At two minutes before noon on September 1, 1923, a massive earthquake struck Japan. Centered below Sagami Bay, thirty miles south of Tokyo, and measuring 7.9 on the Richter scale, the first shocks lasted for fourteen seconds. Powerful seismic waves instantly toppled almost every building in the port city of Yokohama, sent a wall of water crashing across the coast of the island of Honshu, and unleashed mudslides that inundated fishing villages and buried inhabitants alive.
But the most horrific phase of one of the twentieth century’s worst natural disasters began minutes later. In densely populated neighborhoods of flimsy wooden houses, charcoal braziers tumbled over, fuel tanks ruptured, combustible chemicals in apothecaries exploded, and high winds fanned the flames through alleys. Within half an hour of the earthquake, 136 fires had erupted in twelve of Tokyo’s fifteen wards. Water mains broke throughout the city, making it impossible for firefighters to douse the flames. The Great Kanto Earthquake and the ensuing conflagration killed 140,000 people, traumatized the country, and set back Japanese industrial production for years.* “The Yokohama and Tokyo disaster,” wrote an editor at the Japan Weekly Chronicle, “did as much damage in twenty-four hours as the warring armies on the Western Front did in four years.”
Two decades later, as battles raged between the US and Japan in the South Pacific, the earthquake loomed large in the minds of Allied war planners. As US forces seized atoll after atoll and advanced to within bomber range of the Japanese mainland, hard-liners advocated a drastic strategy: the indiscriminate firebombing of Japanese cities that would replicate the mass death and destruction of 1923. “The type of bomb concentration discussed is calculated to start sweeping fires in heavily built-up urban areas,” declared an intelligence report in October 1943, “utilizing the combustible materials in Japanese construction as ‘kindling’ for conflagrations capable of destroying factories and other military objectives over wide areas.”
The prospect of widespread firebombing obsessed military planners. In 1944 US Air Force officers even consulted Canadian and British insurance adjusters who had worked in Tokyo at the time of the earthquake, including one who had assisted with the redesign of the city. Incendiary bombs, they calculated, “would destroy 70 per cent of the houses in the six major cities and would result in the estimated death of 560,000 persons.” Apocalyptic destruction of city after city, they believed, would break the will of the Japanese to continue the war.