During the interwar period a number people advocated major changes in military doctrine and organizations, particularly in the use of airpower. Three important airpower advocates were Giulio Douhet, Hugh Trenchard, and Billy Mitchell, who all insisted that the air arm should be independent of the army and navy. Trenchard in fact was the commander of the first independent air force in the world, the Royal Air Force (RAF), while the United States Air Force (USAF) did not become fully independent of the Army until 1947. Both Douhet and Mitchell were sufficiently outspoken in their support of airpower that they made enemies among traditionalist generals, and both faced court-martials for their views. In the low-budget years of the 1920s and 1930s, Trenchard also had to battle the army and navy for scarce resources and to protect the survival of the independent air arm from the rival services. He was also a convinced supporter of Douhet's main theory that massed strategic bombing of the enemy's industry, cities and transportation could win a war and spare armies from the mass slaughter in the trenches that had occurred during World War I. Mitchell was also an early supporter of strategic bombing, and was the first to actually sink a battleship from the air. He and Trenchard would also have launched a strategic bombing campaign against Germany even in World War I had the war not ended in November 1919. Although neither Trenchard nor Mitchell ignored the important role of fighters and tactical air power, both the RAF and Army Air Corps entered the Second World War committed to a policy of strategic bombing, although they underestimated the losses that bombers would suffer to the Luftwaffe without fighter escorts, and the difficulties of locating and hitting targets in the dark and during bad weather.
Douhet and his important disciples like Mitchell and Trenchard, always insisted that the independent air arm should have both bomber and fighter units, while the army and navy would have tactical air units tailored to their own unique missions. Most importantly, the independent air force would concentrate on bombing the enemy country, including its industry, cities, government offices, transportation and communications. It would also destroy the enemy air forces and the industries that supported them, and take command of the enemy's airspace. Douhet insisted that offense was the best defensive measure against air attacks, particularly destroying the enemy airbases and attacking their planes on the ground rather than fighting battles in the air.[footnoteRef:1] Along with Winston Churchill, Trenchard always regarded airpower as an offensive weapon, and very successfully so in desert countries like Iraq, even with 1920s technology. From these early experiences the RAF derived the lesson that bombing or the threat of bombing would be sufficient to control a country, even in the absence of large ground forces.[footnoteRef:2] Douhet's and Trenchard's strategic bombing concepts also became the "Bible' of the U.S. Army Air Corps in the 1920s and 1930s, thanks in part to Mitchell's strong public advocacy, especially as the German Lutwaffe was being rapidly revived after 1933. According to Raymond Flugel, instructors Air Corps Tactical School (ACTS) were already familiar with the ideas of Douhet and Trenchard by the early-1920s, especially because these were transmitted via Billy Mitchell.[footnoteRef:3] Even so, critics like Bernard Brodie, who claimed that tactical airpower had actually proven far more successful and valuable than strategic bombing, pointed out that Douhet had also overestimated the damage caused by bombing, at least prior to the development of nuclear weapons and smart bombs.[footnoteRef:4] [1: Giulio Douhet, "Aerial Warfare," in Command of the Air. USAF Warrior Studies (Washington DC: Office of Air Force History, 1983).] [2: Alan Stephen. "The True Believers: Airpower between the Wars." In Alan Stephen (ed), The Wars in the Air: 1914-1994 (Maxwell Air Force Base, AL: Air University Press, 2001), p. 33.] [3: Raymond R. Flugel. United States Air Power Doctrine: A Study of the Influence of William Mitchell and Giulio Douhet at the Air Corps Tactical School, 1921-1935. Ann Arbor, MI University Microfilms International, 1985.] [4: Bernard Brodie, From Crossbow to H-Bomb: The Evolution of the Weapons and Tactics of Warfare (Bloomington: Indiana University Press, 1973).]
Airpower's chief appeal in 1918-39 was its supposed ability to overcome all geographic barriers in a short time and destroy the enemy's ability to wage war. Compared to ground fighting, and the huge casualties in the mostly pointless battles of World War I, air combat was still viewed in mythical or romantic terms. Limited budgets in the 1920s and 1930s affected all the services, and neither Britain nor the U.S. had sufficient numbers of modern bombers and fighters on hand when World War II began in 1939.[footnoteRef:5] British planners were well-aware that they needed bases in France and the Low Countries to mount a Douhet-style air offensive against Germany, and were also rightfully concerned about the great threat to Britain should those bases fall into German hands.[footnoteRef:6] As it turned out, though, Germany lacked the resources to build up a force of heavy strategic bombers, much less a naval air arm, and the Lutwaffe "existed primarily to support land forces," as did the air forces of France, Italy and Russia.[footnoteRef:7] German airpower doctrines started from the premise that the air force would always be used in coordination with ground operations, including bombing of enemy industry, cities and transportation systems. Even the Battle of Britain in 1940 was only waged in anticipation of an invasion that never occurred -- Operation Sea Lion.[footnoteRef:8] [5: Murray A. Williamson, "Strategic Bombing: The British, American, and German Experiences" in Murray A. Williamson and Allan R. Millet (eds) Military Innovation in the Interwar Period (Cambridge University Press, 1996), p. 98.] [6: Williamson, p. 106.] [7: Stephen, p. 53.] [8: Williamson, p. 131.]
In the 1920s and 1930s, airpower theorists began to identify industrial bottlenecks that could cripple the enemy's war production, such as the ball bearing factories and synthetic oil refineries in Germany, which were both heavily bombed by the 8th Air Force in 1943-44. New developments like the B-17 four-engine bombers and the Norden bombsight convinced American air planners that heavy bomber forces could fly above antiaircraft fire and enemy fighters at 25,000 feet or higher. They would not be escorted to their targets, and in any case no fighter aircraft yet existed that had the same range as the heavy bombers. As actual combat experience in World War II demonstrated, however, the interwar planners had underestimated the damage a defending force could inflict on unescorted bombers, particularly with new inventions like radar. Early examples like the Spanish Civil War and the Japanese air war over China also showed that unescorted bombers would suffer unacceptably high losses against an effective enemy air defense. In addition, there were problems with navigation and target identification in bad weather or even locating the correct industries -- assuming they had not been moved underground.[footnoteRef:9] Fighters did advance greatly by the late-1930s, including new single-wing planes like the British Spitfire, while radar improved defensive capabilities. Bombing was not nearly as accurate as Douhet had predicted, with one-third of British bombers unable to even find their targets as late as 1941 while the majority that did were unable to drop their bombs within five miles of the aiming point. These factors, along with the huge losses at the hands of the Luftwaffe fighters, caused Arthur Harris and British Bomber Command to switch to the more controversial strategy of night area bombing (or carpet bombing) of German cities.[footnoteRef:10] Ironically, both Britain and the United States had insisted in the 1920s and 1930s that carpet bombing of civilians violated the international law and the laws of warfare, but in the firebombing of Hamburg, Dresden and Tokyo during World War II these restrictions were completely forgotten. More recent conflicts involving the use of airpower such as the First Gulf War of 1990-91 and the Kosovo War of 1998-99 seem to have vindicated the beliefs of early theorists like Douhet, Trenchard and Mitchell that the independent air arm could win wars on its own, without the help of the army and navy. Needless the say, the other services resented that idea just as much in the 1990s as they had in 1925, when Billy Mitchell was forced out of the army for these provocative ideas. Perhaps the First Gulf War really did represent the "apotheosis of twentieth-century airpower," an officer's war in which aircraft devastated and routed the enemy armies completely, destroyed their morale, and left the ground forces with little to do but accept the surrender.[footnoteRef:11] Certainly ground troops that suffer constant air attacks with no sign of effective defense from their own side may lose morale, although this did not occur in the Korean and Vietnam Wars, or in the more recent guerilla war in Afghanistan. In all of those wars, the U.S. military had complete control of the air from the start and could call in airstrikes at will, yet the enemy's morale did not break…