Before the atomic bombs, the USA hit Japan with one of the most overlooked (but deadly) campaigns in WW2

The campaign’s planning began in the American West, with a chillingly calculated experiment: the construction and destruction of full-scale mock Japanese homes, designed to test the best way to set them alight and inflict maximum destruction.

“They made model Japanese houses and tried to find out the best way to destroy them by fire,” says historian Richard Overy, author of Rain of Ruin: Tokyo, Hiroshima and the Surrender of Japan, speaking on the HistoryExtra podcast. “Japanese housing was extremely vulnerable and burned very easily. And yes, of course they were thinking of civilians, you’re not thinking about industry or factories: you’re thinking about civilians.”

From precision bombing to incendiary raids

In Europe, the US Army Air Forces had built their strategy around precision daylight bombing – targeting military and industrial sites with the aim of minimising civilian casualties. This approach depended on accuracy, reliable weather and long-range fighter escort, all of which took time to develop. Many assumed the same doctrine would be applied in the Pacific.

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“The initial strategy [was] precise daylight raiding,” explains Overy. But over Japan, precision raids failed for several reasons. Cloud cover often obscured targets, distances stretched aircraft to their limits and Japanese industry was dispersed into small workshops integrated into residential areas. If factories could not be destroyed effectively, the logic shifted: destroy the urban areas themselves.

“Only when that proved impossible,” says Overy, “the strategy shifted to the fire-bombing of Japanese cities.”

The radicalisation of total war

By 1944, the global conflict had entered a phase of extreme brutality. The concept of ‘total war’ – in which the enemy’s civilian population was considered part of the war effort – was now deeply rooted within Allied as well as Axis strategy.

“What that raises is an important point about the radicalisation of strategy. As total war becomes more bitter, even the democracies embrace strategies [that] they would otherwise have rejected before the war started,” Overy says.

In this environment, the firebombing plan that had been tested on model Japanese houses was embraced as a legitimate pathway to winning the war. Destroying homes, and those inside them, was seen as a means of breaking Japan’s capacity and will to fight.

Curtis LeMay takes command

The man chosen to execute this new and indiscriminate strategy was General Curtis LeMay, a bomber commander with experience in the European theatre. By early 1945, US Army Air Forces chief Henry ‘Hap’ Arnold was frustrated with the lack of progress in Japan and wanted someone prepared to deliver decisive results, pushing the war towards an end.

“Arnold thought that LeMay was the man he needed, that he was ruthless enough. If [LeMay] couldn’t bomb in precise raids, he decided to bomb with incendiary raids and see what that would achieve,” Overy explains.

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LeMay abandoned high-altitude bombing in favour of low-level night raids using incendiary cluster munitions. The goal was to create firestorms – blazes so intense they generated their own wind, pulling in oxygen and engulfing entire neighbourhoods.

The first of these mass raids, on Tokyo in March 1945, destroyed 16 square miles of the city and killed an estimated 100,000 people in a single night – more than the immediate death toll at Hiroshima.

An urban apocalypse

Once the incendiary raids began, US commanders considered them a grim success.

“Within five months [they] destroyed 60 per cent of Japan’s urban area,” Overy notes. “They killed a quarter of a million Japanese people, [the] overwhelming majority women, children and old people. 10 million fled to the countryside but it became difficult to feed them.”

Japan was one of the most urbanised societies in the world at the time. So, the destruction didn’t just kill civilians – it wrecked infrastructure, disrupted transport and severed vital supply lines. By the summer of 1945, entire urban areas had been reduced to ash without a single American soldier setting foot in them.

The campaign that history forgot

When the war ended, the moral and political debates that followed largely ignored the firebombing campaign, despite its scale and death toll.

“After the war, all the attention was on the atomic bombs. There was little sense of how deadly and extensive the conventional bombing campaign was,” Overy says.

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The same justification used for the atomic bombs – that they would save American lives by forcing Japan’s surrender – was applied to the firebombing, though it was less publicly discussed.

“The moral argument was that you had to save American lives,” says Overy, explaining the doctrine asserted by President Truman and the leaders of the US military. “Whatever the moral issues, it would save American lives and shorten the war.”

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Forgotten flames

Between March and August 1945, conventional bombing killed more Japanese civilians than the nuclear attacks combined. The decision to target entire urban areas was driven by a calculated strategic plan to destroy the homes and lives of ordinary people.

But today – perhaps due to the looming legacy of nuclear weaponry – the firebombing of Tokyo and other Japanese cities remains overshadowed by Hiroshima and Nagasaki. Yet by the time the Enola Gay took off for its mission on 6 August 1945, the United States had already demonstrated its willingness – and its ability – to obliterate cities, and had tested how best to burn them, well before the age of nuclear warfare truly began.

Richard Overy was speaking to Elinor Evans on the HistoryExtra podcast. Listen to the full conversation.