Nagasaki was destroyed by a plutonium atomic bomb seventy five years ago, on August 9, 1945. Called “Fat Man,” it was the same design that had been tested in the New Mexico desert less than a month before, spreading intense radioactive fallout over a wide area. A day before, on August 8, 1945, the Soviet Union had declared war on Japan, having been neutral until then. Japanese wartime leaders had been divided about surrender for weeks; now, facing a two-front war, the debate became more urgent and intense. Susan Southard’s account of the debate in the Japanese councils of war notes that “the news of the second atomic bombing bombing had no apparent impact on their deliberations [on August 9], which, according to notes from their meeting continued throughout the day and with no further mention of Nagasaki.” The specter of occupation by the Soviets and the hopelessness of the two-front war seem to have decided the Emperor of Japan that very night to signal a surrender to the United States, which duly happened on August 15, 1945. This much seems well-supported by the facts; despite that the controversy rages. What is even less debated is the timing of the use of the bombs and the targeting of Japan. In a blog post three days ago, I recounted, once again, that the decision to not target Germany and, instead, to orient the bomb to the Pacific theater had been taken on May 5, 1943, more than two years before Hiroshima and Nagasaki were destroyed. The bombs were used as soon as they were ready and the weather permitted — August 6 and 9. On August 9, Nagasaki was not even the intended target; it was Kokura, but there were too many clouds over that city. So Nagasaki, a secondary target that had already been bombed with more mundane explosives, had the atomic misfortune instead. The main targets were cities that had deliberately been spared conventional bombing; the object was to measure the impact of the atomic bomb with as much scientific precision as possible. Prior...