The officially recognized campaign “Air Offensive, Japan” extended from April 17, 1942, the day before the Doolittle raid on Tokyo, to September 2, 1945, the day the war ended. Although the Doolittle raid—a small raid by later standards, but a tremendous psychological shock to the Japanese—opened the air offensive, no more attacks on Japan occurred until 1944. Part of an overall effort intended to prepare for the invasion of Japan scheduled for November 1945, the air offensive against Japan was conducted by B-29 Superfortress long-range heavy bombers of the U.S. Army Air Forces (USAAF) 20th and 21st Bomber Commands from June 5, 1944, to the end of the war. The air offensive, which the Japanese could not effectively contest, devastated Japan through destruction of arms and armament factories, widespread incendiary bombardment of cities and urban areas, and the mining of Japanese waters. Culminating finally in the loosing of two atomic bombs, the air offensive contributed greatly to the surrender ending World War II. Conducted at first from bases in India, and later from the Mariana Islands in the Pacific, the air offensive featured a number of innovations. Originally intended to be conducted according to the theory of high-altitude daylight precision strategic bombardment developed by senior USAAF officers before the war, the air offensive evolved as it encountered problems of a type and scope never before experienced in aerial warfare. The immense distances of the theater of operations in which the B-29 fought placed a premium on aircraft—and aircrew— performance. The B-29s had to climb over the highest mountains in the world, the Himalayas. High-speed, high-altitude “jetstream” winds over Japan blew planes and bombs off course. Frequent poor weather prevented precision bombardment.
The B-29 Superfortress represented a challenge in and of itself. Based on cutting-edge technology, the B-29 featured the most powerful engines, (Wright R-3350 radials of 2,200 horsepower each, yet adapted for any production bomber); an innovative, centrally controlled defensive machine-gun fire system; and a pressurized cabin. Rushed into production, the plane brought to combat technical problems that normally would have been worked out during a prolonged testing and development period. Among other problems, the B-29’s engines were fireprone, and its clear plastic gun-sighting blisters often blew out.
USAAF officers, both in the field and back in Washington, created solutions to which the B-29 and its aircrews proved remarkably adaptable. Thousands of technical fixes were made; new maintenance methods were introduced; and bombing altitudes were lowered to get away from the jetstream. Night area incendiary bombardment of Japanese cities— less affected by bad weather than daylight precision bombardment—increased the air offensive’s effect.
The idea of a bombing offensive against Japan extended as far back as the beginnings of the U.S. rivalry with Japan early in the century. Both the Japanese and the Americans realized that Japanese urban areas, built largely of wood, were vulnerable to bombardment, whether from aircraft or ship. As prewar discussions evolved into strategies and tactics on how to fight a possible war with Japan, the idea of a long-range heavy bomber grew. A number of U.S. Army Air Corps career officers advocated strategic bombardment to reduce or even eliminate an enemy’s warmaking capacity through destruction of arms and munitions factories. As war clouds gathered, the United States began arming itself for a role in the fighting in Europe as well as against Japan. Although a number of state-of-the-art bombing planes were under development, the chief of the Army Air Corps, General H. H. Arnold, solicited bids from aircraft manufacturers that called for an aircraft to redefine that state.
Two serious prototypes were considered: Boeing’s B-29 and Consolidated Aircraft’s B- 32. Eventually settling on the B-29, Arnold, a strategic bombardment proponent, ordered the aircraft while it was still in blueprints—a highly unusual move for an industry accustomed to careful testing of new designs. This caused the B-29, and Arnold, many headaches in the days ahead. Nonetheless, he felt he could not afford to wait for normal development to wend its way to completion; the enemy certainly would not. (The B-32 was placed in limited production as a backup in case the B-29’s problems became overwhelming.) Arnold pushed the program, although there were setbacks. On February 18, 1943, famed Boeing test pilot Eddie Allen was killed when his B-29 crashed into downtown Seattle as a result of engine fires.
In early 1943, after much discussion reflecting interservice and theater rivalries, Arnold ordered 20th Bomber Command (20 BC) activated. To avoid intra-theater rivalries over command and control of the B-29 bombing force, the Joint Chiefs of Staff agreed that the 20th would be under their direct control, with General Arnold as their “executive agent.” This unusual arrangement was another innovation by the pragmatic Arnold to overcome obstacles and objections and to ensure the success of U.S. air-power. Arnold in turn appointed General K.B.Wolfe, who had been heading up B-29 development, to command the 20th.
Determining that Germany was already practically defeated, Allied leadership at the Trident Conference in Washington (May 12–27, 1943) earmarked the B-29 for use against the Japanese. Initial plans called for the planes to be based in China to reinforce the alliance with Chiang Kai-shek. Lack of success in the ground war in China meant that bases were not available in range of seaports which could supply the vast amounts of fuel, bombs, and parts needed by the B-29s. General Joseph Stilwell, the theater commander, suggested basing the B-29s in India—far out of the planes’ range of Japan— instead of China. The planes would shuttle through airfields in the Cheng-tu area of China, which was held by friendly forces, and then refuel and take off for Japan. Far from roads or seaports, these airfields would have to be supplied entirely by air. Inasmuch as competing demands such as the Fourteenth Air Force, based in the Cheng-tu area, stretched air transport resources razor thin, the B-29s themselves would have to fly in the gasoline they needed to refuel for the long flight to Japan. Although any such operations would be difficult at best, the Joint Chiefs eventually approved this method, and General Arnold in September 1943 directed General Wolfe to work up a plan—Operation Matterhorn—for bombing Japan from bases in India, after shuttling through China. General Wolfe ordered that bases be constructed in India and China.
Concurrently, USAAF planners—General Heywood S. Hansell, in particular—noticed that B-29 operations out of India would never be easy and recommended that the Mariana Islands be seized from the Japanese. Consisting of three principal islands (Guam, Tinian, and Saipan), the Marianas were located in the central Pacific ocean within B-29 range of Japan. They enjoyed good weather and could be supplied easily. A longtime U.S. possession, Guam had been garrisoned by marines before the war. The navy, which viewed the islands as important bases for the invasion of Japan, concurred. The nascent bombardment campaign received further impetus in November when General Hansell managed to convince the Joint Chiefs of Staff to issue a position paper at the Sextant Conference in Cairo, admitting the possibility that heavy bombardment and sea mining might win the war without the necessity of an invasion.
Logistics, command, the war itself, and such local difficulties as labor and weather delayed completion of the B-29 bases in India and China. Finding no progress as late as January 1944, General Wolfe borrowed the 853d Engineer Aviation Battalion and the 382d Engineer Construction Battalion from Stilwell’s Ledo Road project, and he also drafted civilians. After two months, 6,000 U.S. troops and 27,000 Indian laborers had the bases in India ready for B-29s. In China, civilians pulled large rollers by hand to tamp down B-29 runways.
Pushing aside studies telling him that the B-29 force might not see action until 1947, and under pressure to reinforce the alliance with Chiang Kai-shek, Arnold ordered that the first group of B-29s fly to India by April 1944. To make the deadline, he pulled mechanics from Boeing’s Wichita assembly line to help ready the first 100 bombers, which he found awaiting repair during a March 9–10 personal inspection at Smoky Hill Army Airfield, near Wichita, Kansas. Working around the clock in cold and snow, mechanics readied enough planes that they could begin leaving for India on March 26, barely three weeks later. Flying over Africa and the Mideast, the first B-29 landed at Kharagpur, about seventy miles west of Calcutta, India, on April 2, 1944. By May 8, there were 130 planes in India; two days later, the bases in China were deemed ready. The 20th’s first mission was not to Japan but from India directly to Japanese-held Thailand, on June 5, 1944, to give the new crews some experience. Sixteen of the hundred bombers scheduled for the mission turned back or were lost because of mechanical problems; clouds prevented formation flying and also forced some forty-eight of the seventy-seven planes that hit the target area to bomb by radar. Bombing results were poor. Although the mission was deemed an “operational success,” the 20th soon learned that problems experienced on this first B-29 operation would characterize later missions.
Impatient with such “training” missions, General Arnold insisted that Wolfe bomb Japan itself. Tactically, he wanted Wolfe to assist Chiang Kai-shek, by taking the heat off Japan’s offensive in China, and to cover an “important operation in the Pacific”: the invasion of Saipan. Wolfe planned a mission to the Imperial Iron and Steel Works at Yawata in northern Kyushu. The B-29s began stocking Chengtu-area shuttle airfields with fuel, flying over the Himalayas and dodging bad weather and Japanese interceptors—a routine they soon termed “flying the Hump.” Each B-29 had to complete roughly six flights over the Hump to accumulate enough fuel in China to fly a bombing mission over Japan. The task complete, on June 15, U.S. forces invaded Saipan; the 20th flew to the Imperial Iron and Steel Works.
Arnold had wanted the mission to fit U.S. bombing doctrine by being flown at high altitude, by daylight, in tight formation. Believing this took more experience than his crews had, Wolfe won a concession from Arnold: The mission would fly at night, with no formations, from medium altitudes of 8,000 to 18,000 feet. Sixty-eight planes of the original ninety-two made it over Japan, and the rest were turned back by mechanical problems. Bombing accuracy was poor. Despite positive stories in the press, General Arnold made some changes.
On July 4, 1944, Arnold promoted Wolfe to head B-29 development and production at USAAF Materiel Command. He replaced him with the Eighth Air Force’s General Curtis E.LeMay. Innovative and imaginative, LeMay did everything he could—in all facets of a unit, from the quality of the food, to aircraft maintenance, to training, to formation flying—to obtain the optimal results from each bombing mission, at first as the head of the famed 305 BG (H) and later of the 3d Air Division, with the Eighth Air Force in England. Operation Matterhorn’s difficulties were tailor-made for his talents. Arriving on August 29, LeMay instituted his training, maintenance, and formation systems. Performance improved but was still short of General Arnold’s expectations. Just weeks before LeMay’s arrival, Guam and Tinian fell to U.S. forces, and Seabee bulldozers began the massive air-fields needed for the huge B-29 forces.
Limited success on repeated missions to Anshan on September 8 (the 20th’s first mission since LeMay’s arrival) and on September 26 generated pressure in Washington for the USAAF to try different tactics. Arnold’s strategists tinkered with the target mixture, concentrating less on steel than on aircraft assembly plants; and in response to repeated suggestions by naval officers they ordered the B-29s to mine waters in Japanese-held areas. Eventually the 58th Bomb Wing dropped 987 mines between August 1944 and March 1945. Discussions also returned to the firebombing of urban areas, rather than the high-explosive precision bombardment of industrial targets.
October and November 1944 saw heartening if limited progress on a number of fronts. Ranging from Formosa to Japan, the 20th’s bombing improved, as LeMay’s crews concentrated on his tactics of formation flying, fuel economy, the “lead crew” concept he had brought from Europe, and “synchronous” bombing (in which the radar operator and the bombardier, with his optical bombsight, worked together to increase bombing accuracy even if clouds hid the target). On November 5, fifty B-29s flew 4,000 miles round trip from India to put the King George VI graving docks out of commission for three months at the Japanese-occupied naval base at Singapore. Ground crews took advantage of maintenance methods brought by LeMay, such as the sharing of technical specialties among units. Modifications to the R-3350 engine increased its reliability. The number of bombers that had to drop out of missions with mechanical problems decreased. The 73d Bomb Wing of the 21st Bomber Command established the air offensive in the Marianas with the first B-29—flown by 21st commander, Brigadier General Hansell, the strategist who had recommended taking the Marianas—arriving at newly constructed airfields on Saipan on October 12. The primary targets would be aircraft and engine assembly plants centered in Tokyo, Nagoya, and Osaka. After briefly training on a few such nearby targets as the great Japanese base on Truk, the 21st, under pressure to produce results, sent 110 bombers to the Mushashino engine plant in Tokyo on November 24. The mission was flown at high altitude, according to precision daylight bombing doctrine, but unexpected high winds and clouds arose. Only twenty-four bombers accurately hit the target, seventeen aborted because of mechanical failures, and six others did not bomb. The 21st Bomber Command had expected more than five hundred Japanese aircraft to oppose the B-29s; about a hundred actually did, bringing down a single B-29 and damaging eight others. Nonetheless, conditions encountered by the 21st on its first mission characterized, and frustrated, its operations for the next month. The B-29 and the air offensive were not living up to their promise. General Arnold decided once again to make changes to improve the B-29’s effectiveness.
In January, Arnold returned General Hansell to Washington; LeMay replaced him as head of 21 BC. LeMay privately thought, as did Hansell, that the B-29s could end the war without landings in Japan, although he continued the official strategy of preparation for an invasion. Despite the improvements in aircraft dependability and aircrew proficiency that had begun under Hansell and were continued by LeMay’s techniques, high winds and clouds continued to hamper accurate high-altitude daylight precision bombing on the sixteen missions LeMay sent to Japan after taking command of 20 BC. Trying to avoid winds and clouds, LeMay noted that Arnold’s strategists had once again turned to area incendiary attacks. Theoretically, area incendiary attacks would encounter the same problems as daylight precision attacks. Soon it became apparent to him, and to the strategists advising General Arnold and the Joint Chiefs of Staff, that success would mean changes to hallowed daylight precision strategic bombardment doctrine.
While LeMay pondered changes to 21 BC’s techniques, B-29 units continued to arrive. Under Brigadier General Thomas S. Power, 314 BW arrived in Guam in February. Iwo Jima, a volcanic island between the Marianas and Japan, was invaded on February 19, to eliminate Japanese fighter interceptions of B-29s from there, and to provide an emergency landing strip for combat-damaged B-29s. Taking of the tiny island would result in fewer ditchings and fewer men lost at sea.
Pushing aside concerns, Arnold ordered a maximum-effort mission to Tokyo for February 25, experimenting with the new firebomb technique. Bad weather forced the B- 29s to bomb from 25,000 feet, about 5,000 feet lower than usual; of the 231 aircraft which flew, clouds covering the target forced 172 to bomb by radar. Despite high hopes, results did not measurably improve. However, mulling over reconnaissance photographs revealing a square mile of the city burned out, LeMay hypothesized that the slightly lower bombing altitude helped to concentrate the firebombs in that area. Consulting with Washington, he changed the air offensive’s direction, discarding long-held tenets of daylight precision strategic bombardment. Navigating and sighting by radar, B-29s would drop firebombs on cities at night, from low altitude. The wind would not blow away planes and bombs; engines would not burn out; weather would not hide targets; and range would increase, increasing the B-29’s bomb load. It took considerable courage for the strategists in Washington to discard the tenets of their own doctrine. Auspiciously, the first B-29 landed on Iwo Jima on March 4. Area destruction was to replace “precision” bombing, and over the next several months several hundred thousand Japanese civilians were about to be incinerated.
Although Washington and 21 BC developed the new tactics in concert, General LeMay took responsibility for their success or failure. Expecting little or no fighter opposition on low-altitude night missions, he ordered all but the tail guns removed from the heavily armed B-29s. The planes would fly singly, instead of in formation, to avoid collisions. With careful training, LeMay taught even the least adept radar navigators how to get to the target. On March 9, 1945, the first firebomb mission went to Tokyo, where 325 planes bombed from 4,900 to 9,200 feet. After so many months of futile attempts and incremental improvement, the results were astounding: 15.8 square miles were burned out in the center of the city, including 25 percent of the city’s buildings. Official figures listed 83,793 people killed and 40,918 injured—many horribly burned. The Tokyo fire raid remains the worst single aerial bombardment in history. Only fourteen USAAF aircraft were lost.
Capitalizing on this success, 21 BC flew five more such missions in ten days, going on March 11 to Nagoya and on March 13 to Osaka, where 8 square miles were burned out. On March 16 Kobe was the target, and on March 19 it was Nagoya once again— exhausting the supply of firebombs in the Marianas and temporarily ending the incendiary offensive. The results of this week’s work were deemed, finally, successful. Almost sixteen hundred bomber flights had delivered 9,373 tons of bombs, which had burned out almost thirty-two square miles of Japanese cities. Washington prepared a list of thirty-three urban areas which had a concentration of heavy industry. Other types of bombing would continue; nighttime low-level area attacks would be mounted in weather not suitable for daylight precision bombardment.
While LeMay instituted a war-winning strategy in the Pacific, General Ramey’s 58 BW wrapped up Operation Matterhorn with a night attack on a oil-tank farm on Bakum Island, near Singapore, on March 29, and prepared to move to the Marianas. Despite the experience gained in operating the B-29 and working out some of its problems, and despite the support given to the Chinese and their pathfinding role in the air offensive against Japan, the official air force history deemed Matterhorn’s ten-month efforts a failure. If there were any successes, they were expensive.
Aerial mining of Japanese waters began as well, after much persistence by both U.S. Navy and USAAF proponents. Drawing on the experiences of 58 BW, the specially trained and equipped 313 BW, commanded by Brigadier General John J. Davies, flew the mining missions. The first mission, on March 27, 1945, mined the key bottleneck Shimonoseki Strait between Honshu and Kyushu. Soon, combined with submarine warfare, the mining caused imports of desperately needed food and supplies to drop tremendously.
On April 13, the B-29s, loaded with incendiary bombs straight from newly arrived cargo ships, burned out an other 11 square miles of Tokyo in the first firebomb raid since March 19. Kawasaki and Yokohoma were hit on April 15. At that point, despite misgivings of USAAF leadership, the 21st ceased strategic bombardment in favor of tactical support of the invasion of Okinawa. The navy credited B-29 poundings of kamikaze airfields with abatement of that danger to the fleet.
With 58 BW’s arrival in the Marianas, Arnold pulled together 20 BC and 21 BC under the Twentieth Air Force, with LeMay in charge as before. On May 14 and 16, released from Okinawa support, the 20th flew daylight incendiary precision attacks to the Mitsubishi engine factory in Nagoya. The bombers firebombed Tokyo on May 23 and again, for the last time, on May 25. The last raid, by more than five hundred B-29 s, burned out 16 square miles. A growing Japanese antiaircraft capability brought down twenty-six B-29s and damaged another hundred. At the end of May, P-51 Mustang fighter planes, based on Iwo Jima, began escorting the B-29s. Ominously, 509 Composite BG under the command of Lieutenant Colonel Paul Tibbetts Jr., began moving into North Field, on Tinian.
After mid-June, LeMay’s photo interpreters reported all of Japan’s larger cities burned out (except for those “reserved” for the atomic bomb, or for other reasons). While daylight precision strikes continued against industrial targets during clear weather, the B- 29s firebombed some fifty smaller cities between June 17 and August 14. The 20th completed its growth, with 315 BW flying its first mission on June 26. Commanded by General Frank Armstrong of European theater Eight Air Force fame, the B-29s of the 315th were equipped with Eagle radar, developed specifically for bombardment. The 315th’s mission was night bombardment of petroleum industry targets. Throughout the summer it dropped 9,000 tons of high explosives, losing just four aircraft, and completed the destruction of the already critical industry.
Portentous developments characterized July 1945. Scientists successfully test-detonated the atomic bomb at Alamogordo, New Mexico, on July 16. The Potsdam Conference on July 26 called for unconditional surrender of Japan; the alternative was “prompt and utter destruction.” To demonstrate to the Japanese their helplessness to prevent bombing, General LeMay began dropping warning leaflets—actually giving the date of the attack—on targets before sending B-29s.
As invasion preparations stepped up, Fifth and Seventh Air Forces fighters and bombers which had fought their way up the southwest and central Pacific theaters, respectively, joined the air offensive in early July. Flying from newly captured Okinawa, by the end of the war they had dropped 7,100 tons of bombs on airfields, railroads, bridges, and industrial and urban targets.
August 1945 brought into clear focus the massive strategic and tactical forces being brought to bear on Japan in preparation for the November invasion, Operation Olympic. General Spaatz officially assumed command of the U.S. Strategic Air Forces, Pacific. LeMay became his chief of staff; Lieutenant General Nathan F. Twining, late of the Fifteenth Air Force in Italy, assumed command of the Twentieth Air Force. Under Lieutenant General James H. Doolittle, the mighty Eighth Air Force began moving from England to Okinawa. The air offensive continued as B-29s wiped out 99.5 percent of Toyama on August 1. A week later, on August 6, the 509th dropped the first atomic bomb—code-named Little Boy—on Hiroshima.
Spaatz sent incendiary-filled bombers to Yawata and Fukuyama on August 8, as Fat Man, the second atomic bomb, took shape on Tinian. On August 9, Fat Man was detonated over Nagasaki. Giving the Japanese a chance to surrender, the 20th waited until August 14 before fire-bombing Kumagaya and Isezaki. Aircraft similarly loaded were recalled the next day upon word of Japan’s surrender. The air offensive came to an end, without an invasion of Japan.
Although the air offensive forestalled an invasion that would have been costly to both sides, it also left a troubling legacy. While night area incendiary bombardment helped to cripple Japanese military and industrial capabilities, it also took the lives of many noncombatant civilians. The bombardment of cities and the use of nuclear weapons have been surrounded by controversy ever since the fateful days of their use over Japan in August 1945.
FURTHER READINGS
Birdsall, Steve. Superfortress: The Boeing B-29 (1980).
Coffey, Thomas M. Hap: The Story of the U.S. Air Force and the Man Who Built It, General Henry H. “Hap” Arnold (1982).
Craven, Wesley F., and James Lea Cate, eds. The Army Air Forces in World War II, vol. 5, The Pacific: Matterhorn to Nagasaki, June 1944 to August 1945 (1953); vol. 6, Men and Planes (1955).
Hallion, Richard P. “Prelude to Armageddon,” Air Power History 42 (1995).
Jablonski, Edward. Air War: An Illustrated History of Air Power in the Second World War, vol. 2, Outraged Skies/ Wings of Fire (1971).
LeMay, Curtis E., with MacKinlay Kantor. Mission with Lemay: My Story (1965).
Maurer, Maurer. World War II Combat Squadrons of the United States Air Force: The Official Military Record of Every Active Squadron (1969).
Wheeler, Keith. Bombers over Japan: World War II (1982).
Werrell, Kenneth P. Blankets of Fire: U.S. Bombers over Japan during World War II (1992).
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