ON SUNDAY, Hiroshima Day, it will be worth remembering that the decision to drop the world's first combat nuclear weapon on that city appears to have been taken largely by one man. This was not President Harry Truman, but General Leslie Groves, the chief of the Manhattan Project, which built the bomb.

Groves was a tough military bureaucrat, with very little knowledge of the world outside military construction. Against all advice, he wanted to drop not one nuclear weapon on Japan but four, in quick succession, without testing Japanese reaction to the first. Years later, he wrote: "As far as I was concerned, there was no limit to the number of bombs that would be used."