Boeing B-29 Superfortress

Even before the United States entered the war, the Army Air Corps had asked for something no one had yet built: a bomber that could carry a heavy load across the vast distances of the Pacific and strike an enemy from bases far out of reach of his fighters. Boeing’s answer, the Model 345, became the B-29 Superfortress — the most ambitious aircraft programme of the war.

It was also the most expensive. Developing and building the B-29 cost the United States around three billion dollars — more than the Manhattan Project that built the atomic bomb it would one day carry. The prototype first flew on 21 September 1942, but the aircraft was so far ahead of existing technology that it reached the front still riddled with problems, rushed into service by the sheer strategic need to bring the war home to Japan.

The Superfortress was a generation beyond any bomber then flying. It had a pressurised cabin that let its crew work in shirtsleeves at altitudes where B-17 crews froze behind oxygen masks; a smooth, high-aspect-ratio wing for long range; and a defensive system of remote-controlled gun turrets aimed through a central, computer-directed fire-control system rather than by hand. It carried up to twelve .50-calibre machine guns and, early on, a 20 mm tail cannon.

All of this rode on four Wright R-3350 radials of some 2,200 hp each — and there lay the aircraft’s great weakness. The big, tightly cowled engines ran hot and were dangerously prone to catching fire, their magnesium crankcases able to burn through a wing spar in minutes. In the B-29’s first year, engine failures and fires killed more crews than the enemy did. It was a magnificent machine balanced on the edge of its own technology.

The B-29 went to war in June 1944 under Operation Matterhorn, flying from bases in India staged forward through China to strike the Japanese home islands. The first raid, against the steelworks at Yawata on 15 June 1944, marked the first attack on Japan since the Doolittle raid of 1942 — a strategic statement more than a military success.

The logistics were crushing. Every ton of fuel and bombs had to be flown over the Himalayan “Hump” to the Chinese airfields, so the Superfortresses spent more effort supplying themselves than bombing the enemy. Results were meagre, losses to accidents high, and it soon became clear that China could never be the base from which Japan was broken. The answer lay in the Pacific.

The capture of the Mariana Islands — Saipan, Tinian and Guam — in the summer of 1944 gave the B-29 the bases it needed: island airfields within round-trip range of Tokyo, supplied by sea. From November 1944 the Superfortresses flew against Japan in growing strength, the first raid on Tokyo on 24 November 1944 opening a campaign that would grind on to the war’s end.

But the high-altitude precision bombing doctrine carried over from Europe failed over Japan. At nearly 9,000 m the bombers ran into the jet stream — winds of over 200 km/h that scattered their bombs for miles — while cloud hid the targets and the temperamental engines strained in the thin air. After months of effort the daylight precision campaign had achieved very little. Something had to change.

The change came with Major General Curtis LeMay, who took over the campaign and made a radical decision. He stripped the guns and gunners from his B-29s, filled them with incendiaries, and sent them in at night, at low level, against the wood-and-paper cities of Japan. It abandoned every principle of the self-defending high-altitude bomber — and it was devastatingly effective.

On the night of 9–10 March 1945, some 330 Superfortresses burned the heart out of Tokyo in a firestorm that killed on the order of 100,000 people and left a million homeless — the single most destructive air raid in history, deadlier in its immediate toll than either atomic bomb. Over the months that followed, the fire raids consumed the centres of more than 60 Japanese cities, systematically destroying the country’s urban industry.

The B-29’s final act gave it a place in history unlike any other aircraft. A specially modified fleet of stripped-down Superfortresses — the “Silverplate” aircraft — was prepared to carry the atomic bomb. On 6 August 1945 the B-29 Enola Gay dropped the first atomic weapon used in war on Hiroshima; three days later Bockscar destroyed Nagasaki.

Within days Japan surrendered. Whatever the long argument over the decision, the aircraft that delivered those weapons — and that had already burned Japan’s cities for five months — was the instrument through which the Pacific war was brought to its end. No other bomber has ever carried so heavy a historical weight.

The Boeing B-29 Superfortress was the most advanced bomber of the Second World War and, arguably, its most consequential aircraft. It solved problems — pressurisation, remote fire control, intercontinental reach — that pointed straight to the post-war age, and around 3,970 were built despite the staggering cost and the trouble that dogged its development.

Its shadow stretched far beyond 1945. The Soviet Union copied three interned examples almost bolt-for-bolt to create the Tupolev Tu-4, launching its own strategic bomber force; the airframe evolved into tankers and the B-50, and the type flew on into the Korean War. But the B-29 is remembered above all for what it did in the summer of 1945: the aircraft that ended one war and, in the same moment, opened the atomic age.

• Kenneth P. Werrell, Blankets of Fire: U.S. Bombers over Japan during World War II (Smithsonian Institution Press).
• Barrett Tillman, Whirlwind: The Air War Against Japan 1942–1945 (Simon & Schuster).
• Steve Birdsall, Saga of the Superfortress (Doubleday).
• Richard B. Frank, Downfall: The End of the Imperial Japanese Empire (Penguin).