28: What do we do with these things?


We have spent a lot of time discussing the budgets, ships, and plans of the Royal Navy. How did those plans begin to shift as war seemed to be more and more imminent.

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Hello everyone and welcome to History of the Second World War Members Episode 28 - Aircraft Carriers Pt. 2 - What to do with these things? Last episode we discussed the evolution of the aircraft carrier concept during the 1920s, with a special focus on the three generations of carriers that would be present in navies around the world at that time: the initial carriers, the Naval Treaty conversions, and then the first generation of dedicated carrier designs. While these three generations of ships were being created, the role envisioned for the carrier would also evolve based on a variety of factors, not the least of which being the continued growth and evolution of aircraft. Another major new factor that would dictate the evolution of carrier doctrine was the fact that other nations were also building carriers. If only one navy had carriers, then it would be easy for its aircraft to provide reconnaissance and spotting, and maybe even attack other ships from time to time. But as soon as both navies possessed carriers the equation greatly shifted, and suddenly control of the air became a contest. The primary challenge with this new reality was that carrier combat was fundamentally different than surface combat that had been taking place since the advent of the naval cannon. By the 1930s the general flow of battleship combat was well known, especially for large fleet actions. The battleships would come into contact with one another, and they would bring themselves into gun range, and then they would just blast away. With ships as large and as heavily armored as battleships this firing would slowly wear down the enemy, with advantages for one battle line cascading as enemy ships were destroyed and fire could be concentrated on those that remained. Carrier combat was very different, and instead of a constant wearing down of the enemy air attacks could come in massive waves. By the late 1930s both sides would have enough raw power in their carrier air groups to destroy the other. Would any navy be able to actually execute on these massive alpha strikes in the 1930s? Probably not, but you still had to plan for the possibility.

Beyond just the fact that they were planning for a new type of warfare, when it came to planning for battles between carriers there were a lot of challenges that had to be overcome. The first was simply that no navy really had enough carriers to truly test carrier vs carrier scenarios during the 1920s. For example the United States would only really have 3 modern carriers into the mid 1930s which made it challenging to do anything but the most theoretical wargame. The second problem was one of rapid aviation evolution, with both land based planes and carrier aircraft getting faster, larger, and gaining greater endurance. This effected carrier battles in obvious ways, bigger bombs and torpedoes, but also had really important impacts on theoretical carrier battles around less obvious areas. The most important was reconnaissance. If you want to attack a carrier the first thing you have to do is find it, and as the experiences of the Second World War would show this was no easy task. It would have been even more difficult 15 years earlier when aircraft had less endurance and were slower, which meant they could cover less ocean area. The third problem was one of vulnerability, up until the introduction of the British Armored carriers in the late 1930s all aircraft carriers were very vulnerable to air attack, this made any possible confrontation very dangerous. There would also be unique challenges for each navy around these topics, with the Americans dealing with trying to fit carriers within their wider War Plan Orange concepts, while also reacting to Japanese aircraft becoming more capable. The Royal Navy was working under the always challenging arrangement whereby the Fleet Air Arm was not actually controlled by the Navy and was instead under the control of the RAF. This resulted in all kinds of administrative challenges as the two services waged an on again and off again battle to turn the Fleet Air Arm into what they wanted it to be. Or in some cases the Royal Navy just trying to convince the RAF that the Fleet Air Arm needed more resources. For the Japanese they were working under the limitation placed upon them by the Washington and then London Navy treaties which meant that the Japanese had to always plan to be outnumbered in a large fleet engagement.

For most of the interwar period planning occurred under the assumption that large capital ships, think battleships and battlecruisers, were not really that concerned about the possibility of air attack. During the 1920s this was probably a reasonable assumption just given the capabilities of aircraft at that time. Aircraft carriers were also still firmly in the fleet utility role during most of this period, with the emphasis of their planning and preparations being placed on how they could help the larger surface ships accomplish their goals. This resulted in a lot of time and effort being put into perfecting techniques like the laying of aerial smokescreens that the battleships should could through or over, while using aerial spotting to adjust their shots to hit the enemy targets. Even when the theory began to shift towards using carriers to attack other ships, it would still be tightly wrapped out the surface fleet confrontation. For example in the mid 1930s the Japanese would have a lot of discussions about how to use carriers in a war with the United States. It was clear that the carriers were becoming more powerful, and the existing instructions for their usage, the Draft Instructions for Air Combat, simply did not meet the requirements of the current carrier force. The biggest issue with these regulations was that they gave the carriers a very narrow set of actions in an fleet action, while also not making a really definitive stance on how carriers should be used. When these were then rewritten the carriers were still performing missions simply in support of the battle fleet. They were to operate under the principle that they were to operate against the enemy fleet before the decisive battle, and they would try and seek out and destroy the enemy carriers and any other ships that were present, but it was not because they would decisively defeat the enemy, but just as a way of weakening their strength before the actual battle, with battleships, took place. While they would not be decisive, the Japanese were making it clear that the focus of carriers was first and foremost to neutralize the enemy carriers, which is what made planning for carrier vs carrier battle became so important. For the Americans and Japanese such planning took center stage due to the emphasis both navies had on the actions in the Pacific, with the Americans planning to move across the ocean while the Japanese planned to stop them. One of the core questions that the Japanese would try to answer was whether or not they should concentrate all of their carriers and all of the carrier aviation assets together into one unit, or if they should disperse them throughout the fleet. The benefits and downsides of either approach were generally well known. Concentrating the three carriers in the Japanese navy in the early 1930s would provide for their greatest possible hitting power. If the three carriers were able to concentrate all of their forces against enemy carriers it gave them the greatest possible chance of success. This was even more important for the Japanese Navy that would possibly be targeting a larger number of American or British carriers. But the downsides to this concentration were that other fleet units were not offered the protection and capabilities of the carriers, which would be a problem if they were not themselves concentrated. The most important downside though was that if the carriers were all together, and they were found by the enemy and came under attack, they were very vulnerable to being disabled. A few bomb hits might put a carrier completely out of action due to the damage done to the flight deck, and if all of the carriers were together it could happen to all of them. The evolution of aircraft, and particularly the growing power of dive bombing amplified both the benefits and risks associated with carrier concentration. As dive bombers particularly grew more powerful having more of them together provided even greater assurance of disabling enemy carriers, while also putting your own carriers at greater risk. Looking into the war, the concentration of carriers would prove to be very beneficial but also dangerous, both of which the Japanese would experience during the war. For example the Kido Butai was able to rampage around the Indian Ocean after the start of the war due to the sheer number of aircraft it could throw at anything in its path. On the negative side, things like Midway could happen, where 4 Japanese carriers would be sunk partially because they were all grouped together.

While the imagined role for carriers was shifting, there were related conversations occurring around which planes carriers should be carrying. All of the navies were aware that the number of aircraft that could be placed on a carrier were limited, and to carry more of one type of aircraft meant that the number of others had to be reduced. In the early years this was not too much of a problem because the carriers were designed almost entirely to carrier reconnaissance and spotter aircraft. But due to all of the evolutions that we have discussed during this episode, the precise mix of reconnaissance vs fighters vs bombers became a hotly debated topic. Reconnaissance was always necessary though, because there had to be some way of finding enemy ships regardless of the role played by the carriers once they were spotted. It was also challenging to build an aircraft that would be a dedicated reconnaissance platform as the war drew closer. This meant for the navies they often just ended up using bombing aircraft that could also serve as scouting aircraft, which is the path that the Americans would pursue, taking their dive bombers, giving them lighter bomb loads, and sending them off to go find the enemy. This was a completely reasonable approach to the problem of which aircraft to use, but the greater problem was the fact that there was not enough time and energy spent on reconnaissance doctrine and training. This resulted in pilots who were not well trained, often were not the top of the line pilots as they all wanted to be piloting attack aircraft, and they were not executing a perfectly thought out plan. This was a problem because as carrier aviation became more and more powerful, finding the enemy grew in importance almost exponentially. When a single wave of attackers can destroy a carrier, being the first to find the enemy and launch that attack wave was critical, as would be born out in the Pacific during the war.

Another type of aircraft with a similarly debate filled history was the fighter. One of the reasons that the role of fighters on carriers was debated, generally only prior to the mid 1930s, was the same reason that strategic bombers were seen as safe from fighters on land: speed. In the age before radar it was very difficult for a fighter to be able to take off and get the altitude in time to make an attack on a bomber. There was also the problem that it was only in the late 1930s that fighters became fast enough to match the speed of two engine bombers. These problems called into question whether or not naval fighters were even viable, because they had to have a speed advantage over their targets to make interception a real possibility, the Japanese believed that fighters needed to be up to 30% faster to be effective. In Japan these problems would prompt some discussion of whether or not fighters were even needed, and whether it might be better just to use the space that fighters occupied aboard ship for additional squadrons of attack aircraft. This idea reached its zenith with the introduction of the generation of new Japanese aircraft between 1935 and 1936, with the Nakajima B5N2 “Kate” carrier torpedo bomber being just a bit slower than the primary Japanese fighter at the time, the Mitsubishi A5M-4 “Claude”, the Mitsubishi G3M “Nell” land based bomber but designed for naval strike capabilities would be far faster than the Claude. It was only with the introduction of the Mitsubishi A6M Zero in 1940 that there was a large jump in fighter speed and also maneuverability which would prove that the fighter had a permanent place on the carrier flight decks. Looking forward into the war years, the Americans would start to place greater and greater emphasis on fighter aircraft on their carriers. And you can see the evolution of the air groups on carriers by looking at ships like the Enterprise, which would go to war in 1941 with 18 fighters out of 72 total aircraft, with the rest being torpedo and dive bombers, and by the late war years there would be more fighters than any other type of aircraft. For the Americans part of this shift was due to the amazing performance of the F6F-5N Hellcat, but there had also just been some general developments that made fighters more useful, particularly radar and more powerful engines that gave greater speed and payload capacity.

Fighters were just one part of fleet defense, and there was great faith placed in the ability of anti-aircraft fire to prevent enemy bombers from executing their attacks. In the Japanese navy on the eve of the war dive bombers were able to hit their targets more than 50 percent of the time, which is a pretty good hit ratio when you consider how much damage a single bomb could do to another ship. While a 50% hit ratio may not seem great, it was a massive improvement from the level bombing techniques used before the widespread adoption of dive bombers to replace those earlier level bombers. The hit ratios for level bombing were so bad that some planning called for entire additional carriers of bombers for each enemy capital ship they wanted to sink. For carriers even a single bomb might completely disable the carrier and prevent the continuation of flight operations, and for large surface combatants the belief was that it would take more than 12 direct hits to put a ship out of the fight. This was an achievable number by carrier aircraft in 1939, assuming a 50% hit rate for dive bombers and the presence of more than one Japanese carrier. But there was a problem with this assumed hit rate, based on prewar exercises, they could not shoot at the oncoming aircraft. All naval vessels had some amount of anti-aircraft armament but it was completely unclear exactly how effective that armament would be against an oncoming air attack. Estimates varied greatly on how much anti-aircraft fire from something like a battleship would impact aircraft in the final moments of their attack runs. Some estimates were that it would decrease the accuracy of bombers by a third, maybe more maybe less. Along with just hitting less bombs, the belief was that anti-aircraft fire would also be simply murderous for the aircraft which would rapidly deplete the enemies squadrons to the point of no longer being effective. When the war started these notions were proved to be partially correct, massed anti-aircraft fire did reduce the accuracy of bombers, but not as much as some naval theorists had hoped. As for the attrition of air groups, it certainly did happen, but that often did not matter on the short term timescales that most naval battles would happen in. It would have drastic ramifications for the Imperial Japanese Navy in the long run, but carrier battles were generally short enough that only one, maybe two large scale air attacks were launched before both fleets disengaged.

When we look at the defense of aircraft carriers from air attack more generally there are a few key problems that would plague planners for most of the interwar period, some of which would be solved by the time of the war and some of which would remain into the war years. The first problem was the logistics of flight operations, which don’t seem to be immediately related to fleet defense, but was in fact critical. Taking the scenario that two carriers knew that the other was in the area and was actively searching for the other, there were a few timings that were very important. How quickly could the carrier find the enemy carrier with scout aircraft? This depended not just on tactics but also some amount of luck. How quickly could a carrier launch all of its strike aircraft against the enemy? How quickly could any combat air patrol aircraft be cycled if they needed to be refueled? and How quickly could a returning strike be turned around to launch another strike, assuming that one was necessary? Different decisions would be made for navies that would alter the answers to these questions. The most important to the overall story of carrier aviation during the war years was where refueling, rearming, and maintenance happened aboard ship. The Japanese would use a system whereby returning aircraft were brought below deck for these activities to happen, which limited their cycle time to how quickly aircraft could be loaded on elevators, moved below, moved off of the elevators, and then moved back on when activities were complete. The Americans instead just did as much as possible on the flight deck, which decreased total cycle time, with some additional risk if an enemy strike arrived with a bunch of American aircraft hanging out with full bomb loads on the deck. All of this was important to direct fleet defense because it also impacted the combat air patrol of fighters that would protect a carrier and a fleet. Fighters could not stay aloft indefinitely and so they would be subject to the same cycle times as any other aircraft, which was less of a problem when strikes were not being launched, but was a serious problem during combat. Some number of fighters would also be sent with the attack aircraft as protection against enemy fighters, and so the remaining fighters would ebb and flow in number based on landing and cycle times. This impacted not just how many were in the air, but also their positioning and elevation. Positioning could also be a problem due to how challenging it could be to get early raid warning in the years before radar was on most large naval vessels. Before radar the general actions taken to try and provide early raid warning were for other smaller ships to form an observation line around the carriers generally quite distant to allow time for aircraft to take off and position themselves to intercept. There would also be flights of floatplanes, launched from other ships in the fleet, that would do their best to provide airborne observation of enemy planes, but neither of these were exactly foolproof. Clouds were of course the biggest problem, with even relatively small whiffs of clouds completely blinding surface observation. If an incoming strike was not detected, even if there were airborne fighters, their positioning on the wrong side of the fleet would make them unable to vector onto the attacking aircraft before they released their bombs or torpedos. The fighters might be able to chase some down afterwards, but any aircraft destroyed would be small consolation if they were able to severely damage a large surface ship. These challenges, along with the limited number of fighters that were present in carriers, meant that the ability of the ship itself to defend itself was critical. There were often many anti-aircraft guns aboard ship, but the effectiveness was generally overestimated. This is true of all navies during the 1930s. The first problem was that most of the anti-aircraft armament was not heavy enough, and therefore did not have the range required to begin firing at oncoming aircraft soon enough to prevent them from entering their attack runs. The second problem was that fire control systems were not up to the task of tracking and engaging the newest generations of aircraft which were much faster than anything before. This resulted in either the fire control systems firing behind incoming aircraft or manual intervention being required which made it more challenging to concentrate fire in a way that was most effective. There were also some anti-aircraft guns that were just not designed to physically traverse fast enough to keep up with aircraft moving against the ship. The third problem was as already mentioned, the simple problem of overestimating the effectiveness of anti-aircraft fire, which caused some of the known issues with anti-aircraft armament to be ignored until it was too late. Next episode we will discuss in more detail the first of the major carrier forces to go to war, the Japanese over China.