter than those of the Izumo (approximately 84 meters) and the Bayan (around 70 meters). However, given that the Italian-built Japanese cruisers themselves were considerably shorter—their length between perpendiculars was only 104,86 meters versus 135 meters for the Bayan—we can say that the citadels of these cruisers extended roughly half the length of the hull. On the Izumo, however, this figure was better—around 69%.
It's also unclear how much the main armor belt extended above the waterline. According to my measurements, the Nisshin and Kasuga were superior in this regard to the Bayan and Izumo. At normal displacement, the Bayan's main armor belt's upper edge was 60 cm above the waterline, while the Izumo's was 74 cm (not 61 cm, as I mistakenly stated earlier). While the Nisshin and Kasuga's was approximately 115–120 cm above the waterline. This was certainly an advantage of the Japanese cruisers.
The 150mm main armor belt extended forward and aft, followed by armor plates of gradually decreasing thickness—120, 90, and 70mm. The Bayan's waterline armor belt was even thicker: 167mm amidships, then 130, 106, and 90mm, gradually thickening toward the upper edge to 200, 150, 120, and 100mm. However, the Bayan's horizontal armor deck ran along the upper edge of the citadel armor plates, while the Nissin and Kasuga's were carapace-shaped and located behind the main armor belt.
Here, again, the Italians took their own approach. Typically, shipbuilders did it this way: within the citadel, the horizontal portion of the armor deck was flush with the upper edge of the vertical armor plates that formed the citadel, and the slopes of the armor deck connected to their lower edges. Outside the citadel, forward and aft, the armor deck became carapace-shaped.
Italian cruisers, as the diagram shows, had a carapace-style armor deck along its entire length. This design meant that outside the citadel, almost immediately behind the main gun turrets, the carapace sloped below the waterline. This, on the one hand, increased the protection of the compartments protected by the armor deck, as a shell striking the ends had a much greater chance of exploding above the carapace deck than within it. However, it also reduced the volume of compartments protected by the armor deck and increased the potential for flooding should the ends become watertight.
Be that as it may, the vertical protection within the Nissin and Kasuga citadels was provided by a 150mm armor belt, a 37mm slope (whether armored or not, I cannot say), and coal pits, which generally provided protection on par with the Bayan. If the 37mm deck was made of armor steel, the Nissin and Kasuga citadels could be penetrated by 13-16 cables with domestic 8-inch/45 model 1892 guns, and by 15-18 cables with ordinary shipbuilding steel. Meanwhile, the Bayan's own 8-inch guns could penetrate the citadel at the waterline to 14-17 cables.
On both Nissin and Kasuga, and on Bayan, the strongest part of the citadel covered only the boiler and engine rooms, not the main battery turret magazine areas. On Nissin and Kasuga, these magazines were located directly beneath the carapace armored deck, forward and aft of the main battery turret feeder pipes, and were protected by 120mm thick side armor plates and 37mm thick slopes on the carapace deck.
An obvious drawback was that the rooms housing the main battery magazines were elevated above the waterline, albeit slightly. Consequently, the likelihood of a hit to the magazines, although small, was still present, and the combination of 120 mm of belt armor and 37 mm of sloped armor did not provide ultimate protection against 8-inch armor-piercing shells.
The vertical armor of the ends was somewhat weaker than that of the Bayan, but the Nissin and Kasuga were protected from the stem to the sternpost, which made them superior not only to the Bayan, but also to the Izumo.
Upper belt
The Kasuga and Nisshin had an upper belt only within the citadel, which we'll discuss below, and were completely absent from the ends. This was a serious shortcoming of the "Italian" ships, but it was somewhat compensated for by the relatively high height of the main armor belt. But only to a certain extent, as both the stern and bow of the ship were susceptible to flooding from water entering through breaches above the main armor belt.
Protection of main and medium caliber artillery, conning tower
Above the main armor belt stood the main feature of the Kasuga and Nisshin cruisers—a towering citadel, reaching to the upper deck. It was formed by 150mm-thick side armor plates and 120mm-thick athwarts, the latter converging at a slight angle to the centerline, protecting the main battery turret feeder pipes. The feeder pipes, extending all the way to the upper deck, had no other protection.
This decision was by no means rational. Of course, if the Nisshin or Kasuga had engaged an enemy abeam while facing the enemy, their broadsides would have been extremely difficult to penetrate. The enemy shells would have struck at such an angle that they would likely have ricochets. However, hitting at a more acute angle would have carried a high risk of damaging the feeder pipes with 8-inch shells.
The classic "all-round" armor of the feeder pipe, which the Nisshin and Kasuga lacked, also had the advantage that in many cases a shell could ricochet off it, while the comparatively "flat" armor plates of the athwart of the Nisshin and Kasuga offered a much lower chance of ricochet. I previously wrote that I consider the 127mm thick athwart of the Izumo a significant drawback of this cruiser's armor scheme. However, the Izumo only had such protection between the middle and armored decks, while the Nisshin and Kasuga had it across almost the entire height of the feeder pipes.
Moreover, above the upper deck, the protection of the Nissin's turrets also left much to be desired. Both the vertical sides of the turrets and the barbette were protected by only 100 mm of armor—it's not even clear whether it was cemented or homogeneous. But with such a thick plate, the latter might have been even better—using extra-soft nickel armor would have improved the chances of ricochets from shells striking the turrets at an acute angle.
Overall, the Nissina's turret protection was quite weak; it could only withstand shells larger than 6 inches at long range or when the shell struck at an acute angle, meaning it deviated significantly from the normal. This is apparently what happened at the Battle of Tsushima.
Only the Kasuga's 10-inch turret received 150 mm of protection, a decent thickness by cruiser standards, for both the turret and the barbette. Below the upper deck, however, its feeder pipe was also protected by only 120 mm of traverse.
Therefore, I am left to state that artillery The main battery of these Italian-born Japanese cruisers proved to be less well protected than the Izumo and significantly less well protected than the Bayan. But the situation with the medium artillery was different: here, the Nisshin and Kasuga led the defense.
Total "Italians" of Japanese fleet They carried 14 x 6-inch guns, four of which were mounted in the open, like the Izumo. And, of course, I can't say enough good things about the protection of the deck mounts. But the main battery of 10 guns of this caliber was housed in a casemate with 150mm thick armor plates facing the enemy, with 127mm thick side walls (the citadel athwart), and inside the casemate, additional 51mm bulkheads between the guns. In other words, the vertical protection of the Nisshin's casemate was significantly better than not only the Bayan's, but also the Izumo's.
Moreover, the "Italians" also had an advantage in horizontal protection—the upper deck above the casemates wasn't 15mm thick like the Bayan, or even 25mm like the Izumo, but 40mm—though, again, it's unclear whether this was armor steel or regular shipbuilding steel. Of course, such a deck wouldn't have been able to withstand a classic high-explosive or armor-piercing 12-inch shell, but the chances of protection against 6-8-inch shells were quite good.
The conning tower had 150 mm of armor.
Horizontal protection
Nissin and Kasuga had the same one as the vertical one - it seemed powerful at first glance, but with some big oddities.
Let's go from top to bottom. As mentioned above, the first level of horizontal protection is the upper deck, which within the citadel was 40 mm thick. A very respectable figure, surpassing both the Izumo and the Bayan.
The second level was the reinforcement of the lower deck (the lower deck on the diagram—apologies if my ignorance of English let me down). This deck was completely ordinary within the citadel, but outside it, it was given an increased thickness of 20 mm. Whether it was armored or not, I unfortunately don't know, but even 20 mm of steel offered a good chance of causing a shell to explode either during penetration or in the space between the lower and armored decks.
And finally, the third level. Sources indicate that it was 37 mm thick only at the slopes, and only 22 mm thick in the flat part. Moreover, the diagram above clearly shows that the 22 mm portion of the deck was present not only within the citadel, but also at the extremities.
While the first two layers of horizontal protection look quite good, the third, and primary, layer is decidedly inadequate. While 37mm slopes are quite respectable, the horizontal 22mm could be penetrated not only by a shell, but even by a shell fragment. Therefore, for example, an 8-inch shell penetrating the end armor of the Nisshin or Kasuga and exploding above the 22mm section of the armor deck could penetrate it and cause damage to the space behind the armor. It could also cause flooding in the compartments below the armor deck.
About the Kasuga and Nissin armor scheme
Overall, this design leaves a rather odd impression. Its advantages—a continuous main armor belt rising significantly above the waterline and the extremely powerful casemate protection of a battery of 10x6-inch guns—are combined with completely inadequate protection for the turrets and their feed pipes, weak horizontal protection, and the absence of an upper belt at the ends. Moreover, the protection of the engine and boiler rooms is no better than that of the Bayan.
On the Bayan's resistance to the effects of Nissin and Kasuga artillery
Since the Nisshin's artillery is very similar to that of the Izumo, the damage it could have inflicted on the Bayan is consistent with what I've described in previous articles. If the Nisshin had been armed with classic armor-piercing shells, it could have penetrated the Bayan's citadel from 16-18 cable lengths, and its turrets, protected by 150 mm of armor, from 21-25 cable lengths.
As for the Kasuga, she had the ultimate, powerful "argument" in the form of a 10-inch gun, and, frankly, the designers of this cruiser should have installed a 10-inch gun instead of the aft turret with two 8-inch guns. Unfortunately, I don't have data on this gun that would allow me to calculate its armor penetration, but it was roughly equivalent in power to the domestic 10-inch/45 gun model 1891, which armed the Peresvet and Oslyabya (but not the Pobeda).
If so, then any armor on the Bayan would have been vulnerable to high-quality armor-piercing shells fired at a 10-inch gun at a range of even 25 cable lengths. However, given that the Japanese lacked conventional armor-piercing shells during the Russo-Japanese War, neither the Nisshin nor the Kasuga had the ability to inflict decisive damage on the Bayan at any range.
On the resistance of the Nissin and Kasuga to the effects of armor-piercing and high-explosive Russian 8-inch shells
The calculation of the resistance of the Nissin and Kasuga to the impact of the Bayan's 8-inch armor-piercing shells is given below in two versions - if the 37 mm slopes of the cruisers are made of armor steel or of shipbuilding steel.
As expected, the situation for Nisshin and Kasuga is worse than for Izumo. Its ends will be penetrated by 8-inch semi-armor-piercing shells at virtually any range, and at 25-30 cable lengths, the 8-inch turrets of the Japanese "Italian" ships also become vulnerable. When Bayan's 8-inch guns switched to armor-piercing shells, which, according to the firing regulations of the 1st Pacific Squadron, was expected to occur at a range of 20 cable lengths, virtually everything except the citadel became vulnerable.
The casemates, the beams covering the supply pipes, the main battery turret magazine protection, the Kasuga's 10-inch turret (except for its front plate facing the Bayan), and the conning tower could all have been penetrated. The citadel, if the deck armor was armor and not shipbuilding steel, had a good chance of being penetrated to 15 kbt. If it was ordinary steel, it would have been reliably penetrated to 15 kbt.
Moreover, the situation for the "Italians" was worsened by the traditionally poor storage system for the main battery ammunition, typical of most Japanese armored cruisers. Just like on the Izumo, a significant portion of the shells were stored in the turrets to compensate for the insufficient feed rate of a single hoist. Given the shimoza's tendency to detonate and the weaker protection of the main battery artillery than on the Izumo, the risk of detonation of the 8-10-inch ammunition significantly increased.
On the other hand, the Nisshin and Kasuga had a quite efficient ammunition supply system for their medium-caliber artillery. 6-inch shells and charges were delivered to the guns via elevators driven by electric motors. V. L. Kofman indicates that there were 16 such elevators in total, but it is unclear whether this includes the supply to the main battery turrets and small-caliber artillery. It is possible that the Nisshin and Kasuga did not have a separate elevator for each 6-inch gun, as the Bayan did, but there is no reason to assume that the elevators were insufficient to supply ammunition in a timely manner. Therefore, there is no reason to believe that the Japanese had to store significant ammunition reserves in casemates, as was the case on their British-built armored cruisers.
Therefore, it can be stated once again: the 6-inch casemated battery of the Nissina and Kasuga was very well protected and did not have the critical vulnerabilities that the Izumo had. However, the protection of the main battery on the Italian-built Japanese cruisers was even worse than that on the British-built ones.
Conclusions
The predicted outcome of a decisive one-on-one battle between the Nisshin or Kasugii and the Bayan is generally consistent with that between the Bayan and the Izumo. At a range of 30–50 cable lengths, such a battle would likely end in a draw, with the Bayan sustaining significantly more hits, which, however, would not have a significant impact on its combat performance. The key here is that the Nisshin's gunners could fire significantly more accurately thanks to their rangefinders, optical sights, and good visibility of their shells hitting the water and impacting.
At the same time, I don't know if the Bayan had a rangefinder, there were no optical sights at all, and the high-explosive steel shells usually didn't explode upon impact with the water. When our shells hit the enemy, they usually exploded behind the obstacle, that is, inside the hull or superstructure of the target ship, and were also almost invisible.
Moreover, due to the fact that the 8-inch turrets of the Nissin were structurally similar to those installed on the Japanese armored cruisers of British construction, the number of 8-inch shells expended in battle by the Bayan and Nissin would have been comparable.
At a range of 20–30 cable lengths, a draw could also be expected, but here the Nissin and Kasuga had a greater chance of sustaining serious damage. The Bayan's accuracy at such a range would have increased, and hits on the turrets and the beams protecting their feed pipes with 8-inch high-explosive shells could have detonated the ammunition or started a fire that could have spread to the magazines.
Finally, having closed to 15-20 cable lengths, the Bayan had a good chance of destroying the Kasuga or Nissin, as at that range the latter's armor offered little protection against 8-inch armor-piercing shells, and the difference in accuracy between optical and mechanical sights would not have been as great as at longer ranges. At the same time, the Bayan's main vulnerabilities to Japanese high-explosive shells—the casemate roofs, the stern unprotected by vertical armor, and the lack of armored grates—generally precluded the Japanese cruiser from inflicting decisive damage on the Bayan.
Perhaps the most the Japanese could hope for was to slightly reduce the Bayan's speed. However, given that the Bayan also had a very good chance of reducing the speed of the Nissin or Kasuga by hitting the latter's ends, and that the Nissin and Kasuga were initially at least two to three knots slower than the Bayan, the Bayan would still have retained its speed advantage over the Italian-born Japanese cruiser.
Therefore, the "recipe" for a successful battle against the Nisshin or Kasuga was exactly the same for the Bayan as it was against the Izumo. Specifically, using its superior speed to close with the enemy to within 8-inch armor-piercing shell range, at which point the Bayan's chances of inflicting decisive damage on the Nisshin or Kasuga would be immeasurably higher than those of suffering it itself.
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