LONDON (AFP) — Britain considered attacking Tokyo with chemical weapons almost a year before the US bombardments that ended World War II in Asia, declassified records revealed on Friday.
The records at the National Archives, which have remained hidden from public view for 65 years, revealed clear proposals to use gas on civilians in 1944.
Although the plan was never put into operation, a detailed memorandum laid out measures to ensure any attack would have the most devastating impact possible.
A Chemical Board note marked "secret" and signed by E.E. Haddon, Secretary, stated: "In his report on his discussions in America... Major General Goldnoy suggested that it might be worthwhile attempting to assess the probable effects of a C.W. (chemical weapons) bombing attack on Tokyo.
"Particulars of the population and layout and photographs of typical buildings and areas in Tokyo were kindly provided by the Director of Military Intelligence, War Office and those have now been studied by Professor Brunt."
Blunt, in a memorandum attached to the document, suggested the initial bombardments should take place in areas of densely packed buildings, using incendiaries "sufficient to set the large areas involved on fire."
Once the inflammable buildings of the Japanese capital have been destroyed, he suggested, a gas attack on the "more modern type of streets" could begin.
However, Blunt warned the military planners that the city's layout could present obstacles to chemical warfare.
"In the densely built areas of Japanese-type buildings, where the streets are narrow, the flow of a gas cloud would be hindered by the narrowness of the streets," he wrote.
The memorandum recommended attacking during the summer season because it said a cold winter could reduce the impact of mustard gas, although heavy rainfall was also highlighted as possibly leading to decontamination.
The memorandum concluded: "Persistent danger from mustard would only be achievable in the intervals between the summer rains."
The document also said "very large numbers of small bombs" would be necessary in densely populated parts of the city.
Phosgene, mustard and incendiaries are all put forward as possible options.
"If mustard were used and it produced the effect of driving the population away from the densely built areas, attack with incendiaries should follow a few days later," it said.
Mark Dunton, Contemporary History Specialist at the National Archives, said: "What is interesting about this file is that it shows we could have been ahead of America in our thinking.
"It seems shocking to modern eyes that the attempt to assess the effect of a chemical gas attack on civilians is described in such an objective way - the pressures of war brought their own terrible logic."
The United States dropped nuclear bombs on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, killing more than 210,000 people.
Less than a week after the Nagasaki attack, Japan surrendered, ending World War II.
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