The use of military aviation as an instrument of war had its first days years before the First World War, and since its birth, it had a dizzying evolution that would make air power an essential element in the war plans of the next two decades. At first, aviation was employed in a role of direct or indirect support to the battlefield and the troops that fought on it, however, with technical evolution in constant development, military strategists were able to devise new ways of waging war. The most advanced way to execute this aerial power was put into practice on attacks in enemy areas in long-distance flights, beyond the other types of bombing. A faster, cheaper and ‘cleaner’ war was promised beyond the frontline.
During the 1914-1918 war, both the British and the Germans planned to attack the enemy’s cities by air: thus several attacks by zeppelins first and huge bombers later were carried out from 1915 with varied results but in general with little or no consequences for the development of the war. Of course, it had been made clear that in future wars, the delimitation of the battlefield no longer existed. It would be fought both in the battlefront as in the home front. This is how the new “warrior” appeared, the one who would suffer the most from the harshness and cruelty of the battles of the 20th century: the civilian population. This new war extended its destructive power even to non-combatants. Modern air warfare was born with the planners of the Kaiser’s Empire: starting from reconnaissance flights over the frontline to destroy a military target that resides in an urban area.
[German armourers ‘bombing up’ a Gotha G.V bomber in November 1917 during the First World War.]
[The Daily News newspaper frontpage on 1 June 1915, following previous night’s raid by German Zeppelin LZ.38 airship, the first one over London.]
With this new way of waging war, another element that strategists and generals would have to count on: moral (which includes morality and morale). Lt Col Ash defines military morale: “If morale is the desire to continue the fight, then strategist must target morale in order to break the enemy’s will to resist. This is why morale is so important. It can lie at the heart of targeting for effect”. That morale also extends, as von Clausewitz said, to the leadership of society. The theory was simple: the enemy nation should also be attacked in its own territory, in its facilities, in its cities and in its homes to nullify the possible future combat capacity of its inhabitants, either as soldiers or as workers of the war effort. Directly choosing moral as an objective involved attacking group goals, cultural histories and traditions, symbols, and ideology. In addition, it should be achieved in this way to break the trust of the society placed in their leaders, and prevent them from continuing to abide by their directives; an army is sustained by soldiers and weapons, so if the people were prevented from filling their ranks, no one would handle the manufactured weapons. On the other hand, this strategy also wanted to achieve the double effect of demoralizing the battlefront soldier, who when seeing his home city -and therefore, his family- reduced to rubble, would lose faith in victory. That is to say, in times of war, the will to fight is attacked. In World War II, the moral bombing strategy involved both positive (which gives strength, given the success achieved) and negative (which, on the contrary, leads to depression and defeat after seeing the enemy superiority).
Ash signaled on the direction of the attacks: “…leadership influence can be eliminated by cutting command or social-structure linkages so that society no longer associates its confidence with its leaders. Another indirect option involves bombing the society at large so as to kill the populace or at least cause loss of sleep and reduced worker performance. That sounds like direct targeting, but it is not. It eliminates the confidence of the victims, but the actual target is the confidence and morale of the surviving population.” 
This attack on morale will be extended and completed with the inclusion of raids on the elements that produce the another’s war effort, such as facilities, factories, oil refineries, docks, warehouses and marshalling yards should be attacked wherever they are, which implied to fly over enemy territory crossing defended airspace in great risk.
In the interwar years, the different powers analyzed the military contributions of strategic air attacks, appearing a whole doctrine of bombing and air warfare, with several representatives who formulated the basic guidelines to follow in future conflicts. In Great Britain (which has always been one of the leading powers in air development) Lord Hugh Trenchard, Chief of the Air Staff, RAF, had a great importance. His are the dogmas that “in air warfare the greatest defense is counterattack”  and that “the country that resisted the bombardment the longest would win in the end.”  He will bet on the creation of a powerful bombardment arm among the British air ranks, believing that the moral effect of the bombings was much more effective than the physical one, and that in the future the bombers would win the battles alone. Critics have accused him of his dogmatic approach to offensive tactics against morale and of promotion of bombing of urban populations.
[Marshal of the RAF, Lord Trenchard (middle), talks with the aircrew of a Fairey Battle light bomber during a tour of AASF Wings in France in 1939.]
Even more extreme were the conceptions of the Italian army General Giulio Douhet in his book Il dominio dell’aria (first published in 1921), head of aviation at the Mussolini’s fascist regime. He considered air warfare as a saving element that would prevent the slaughter between soldiers on the ground; the bomber would break the stalemate of the war, seeking the surrender of the enemy by annihilating its defences, for which, according to him, the large-scale slaughter of civilians was justified. Douhet also approved the bombardment with toxic gases, with attacks that “slowly emit gas, thus poisoning the atmosphere for weeks”. He appropriated Trenchard’s basic idea and carried it to its logical, amoral conclusion. Douhet believed that the decisive action against the enemy should be the attack on the population itself and that the instrument for this was the bomber. Frankland says that the figure of the Italian general as the sole mentor of this doctrine is questionable, but he granted his later influence in the USA, meanwhile Taylor believes that Trenchard’s ideas, and even Douhet’s, could carry deterrence at their heart:“So terrible would be the damage the bombers would inflict that in the future no sane leader could envisage unleashing a European war.”. Friedrich states of the impossibility of dissociating the concepts of “bomber”, “State” and “war” since then, and that“making war means, above all, to bomb cities. This was indicated by the Trenchard doctrine, the raison d’être of the Royal Air Force”, a highly accusatory judgment, possibly because its country of origin (Germany) was the main victim of these theories.
The evolution of these theories after the First World War led to an increase in the air branch of each nation, especially the bombing arm, with a constant technical improvement that allowed the maximum bomb load to be carried as far as possible.
Bombing aircraft were the weapon of the future, and with them the enemy would be defeated. In the 30s, the “Multiplace de combat” theory, would pick up this concept, with large and heavy bombers -but slow- armed with numerous machine guns in turrets, for self-defense, that would make their way into the enemy’s skies alone.
The great conflict of that decade, the Spanish Civil War (1936-1939), would further contribute to assert this principle. From Spain experiences, great powers drew very wrong conclusions (and which would pay on the first years of the imminent world war), led to the conviction of the bombing aircraft power and its ability to survive against enemy defences alone, but this was due to the very special circumstances of warfare of the Spanish conflict (a mix of traditional strategies and new weapons yet to be tested). Germany, Italy and the Soviet Union tested bombing aircraft in Spain, developing their weapons and training their crews. Both Germans and Soviets started to develop a new type of bomber too: the sleek, monoplane, and fast plane which carried a small bomb load designed to penetrate enemy airspace and leave behind the fighters thanks to its greater speed and defensive fire (examples of that were the Luftwaffe’s Heinkel He 111 or the Soviet SB-2 Katiuska).
The civilian population would suffer for the first time a sustained and aimed bombing campaign targeted to break its resistance: Madrid, the capital city, had the “honour” of being the first city in the world to suffer the moral bombing strategy (since October 1936) with daily attacks by German and Fascist Italian aviation which supported General Franco [see our “Evacuad Madrid” post]; the following year both Barcelona and Valencia cities would suffer daily punishment from the air with hundreds of civilian killed, just as the most famous air bombing was also carried out in Spain by Legión Cóndor aircraft: Guernica (or Gernika), on April 26th, 1937.
[A Spanish Republican Potez 540 bomber, the French ”multiplace de combat”, employed during the first months of the Spanish Civil War by the government air forces against the military coup.]
[This image, taken by Juan Miguel Pando Barrero during the war, shows that Spanish civilians used Madrid subway every night as an air-raid shelter to refugee from Franco’s bombers, as they would do years later Londoners or Berliners.]
[A Spanish Nationalist Heinkel He 111B (in the foreground) parked next to its predecesor in the German bombing arm: the Junkers Ju 52 -a converted bomber from the famous civilian airliner- seen at the end of the Civil War.]
[Aerial bombing of Barcelona, 17 March 1938, by Fascist Italian Aviazione Legionaria aircraft.]
Both Great Britain and the United States carefully studied the operations and experiments carried on in Spain and China (where the Japanese bombed civilian targets like Shanghai or Chengdu during the Second Sino-Japanese War), knowing that they were a prior act of the air war that would be fought in the incoming years. What was learned was put into practice, in different ways, against the inhabitants of Europe (and months later in other parts of the world).
Strategic moral bombing was an attack against community, which in the case of World War II experienced the most critical and high mark moments, although at times it achieved just the opposite result of that aimed by strategists. Civilians morale, far from declining increased, due to the feeling of hatred towards the enemy bomber that bring devastation to their homes. And among the attacking aircrews, the effort and toughness encountered led to demoralization in the face of the losses experienced and the poor visible results.
 FRANKLAND, Noble: Bomber Offensive: The Devastation of Europe, Ballantine Books, 1970, p 10.
 OVERY, Richard: Why The Allies Won, Pimlico, 2005, p 150. Overy is also author of a monograph about RAF Bomber Command (Overy, R. Bomber Command, 1939-1945, Bookmart Ltd, 2000.).
 During World War I, the German bombing offensive on British cities had begun on the night of January 19-20, 1915. Attacks were carried out during the following months against Dover, Yarmouth or London. The British, for their part, had already carried out attacks on enemy installations such as zeppelin hangars in places as far away as Cologne or Dusseldorf during late 1914. Ibid. About the London air-raids Taylor says that “For a while an atmosphere of near panic infected the highest circles of British government”. TAYLOR, Frederick: Dresden: Tuesday, February 13, 1945, Bloomsbury, 2005, p 118. The author includes figures about the Anglo-French bombing campaign of that war: in 675 strategic raids mounted against Germany 746 German soldiers and civilians had died and a total of 1.2 million pounds’ worth of damage had been inflicted, compared to losses of 352 aircraft and 246 crew members killed or missing, p 119. See also FRIEDRICH, Jörg: Der Brand Deutschland Im Bombenkrieg 1940-1945, Verlag Ullstein, 2005, p 61. Further reading about the London bombing campaign in CASTLE, Ian: London 1917-18: The bomber blitz, Osprey Publishing, 2010.
 TAYLOR: op. cit., p 117.
 ASH, Eric: Terror Targeting: the Morale of the History. Air and Space Power Journal, Winter 1999, p 34. <https://www.airuniversity.af.edu/Portals/10/ASPJ/journals/Volume-13_Issue-1-4/1999_Vol13_No4.pdf
 Ash states that “Morale during World War II was usually higher in active theaters [of combat] than in noncombat areas, despite the increased danger”. op. cit., p 35.
 FRANKLAND: op. cit., p 12.
 TAYLOR: op. cit., p 122.
 ASH: op. cit. p 38.
 TAYLOR: op. cit, p 125; ASH, op. cit., p 35.
 TAYLOR: op. cit., p 125. FRANKLAND: op. cit., p 12.
 FRIEDRICH: op. cit., p 64.
 France was the country that developed longer this theory with its ‘Multiplace de combat’, designing a high number of huge and bulky planes with gun turrets, which despite its conviction, would be a total failure when operationally tested in the war over Spain (in this case the Potez 54 bomber).
 First air raid on Madrid was made on 27 August 1936, and the first one in daylight on October 23rd of the same year. REVERTE, Jorge: La batalla de Madrid, Crítica, 2004, pp 117-118. In 2019, two Spanish architects, Luis de Sobrón y Enrique Bordes, have published the first complete and well-researched bombing map of Madrid: https://diario.madrid.es/carteles/madrid_bombardeado/
 Further reading about the air bombing raids during the Spanish Civil War in SOLÉ I SABATÉ, Josep Maria; VILLAROYA, Joan: España en llamas, Temas de Hoy, 2003. During the Guernica air attack were killed about a hundred civilians, SALAS LARRÁZABAL, Jesús: “La campaña del Norte”. Enciclopedia de la Aviación Militar española, Quiron Ediciones, Nº 10 (2000), p 151. For an overall study of the air war over Spain, see PERMUY LÓPEZ, Rafael: Air War over SPAIN, Ian Allan Publishing, 2009.
- About the author: Pablo López Ruiz researches the bombings of Germany and the Third Reich by Allied forces during WW2. His work was defended as Bachelor’s Degree Final Project as part of his BA in History at the Universidad Complutense de Madrid in 2007.