The world is now marking the 75th anniversary of the atomic bombing of Hiroshima, Japan, on Aug. 6, 1945, and of Nagasaki three days later. Naturally, much of our attention is riveted on the first — and last — atomic bombs dropped during wartime. But don’t forget the aircraft that delivered them. The B-29 Superfortress was the biggest and deadliest aircraft in the biggest and deadliest war in history. No B-29, no Hiroshima: No other bomber had the range or capacity to deliver the atomic bomb.

After World War II, the propeller-driven B-29 would be rendered obsolete by the advent of jet aircraft such as the B-52 Stratofortress. So it is easy to forget how revolutionary, costly and important it was — and how the B-29’s brutal employment had already made the mass killing of Japanese civilians from the air seem routine well before the atomic bombs were dropped. (I told the story in my 2006 book, “War Made New: Technology, Warfare and the Course of History, 1500 to Today.”)

“The B-29,” wrote historian Eric Larrabee, “was the greatest U.S. gamble of the war — greater even than the atom bomb ($3 billion invested, as opposed to $2 billion for the bomb, on a similar absence of hard evidence).” The Very Long-Range Bomber project, which eventually produced the B-29, was launched a few months after Germany’s invasion of Poland in 1939 and rushed through development and production in record time. The first prototype B-29 rolled off the Boeing assembly line on Sept. 11, 1942. By war’s end, 3,432 would be produced.

With a wingspan nearly as wide as a football field, a tail fin as tall as a three-story building, a plexiglass cockpit, and a metallic silver fuselage, the B-29 looked sleek and futuristic. Powered by four mighty engines, it had a range of 5,800 miles and a bomb load of 10 tons, which made it the perfect weapon to strike Japan across the vast expanse of the Pacific.

It was not only the first combat plane with a pressurized cabin for its 10 crew members. It also had a state of the art system from General Electric that allowed gunners to remotely fire its .50-caliber machine guns, a Norden bombsight that employed an analog computer to calculate a bomb’s optimal release point, and the most advanced radar installed on any airplane to date. To keep a B-29 running required 150 electric motors powered by seven generators and connected by 11 miles of wiring.

Since the B-29 was an experimental aircraft, it underwent major upgrades after it left the factory. The final push to get it ready came during a harsh winter in early 1944 at “modification centers” spread across the Kansas plains, with mechanics braving the cold in high-altitude flight suits. The first aircraft were ready to go at the end of March 1944.

The B-29s weren’t deployed in Europe, where the shorter-range B-17s and B-24s were already pulverizing Germany. They were needed to hit Japan, but initial attempts to launch them from China failed; those bases were too far from their targets and too difficult to supply over the Himalayas. By the fall of 1944, the aircraft were operating from the newly liberated Northern Mariana Islands — Guam, Tinian and Saipan — but their high-altitude bombing from 20,000 to 30,000 feet was not producing much damage. The B-29s became effective killing machines only when a new commander, Maj. Gen. Curtis LeMay, decided to brave enemy fire by flying low at just 5,000 to 8,000 feet to deliver a new incendiary known as napalm on Japan’s wood-constructed cities.

The aircrews were afraid they were going to be slaughtered when they were sent to bomb Tokyo on March 9, 1945, but they were the ones who did the slaughtering. Their napalm bombs whipped up a firestorm that destroyed much of central Tokyo and killed some 100,000 people — fewer than at Hiroshima (roughly 130,000 dead) but more than at Nagasaki (more than 60,000 dead). Descriptions of the firebombing of Tokyo are as revolting as those of the atomic bombing of Hiroshima; even the aircrews were sickened by the smell of roasting human flesh.

The B-29s went on to target more than 60 of Japan’s largest cities in similar fashion. They laid waste to 178 square miles — nearly three times the size of Washington, D.C. — and only 3.5 percent of the total area damage was inflicted by the atom bombs. If President Harry S. Truman was not overly troubled by the decision to use the atomic bomb, it was in part because he realized that the U.S. Army Air Forces had already been killing German and Japanese civilians en masse. It would not have mattered much to the average Japanese whether death came from atomic or napalm bombs. The major difference is that while it took 334 B-29s to demolish central Tokyo, only one B-29 was needed over Hiroshima and Nagasaki.

“I suppose if I had lost the war, I would have been tried as a war criminal,” LeMay later said. The United States won the war, but only by displaying a willingness to kill civilians from the air on a scale unmatched in history. The B-29 was a technological marvel and a war-winning weapon but at a terrible cost. The B-29 was the original “weapon of mass destruction.”

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