By the mid-1930s, Air Corps theory centered around strategic bombing—the use of large bombers to destroy specific industrial targets and thereby cripple an opposing army for lack of essential supplies and win a war without a costly ground assault. Not only was such a campaign relatively inexpensive, it also created an argument for air force independence, since this was a mission unique to airpower. The strategic bombing theory entailed a number of corollary assumptions. First was the belief that the bomber would always reach the target. The aircraft envisioned by army leaders were large, fast, and heavily armed. As a result, there was little development of long-range fighter aircraft prior to the war, since escorts were held to be unnecessary. Another assumption involved the denigration of tactical aviation—aircraft used to support the immediate needs of the battlefield. Leaders believed that by tying aircraft to ground forces, airpower lost its unique advantage along with the justification for independence. These ideals were epitomized by Major General Henry "Hap" Arnold, who became chief of the Army Air Corps in October 1938 and held that post throughout the war.
Whatever theory existed, tight budgets and isolationist views in Congress limited the growth of American aviation between the world wars. In 1939, even with war clearly on the horizon, the American aviation industry delivered only 921 aircraft to the U.S. Army and U.S. Navy. Changes quickly ensued following the German invasion of Poland in September 1939. European governments placed large orders with American aircraft firms. And earlier, in November 1938, President Franklin D. Roosevelt, long concerned about the threat posed by Adolf Hitler's Germany had privately expressed a desire for an Air Corps of 20,000 aircraft, but publicly, he sought half that number. At the time, the Air Corps only possessed some 1,600 aircraft. Following the fall of France in May 1940, Roosevelt increased his goal to 50,000 aircraft for the army and navy together.
Despite massive orders, the aviation industry mobilized slowly. By 1941, the Air Corps possessed only 5,500 aircraft, and few matched the performance of their European counterparts. Only in heavy bombers, with the Boeing B-17, did American equipment approach that of Europe. In March 1941, Robert Lovett became assistant secretary of war for air, and he immediately set about increasing U.S. production. Output rose from 12,000 aircraft annually to 96,000 by the end of 1944. Manpower also increased dramatically. From 43,000 personnel in 1939, the number of people serving in the Air Corps rose to 300,000 by December 1941. To meet increased manpower requirements, the Air Corps lowered its standards, but it remained much more difficult to enter the Air Corps than other services.
The organization of the corps also changed with expansion. In 1941, the Air Corps gave way to the U.S. Army Air Forces (USAAF), with Arnold as chief; it was coequal with the Army Ground Forces and the Army Service Forces. In return for greater autonomy, Arnold verbally promised Army Chief of Staff General George C. Marshall, himself a strong supporter of airpower, that he would not seek independent status for the air force for the duration of the war.
Individual theaters each had their own numbered air forces, sometimes further divided by primary mission. For example, the First Air Force remained in New York, provided training, and oversaw the defense of the Northeast region of the United States; the Eighth Air Force served in Great Britain and undertook the strategic bombardment of continental Europe; and the Ninth Air Force, which began in the Mediterranean Theater, moved to Britain in 1943 as a tactical air force for the invasion of France. By the end of the war, there were 16 numbered air forces.
In 1941, to utilize airpower properly, the Air War Plans Division wrote AWPD/1 as an annex to the army's comprehensive plan to defeat the Axis powers. AWPD/1 embodied the tenets of strategic bombardment. It called for 1,060 medium bombers, 3,740 heavy bombers, 3,740 very heavy bombers, and 2,000 fighters to destroy 154 specific industrial targets in Germany—primarily aircraft-manufacturing sites, followed by power plants, the transportation network, and synthetic petroleum plants. In six months, the authors argued, Germany would be unable to resist the Allied armies, and civilian morale would be shattered, making an invasion unnecessary. These attacks were to be carried out in precision daylight strikes.
With the American entrance into the war on 7 December 1941, the USAAF could not immediately launch the kind of offensive action envisioned in AWPD/1. In the Pacific Theater, the Japanese advanced so rapidly that American forces found themselves fighting defensive battles for their very survival. With the American aircraft industry just beginning to gear up, it would take time to deploy the kind of force called for in AWPD/1 to defeat either Japan or Germany.
Major General Carl Spaatz commanded the Eighth Air Force, charged with carrying the air war to Germany. Activated in January 1942, the Eighth did not fly its first mission until 4 July 1942, when American medium bombers joined British aircraft attacking German airfields in the Netherlands. On 17 August 1942, American strategic bombardment began when 12 B-17s attacked the railroad marshaling yard in Rouen, France. That November, the Eighth lost much of its force to the Mediterranean Theater, where Allied troops had invaded North Africa. The North African Campaign provided valuable experience to American airmen. Most important, the Americans learned from the British the value of close cooperation between air and ground forces.
In January 1943, President Roosevelt, British Prime Minister Winston L. S. Churchill, and their respective military staffs met in Casablanca to discuss strategy. Despite British pressure for the USAAF to join the Royal Air Force in its area attacks against German cities at night, the Americans argued for daylight precision strikes, which meant that Germany would be bombed around the clock. From the meeting came a directive for the Combined Bomber Offensive (CBO) that eventually destroyed Germany's industrial base as well as its civilian morale. To accomplish the goals of the CBO, Brigadier General Ira Eaker, the new commander of the Eighth Air Force, oversaw the development of the Pointblank Directive, which called for establishing air supremacy first by using the bomber to attack aircraft-manufacturing plants. To protect themselves from enemy fighters, bombers flew in large box formations that massed defensive firepower. The first large Pointblank raid was against the Schweinfurt ball-bearing works, with a second mission against the Messerschmitt plant at Regensburg. American P-47 fighters had only enough range to escort the bombers to the German border. As a result, the Eighth lost 60 bombers, one-sixth of the attacking force. A second raid in October cost an equal number of bombers during a day referred to as "Black Thursday." The USAAF could not sustain such losses, and American bombers suspended raids deep into Germany until long-range escorts became available. Meanwhile, Arnold questioned the leadership of the Eighth and replaced Eaker, whom he sent to the Mediterranean, with Major General James H. Doolittle. Spaatz returned to England to oversee all American air operations as commander of the U.S. Strategic Air Forces in Europe.
Technical changes improved USAAF performance. By January 1944, external fuel tanks and increased tankage permitted P-47 and P-38 fighters to escort the bombers far into Germany. Finally, P-51 Mustangs began reaching units in Britain; they could escort bombers as far as Berlin.
In February 1944, the Americans launched Operation argument, a coordinated attack on the German aircraft industry by both the Eighth Air Force and the Fifteenth Air Force flying from Italy. "Big Week," 20–25 February 1944, witnessed thousands of sorties. The loss rate was only one-sixth that of the previous year, and U.S. fighter escorts began to take a grievous toll on inexperienced German pilots. In the air battles of 1944, the USAAF gained mastery of Europe's skies not directly through bomb damage but rather through the attrition of German pilots. In March 1944, Spaatz began the systematic bombing of Germany's petroleum industry. German fighters had to defend their source of fuel. Attrition among German aircrews could not be replaced, and the lack of fuel meant replacement pilots had greatly reduced training time. By the date of the Allied invasion of France on 6 June 1944, the German air force could not challenge Allied airpower. The appearance of Germany's jet and rocket fighters, the Me-262 and Me-163, created brief consternation within the USAAF, but these aircraft were too few in number and their pilots were too inexperienced to pose a serious threat.
On the other side of the world, the USAAF provided support for General Douglas MacArthur's ground forces in the southwest Pacific. Initially, the Pacific Theater lacked large industrial targets within range; however, heavy bombers did contribute to the ultimate victory. More important were the medium bombers of the Fifth Air Force commanded by Major General George C. Kenney. Operations tended to be directed against Japanese island garrisons and shipping. To meet the low-level operations found in the theater, Kenney modified many B-25 bombers to carry additional machine guns or cannon in the nose. His pilots also practiced bombing from treetop level using fragmentation bombs slowed by parachutes. Finally, to better strike ships, Kenney's bombers attacked from mast height.
The USAAF also flew missions in the China-Burma-India Theater, although operations there were decidedly of secondary importance. Part of the problem involved logistics. The Japanese controlled all of coastal China as well as Burma. To supply China and the American forces there, the USAAF developed an aerial route over the Himalayas, referred to as "the Hump." By July 1944, despite a slow start, the operation was finally delivering sufficient matériel to meet operational needs, although at a very high cost. In China, Major General Claire Chennault led the Fourteenth Air Force in its efforts to push back the Japanese. Always operating at the limits of supply, his forces enjoyed only moderate success.
By 1944, the U.S. Navy's advance through the Central Pacific included the Mariana Islands. These islands provided bases for the Boeing B-29 Superfortresses then entering service. To ensure the proper use of the new bombers, Arnold maintained operational authority over their employment by controlling the Twentieth Air Force directly from Washington. Though the bombers were initially deployed in India and China, the Marianas proved far superior as bases, and all of the bombers eventually flew from there. But initial efforts to strategically bomb Japan did not fare well. The B-29 was unique in that it was the first aircraft to contend with the jet stream, making bombing accuracy more difficult than normal. Not until January 1945, when Major General Curtis LeMay arrived in the Marianas to improve effectiveness, did the B-29s have a vital impact on Japanese industry. Instead of high-altitude, precision strikes against industrial targets, the B-29s switched to low-altitude, night incendiary attacks against cities. The largely wooden structures in Japan became so much kindling. The most destructive of these raids—and probably the single most destructive raid in the history of air warfare—occurred on the night of 9–10 March 1945, when the B-29s set 16 square miles of Tokyo aflame, killing at least 90,000 people. The destruction of cities peaked on 6 August 1945, when the B-29 Enola Gay dropped the first atomic bomb on Hiroshima. A second atomic bomb fell on Nagasaki three days later.
The U.S. Army Air Forces fought in every theater of World War II, contributing substantially to the Allied victory. As Germany and Japan surrendered, teams from the United States conducted a survey of the exact impact of the bombing. The U.S. Strategic Bombing Survey (USSBS) concluded that airpower had a notable impact on Germany and Japan, yet bombing itself could not have won the war. Aircraft played an integral part in the Allied war-fighting capabilities, making victory possible. The most effective uses of bombing were the systematic assault on the German petroleum industry late in 1944 and the assault against transportation. In the Pacific, to avoid conflict with the navy, the USSBS assessed the USAAF campaign as part of the overall force applied against Japan. The report concluded that the atomic bombs simply compelled Japan's leaders to accept reality.
By the end of the war, the USAAF had taken delivery of some 158,800 aircraft, including 51,221 bombers and 47,050 fighters. A total of 22,948 aircraft were lost in action. During the conflict, the USAAF flew 2,363,800 combat sorties and dropped 2,057,000 tons of bombs, 75 percent of them on Germany. By March 1945, the USAAF had more than 1,831,000 personnel, representing 22.4 percent of the army's total strength. USAAF personnel casualties over the course of the war came to 115,382, including 40,061 dead. Even without the unqualified endorsement of the USSBS, the USAAF had proved its worth, leading to its independence from the army in 1947. Rodney Madison
Craven, Wesley Frank, and James Lea Cate, eds. The Army Air Forces in World War II. Vol. 4, The Pacific: Guadalcanal to Saipan, August 1942 to July 1944. Washington, DC: Office of Air Force History, 1983.; Nalty, Bernard C., John F. Shiner, and George M. Watson. With Courage: The U.S. Army Air Forces in World War II. Washington, DC: Air Force History and Museum Program, 1994.; Perret, Geoffrey. Winged Victory: The Army Air Forces in World War II. New York: Random House, 1993.