World War II began in 1939 with the invasion of Poland, the bombing of its major cities, and the immediate destruction of the Polish air force by the German Luftwaffe (airforce). In 1940 the defeat of Denmark, Norway, Holland, Belgium, and France was effected partly through air support. The Battle of Britain, in August-September 1940, concluded with the RAF Fighter Command fighting off the Luftwaffe. Strategic bombing efforts to destroy British factories and civilian morale had failed. The entry of the United States into the war began with the Japanese carrier-borne aircraft attacks on Pearl Harbor and the Philippines. Such attacks quickly destroyed most American land-based combat aircraft in the Pacific.
In the European theater of operations, air-defense systems in England were greatly aided by the development of radar to guide interception, as well as by the inability of German fighter planes to escort their bombers because of low fuel capacity. The development of night-fighter systems by the Germans did not begin until after British night bombers began large-scale raids on Germany, such as the 1000-plane raid over Cologne in May 1942. At the same time, American bombers were carrying out early daylight attacks on specific industrial and military targets. This Combined Bomber Offensive included the costly Ploesti mission of August 1, 1943 (planes launched from Africa to bomb Romanian oil fields) and the Regensburg-Schweinfurt mission of August 17 (the first large-scale American attack on Germany, launched from bases in England). American losses in these and other offensives were heavy until 1944, when long-range P-47 and P-51 escort fighters became available and made it possible for bombers to reach sites deep within Germany in relative safety. The Allies then gained air superiority by destroying German aircraft and aircraft-production facilities. On D-Day (June 6, 1944), Allied air superiority permitted only a few sorties by the Luftwaffe against land invasion forces.
German developments, however, indicated the future of air warfare. Their V-1, or buzz bomb, a pilotless jet-propelled plane carrying 907 kg (2,000 lb) of explosives, was directed against England in June 1944. The V-2, a true guided missile capable of carrying 748 kg (1,650 lb) of explosives some 320 km (200 mi), was launched in September 1944. These attacks came too late to affect the final outcome of the war, as did the failure of the Germans to use the Me 262 as a jet fighter until 1945.
In the early days of the war, the China-Burma-India theater was the site of the efforts of the American Volunteer Group, better known as the Flying Tigers. After the Japanese conquest of Burma (now known as Myanmar), supply flights from India to China over the Himalayas were as important as combat efforts. Bases in China later served in launching bombing operations against Japan.
In the Pacific theater, the Battle of Midway in June 1942 was a great victory for American carrier-based naval air power. The battles for the Gilbert, Marshall, and Mariana islands eventually provided bases for bomber attacks on Japan. The Japanese had not developed strong air defenses at home, and the use of the Boeing B-29 Superfortress, starting in 1944, caught them unprepared to detect bombers or to coordinate army and navy efforts. On March 9, 1945, a massive incendiary raid destroyed about one-fourth of the buildings in Tokyo, and on August 6, the B-29 Enola Gay dropped the first atomic bomb on Hiroshima.
The use of air power resulted in the defeat of Japan without an invasion and indicated to some that, in a future general war, ultimate defeat or victory could be determined by air battles. Some 20 years later, in 1967, this was demonstrated in the Six-Day War between the Arabs and Israel, which was decided in the first three hours when the Arab forces lost 452 aircraft.