Air warfare was a major component of World War II in all theatres and, together with anti-air defense, consumed a large fraction of the industrial output of the major powers. Germany and Japan depended on air forces that were closely integrated with land and naval forces; they downplayed the advantage of fleets of strategic bombers, and were late in appreciating the need to defend against Allied strategic bombing. By contrast, Britain and the United States took an approach that greatly emphasized strategic bombing, and to a lesser degree, tactical control of the battlefield by air, and adequate air defenses. They both built a strategic force of large, long-range bombers that could carry the air war to the enemy's homeland. Simultaneously, they built tactical air forces that could win air superiority over the battlefields, thereby giving vital assistance to ground troops. They both built a powerful naval-air component based on aircraft carriers, as did Japan; these played the central role in the war at sea.
Before 1939 all sides operated under largely theoretical models of air warfare. The Italian theorist Giulio Douhet in the 1920s summarized the faith that airmen during and after World War I developed in the efficacy of strategic bombing. Many said it alone could win wars, as "the bomber will always get through". The Americans were confident that the Boeing B-17 Flying Fortress bomber could reach targets, protected by its own weapons, and bomb, using the Norden bombsight, with "pickle barrel" accuracy. Japanese aviation pioneers felt that they had developed the finest naval aviators in the world.
The Luftwaffe was the German Air Force. The pride of Nazi Germany under its leader Hermann GÃ¶ring, it learned new combat techniques in the Spanish Civil War and was seen by Hitler as the decisive strategic weapon he needed. Its advanced technology and rapid growth led to exaggerated fears in the 1930s that helped to persuade the British and French into appeasement. In the war the Luftwaffe performed well in 1939â€“41, as its Stuka dive bombers terrified enemy infantry units. But the Luftwaffe was poorly coordinated with overall German strategy, and never ramped up to the size and scope needed in a total war. It never built any significant number of large, strategic bombers, having only the troublesome Heinkel He 177 to use for such missions, was deficient in radar, and could not deal with the faster, more agile P-51 Mustang pursuit planes after 1943, or Britain's increasingly lethal defensive fighter screen after the Battle of Britain.
When its fuel supply ran dry in 1944, it was reduced to anti-aircraft flak roles, and many of its men were sent to infantry units. By 1944 it operated 39,000 flak batteries staffed with a million people in uniform, both men and women.
The Luftwaffe lacked the bomber forces for strategic bombing, because it did not think such bombing was worth it. They did attempt some strategic bombing in the east, basically with only having the He 177 for such. Their one success was destroying an airbase at Poltava Air Base, Ukraine, which housed 43 new B-17 bombers and a million tons of aviation fuel.
Introduction of turbojet-powered combat aircraft, mostly with the Messerschmitt Me 262 twin-jet fighter, was pioneered by the Luftwaffe, but the delayed period (1944â€“45) of their introduction meant that they were introduced "too little, too late", as so many other advanced German aircraft designs (and indeed, many other German military weapon systems) had been during the later war years.
Although Germany's allies, especially Italy and Finland, had air forces of their own, there was very little coordination with them. Not until very late in the war did Germany share its blueprints with its ally Japanâ€”too late for Japan to improve its weapons systems or to make synthetic oil.
The British had their own very well-developed theory of strategic bombing, and built the long-range bombers to implement it.
Once it became clear that Germany was a threat, the RAF started on a large expansion with many airfields being setup and the number of squadrons increased. From 42 squadrons with 800 aircraft in 1934, the RAF had reached 157 squadrons and 3,700 aircraft by 1939. They combined the newly developed radar with communications centres to direct their fighter defences. Their medium bombers were capable of reaching the German industrial centre of the Ruhr, and larger bombers were under development.
The RAF underwent rapid expansion following the outbreak of war against Germany in 1939. This included the training in other Commonwealth nations (particularly Canada) of half of British and Commonwealth aircrews, some 167,000 men in all. The RAF also integrated Polish and other airmen who had escaped from Hitler's Europe. In Europe, the RAF was in operational control of Commonwealth aircrews and Commonwealth squadrons although these retained some degree of independence (such as the formation of No. 6 Group RCAF to put Canadian squadrons together in a nationally identifiable unit)
The RAF had three major combat commands based in the United Kingdom: RAF Fighter Command charged with defence of the UK, RAF Bomber Command (formed 1936) which operated the bombers that would be offensive against the enemy, and RAF Coastal Command which was to protect Allied shipping and attack enemy shipping. The Royal Navy's Fleet Air Arm operated land-based fighters in defence of naval establishments and carrier-based aircraft. Later in the war the RAF's fighter force was divided into two Air Defence of Great Britain (ADGB) for protecting the UK and the Second Tactical Air Force for ground offensive support in the North West Europe campaign.
Bomber Command participated in two areas of attack â€“ the strategic bombing campaign against German war production, and the less well known mining of coastal waters off Germany to contain its naval operations and prevent the U-boats from freely operating against Allied shipping. In order to attack German industry by night the RAF developed navigational aids, tactics to overwhelm the German defences control system, tactics directly against German night-fighter forces, target marking techniques, many electronic aids in defence and attack, and supporting electronic warfare aircraft. The production of heavy aircraft competed with resources for the Army and the Navy, and it was a source of disagreement as to whether the effort could be more profitably expended elsewhere.
Before 1944, however, the main German industrial targets were out of range, so the RAF bombers concentrated on military and transportation targets in France and Belgium.
By the end of the war, Soviet annual aircraft production had risen sharply with annual Soviet production peaking at 40,000 aircraft in 1944. Some 157,000 aircraft were produced, of which 126,000 were combat types, while the others were transports and trainers.
During the war the Soviets employed 7500 bombers to drop 30 million bombs on German targets, with a density that sometimes reached 100â€“150 tons/ sq kilometer.
Before the Battle of Pearl Harbor, President Franklin D. Roosevelt gave command of the Navy to an aviator, Admiral Ernest King, with a mandate for an aviation-oriented war in the Pacific. FDR allowed King to build up land-based naval and Marine aviation, and seize control of the long-range bombers used in antisubmarine patrols in the Atlantic. Roosevelt basically agreed with Robert A. Lovett, the civilian Assistant Secretary of War for Air, who argued, "While I don't go so far as to claim that air power alone will win the war, I do claim the war will not be won without it."
Army Chief of Staff George C. Marshall rejected calls for complete independence for the Air Corps, because the land forces generals and the Navy were vehemently opposed. In the compromise that was reached it was understood that after the war the aviators would get their independence. Meanwhile, the Air Corps became the Army Air Forces (AAF) in June, 1941, combining all their personnel and units under a single commanding general, an airman. In 1942 the Army reorganized into three equal components, one of which was the AAF, which then had almost complete freedom in terms of internal administration. Thus the AAF set up its own medical service independent of the Surgeon General, its own WAC units, and its own logistics system. It had full control over the design and procurement of airplanes and related electronic gear and ordnance. Its purchasing agents controlled 15% of the nation's Gross National Product. Together with naval aviation, it recruited the best young men in the nation. General Henry H. Arnold headed the AAF. One of the first military men to fly, and the youngest colonel in World War I, he selected for the most important combat commands men who were ten years younger than their Army counterparts, including Ira Eaker (b. 1896), Jimmy Doolittle (b. 1896), Hoyt Vandenberg (b. 1899), Elwood "Pete" Queseda (b. 1904), and, youngest of them all, Curtis LeMay (b. 1906). Although a West Pointer himself, Arnold did not automatically turn to Academy men for top positions. Since he operated independent of theater commanders, Arnold could and did move his generals around, and speedily removed underachievers.
Aware of the need for engineering expertise, Arnold went outside the military and formed close liaisons with top engineers like rocket specialist Theodore von Karmen at Cal Tech. Arnold was given seats on the US Joint Chiefs of Staff and the US-British Combined Chiefs of Staff. Arnold, however, was officially Deputy Chief of [Army] Staff, so on committees he deferred to his boss, General Marshall. Thus Marshall made all the basic strategic decisions, which were worked out by his "War Plans Division" (WPD, later renamed the Operations Division). WPD's section leaders were infantrymen or engineers, with a handful of aviators in token positions.
The AAF had a newly created planning division, whose advice was largely ignored by WPD. Airmen were also underrepresented in the planning divisions of the Joint Chiefs of Staff and of the Combined Chiefs. Aviators were largely shut out of the decision-making and planning process because they lacked seniority in a highly rank-conscious system. The freeze intensified demands for independence, and fueled a spirit of "proving" the superiority of air power doctrine. Because of the young, pragmatic leadership at top, and the universal glamor accorded aviators, morale in the AAF was strikingly higher than anywhere else (except perhaps Navy aviation.)
The AAF provided extensive technical training, promoted officers and enlisted faster, provided comfortable barracks and good food, and was safe. The only dangerous jobs were voluntary ones as crew of fighters and bombersâ€”or involuntary ones at jungle bases in the Southwest Pacific. Marshall, an infantryman uninterested in aviation before 1939, became a partial convert to air power and allowed the aviators more autonomy. He authorized vast spending on planes, and insisted that American forces had to have air supremacy before taking the offensive. However, he repeatedly overruled Arnold by agreeing with Roosevelt's requests in 1941â€“42 to send half of the new light bombers and fighters to the British and Soviets, thereby delaying the buildup of American air power.
The Army's major theater commands were given to infantrymen Douglas MacArthur and Dwight D. Eisenhower. Neither had paid much attention to aviation before the war (though Ike learned to fly).
Offensive counter-air, to clear the way for strategic bombers and an eventually decisive cross-channel invasion, was a strategic mission led by escort fighters partnered with heavy bombers. The tactical mission, however, was the province of fighter-bombers, assisted by light and medium bombers.
American theater commanders became air power enthusiasts, and built their strategies around the need for tactical air supremacy. MacArthur had been badly defeated in the Philippines in 1941â€“42 primarily because the Japanese controlled the sky. His planes were outnumbered and outclassed, his airfields shot up, his radar destroyed, his supply lines cut. His infantry never had a chance. MacArthur vowed never again. His island hopping campaign was based on the strategy of isolating Japanese strongholds while leaping past them. Each leap was determined by the range of his air force, and the first task on securing an objective was to build an airfield to prepare for the next leap. Eisenhower's deputy at SHAEF was Air Chief Marshal Arthur Tedder who had been commander of the Allied Mediterranean Air Command when Eisenhower was in charge of Allied operations in the Mediterranean.