"Armoured versus unarmoured" Topic

I was watching a rather good video on Youtube about IJN Taiho.

It touched upon the change made to the usual Japanese practice of having unarmoured flight decks (like the Americans) to armoured (including belt armour), like the British practice.

Is there any consensus which is better?

I think an armoured flight deck was better against kamikazes and was less vulnerable to an aviation fuel fire on the deck.
On the minus side, it probably was harder to repair minor damage.

It also made the ship more top-heavy and, in the British ships at least, brought the flight deck closer to the waterline. In RN practice the flight deck was the strength deck, while in USN usage, that would be the hangar deck, with the flight deck being superstructure.

And there were damage control trade-offs as well. Since the USN hanger was on the strength deck, damage above that might put the ship out of action, while damage in the hangar on a British carrier could well sink the ship, or at least damage it beyond repair. No British carrier could have survived the pounding that the USS Franklin took.

The fact that modern carriers have armoured flight decks is because of the fundamentally different type of aircraft than those used in WW2?

From my (limited) reading, it was the heroism of damage control parties (& some luck) that saved the Franklin & the Bunker Hill.

With all due respect, rmaker, you are making questionable statements here.

A properly designed ship would not be "top heavy" regardless of whether or not it had an armored flight deck.

WRT your claim that "No British carrier could have survived the pounding that the USS Franklin took.", in the 3/19/1945 incident, Franklin was hit during a low-level bombing run by two 550 pound SAP bombs, which penetrated the flight deck, causing secondary explosions on fueled and armed aricraft. These bombs likely wouldn't have penetrated the armored flight deck of a British Illustrious class CV, which was designed to resist 500 pound bombs dropped from altitude. The bombs which damaged Illustrious in the Med were in the 1000 and 2000 pound range, dropped from dive bombers.

I always understood that the armored flight deck limited the number of planes a British carrier could hold since it wasn't just the deck that was armored. It was an armored box with a ship built around it.

It isn't a question of better, just appropriate. British carriers were designed with one eye on operating in the congested waters of the North Sea and Mediterranean , within range of more land based air than you could share a stick at.

One American admiral commented about carrier damage from kamikaze attacks off of Japan: a kamikaze attack on a US carrier was six months repair at Pearl Harbor, on a British carrier it was up sweepers.

Minor damage to a British carrier flight deck was often repaired with quick set concrete – permitting air operations to quickly resume.

When the armoured carriers were designed in the 1930s radar was not thought of, so there was no way of being sure its fighters would be able to find and intercept incoming strikes. Even if they could, the compromises required for carrier operability meant that carrier fighter performance could not be expected to match that of land-based air.

So the thinking was that you should expect to get hit, and so your carriers should be able to survive getting hit. The flight deck was the strength deck and it was treated like a magazine.

It all made sense in 1935. By 1940, less so.

Illustrious duly took six hits to the flight deck from Stuka bombs of 500 and 1,000kg weight. There's no instance of any other carrier taking that and surviving. Akagi was twice the size and was destroyed by one 1,000lb bomb.

On the other hand, there is an argument that the carriers only got hit on their armoured deck in the first place because of that armoured deck. All that weight high up raised the metacentric height and so it had to be set as low as possible. This in turn reduced the size of the hangar and the number of aircraft it could carry, including fighters. If the air group had been bigger, goes the argument, the bombers would never have got past the fighters, the bombs would never have hit it in the first place, and so you didn't need an armoured deck at all. Ergo, you want an unarmoured flight deck and a 70-plane air group that's 2/3rds fighters. 1/3 go off to bomb escorted by half the fighters, while the other half defend the carriers.

This design worked brilliantly in the 1944 carrier battles, but ironically the British approach worked better in 1945 when the Japanese did the unexpected with their kamikazes. These bombers did get through, by overwhelming the defences with 100+ one-plane raids, and did huge damage to unarmoured carriers. It is a myth that they did no damage to the armoured carriers though. Although they survived kamikazes better, at least one was permanently slightly bent thereafter.

Taiho's story is very typical in a way. Japanese carriers were kind of cargo cult designs. They looked like carriers, but as though built by people who'd read descriptions of them, but had never seen one. So they had flat tops and air groups, but they often had the islands on the wrong side or no island at all. Some had motorbike exhausts along the edge of the flight deck or outward leaning funnels to vent the smoke. They had AA but most of it was so short-ranged it could only hit targets already diving on them. None had proper damage control. In a US carrier, everyone had a job and a damage control station. In a Japanese carrier, there was a damage control department, unless they got included in the damage in the first place, in which case there wasn't. Who needed damage control on a Japanese carrier anyway? It would always be the IJNAF doing the bombing.

Taiho was likewise an armoured carrier but not a proper one, because the hangar wasn't treated as a magazine. She was lost because a torpedo hit and fractured the avgas storage tanks, and someone switched on the aircon to get rid of the smell. The fumes distributed through the ship inevitably found a naked flame and blew her up.

The optimal solution of course is to make the carrier twice the size, so it can have deck armour, and a big air group, and enough deck-edge real estate to establish some really, really lavish organic AAA, as per the Midway-class CVBs of 1945.

There was something about the elevators on the Taiho being very deep: below the waterline, in fact.

The av gas fumes collected in there & were spread through the ship. It wasn't "to get rid of the smell" that the mistake was made. You're underestimating the Japanese. Admittedly, it was a bungle by damage control but they were trying to rid the ship of volatile fumes. What happened was what they feared.

It is a myth that they did no damage to the armoured carriers though. Although they survived kamikazes better, at least one was permanently slightly bent thereafter.

SFAIK, only "permanent" in the sense that it was decided to keep them (most notably HMS Illustrious) in service with inadequate repairs, rather than to send them to a dockyard for complete repairs – a common occurrence in wartime. In the case of HMS Illustrious, the ship was already damaged prior to the last kamikaze attack, including the hull and shafting.

Here's something from the Internet (not requiring a book purchase): link

Compare two equivalent Carriers: The HMS Illustrious was 23000 tons, commissioned 1940, top speed 30 kts. She initially carried 36 aircraft, rising to 53 at the end of the war. The USS Hornet was 20000 tons, commissioned 1941, top speed 32.5 kts. She carried 90 aircraft. I'd say the trade-offs for the armored flight deck were pretty steep.

Yep – that's why Illustrious was sunk and Hornet wasn't.

4th Cuirassier gives a very good summary of the armoured carrier concept. For a detailed analysis of the design and operation of armoured aircraft carriers in WW2 I thoroughly recommend this website: armouredcarriers.com

There is a huge amount of information and detailed historical reports etc. on this website. Some very good operational details and damage reports as well as discussions on armoured v unarmoured.

The pounding Illustrious took off Malta and survived is testament to the construction of these ships and also the excellent damage control. She took 2 hits from 500lb bombs (250kg); 2 hits from 1100lb (500kg) bombs; 2 more hits from either 500lb or 1100lb bombs; and a hit from a 2200lb (1000kg) bomb as well as three near misses. Read about the damage and the efforts taken to save the ship here: link

It would take 9 months to repair the damage and the ship had problems with her propeller shaft for the end of her life. By 1945 ships like Illustrious were worn-out by 5 years of conflict just like Enterprise but both ships continued to provide good service. Illustrious was withdrawn from operations in the Pacific in April 1945 following a very near miss from a 2200lb bomb exploding under water.

Given the design restrictions the first class of armoured carrier (Illustrious, Formidable, Indomitable & Victorious) were originally designed to carry 36 aircraft, this later increased to a maximum of 57 aircraft using deck parks. The two Implacable class armoured carriers could carry 81 aircraft.

The Yorktown class of US aircraft carriers were designed to carry 90 aircraft but that included aircraft broken down in crates. For example USS Yorktown operated 53 aircraft at the Battle of Coral Sea (with 13 spares) and at Midway would operate 75 aircraft. None of this class were able to operate 90 aircraft – only the much larger Essex class could do that.

Still, half the planes on a hull is a big sacrifice. What if the air strike on Taranto were made with twice the planes?

What if it were made by none because each carrier had previously been taken out by one bomb? That was the concern the armoured carriers were built against.

The US carriers faced the opponent they expected, usually with numbers on their side, and four were sunk. The RN carriers also faced the opponent they expected and they all survived. So the design was pretty effective, I would suggest, although definitely not future proof to fundamental changes in aircraft type.

@Murvihill

The air strike on Taranto was only 21 planes, not because the Illustrious couldn't carry more, but because the RN didn't have them. If you look at air group numbers prior to the RN getting large numbers of lend-lease aircraft, carriers almost always carried less than their designed air groups. I guess the RAF had priority for available production, including Bomber Command of questionable cost-effectiveness.

Hornet was not taken out by one bomb. It was taken out by three bombs, one kamikaze, 16 torpedoes and 400 5" shells.

Nobody said Hornet was taken out by one bomb, but it was entirely possible for this to befall an unarmoured carrier. I can think of two examples offhand, namely Akagi at Midway and Princeton at Leyte Gulf.

The Ark Royal was taken out by one torpedo, does that make the British aircraft carrier more susceptible to torpedo damage than the American fleet? Your position appears to be that a more defensible ship is more important than more airplanes and mine is that as an offensive weapon more airplanes is more important. I don't think we're going to come to an agreement.

My point is simply that there were solid reasons to accept a smaller air group, so – in response to the OP's question – it is difficult to conclude that either was better.

Ark Royal was unarmoured, so was closer to the US design, for the same reason: to maximise offensive power. It clearly carried risks.

The offensive ability of Ark Royal, Lexington, Yorktown, Hornet and Wasp was significantly eroded by being sunk.

The optimal design was clearly both an armoured deck and a large air group, which is why the USN's Midway and the RN's (cancelled) Malta class.

The offensive ability of Ark Royal, Lexington, Yorktown, Hornet and Wasp was significantly eroded by being sunk.

Not just the Ark Royal. Several other British carriers also had their offensive capabilities significantly eroded by being sunk:
HMS Hermes
HMS Eagle
HMS Glorious
HMS Courageous

Now we can say that none of these had armored flight decks. Fair enough.

But I would also observe that only one of these was sunk by aerial attack, and quite honestly for Hermes, small, old, slow girl that she was, with only 6 Fairey Fulmars to defend her, and one obsolete destroyer as her escort, facing the Kido Butai, it hardly mattered if she did or didn't have an armored flight deck. Do we really think that HMS Illustrious, even with her armored flight deck, would have fared better against the 85 Vals of the KB's first strike?

Among the rest, one (Glorious) was sunk by naval gunfire, and the rest (3 fleet carriers in total when we include Ark Royal) were sunk by torpedoes from U-Boats.

None of those results, and I doubt even the Hermes result, would have changed if they had armored flight decks. But it is entirely possible that two dozen more aircraft per carrier might have prevented one, or more, of the U-boat attacks.

We know, from the Atlantic campaign, that air patrols were one of the MOST effective deterrents to u-boat attacks and among the MOST lethal weapons against u-boats.

Is there any instance of a fully operational US fleet carrier being sunk by submarine attack in WW2? It's not like the IJN didn't have submarines, or that those submarines were not actively looking for USN capital ships to sink.

One might make the case that the British, by reducing their airgroup capacity in favor of an armored flight deck, were focusing too narrowly on defending from only one form of attack.

Even then, it is debatable if it was the right defensive mechanism. Are more fighters a better defense than armor? How will an armored flight deck compare to 12 more fighters (and so perhaps 2 to 4 more on standing CAP in the era when you don't have radar) when the land based aircraft that come at you are SM.79s or HE-111s with torpedoes, instead of Stukas with HE bombs?

It is a bit of odd perspective that the navy that was willing to build battleship-sized gunships without battleship-equivalent armor, was the same navy that built aircraft carriers with more than aircraft carrier-equivalent armor. After all, battlecruisers were specifically made to go within gunnery range of the enemy, while carriers were not (at least not since they took the big guns off of the Furious).

-Mark
(aka: Mk 1)

Hi Mark

Hermes only had Swordfish embarked at the time she was lost, so she had no fighter cover at all and could not have repelled any attack with any number of such types. She would have been better used attached to convoys as a sort of escort carrier avant la lettre.

ASW was what Courageous was doing when she was sunk. The value of air power against submarines was understood, but the conclusion from her loss was that fleet carriers were simply too valuable to be risked in this way. As Britain in 1939 was the only country operating aircraft carriers that was at war, there was no previous experience to draw on from which this lesson might have been absorbed. Had it been the USA at war in 1939, maybe it would have been one of their carriers lost that way – we just don't know.

Glorious wasn't flying any aircraft at all when sunk, for reasons that I think remain unknown. Having more aircraft on board would have just meant she sank with more aboard.

You raise a good point about torpedoes. Taiho was likewise built to be as bomb-proof as possible and was then of course torpedoed. The armoured carrier approach dated from the mid-1930s, however, and reflected 1930s assumptions about the opposition. The performance of torpedo bombers at that time was marginal, and they were also rare. ISTR that in 1940 the USN had a total of 50 aerial torpedoes in inventory, so enough for one war cruise by one carrier. The Luftwaffe was as badly off, I don't think it even had an anti-ship bomb, and it had no squadrons trained to use either (Fliegerkorps X weren't anti-ship specialists until 1941). Carriers were also seen as simply another type of ship to be added to an admiral's command. The first officer to think of massing them together was Fuchida, who had the idea as he was stepping off a tram in 1941.

There is little evidence, however, that having more aircraft on board your carriers solved the tactical dilemma and / or conclusively showed this to be the better approach. The RN's carriers expected to face land-based air which would score hits, so they were built accordingly with small air groups and duly received and survived the predicted hits, as designed.

The US and IJN carriers were designed to have large air groups supposedly in part to prevent the hits at all. To draw inferences about the success of this from the actual combat record, it's necessary to disentangle what outcomes were due to large air groups from those that were due to numerical superiority.

So at Coral Sea, the large air groups did not prevent carriers being sunk on either side. At Midway, the large air groups did not prevent carriers being sunk on either side. At Eastern Solomons numbers were about equal and the large air groups did not prevent carriers being sunk on either side. At Santa Cruz the numbers were about equal and the large air groups did not prevent carriers being sunk on either side. I venture to suggest that had it been Enterprise instead of Hermes off Ceylon in April 1942, she'd have been sunk, too.

In short, I'm not really seeing the evidence that large fighter air components were ever successful at preventing ships from being bombed or torpedoed. In every battle fought among such ships, carriers were sunk anyway. What was unquestionably effective in these battles was having a numerical advantage. At Midway, the US outnumbered the Japanese 3 to 2 in the air when you include the forces on Midway, and the outcome was losses in the US' favour. At the other encounters, with evenly matched numbers, the outcomes were also more even. Neither side's fighters could stop the other side's bombers getting through.

By the time we get to 1943-4, the USN's numerical advantage was so immense that the size of the air groups became incidental. They won at Tarawa and the Philippine Sea not because the individual carriers' air groups were so large but because Japan no longer had any naval air at all to speak of. If a Japanese strike did get through, eg Princeton, it had a good chance of being a terminal event for the ship, however.

By 1945, when the kamikazes showed up, the large air groups weren't able to prevent ships being hit, so the assumption that you should expect this to happen proved more durable than the assumption that a large fighter group would prevent it happening at all.

So I dunno. In theory you'd think more planes = more versatile = better, but I struggle to think of any encounter where this was demonstrably true, while several other campaigns suggest it wasn't. And having enormous aerial superiority clearly wasn't part of the USN's thinking about carrier design and use in the 1930s, because if it were, they'd have built 30 Yorktowns instead of three.

"So at Coral Sea, the large air groups did not prevent carriers being sunk on either side. At Midway, the large air groups did not prevent carriers being sunk on either side. At Eastern Solomons numbers were about equal and the large air groups did not prevent carriers being sunk on either side. At Santa Cruz the numbers were about equal and the large air groups did not prevent carriers being sunk on either side." Let's put British aircraft carriers in place of either side's carriers in equal numbers and see if the results are different.

If the result were the same, that would prove the larger air group made no difference to the carrier's ability to survive.

You'd need to find an instance of a carrier with a large air group driving off a strike thanks to its large air group (and not to being one of twenty such carriers in the area). I can't think of one.

How would a Yorktown have fared under Illustrious' pounding? 2 x 551lb hits, 2 x 1,100lb hits, 2 x 551lb or 1,100lb hits, and a 2,200lb hit. Among the near misses was one that bounced off the armoured deck and exploded alongside.

When the US carriers were sunk or beaten up, where were their large air groups, what were they doing, and why weren't they able to prevent the hits?

Hermes only had Swordfish embarked at the time she was lost, so she had no fighter cover at all …

My understanding is that Hermes had no aircraft embarked at all at the time of the attack. Rather, the air group had been flown off before the IJN strike arrived. And a flight of 6 Fulmars had been sent to provide CAP, which arrived prior to the IJN strike, with 3 of the Fulmars being shot down by the 9 plane IJN Zero escort.

But I could be wrong. Don't claim the RN's WW2 combat history as a particular area of expertise.

I find some discord in the following line of reasoning:

What was unquestionably effective in these battles was having a numerical advantage. At Midway, the US outnumbered the Japanese 3 to 2 in the air when you include the forces on Midway, and the outcome was losses in the US' favour.

Let's call this a statement of facts, with information on the ratio of aircraft vs. the success in inflicting losses, as well as a conclusion, that it was "unquestionably effective" to have "a numerical advantage".

But those statements were, somewhat oddly, introduced with with:

In short, I'm not really seeing the evidence that large fighter air components were ever successful at preventing ships from being bombed or torpedoed.

Do you not see that having a larger air component can contribute, in some mysterious way, to having a numerical advantage?

Put the British fleet carriers at Coral Sea and, with the same number of carriers you will be at a 1:2 disadvantage (approximately) in the number of aircraft. Does your unquestionable conclusion not give you some guidance on what will result from that?

You say there is no evidence that having a larger airgroup can stop all possible strikes on the ship with fighters. But in a prior post you observe that having a carrier sunk constrains it's combat capability. Does that not apply to your opponent's carriers?

I would suggest that British fleet carriers at Coral Sea and Midway would have been crushed, with substantially less damage done to the IJN carriers as a result. And of course, after those two engagements there is also that next major carrier action you failed to examine, the Battle of the Philippine Sea. Should we examine that case and also conclude the large airgroups of the USN carriers weren't able to prevent the loss of so many fleet carriers …

I understand that carrier design in the 1930s could not foresee everything that would evolve in 1940/41/42. I don't begrudge the RN their decisions. But that doesn't mean that I have to believe they made the right choice. There is one instance of an armored flight deck contributing to an RN carrier surviving what might have sunk USN or IJN fleet carrier. And several instances of an armored flight deck providing no protection to an RN fleet carrier. And several instances where reasonable interpretations suggest that larger air groups led to USN success that would not have been achieved with smaller air groups.

If we accept only 2 variables, I find the evidence mixed, but strongly weighted in favor of larger air groups first, armored flight decks a distant second.

-Mark
(aka: Mk 1)

Hi Mark

Perhaps I'm being dim but I don't see many of these issues.

Hermes was an unarmoured carrier with no organic combat air patrol. She had neither of the defences we've been discussing at all.

Re numerical advantage, the observation I am making is that large carrier air groups proved demonstrably unable to repel air attacks. We know this because Hermes aside, all the 1942 to 1943 carrier losses were inflicted upon carriers with exactly such large air groups. This was despite the warning time and the fighter performance both being substantially ahead of what was foreseen in either 1935 or 1938.

You suggest that British carriers at Coral Sea or Midway would have been crushed, but of course USN and IJN carriers at both battles actually were crushed. Every attack got through. The Japanese suffered nine 500lb and 1,000 lb bombs on target at Midway in the morning strike and this was enough to cost them three carriers. Yorktown was counter-attacked by small numbers of aircraft from Hiryu that were outnumbered by the 28 F4Fs assembled to protect her. Despite their small numbers the Japanese bombers still broke through and clobbered her, then flew home, rearmed, and did it again. The Admiralty's prediction that strikes would get through thus seems to have been accurate for all years of the war except 1944.

The Philippine Sea is not an instance of large carrier air groups saving the carriers, but of enormous numerical and qualitative advantage. The USN didn't win Philippine Sea because they had 70 rather than 45 aircraft per carrier. They won because they had 15 carriers (surrounded by hundreds of other ships contributing AA) against 9, and the Japanese pilots were almost entirely green.

We actually do have examples of armoured carriers being bombed and surviving it. We don't have any examples of 50- or 100-plane strikes from, say, two carriers being beaten off by the fighters of two other carriers. Those strikes always got through.

You raise a fair point about the adequacy of outgoing strikes but armouring the decks was a defensive measure, not an offensive one. As such it seems to have been second only to outnumbering the enemy massively.

On 14 April 1942 Churchill wrote to the Admiralty

Let me have the estimated aircraft of different patterns borne on each of the five Japanese Aircraft Carriers in the Indian Ocean and in our INDOMITABLE, ILLUSTRIOUS, FORMIDABLE. Let me also have the tonnage on both sides.

What is the explanation why the Japanese are able to carry so many more aircraft than we do?

The response was:

(i) With the possible exceptions of the SHOKAKU and ZUIKAKU, they are unarmoured and are therefore larger for the equivalent weight. (Our COURAGEOUS (unarmoured) Class carried as many, of [sic] not more, than the Japanese carriers of equivalent tonnage.)
(ii) Their actual tonnage is probably in excess of that disclosed.
(iii) Accommodation for personnel is more congested than would be acceptable for Europeans.
(iv) They are possibly carrying and operating a deck cargo of aircraft as is the practice of the U.S.A. aircraft carriers.

The implication of the latter point is that this practice would have been and later was adopted if it should prove useful to carry a bigger air complement.

You suggest that British carriers at Coral Sea or Midway would have been crushed, but of course USN and IJN carriers at both battles actually were crushed.

Well, no. The USN carriers at Midway were not crushed. Yorktown took 3 bomb hits and, despite having no armored flight deck, was back in action, making 19kts and carrying on flight operations within the hour. It was only after being torpedoed twice by the second attack that Yorktown was taken out of the battle. But she wasn't sunk until hit by two more torpedoes from the I-168, and perhaps also by depth charges detonating below her hull from the destroyer USS Hamman (which, alongside the Yorktown had also taken an I-168 torpedo and quickly sunk).

We actually do have examples of armoured carriers being bombed and surviving it.

And we have actual examples of unarmored carriers being bombed and surviving it. What we don't have, is any indication that either sort of carrier survived torpedo attacks well.

I don't see any examples that an Illustrious class carrier would have done any better than Yorktown. 3 bombs leading to resumed flight ops in 1 hour? Oh, and that's after bomb damage from Coral Sea had also been repaired.

It was only torpedoes that put her (or the Lexington at Coral Sea) down, and there's no indication that the British CVs faired any better vs. torpedoes.

You raise a fair point about the adequacy of outgoing strikes but armouring the decks was a defensive measure, not an offensive one. As such it seems to have been second only to outnumbering the enemy massively.

The primary anti-ship weapon of the carriers, whether British, Japanese or American, was the air launched torpedo. This was limited, though, by the dreadful performance of USN torpedoes until mid-1943.

However, criticisms of the US torpedoes aside, as you note, outnumbering the enemy is the key. It should be pretty simple to understand that British air groups in 1942 would ALWAYS be outnumbered. The USN, on the other hand, could put up a larger airgroup with 3 carriers than the IJN could with 4, and it would have taken 6 or 7 RN carriers to even get into that range.

You can suggest that the armored flight decks were a defensive measure, but they in fact contributed nothing to defending the carrier from the primary danger, and drastically reduced it's ability to use the best defense, which was a good offense.

They did have a LOT fewer planes. If the 3 USN fleet carriers at Midway had been replaced by RN fleet carriers, the carrier force would have fielded, at full strength, no more than 108 planes. This, compared to an actual USN complement of 233 planes at Midway. So something less than half the planes, meaning greatly reduced probability of sinking the IJN carriers. So probably a notably stronger Japanese counter-strike, meaning a lot more torpedoes in the water around the carriers, and no indication of better survival prospects once hit.

Again, I'm not saying I don't understand their reasoning. But I do suggest that, in hindsight, it was the wrong decision. Carriers that don't sink the enemy carriers are not going to defend themselves any better just because they have some armor. If Yamato's armor wasn't enough to defend it from carrier strikes, how much are you going to put on a carrier?

-Mark
(aka: Mk 1)

The USN carriers at Midway were not crushed. Yorktown took 3 bomb hits and, despite having no armored flight deck, was back in action, making 19kts and carrying on flight operations within the hour.

The Japanese never found Enterprise and Hornet; hence no damage. Yorktown was crippled by those 3 (small, 250 kg) bomb hits when the torpedo attack came in, which is a big reason why she was torpedoed in the second attack. The bomb which did most of the damage hit Yorktown in a location protected by the armored flight deck on an Illustrious class CV.

They did have a LOT fewer planes. If the 3 USN fleet carriers at Midway had been replaced by RN fleet carriers, the carrier force would have fielded, at full strength, no more than 108 planes.

In 1945 the first 3 Illustrious class CVs operated air groups of 54 aircraft, and Indomitable of 56 aircraft, using deck parks as in the USN. The smaller air groups earlier in the war were due to doctrine and/or inadequate aircraft stocks, rather than inherent limitations of the design. If you factor out doctrinal issues, 3 such ships would have operated 164 aircraft at Midway, rather than your 108 aircraft.

MH

My challenge in respect of Midway really is two simple observations, namely

- the supposedly superior large air group was demonstrably unable to defeat two weak attacks, even though radar enabled the concentration of more than one carrier's fighter complement over their target; and

- the damage done in the initial strike to the unarmoured Japanese carriers consisted of just nine 500lb hits distributed among three carriers, which destroyed all three.

Hence, and largely as predicted by the RN pre-war:

1/ fighters could not repel air strikes, so
2/ a handful of the resulting hits would be enough to write off the carrier.

This turned out to be true at Coral Sea, Midway, Santa Cruz, and Eastern Solomons. It ceased to be true only when one side's carrier numbers became enormous, and became true again once kamikazes became the preferred method of carrier attack.

It wasn't part of anyone's pre-war doctrine to have enormous numbers of carriers but I do agree that having this makes otiose the question of whether they're armoured or not.

- the damage done in the initial strike to the unarmoured Japanese carriers consisted of just nine 500lb hits distributed among three carriers, which destroyed all three.

According to "Shattered Sword" (and my memory), one hit on Kaga may have been 1000 lbs, all 3 on Soryu were 1000 lbs, and the single hit on Akagi was 1000 lbs; all GP high explosive bombs.

MH

According to "Shattered Sword" (and my memory), one hit on Kaga may have been 1000 lbs, all 3 on Soryu were 1000 lbs, and the single hit on Akagi was 1000 lbs; all GP high explosive bombs.

This agrees with all of the more current analysis I have seen.

Worth noting is that the single hit on Akagi was on the flight deck elevator, which even on the RN carriers was not armored.

Yorktown was crippled by those 3 (small, 250 kg) bomb hits when the torpedo attack came in, which is a big reason why she was torpedoed in the second attack.

Yorktown was steaming at 19 kts, and was still working up speed, when the second attack came in. She had also re-started flight operations by the time the second attack game in. But she had very few planes aboard.

Much as with the Japanese CVs, Yorktown was caught at her most vulnerable moment. She needed to recover and refuel her CAP, and to recover the aircraft returning from the strike. The strike was being recovered when the first inbound attack was detected.

As soon as the inbound attack was detected the returning/landing strike aircraft were vectored away (out of AA range). Ready aircraft (Wildcats and Dauntlesses) were scrambled to provide close defense, while the already airborne CAP, despite low fuel, went out to intercept. After the attack all of these aircraft had to land on the other USN CVs, as the Yorktown's flight deck was under repairs.

Those repairs were sufficiently completed that flight operations resumed after one hour. If she had more aircraft aboard, she would have been able to scramble more aircraft for defense against the second strike.

In the first strike Yorktown was struck not only by the tree bombs but also by one of the Vals that had dropped the bombs. The crashing Val did about as much damage as any of the bombs.

One of the bombs struck an elevator (which was also not armored on the RN CVs).

The bomb which did most of the damage hit Yorktown in a location protected by the armored flight deck on an Illustrious class CV.

The bomb that did the most damage exploded inside the Yorktown's funnel, snuffing out 5 of her 6 boilers. That was the reason that she was slowed to a stop after the attack. But once the boilers were re-started she began building steam and speed again.

I would be interested to know if or how the Illustrious class CV armor scheme would have protected them from such a strike. It may well be that they would not have been so affected. But in the case of Yorktown the main harm from this bomb was quite temporary, as the ship was building steam and under way within the hour.

With the exception of the bomb that penetrated the funnel, and the bomb that struck the starboard elevator, none of the other bombs or crashing plane penetrated the hanger deck.

This is the part so often missed when the discussion is phrased as one of "armored vs. unarmored" carriers. The USN carriers were armored -- but the flight deck was not the armored deck. The hanger deck was. You can protect the innards of the ship every bit as well by armoring the hanger deck as the flight deck. But the hanger will be exposed to more risks. You need good discipline for how you handle the flammables/explosives around the hangers. The reason the IJN carriers where destroyed by dive bombers is not because they didn't have armored flight decks, but because they had fueled planes and stacks of ordnance all over the place at the moment they were struck. Most significantly they didn't have good procedures and discipline for managing aviation fuel. Armored flight decks or not, if you have a bunch of fueled aircraft and explosive ordnance scattered around, you are at risk.

In 1945 the first 3 Illustrious class CVs operated air groups of 54 aircraft, and Indomitable of 56 aircraft, using deck parks as in the USN. The smaller air groups earlier in the war were due to doctrine and/or inadequate aircraft stocks, rather than inherent limitations of the design. If you factor out doctrinal issues, 3 such ships would have operated 164 aircraft at Midway, rather than your 108 aircraft.

The no-deckpark was part of the same doctrine that led to the armored flight deck. The doctrine under which the RN CVs were developed was a doctrine of getting the planes out of the sky when the enemy air strike approached. Rather than putting planes up to defend, they were to be struck down below.

That doctrine was not compatible with a deckpark of aircraft. How is your armored flight deck going to protect you when you have 20-30 aircraft, with fuel and munitions, all up above the armored deck? My God, man, you talk like an American!

It was only after abandoning the idea that AA and armor was all you needed to defend the ship that the deckpark could be considered.

Hence, and largely as predicted by the RN pre-war:

1/ fighters could not repel air strikes, so
2/ a handful of the resulting hits would be enough to write off the carrier.

It might be worthy to note that the only reason Soryu could launch the strikes that hit Yorktown was because she had a big airgroup. If you cut her airgroup in half, she doesn't get the second strike at all. And if she had launched the size of the strike as was launched against Midway at the start of the day, she would not have gotten even the first strike against Yorktown.

I would suggest that the prediction that was validated by wartime experience was:

1/ In any engagement you must cripple the enemy air capacity first
2/ As you consider design alternatives to protect you from air attack, refer back to item 1 above

The suggestion that you should limit your abilities to achieve item 1 above is only a path to accepting the probability of destruction of your carrier, as there is / was no evidence that an RN carrier could withstand the torpedo hits that sank Lexington at Coral Sea, Yorktown at Midway (nor even Taiho, despite her armored flight deck, at Philippine Sea).

If you are going to build a 60,000grt ship, you can put an inch of armor on your flight deck without giving up hanger space. And if you don't give up hanger space (and/or stability!) there is no reason NOT to have it. But put torpedo bulges in first, because they were/are a LOT more important.

However if you are building a 25-30,000grt ship, the only way you can afford that much weight above the working spaces of your ship is to save weight and height, meaning smaller enclosed spaces, meaning smaller hangers. It's not a question of abstract value, but comparative priorities. You are prioritizing being able to protect your parked aircraft from an attack over being able to protect your ship from an attack. If you think you protect your ship by putting the same amount of armor higher up, refer to item 1 above. It's a bad trade off.

-Mark
(aka: Mk 1)

The bomb that did the most damage exploded inside the Yorktown's funnel, snuffing out 5 of her 6 boilers. That was the reason that she was slowed to a stop after the attack. But once the boilers were re-started she began building steam and speed again.

I would be interested to know if or how the Illustrious class CV armor scheme would have protected them from such a strike. It may well be that they would not have been so affected. But in the case of Yorktown the main harm from this bomb was quite temporary, as the ship was building steam and under way within the hour.

My sources disagree with this (including Lundstrom and "That Gallant Ship" by Cressman). Both sources say the hit which damaged the boiler uptakes hit the flight deck at frame 95 about 10 feet inboard of the Island, angling outboard to starboard, piercing the port side of the uptakes in the hanger. The damage immobilized the ship for more than an hour, and repairs did not restore top speed by the time of the second Hiryu attack. Note that the critical bomb hit would not have penetrated on an Illustrious class CV. In turn, the engineering plant wouldn't have been damaged; the ship wouldn't have been brought to a stop; the CAP would still have been able to operate and be directed efficiently from the Yorktown, etc. Much less likely to be torpedoed in that scenario, correct?

How is your armored flight deck going to protect you when you have 20-30 aircraft, with fuel and munitions, all up above the armored deck?

That is exactly the situation which applied during 1945, when the BPF carriers were hit by kamikazes. The armored flight deck did in fact provide significant protection in such cases. You might want to do some reading on this. Suggest you read this: armouredcarriers.com

It might be worthy to note that the only reason Soryu could launch the strikes that hit Yorktown was because she had a big airgroup.

You mean Hiryu (not Soryu).

MH

One more comment:

The no-deckpark was part of the same doctrine that led to the armored flight deck. The doctrine under which the RN CVs were developed was a doctrine of getting the planes out of the sky when the enemy air strike approached. Rather than putting planes up to defend, they were to be struck down below.

Originally this was true, but not later in the war. The OP for this thread asks about armored flight decks (a design issue). Your "108 plane" figure is deceptive, as it implies an inherent design issue, rather than merely a doctrinal issue.

MH