The United States entered World War II deficient in doctrine, technology, and force structure. Because the United States had an Army Air Corps rather than an independent air force, over the interwar era the doctrinal pronouncements of the Army Air Corps (which became the Army Air Forces [AAF] in 1941) stressed the subordination of aviation forces to the service’s ground commanders. This drove development of “O”-prefixed spotter aircraft and “A”-prefixed attack aircraft, intended for battlefield air operations. “B”-prefixed bombers were intended for interdiction strikes against lines of communications, supply points, and the like. “P”-prefixed (for “pursuit”) fighters were intended for defensive operations, including destroying enemy observation, attack, and bomber aircraft and protecting the operations of friendly aircraft. The Army Air Corps made a small investment in aerial resupply, logistical support, and medical evacuation, acquiring military derivatives of American civil air transports (such as the DC-3, which became the C-47). By Pearl Harbor, the AAF had approximately 125 modern transports, the core of a force that would expand almost sixtyfold over the next three years.

The Technical and Industrial Dimensions

Watching the remarkable development of American civil aviation, army and naval airmen increasingly championed applying this design (and performance) revolution to the Air Corps’ own force structure, necessarily affecting both doctrine and combat capabilities. Largely through the Air Corps Tactical School (predecessor of today’s Air University) at Maxwell Field (now Maxwell Air Force Base [AFB]), they argued vigorously for a more offensive and strategic view of airpower, exemplified by the drive to produce long-range bombers capable of striking at any enemy threatening American possessions or the homeland, or striking deep into the heart of an enemy nation against its leadership, means of production, and war-making capacity. At great effort, they succeeded in forming a so-called GHQ Air Force that served a vital nurturing function for America’s wartime strategic bomber force.

While the Navy and Army made commendable progress in two major aircraft types—maritime patrol planes and long-range bombers, typified by the PBY Catalina and B-17 Flying Fortress—progress on other types was less satisfactory. At the time of the Blitzkrieg in 1939, both the Army Air Corps and naval aviation were forces in transition. The Army Air Corps was transitioning from early monoplane fighters such as the P-26, P-35, and P-36 to the P-38, P-39, and P-40; the P-47 and P-51 were yet to come. The Navy was still operating mixed biplane and monoplane Carrier Air Groups—Japan, at the time, had all-monoplane Carrier Air Groups—but was transitioning into the era of the F4F fighter, SBD scout/dive bomber, and TBD torpedo bomber with the F4U fighter in design (and the F6F, like the Army’s P-47 and P-51, still to come). Much as the Air Corps rejected operating in a “support only” role, naval aviators demonstrated using carriers in pairs to achieve maximum effect, operating as a vital strategic and operational striking force with torpedo planes and dive bombers. In this, the U.S. Navy had greater insight and operational boldness than the Royal Navy (which had evolved the first aircraft carriers) though less than the Imperial Japanese Navy, as was sadly evident on the morning of December 7, 1941.

On the eve of Pearl Harbor, the United States possessed tremendous innate productive and training capacity as well as a mastery of relevant military technologies largely reflecting the dual-use civil-military industrial base developed over the previous fifteen years. While each of the major combatants in Europe and Asia at that time—France, Germany, Great Britain, and Japan—had larger aviation workforces than the United States, America’s was arguably the most highly trained and most sophisticated in employing mass production techniques. Its productivity exploded, with aircraft production doubling between 1939 and 1940, and doubling again by the end of 1941, when it reached 26,277, of which 19,433 were military airplanes. Between the outbreak of war in Europe and the Japanese attack on Pearl Harbor, the United States began to serve as a major weapons supplier to the Allies; by mid-August 1940 Great Britain had already placed orders for 20,000 American airplanes and 42,000 engines. After Pearl Harbor the industry expanded further, adding new plants and distributing production among multiple facilities.

Confronting Flawed Doctrinal and Operational Assumptions

Overconfidence, flawed prewar assumptions, and inept leadership caused problems that were largely resolved by the end of 1943. The military services did not profit as much as might be expected from having studied air operations in the Spanish Civil War (1936–39), the Sino-Japanese War (1937–45), and the Battle of Britain (1940). All afforded important lessons that were largely missed, in large measure because these conflicts did not conform to expectations of what planners considered “real” air war.

The Battle of Britain offers a particularly disturbing case of valuable lessons missed, for Air Corps observers were present on scene throughout. While recognizing by mid-September 1940 that the Royal Air Force was winning, the observers tended to dismiss its outcome, one then-planner astonishingly writing afterward that “concrete ‘lessons’ simply did not materialize.” Three missed lessons proved particularly costly: the value of comprehensive radar coverage, the vulnerability of unsupported bombers, and the need for longer-ranging fighters to protect bombers. Missing the first helped ensure the success of Japan’s attack at Pearl Harbor. Missing the second and third led to the high bomber loss rates over Germany in the late summer and fall of 1943, pending changes in fighter strategy and introduction of the new long-range P-51.

For America, 1942 constituted a year of holding off the Axis and positioning forces for sustained combat in the Pacific and Europe. The Pearl Harbor attack and the loss of Wake, Guam, and the Philippines shattered prewar illusions of any innate superiority of American airmen over their Japanese counterparts. The Doolittle raid on Tokyo in April 1942 set an important standard for future joint operations as well as demonstrated to the Japanese that the Home Islands were not immune from attack. Hard-won U.S. victories at Coral Sea in May and Midway in June halted Japan’s advance, eliminated many of its prewar cadre of trained naval aviators, and rendered easier the establishment of footholds in the Solomons from whence America began its Pacific counteroffensive. Japanese forces landed in the Aleutian Islands, triggering a year-long war in which American and Canadian airmen faced greater challenges from the bitter environmental conditions (including blizzards, fogs, and winds) than from enemy action. In the European theater, the AAF built up both its strategic bombing and fighter forces; not until mid-1943 were American air forces in Great Britain ready to significantly participate in the European air war.

Joint service sea-air-land invasions of the Solomons in August 1942 and North Africa in November 1942 marked the beginnings of two major campaigns: in the Pacific against Japan, and in North Africa against German and Italian forces then already retreating toward Tunisia. The two campaigns had very different but highly significant outcomes. Fighting in the Solomons resulted in establishment of a true joint air command with responsibilities shared among Navy, Marine, and AAF units. Nicknamed the “Cactus Air Force,” it secured control of the air over Guadalcanal, extended it more generally over the Solomons, and then used that control to prosecute sea control and anti-access strikes that disrupted and then severed Japanese sea lines of communication, leading to the collapse of Japanese resistance ashore. By early 1943 coalition air operations over the Solomons and over eastern New Guinea had effectively achieved air denial over opposing Japanese forces and Allied airmen were preparing to extend Allied air control more broadly over New Guinea and New Britain.

Air operations in North Africa revealed the bankruptcy of prewar and early wartime air-land operational doctrine, exemplified by FM 1-5, FM 1-10, and FM 31-35, which dictated the control of air forces in support of ground forces. The humiliating defeat of American forces at the Battle of Kasserine in February 1943, where too-restrictive air control procedures had constrained AAF participation, resulted in an immediate review and rewriting of American air doctrine. The new guidance, issued as FM 100-20 “Command and Employment of Air Power,” dramatically reshaped and transformed the nature of relations between the AAF and Army ground forces. FM 100-20 famously declared (using upper-case lettering for startling effect) “LAND POWER AND AIR POWER ARE CO-EQUAL AND INTERDEPENDENT FORCES; NEITHER IS AN AUXILIARY OF THE OTHER.” It stipulated three sequential air priorities: (1) air superiority, (2) air interdiction, and (3) battlefield air support. For the rest of World War II, FM 100-20 governed the employment of AAF airpower, and its historical legacy has influenced profoundly the postwar U.S. Air Force (USAF) to the present.

The year 1943 was the Allies’ year of testing and preparation prior to 1944, the year of great offensives. In the Pacific, the AAF began a comprehensive program of antishipping strikes against Japanese maritime traffic supporting deployed Japanese forces and on supply convoys transporting raw materials from the Dutch East Indies and Southeast Asia to Japan. In the Battle of the Bismarck Sea, a mixed Australian-American attack force sank twelve of sixteen vessels, including all eight transports and four of eight escorting destroyers. It was a signal that Japan, having lost control of the air over the Bismarck Sea, could no longer expect to supply its forces in New Guinea. In the far north 1943 marked the expulsion of Japanese forces from the Aleutians and the beginning of Allied air operations from those islands against the Japanese homeland’s northern flank. At sea the U.S. Navy had made good its losses from Pearl Harbor and the fleet actions of 1942 and now fielded new and powerful fleet carriers of the Essex class; a superb new carrier fighter, the F6F (which “made” more fighter aces than any other American aircraft of any service); and the TBF, an excellent torpedo bomber. Thus, for the Navy in the Pacific, 1943 constituted a period of “working up” prior to the great island campaigns and fleet battles to come in 1944–45. Informed by Ultra signals intelligence, the Navy and AAF prosecuted an extensive antisubmarine campaign in the Atlantic and Caribbean Sea, using a mix of shore-based, long-range maritime patrol bombers (including those of the AAF) and flying boats coupled with small escort carriers deployed in “Hunter-Killer” teams. Overall, the Allied coalition’s antisubmarine air effort effectively won the Battle of the Atlantic in 1943, reducing losses of shipping to levels that, if still unfortunate, were at least tolerable.

In Europe FM 100-20 received its combat test during air operations in the Sicilian campaign, which was also noteworthy for being the first great test of American airborne forces. The latter took heavy losses during the invasion of Sicily from friendly fire, illustrating the need for better command, control, communication, and coordination among joint and combined air, sea, and land forces. The invasion of Italy in September 1943 and the collapse of the Mussolini regime enabled air operations by the 15th Air Force against targets in the Mediterranean theater and across the Alps to Germany, Austria, and various captive nations. Over Germany the 8th Air Force experienced stinging losses in its first deep forays. During the Regensburg-Schweinfurt mission on August 17, 1943, it lost 60 of 346 bombers; Schweinfurt on October 14, 1943, was worse, with 60 lost out of 291. As a consequence, bomber and fighter tactics were reviewed, new leaders—generals Carl Spaatz and James Doolittle—assumed command of the “Mighty Eighth” and its fighter component, fighters were freed from escort and allowed to sweep ahead and to the side of bomber formations to destroy intercepting fighters before they engaged the bombers, and the superlative P-51—having innately long range due to exceptionally streamlined design, jettisonable drop-tanks, and a low-drag wing affording high internal fuel capacity—entered operational service at year’s end, complementing the P-38 and P-47.

The Maturation of American Wartime Airpower and Its Implications

The year 1944 marked the beginning of the liberation of captured territories in Europe and the Pacific. In this year of great invasions, airpower played a crucial role. Protected even on strikes deep into Germany by drop-tank-equipped P-38, P-47, and new P-51 long-range fighters, British and American bomber operations in Europe now reached a full and deadly maturity. During “Big Week” (Operation Argument, February 20–25, 1944) the German fighter force was severely mauled by the new tactic of fighter sweeps, never to recover from the combined loss of increasingly scarce aircraft and skilled airmen. As a consequence, in the buildup to the Normandy invasion on June 6, 1944, the Allies enjoyed not merely air superiority but (as Gen. Dwight Eisenhower told his son) air supremacy.

The liberation of France and the Marianas-Philippines campaign in 1944 marked the apotheosis of American land-based and naval airpower during the war. Afterward the Axis had no chance to reverse the decline in its fortunes, and by early 1945 industrial output in both Germany and Japan had come to a halt. In Europe the Nazis’ “V”-weapon (cruise and ballistic missile) campaign, the introduction of jet fighters and bombers, and the Bulge offensive in December 1944—the latter undertaken in winter precisely to minimize Allied air attacks—could only slow, not stop, the inexorable Allied advance into Germany, an advance undertaken under the protective cover of American and Allied airpower. In the Pacific, the last-ditch kamikaze campaign, while terribly costly in lives lost and shattered and ships lost or damaged, could likewise do little against the massive joint-service, land-based, and maritime airpower forces deployed against the Home Islands. The dropping of two atomic bombs by B-29 bombers on August 6 and 9, 1945, brought the war to a sobering end, launching the atomic era and an uncertain peace that soon created its own challenges and quandaries.

World War II: Observations, Lessons, and Reflections

World War II taught many and varied airpower lessons, of which these constitute some of the more significant.

Overall, World War II marked the ascendency of airpower to a level coequal to land and sea power. While airpower was not superior to either, neither land forces nor sea forces could function effectively without considering the air dimension, both in its offensive and defensive perspectives. At the operational and tactical levels of warfare, air attack had overturned traditional notions of what constituted maneuver warfare, Germany’s Vice Adm. Friedrich Ruge noting immediately after the Normandy invasion that American and British airmen had effectively transformed what constituted “modern type of warfare” by “turning the flank not from the side but from above.” Indeed, one can go further and state that, by early 1943, Britain and the United States had established what effectively constituted a new “Anglo-American” form of warfare, joining traditional surface forces to powerful, robust, and land- and sea-based aviation forces. These forces had the ability to strike with unprecedented power across the levels of warfare, from tactical through strategic, and with power ranging from that of a machine gun through 4,000-pound bombs. In 1945 that would rise into the kilotons with the atomic bomb.

In the aftermath of World War II few argued (and none persuasively) against the establishment of an independent United States Air Force. The most important justification for that transformation was arguably not America’s own wartime experience (impressive though it had been) but, rather, Great Britain’s. British airmen validated the concept of an independent Royal Air Force by their victory in the Battle of Britain. While this battle was at once more complex and nuanced than simply an “airpower victory,” it was nevertheless undeniably a victory made possible by airpower, as was plainly evident to the British citizens in southeastern England during the late summer and fall of 1940. Britain arguably would have lost the battle had it not established an independent air force in 1918. It is impossible to imagine the British Army supporting and funding development of the integrated radar- and telecommunications-based air defense network along Britain’s eastern and southern coast that did so much to save Britain in 1940, let alone establishing Fighter Command with its expensive high-performance aircraft.

After the war, with the tremendous record of the virtually independent AAF around the globe, it was inconceivable that this post–FM 100-20 genie could be put back in a pre-1943 doctrinal “air in support of” bottle. The same was true of the Navy. The days of a battleship-centric force relying on aircraft for “scouting” and fleet protection while seeking the climax of big-gun, battle-line surface combat were over. The airplane and the submarine, the two great progenitors of twentieth-century three-dimensional warfare, had generated a transformation so powerful that it effectively rendered traditional naval surface maneuver forces both dependent upon them and subject to them.

The war highlighted as well the value of air mobility, resupply, transport, and logistical support. In this respect, America possessed more robust air transport forces at the beginning of the war than other combatants, a reflection of the tremendous investment made in the interwar period in civil air transport design. The most emblematic transport aircraft of the war, the Douglas C-47, was a militarized civilian airliner, the DC-3. The United States built upon its prewar accomplishment to develop more capable (i.e., higher capacity and longer range) aircraft such as the C-46 and C-54 (civil DC-4). It likewise became the major supplier of transport aircraft (such as the C-45, C-47, and C-54) to the Allied powers. By 1945 more than two hundred flights per week were crossing the North Atlantic, and within just months after the end of the war “demobilized” transports were appearing in civil service, together with literally thousands of C-47s.

Finally, the war demonstrated that airpower forces required the same extensive investment in science, technology, and industry that had previously characterized the rise of navies (and to a far lesser extent armies), and that they needed to operate according to sound doctrinal principles rooted in a thorough understanding of modern war. Powers that might otherwise have fared far better against their opponents—France, Italy, Japan, and, ultimately, Nazi Germany itself—had been undone by failures to develop comprehensive balanced strengths across all these areas. While all four of these nations had produced some remarkable aircraft, various failures in research and development, acquisition, production, operational concepts, and (common to all four countries) air doctrine led to disaster against enemies that, in some cases, possessed only slight but still critical advantages in these same areas over them.

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