93: Where do you expect us to go when the bombs fall?


A major topic of conversation during the interwar years was the ideas, power, and future of strategic bombing.


  • British Intelligence on the German Air Force and Aircraft Industry, 1933-1939 by Wesley K. Wark
  • Case Studies in the Development of Close Air Support Edited by Benjamin Franklin Cooling
  • The Development of the Italian Air Force Prior to World War II by James J. Sadkovich
  • The Strategic Dream: French Air Doctrine in the Inter-War Period, 1919-39 by Robert J. Young
  • History and Evolution of Close Air Support: World War I to the Korean War by Michael J. Chandler
  • The Origins of American Airpower Theory by James R. Cody
  • The Price of Air Power: Technological Change, Industrial Policy, and Military Aircraft Contracts in the Era of British Rearmament, 1935-39 by Sebastian Ritchie
  • Airpower and the Cult of the Offensive: Royal Air Force, 1918-1938 by John R. Carter
  • The Royal Air Force, Air Power and British Foreign Policy, 1932-37 by Malcolm Smith
  • Strategy for Victory: The Development of British Tactical Air Power, 1919-1943 by David Ian Hall
  • The War in the Air 1914-1994 Edited by Alan Stephens
  • Why Air Forces Fail: The Anatomy of Defeat Edited by Robin Higham and Stephen J. Harris
  • The Air Panic of 1935: British Press Opinion between Disarmament and Rearmament by Brett Holman
  • Trenchard and “Morale Bombing”: The Evolution of Royal Air Force Before World War II by Phillip S. Meilinger
  • The Heavy Bomber at its Inception by Jerry Hendrix and James Price
  • Rhetoric and Reality in Air Warfare: The Evolution of British and American Ideas about Strategic Bombing, 1941-1945 by Tami Davis Biddle
  • Incubate Innovation: Aviation Lessons from the Interwar Period by Lieutenant Philip d. Mayer
  • Strategy for Defeat the Luftwaffe 1933-1945 by Williamson Murray
  • Military Innovation in the Interwar Period Edited by Williamson Murray and Allan R. Millett
  • The Paths of Heaven: The Evolution of Airpower Theory by The School of Advanced Airpower Studies


Hello everyone and welcome to History of the Second World War Episode 93 - Interwar Airpower Pt. 2 - Where do you expect us to go when the bombs fall? This week a big thank you goes out to Gareth for choosing to support the podcast by becoming a member, members get access to ad free episodes and special member only episodes roughly once a month. Member subscriptions are available through Apple Podcast Subscriptions and Patreon, head over to historyofthesecondworldwar.com/members to find out more. While air power in general was important to the overall course of the Second World War, there were many different facets to how air power was used in an attempt to achieve military objectives. One of the largest, in terms of resources and manpower, was the strategic bombing campaigns that would take place throughout the course of the war. The largest of these campaigns would be launched by the British and Americans against Germany, and by the Americans against Japan. The destructive power of these campaigns was on a level never seen in previous conflicts, but there is still some continuing debate about their efficacy when it came to turning effort and resources into damage to the enemy’s war effort. We will not get too much into those debates during this episode, and we will instead focus on the growth and evolution of strategic bombing, and the assumptions made about what it would mean for the future of warfare during the interwar years. It would be during those years that the ability of aircraft to launch strategic bombing campaigns, to strike at the very heart of the enemy, would begin to gather a vocal following who would argue that it would be the most important usage of airpower during a future war. There were many reasons why strategic bombing took on such importance during these years. There were military reasons learned from the First World War, mostly around the recognition that it was no longer enough to defeat an enemy on the battlefield, and that it was also important to be able to strike at the enemy’s industrial and economic foundations. There were economic reasons as well, with the desire to find literally any other possible avenue for development that could prevent another attritional based conflict like the Great War. And it was also driven by fear, fear that if you did not have strategic strike capabilities, the enemy would, and there would be nothing that you could do to stop them. Or to quote the quite famous quote from Stanley Baldwin: “In the next war you will find that any town within reach of an aerodrome can be bombed within the first five minutes of war to an extent inconceivable in the last war. . . . I think it is well also for the man in the street to realise that there is no power on earth that can protect him from being bombed. Whatever people may tell him, the bomber will always get through. . . . Imagine 100 cubic miles covered with cloud and fog, and you can calculate how many aeroplanes you would have to throw into that to have much chance of catching odd aeroplanes as they fly through.” All of the arguments in the support of strategic bombing, and all the fears that strategic bombing caused, were all based on one core foundational assumption: that bombing could, and most certainly would, be capable of greatly influencing the course of a war, and of causing significant and unavoidable damage to its intended targets. This core assumption then spooled out into many many more assumptions about the damage that could be dealt with specific bombing payloads, of the effect that the damage would have on the enemy war effort, the ability of fighters and anti aircraft guns to interdict bombing raids, how many bombers were needed to have a decisive effect, the list goes on and on. Or to quote Strategic bombing: The British, American, and German experiences by Williamson Murray “Perhaps the greatest problem that confront airmen and innovators was the extent and range of assumptions they had to make in thinking about the preparing for strategic bombing”. I think the most interesting thing about the preparations made for strategic bombing campaigns during the interwar years are these assumptions, not just of air forces about themselves and their capabilities, but also about their enemies, they are not just snapshots of a belief at the time, but they would also have crucial impacts on how nations planned and prepared their bomber fleets. It would be the assumptions, decisions, and beliefs of the mid 1930s that would create the air forces that would meet in the air over Europe in the first two years of the Second World War. We will discuss all of these things throughout this episode, which means that we should probably dive in.

In the years immediately after the First World War one of the most important theorists on air power and its role in future conflict was the Italian General Guilio Douhet. Even during the war he had been a forward thinker, constantly suggesting changes and reforms that would allow the Italian army a greater chance of success. Now, for those who have not listened to History of the Great War, or are not as up on their First World War history, the Italian army was not exactly known for its innovation or for its ability to adapt to problems that it faced. There were after all 11 battles of the Isonzo, 11. Eventually, Douhet after a bit of a rocky relationship with the military during the war years would retire in June 1918, at least partially due to his annoyance that nothing was really changing. Then after the war it would take him just 3 years to publish The Command of the Air, his most famous work. Douhet’s entire concept of a future war rested on the power of a strategic strike force that could take the war directly to the enemy. He was adamant that planes, bombs, and effort should not be wasted on supporting operations on the ground, or even on defensive efforts against enemy planes, everything should be focused on strategic effort. He would even go so far as to call ground attack aircraft and pursuit, or what would later be called fighter, aircraft ‘auxiliary aviation units’. Instead he wanted complete focus on attacking an enemy nation and its vital industries and other areas behind the fighting line. To do this Douhet believed that nations should focus strictly on building the largest, most modern, and most capable force of bombers that were possible. The only other type of aircraft that might be required was a really fast one with some cameras on it to do some recon work, other than that everything should be big, should be able to carry bombs, and have the range to carry them deep into enemy territory. This would allow them to attack an enemy and to destroy that enemy’s will to continue the conflict. To try and dive deeper into these various theories and beliefs, lets look at some quotes from The Command of the Air “War is a conflict between two wills basically opposed to one other. On one side is the party who wants to occupy a certain portion of the earth; on the other stands his adversary, the party who intends to oppose that occupation, if necessary by force of arms. The result is war.” In attacking an enemy’s will, the place to hit was not the front lines of the army, they were expecting to be attacked and they would prepare defenses, instead the targets should be easier to locate, attack, and damage, targets from from the focus of the fighting. Cities, factories, and homes were all quite easy to destroy, unlike trenches and pillboxes they were not designed to withstand the explosive power of air delivered bombs. “We should always keep in mind that aerial offensives can be directed not only against objectives of least physical resistance, but against those of least moral resistance as well. For instance, an infantry regiment in a shattered trench may still be capable of some resistance even after losing two-thirds of its effectives; but when the working personnel of a factory sees one of its machine shops destroyed, even with a minimum loss of life, it quickly breaks up and the plant ceases to function.” Once this bombing was complete, Douhet would argue that the end result was obvious and predictable A complete breakdown of the social structure cannot but take place in a country subjected to this kind of merciless pounding from the air. The time would soon come when, to put an end to horror and suffering, the people themselves, driven by the instinct of self-preservation, would rise up and demand an end to the war." To achieve all of these things air power could not just exist, it had to be structured around achieving these objectives: air power had to be seen as a purely offensive weapon. He completely dismissed the idea that air power should be used in defense, and he would discuss what he believed were some of the reasons that it could not be useful in a defensive posture “an aerial force is a threat to all points within its radius of action, its units operating from their separate bases and converging in mass for the attack on the designated target faster than with any other means so far known. For this reason airpower is a weapon superlatively adapted to offensive operations, because it strikes suddenly and gives the enemy no time to parry the blow by calling up reinforcements.” According to Douhet any resources, time, and manpower spent on these defensive preparations was not just a waste of time, but actively harmful to achieving the end goal of projecting as much power as possible against the enemy. He was also a strong advocate for using all available tools in these bombing campaigns, not just high explosive bombs, but incendiary and poison gas as well. Douhet would point out that gas was a great way to prolong the effects of an air raid, as the gas would remain in the target area at lethal concentration levels far after explosives had done their damage, and after fires had been extinguished “Gas attacks must be so planned as to leave the target permeated with gas which will last over a period of time, whole days, indeed, a result which can be attained either by the quality of the gases used or by using bombs with varying delayed-action fuses.” Finally, and crucially, Douhet argued that even if one nation did not want to launch these kinds of campaigns, if they did not want to bomb factories, drop incendiary bombs on civilian targets, drop poisonous gases in the middle of cities, that just meant they were going to lose the war, because their enemies might do all of those things, and there would be nothing that any nation could do to stop it, unless they were able to strike harder, better, faster, stronger. With all of that said, Douhet would make a lot of assumptions, obviously because he was trying to predict the future. A line by line refutation of Douhet’s theories from the book, especially as they related to events that were 20 years after it was published would be a bit tiresome, but I will reference one foundational mistake and then a few incorrect predictions Douhet would make that would reinforce his beliefs and directly contribute to his incorrect conclusions. In the mistake category, Douhet simply overestimates the physical damage that bombs can do to the targets he is suggesting should be bombed. He tries to base his damage estimates on some math, including the exact destruction radius of a bomb, how much explosives bombs should have, and how many needed to be dropped, and all of these calculations were very optimistic. This causes him to believe that bombers would have a much greater impact relative to their bomb carrying capacity than they actually would during the Second World War. In the bad prediction category: Douhet really overestimates the psychological effect that bombing will have on a civilian population. Douhet believes that relatively small attacks and the damage that they cause over a short period of time, will be enough to prompt full on revolution and revolt by the people. If anything the events of the Second World War would prove that the effects of bombing attacks would often be the exact opposite, with many civilians in cities that were bombed simply hardening their resolve and determination, even with far greater weight of bombs dropped over a far longer period of time. The second bad prediction, and one that I do not think is something that warrants too much criticism, is that Douhet was unable to predict the vast advances that would be made in the realm of aerial defense. Radar, faster fighters, and other technological advancements would remove many of the limitations that Douhet believed made the defender’s task impossible. But this mistake also ties back into the first two items that we have discussed, because Douhet believed that a hard hitting aerial campaign could end wars quickly, before whatever defenses that could be mounted and which could have a limited success rate could chip away at the ability of the bombers to have their decisive impact. At the end of the day Douhet was a zealot, with all of the negative parts of that word included, he so strongly believed in his views on strategic bombing, views that would only grow in intensity later in life, that he was incapable of properly considering everything that might go wrong, or the things that might change that would make his views incorrect. But during the interwar years Douhet would be an important writer on the subject, although there would also be others in other nations. There were shared ideas between all of them, and they all built on each other, creating a narrative around how a future war would be shaped by the unstoppable power of strategic bombing, narratives that would influence the technical designs of aircraft and the strategic planning of nations during the 1920s and 1930s.

While the development of strategic bombing concepts and capabilities was led by military leaders and theorists like Douhet, it was also one topic that was well publicized and had a distinct public component to the discussions during the interwar years. A key part of that public concern and discourse was the well known fact that strategic bombing was a direct threat to civilian lives. We do not have the type of hyper accurate public opinion polling for this period that we have for the modern day, but when we look at second hand sources, like newspaper articles, we see a good amount of discussion about strategic bombing and the threat that it posed to civilians. One of the ideas that became quite popular was that the next major war would start with massive aerial raids that would cause massive damage and might even result in the end of the war just days or weeks after it started. This theory was known as the “knock out blow” theory, and it was very prevalent in some nations but particularly Britain during the 1920s and 1930s. It would also enjoy a good amount of political backing as well, and these concerns and that political support would be bolstered by air power advocates who saw it as an easy path towards additional funding and resources, an important aspect for any military arm in the highly resource constrained 1920s, and then in the competitive rearmament atmosphere of the 1930s when in each nation all military disciplines jockeyed for a limited pool of resources. The idea of the knock out blow was very difficult to challenge directly, and those who did not agree that it would happen did not necessarily have a great reason to say that it would not be the case. Just as the knock out blow advocates were basing their predictions on a lot of conjecture and assumptions, those who pushed back against the concept had little other than the same type of conjecture and assumptions. All of these fears were very acute in Britain, where the threat of a land invasion was always much lower than any area of continental Europe. This meant that the only way in which many Britains felt they were under a direct threat was from the air, giving conversations about air raids and the damage they could do much greater importance. Not every concern was rooted in in illogical fear, there were also some real technical challenges that seemed insolvable. For example, bomber interception. Until just the last few years before the war there was little that could be done to stop bombers from reaching their targets and dropping their bombs. Radar did not yet exist, and the speed and rate of climb of fighter aircraft in the 1920s and early 1930s meant that intercepting bombers would be a real challenge. The math between altitude, climb rate, and speed just did not work out in favor of the interceptors, and while it would be possible to get early warning of bombing raids, through the manual process of human lookouts and spotters, those type of systems were very brittle and porous. This resulted in conversations about the concerns of being bombed devolving into the discussions not just about defensive operations, which seemed largely impossible with the technology of the day, but instead into a first strike capability, just as Douhet predicted. The only option appeared to be to drop more bombs on the enemy before they could launch their own bombers. And when discussing offensive bombing operations the question of targets would eventually have to be discussed. At the most gruesome, and I would say also the most honest, was this quote from Stanley Baldwin “The only defence is in offence, which means you have got to kill more women and children more quickly than the enemy if you want to save yourselves.” That quote was in the context of Baldwin pushing for greater disarmament efforts in the early 1930s, and he used that quote as an example of why disarmament was so important. It was perhaps an exaggeration and simplification of the military objectives of strategic bombing, but as would be proven during the Second World War, it was not necessarily incorrect. There were many and serious conversations about what targets should and should not be prioritized given the fixed amount of bombers that any nation would have available in time of war. For an example of the conversations and the resulting doctrine, we can look at AP 1300, which was the Royal Air Force War Manual after it was published in July 1928. I will give a quote from Trenchard and “Morale Bombing”: The Evolution of Royal Air Force Before World War II by Phillip S. Meilinger which does a good job of summarizing and analyzing some of the contents of the manual, and Meilinger includes this summarization concerning how bombing objectives were chosen: “The choice of bombing objectives was dependent on five factors: the nature of the war and the enemy; the general war plan of the government; diplomatic considerations; the range of the bombers; and the strength of the enemy air defenses. As a general rule, the manual opined that “objectives should be selected the bombardment of which will have the greatest effect in weakening the enemy resistance and his power to continue war”.” The interesting thing about AP 1300 is that it did contain references to how important it was to break the enemy’s morale, and even directly to break civilian morale, but it never directly discussed bombing raids that would target civilian targets, causing civilian damage, suffering, and death. There was a distinction made between normal civilians and workers, especially munitions workers, but there was some hesitancy to formally and fully endorse the indiscriminate bombing of targets, especially cities or purely civilian targets. Some would also argue that no matter what was happening to civilian targets, no matter how much you targeted them, it would still result in less overall suffering and brutality than another war like what had happened between 1914 and 1918. That is not because bombing civilian targets would not cause civilian suffering, just that it would cause less suffering than other options. Or to quote Hugh Trenchard, leader of the RAF in 1928: “I emphatically do not advocate indiscriminate bombardment, and I think that air action will be far less indiscriminate and far less brutal and will obtain its end with far fewer casualties that either naval blockage, a naval bombardment, or sieges, or when military formations are hurled against the enemies’ strongest points protected by barbed wire and covered by mass artillery and machine guns.” What ends up happening during the war, and the bombing of civilian cities in the area bombing campaigns, the Blitz, the firebombing of Dresden, the atomic bombs in Japan, and other such events are conversations that we will have on the podcast eventually. But what I will say now is that for interwar military leaders in nations like Britain there was a difference between decisions that might be made in time of war, and planning to do things during peacetime. During the Second World War decisions were made within the confines of a conflict that had already seen civilian bombing from both sides, massive civilian suffering for other reasons as well, so many other atrocities throughout the conflict. But to plan to do that bombing, to make it clear in peacetime that the goal of the Royal Air Force’s strategic bombing squadrons was to kill enough civilians to end the war, well that was something that was better left unsaid. Then when the war does start something really interesting happens, every air force suddenly realizes that actually achieving real objectives through a bombing campaign that targets civilian morale is incredibly difficult. The ability of civilians to continue to support the war effort is something that far exceeds the ability of strategic bombing forces to destroy. One of the major lessons in general about strategic bombing that made many prewar predictions incorrect was simply how many munitions would need to be delivered onto targets to have the expected impact on a nation’s war making capabilities. It would be a staggering amount, which made the fears about the capabilities of strategic bombing both completely unfounded and prophetic at the same time. At the beginning of the war the fears were completely unfounded, because nobody had enough bombers to deliver the early knock out blow that was so prevalent in interwar writings, but then by the end of the war bombers were capable of dropping nuclear bombs that could flatten entire cities, and for the first time a nation possessed the kind of knock out blow capabilities that had driven those interwar fears. So that fear would end up being legitimate, nuclear bombing is something to be feared, but it was just a bit too early to be concerned about the capabilities of the strategic bombing capabilities of other nations in the 1930s.