On the night of March 9, 1945, U.S. warplanes launch a new bombing offensive against Japan, dropping 2,000 tons of incendiary bombs on Tokyo over the course of the next 48 hours. Almost 16 square miles in and around the Japanese capital were incinerated, and between 80,000 and 130,000 Japanese civilians were killed in the worst single firestorm in recorded history.

Early on March 9, Air Force crews met on the Mariana Islands of Tinian and Saipan for a military briefing. They were planning a low-level bombing attack on Tokyo that would begin that evening, but with a twist: Their planes would be stripped of all guns except for the tail turret. The decrease in weight would increase the speed of each Superfortress bomber—and would also increase its bomb load capacity by 65 percent, making each plane able to carry more than seven tons.

Speed would be crucial, and the crews were warned that if they were shot down, all haste was to be made for the water, which would increase their chances of being picked up by American rescue crews. Should they land within Japanese territory, they could only expect the very worst treatment by civilians, as the mission that night was going to entail the deaths of tens of thousands of those very same civilians.

The cluster bombing of the downtown Tokyo suburb of Shitamachi had been approved only a few hours earlier. Shitamachi was composed of roughly 750,000 people living in cramped quarters in wooden-frame buildings. Setting ablaze this “paper city” was a kind of experiment in the effects of firebombing; it would also destroy the light industries, called “shadow factories,” that produced prefabricated war materials destined for Japanese aircraft factories.

The denizens of Shitamachi never had a chance of defending themselves. Their fire brigades were hopelessly undermanned, poorly trained and poorly equipped. At 5:34 p.m., Superfortress B-29 bombers took off from Saipan and Tinian, reaching their target at 12:15 a.m. on March 10. Three hundred and thirty-four bombers, flying at a mere 500 feet, dropped their loads, creating a giant bonfire fanned by 30-knot winds that helped raze Shitamachi and spread the flames throughout Tokyo. Masses of panicked and terrified Japanese civilians scrambled to escape the inferno, most unsuccessfully. The human carnage was so great that the blood-red mists and stench of burning flesh that wafted up sickened the bomber pilots, forcing them to grab oxygen masks to keep from vomiting.

The raid lasted slightly longer than three hours—and continued again the next day. “In the black Sumida River, countless bodies were floating, clothed bodies, naked bodies, all black as charcoal. It was unreal,” recorded one doctor at the scene.