Summary 5: Interwar Airpower

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Tracks the evolution of interwar airpower doctrine and industry across the major powers as they prepared for a new kind of war in the skies.

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Summary - Interwar Airpower

Hello everyone and welcome to another History of the Second World War summary episode. As a reminder, these summary episodes are built around the concept that there have been a lot of episodes on this podcast, and sometimes there is important information from episodes released years ago that I think would be good to give everybody a reminder on. This time we are going to be looking at the Interwar Airpower series which released back in 2022. The series looked at the evolution of airpower theory during the interwar years, the impact that the experiences of the First World War had on that theory, and how those theories were turned into reality by the European air forces in the years before the start of the Second World War. The best place to start this episode is to clearly state that, in reality up until lets say 1936 and the start of the Spanish Civil War nobody really knew what was and was not an effective airpower doctrine. Theorists all over the world could look back at what had happened during the First World War, but as the years went by throughout the 1920s and early 1930s the lack of a major conflict meant that the experiences of 1918 became less and less relevant due to the constant changes and advancements in technology. The fighters, bombers, and other aircraft that were equipping squadrons in 1939 with their large engines, single wing, all metal designs bore little resemblance to the much slower biplanes that had been the norm over the battlefields in 1918. This meant that in many instances they got things wrong, and made incorrect assumptions, and often when that occurred it was multiple different nations making the same mistakes. This ranged from a lack of emphasis placed on air to ground coordination all the way to just an absolutely fundamental misunderstanding of what would be required to stage a successful strategic bombing campaign. These theoretical miscues then led into bad design aircraft design choices, aircraft were often designed based on what a nation’s airpower leaders believed they would need during a war, but when those beliefs were incorrect the resulting aircraft would be incorrect as well. To complicate things even further, sometimes the design was not even bad but instead simply overtaken by new aircraft introduced by the enemy that made the entire earlier concept obsolete. The best example of this would be the variety of light bombers introduced before the war that planned to use their speed as their protection at a time when the fastest military aircraft in the world were dual engined and nobody had early warning radar so it was impossible to vector intercepts into place. These same bombers would be very vulnerable when both of those facts were changed due to a new generation of mono-engine fighters and the introduction of radar. The final topic to mention before we get into the episode is that everything was a moving target when it came to how to use air power, the aircraft involved, and the capabilities of the enemy. Especially during the late 1930s the overall situation in an air war drastically swung in various directions. For much of the mid 1930s the Italian Regia Aeronautica was considered the strongest in the world, then overtaken by the German Luftwaffe in the later 1930s, and if the war had been delayed another few years it is likely that the French and British would have been in a better position than the Germans. it was all based on when they planned to invest in their air forces, what they were investing in, and then how they planned to use them, all of which were complicated by incorrect beliefs about what airpower was and was not capable of.

Much like what would happen during the Second World War, there would be a tremendous evolution of airpower during the First World War. All of the armies involved in 1914 had some kind of airplanes but they were very flimsy machines made out of wood and canvas and more importantly they were not designed for combat in anyway. They were instead a scouting and reconnaissance platform with the most important weapon that they contained being the eyes of the pilot and observer. From these humble beginnings the air forces of Europe would rapidly evolve, introducing first weapons, then specialized pursuit aircraft, and then even the first strategic bombers. By the end of the war there were a wide variety of combat aircraft that were designed for most of the specialized roles that exist in air combat today: fighters, bombers, close air support, reconnaissance, and transportation were all represented in the designs. Beyond the improvement in design and manufacturing there were also important technological changes that would be introduced: interrupter gears that allowed pilots to fire through the propellers, various wing configurations for different tasks, new building materials, and perhaps most important for the future the introduction and widespread adoption of the radio. The ability to put radios into aircraft, which would be mainly a late war development, would be a crucial moment for the future of airpower. Before it was introduced once an airplane took off from its airfield it was entirely on its own, it could not effectively be communicated to from the ground and it was also challenging to try and communicate back to the ground. To emphasize this a bit, during early attempts to use spotter aircraft for artillery spotting the best way that could be determined to communicate back to the ground was for the aircraft to literally write down notes on some paper and fly over the artillery battery and drop those notes in a canvas bag. That is the best that they could do. Radio changed all of this, and the ability to communicate in real time made some things much easier, like artillery spotting, and also introduced entirely new possibilities, with close air support being a good example of a mission that greatly benefited from the pilot in the aircraft being able to receive up to date information from the ground. All of these improvements and innovations during the First World War made one thing clear: airpower was an important part of conflict, and it was critical that all military powers around the world were able to project airpower over the battlefield and against their enemies.

No topic would occupy as much mental capacity or be subject to as much theory crafting during the interwar years as the topic of strategic bombing. During the First World War there had been dedicated bombers that had been produced and there were even bombers that could be classified as strategic heavy bombers like the Russian built Sikorski Ilya Muromets which had 4 engines and a range of over 500 kilometers. German Zeppelins also took bombing to new levels of range through their bombing campaigns against Britain and France. The efforts of these bombers, and the large number of tactical bombing raids done during the war would seem to point to a new way to persecute a war. During the 1920s this idea would be taken much further by airpower theorists all over the world, but first among them both in theory and in impact for the future of strategic bombing was an Italian, Giulio Douhet. Douhet would write, among other things The Command of the War, which was widely read during the 1920s and also aligned with the thoughts of many airpower theorists in other nations. Douhet’s work contained 3 key assumptions that would be critical to the formulation of strategic bombing during the 1920s and 1930s. The first of these would be that there was very little that could be done to defend against long range strategic bombing. Douhet discounted the impact of both airborne interception by fighters and the possibility of destroying bombers with ground based anti-aircraft. In both cases when Douheet was writing in the early 1920s he was quite correct. Without any kind of early warning radar, and with the slow climb rate possessed by fighters during those years, intercepting bombers was an incredibly difficult proposition. This was especially true if there were several bombers all coming in from different directions which Douhet would advocate for. This was the root of the famous statement that “the bomber will always get through” which was said by the British politician Stanley Baldwin in 1932. Even over a decade after Douhet wrote his famous work, it was still not a bad assumption because while fighters had grown in capability, bombers could fly higher and faster than ever before. It was a challenge that the fighters would not be able to rise to the occasion of until just the last few years before the start of the war. The second key assumption that Douhet made, was that civilian populations were very vulnerable to the effects of strategic bombing. Up until the advent of the airplane, warfare did not really reach far behind the front lines. If you were a civilian and you were more than say 50 kilometers from the armies involved there was not way it could really impact you. Strategic bombing completely changed this, and suddenly there was a huge concern about the impact that bombing would have on civilian morale. Key to this fear was the idea of a bolt from the blue style of attack where enemy bombers just appeared over major cities and started dropping bombs with no real warning. The concern was that this would cause civilian morale to collapse instantaneously, causing a public outcry for peace. This would prove to be completely inaccurate during the Second World War, and in fact the resiliency and bravery that civilian populations all over Europe met bombing was incredible. Not only did it not cause a collapse of civilian morale, but at times it would bolster the will to resist among the people being bombed. This was the case even though Douhet’s third assumption would prove to also be completely incorrect, which was that the bombers of the 1920s and 1930s had the capability to actually hit things and that they would be able to deliver a sufficient number of bombs to actually knock a nation out of the war. When it came to hitting things with the bombs the general assumptions about the accuracy of bombing were based around estimations and tests for how many bombs would be placed within a certain radius of the target and then that was multiplied by the estimated impact based on the study of bombs during the First World War. The challenge was that there was an underestimation of how much harder it would be to hit things with bombs as bombers became faster, started flying at higher altitudes, and were being shot at by more and more types of anti-aircraft guns and other aircraft. As experiences during the Second World War would prove, hitting things with strategic bombers was actually incredibly hard, even getting within hundreds of meters of the target, hard. But for many airpower theorists during the interwar years, they were assuming a level of accuracy that would not be truly possible until the advent of guided bombs over 50 years later. All of these assumptions meant that strategic bombing advocates greatly overestimated the impact that bombing would have on the enemy. For those advocates, strategic bombing was the only thing that mattered, and could win the war by itself. The logical next step from that assumption was that the only thing that nations should spend money on were more and more strategic bombers. Which was the root of the arguments in every nation as the debates raged about how the air forces should spend their money.

While the theory of strategic bombing basically became sacred theory, not to be assailed in any instance, both advocates and critics of strategic bombing theory had to deal with the fact that technology was advancing very quickly. From 1921 to the start of the Second World War the top speed of aircraft almost doubled, with the airspeed record in 1921 being about 330 kilometers per hour and a BF-109 reaching a top speed, although not combat loaded, of 611 kilometers per hour. While speed was the most obvious change in capabilities one that was just as important was to rise in service ceiling, with greater altitude being an important aspect of aerial combat at time when there was a significant speed advantage that could be gained by diving on an enemy. Both an increase in speed and in altitude made bombing more difficult, because it was simply harder to hit things on the ground that were further away, but it brought significant advantages in terms of safety as long as your aircraft was the fastest. The problem was trying to be the fastest and stay the fastest over time. This was because of the somewhat frantic pace of developments in military aviation particularly in the 1930s as all of the nations around Europe began their own rearmament campaigns. Starting in the mid 1930s each generation of aircraft brought with them a jump in performance and capabilities that made it more and more difficult for older models to fulfill their missions. A state of the art fighter might be leap frogged by an enemy design just years after it was unveiled, making the investment in design and manufacturing look like a mistake in retrospect. Fighter development had a particularly potent impact on other types of aircraft due to the fact that the speed of fighters increased so much during this time. With many of the assumptions about strategic bombing being that they could outrun enemy fighters, when that was no longer the case the vulnerability of the bombers became a major problem. This would be apparent as early as the Spanish Civil War when German bombers were intercepted by Soviet fighter planes, and it would be a lesson learned at ever greater cost by every air force that launched bombing campaigns during the war. One of the ways to try and solve this problem, and the path that would be chosen particularly by the American and British would be making the bombers slower but far more heavily armed, with the peak examples of this strategy being the B-17 and the Lancaster. Divorcing themselves of any belief that they could outrun the enemy they instead just threw a bunch of heavy machine guns and men to fire them on board the bombers in the hopes that this would be able to protect the bombers from the enemy, to somewhat dubious results.

The final technological innovation to discuss from before the war was the introduction and then proliferation of radar. The impact of radar to the overall course of the air war cannot be overstated, and it would be as impactful as radio had been during the First World War. It helped to solve the greatest problem when it came to reacting to an enemy attack: knowing when it was going to happen and where it was coming from. This had been such a problem before the introduction of radar because of the length of time that it took an aircraft to go from being on the ground to reaching the appropriate altitude to intercept an enemy formation. This time continued to increase as planes were flying higher and higher. It was the general lack of information that made bomber interception seem impossible, until there was a machine that could tell you if an enemy was coming and at least the very basics of their altitude and direction. By 1939 all of the major powers were either hard at work on radar or had at least basic examples of the technology in use, with the British Chain Home system being by far the most famous radar system at the time, and you might make the case the most famous one ever. Radar would see a huge amount of evolution during the war, but even at the earliest stages it was able to answer the basic questions that they needed it to, to great effect for all of the air forces, and whether that effect was good or bad depended on which side of the radar you were on. There are a huge number of other technologies that could be discussed here, but this is a summary episode so the best you can get is just a quick hitter list of some of them: retractable landing gear, proximity fused anti-aircraft munitions, variable pitch propellers, engine capacity and power, navigation systems, and airborne cameras.

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When the war started in 1939 every air force around Europe was in a different state of readiness and preparation to participate in a conflict. There were three primary ways to judge whether or not an air force was prepared: did they have the right aircraft, did they have enough of those aircraft, and did they have pilots to fly those aircraft. Using these questions to judge the various air forces they can be broadly categorized into a few different groups. The first group were those who were not really prepared for a war, even though they were going to be in one. One of the nations on this list was Poland. The problem for the Poles was, and always would be, a problem of numbers. Some of the aircraft that they were flying were capable of airborne victories, like the P.11c fighter which had some areas where it was stronger than the Bf-109 like in maneuverability. It also had one of the newest bombers in the world in the PZL.37, which was just as capable as any other bomber in service at the time that the war started. But there would simply never be enough aircraft to match up with the Germans, and at some point the Polish pilots who were of a reasonable skill level should not trade at a high enough exchange rate to prevent the Polish squadrons from simply being attrited into nothing. It did not help that things were also going quite poorly on the ground for the Polish military which forced the Polish Air Force to constantly displace from one airfield to the next, which just made everything more difficult. The next air force that would probably fall into the unprepared category was the French Air Force. The French had ended the First World War with one of the most powerful air forces in the world, and during that conflict they had been innovators. But then during the interwar years due to a lack of investment in aviation manufacturing and military aircraft in general, they would never be able to match their enemies in terms of the number or quality of aircraft. They certainly tried though, and after French rearmament started in 1936 there would be many efforts to reform the aviation industry in France through both private means and by nationalizing poorly performing factories. There were also many efforts to purchase aircraft from the United States, efforts that would prove to be too little too late to match up to the Luftwaffe once the war started.

The next category of air forces is one that you could refer to as being in a weird space, and it is a space that is occupied by both the Italian Regia Aeronautica and the Soviet Red Air Force, but they are in this zone for two different reasons. Starting with the Soviets, unlike some other nations their problem was never in the number of aircraft that they had in the air force, and in fact in 1938 the Red Air Force was the largest in the world. The challenge instead was the quality of the aircraft and the quality of the ability of the Soviet military to use them. The Red Air Force put a lot of effort and resources into building bombers and fighters using designs from the mid 1930s, many of which would out paced by the German designs that they would face during the war. There would be another generation of aircraft introduced between 1939 and 1941, and Soviet industry was producing a lot of them, with over 10,000 aircraft built in both 1939 and 1940. Even if some of their aircraft were aging designs, the greatest problem for the Red Air Force was properly utilizing all of the aircraft that they had, with not enough resources being dedicated to ground crew and facilities. This made it difficult to actually utilize the large numbers of aircraft that were available when they needed to. The Italians would experience a very different problem in the years before the war. During the early and mid 1930s the Italian aviation industry was one of the worlds best, with Italian manufacturers holding many world records in speed and endurance. This was utilized by Mussolini’s regime to build out a very capable air force that was an important factor when other nations considered the risk of a possible war with Italy. The aircraft available would then be used in Ethiopia and then the Spanish Civil War where they would distinguish themselves. The problems would then come in after Italy was embroiled in those two conflicts. The first was that being involved in both wars drained the Italian military budget at a time when other nations were rapidly expanding their military industries. This made it difficult to properly fund maintenance and replacement efforts during the late 1930s. The second problem was that Italian manufacturers, while some of the best in terms of technical capabilities, would prove far less adept at expanding their productions to the capacity required, and with the ability to innovate, to keep pace with other nations. This meant that the all important next generation of aircraft that were introduced in the late 1930s to match up with the latest examples from other nations were not produced in sufficient quantities before or after Italy’s entrance into the war in 1940.

When the Royal Air Force entered the war it had some of the same problems as their allies the French and Polish, they had started to seriously invest in rearmament later than their German enemies, and even then there were limits to how much they were willing to spend to build out the RAF in the short term. However, their ability to ramp up production outpaced even the Germans, with the two nations producing roughly similar numbers of aircraft during 1939. The problem for the British is that their production numbers for earlier years lagged far behind the German production figures. Along with the ability to produce a larger number of aircraft the British would also have some challenges and make some mistakes. The first of these mistakes was the belief among Bomber Command that the RAF was capable of launching a strategic bombing campaign against Germany in the late 1930s. This is an area where we have to put aside what the RAF would become, and the incredible volume of munitions that they would drop on Germany later in the war. At the beginning of the conflict the RAF did not have the technology, the aircraft, or the tactics in place to launch almost any kind of bombing campaign. When it came to strategic bombing the navigational equipment was not available to make sure the planes could find their targets, and the bombers that they had did not have the bombing capacity to make the desired impact. Even from a tactical bombing perspective Bomber command would find itself unable to drop the required bombs where it wanted to when it wanted to. This would be demonstrated in France during operations like the attempts to bomb the bridges across the Meuse to prevent the German crossing. Bomber Command would eventually find their footing and a new generation of British bombers would be able to change their fortunes later in the war, with the ability of the British to build out their new bombing force a testament to the British aviation industry. That same industry would be important during the Battle of Britain as well, with the investments in the industry paying off at the most critical moment. Much like the Germans the British benefited from at least a few really good design choices before the war, with the most famous being the Spitfire. They would also have a technological advantage when it came to radar, with the Chain Home system which was first put in place in 1938. The radar could not shoot down German aircraft, but it greatly reduced the advantage that the Germans enjoyed in other theaters due to the number of aircraft in the Luftwaffe. It acted for the British like a force multiplier, allowing them to use their numbers as wisely as possible, something that other air forces that faced the Luftwaffe in the early war were unable to do.

When the Germans started the war the Luftwaffe had a few key advantages of the other air forces that it would face in the opening months of the Second World War. The first advantage is that the German rearmament efforts had really gotten started before those of their enemies, and they had pursued them with more vigor. There were many problems for the German economy due to rearmament campaign, and the Allied efforts would eventually eclipse what the Germans were capable of, but for the years in the mid 1930s the Germans were far ahead. The numerical advantage built up during the prewar years would still be present in September 1939, allowing the Germans to enter the war roughly at parity in terms of modern combat aircraft with their three largest enemies combined, that being the Polish, French, and British air forces. However, the Germans would enjoy a much better position when it came to the air war due at least partially to geography and the decisions made by the British and French all the way up to the fall of France. Basically, they would be largely allowed to defeat their enemies in detail, until they arrived over Britain and then it would not go quite so well. One of the reasons that they would experience so many challenges over Britain was due to the specific make up of the Luftwaffe. It was an air force that was built first and foremost to support the army on the ground. With light and medium bombers designed to hit targets relatively close to the fighting, like railways and troops concentrations, not one prepared to launch a true strategic bombing campaign. They also had the premier dive bomber during the early war years with the Ju-87 Stuka, which had been introduced in 1936 which gave the Germans plenty of time to produce them in quantity. Along with the Stuka the Bf-109 was probably the most famous German aircraft of the war, being introduced in early 1937. This was really important for the overall course of the air war because it was early enough that the Germans could build them in sufficient quantity to meet their needs, even given their material shortages. It was helpful that the Germans had a solid run of designs with aircraft like the Stuka, Bf-109, and then bombers like the He-111. All of these aircraft would quickly begin to show their age after the war started, but it allowed them to enter the war at the top of their game, well mostly. One of the criticisms that would be leveled at the Luftwaffe after the war would be the lack of investment made into a true heavy strategic bomber, something with four engines, long range, and a large bombing capacity. These were not really necessary for some of the campaigns that the Germans planned to fight, but the lack of focus on such a design, particularly after the death of Walther Wever in 1936. Wever was a strong advocate for the heavy bomber project, and with his early death there was no longer a strong voice within the Luftwaffe for such projects. While they would not have a heavy bomber project anywhere near completion in 1939, the Germans would have one more major advantage and that would be in experience. During the Spanish Civil War the Luftwaffe would send the Condor Legion to Spain where they would gain valuable experience in all aspects of airpower. All of these advantages, along with a focus on cooperation with the German ground forces would make the Luftwaffe the best air force at close air support early in the war, which when combined with their ability to interdict enemy air forces through the use of the Bf-109 would put them in a good place during the war’s early campaigns. There would be challenges later in the war, but in 1939 those would be in the future.