[wagglebee]

I wonder how long it took for any real understanding of what had hit Hiroshima to permeate the consciousness of the Japanese people as a whole.

I think it probably took weeks or even months. Japan was in ruins and communication was very minimal.

[henkster]

It probably took a few months for the atomic bombs to permeate the national consciousness of Japan as an entire country. The people of Hiroshima and Nagasaki glommed on very quickly; the intense flash of light and heat, the tremendous roar of sound, the massive destruction all spoke of a tremendous power being released. But it wasn't for a week or two afterward that people began dying from lack of an immune system. The intense burst of radiation had destroyed their bone marrow, and without a functioning immune system, the Japanese were defenseless against the onslaught of germs our bodies slough off every day. The loss of platelets caused them to suffer and die from internal hemorrhage.

When those things started happening, the Japanese on the spot knew the full horror of nuclear war. As you wrote, news of that took a while to percolate through the country due to the shattered communications system. But word of mouth travels very quickly about something like this. I would guess that by the end of September, most Japanese knew they had been subjected to a new form of warfare. For all the implications to sink in took much longer, though. Even in the United States and the Soviet Union, it took a while for the full impact to sink in. I'll write more about the Soviet reaction in a few days.

As for the leadership, they were in denial about the bomb for a few days. First, the Japanese weren't exactly sure what the bombs were until their own physicists traveled to Hiroshima. The physicists' first reaction upon seeing Hiroshima from the air was they knew it was an atomic bomb. Their second reaction was amazement that we had actually built one. Their third reaction was that we could not possibly have built more than one. Ironically, that was on August 9, the same day Nagasaki was bombed.

The military leadership, when informed by the physicists what had been used, didn't really understand. They were old men and nuclear physics was simply beyond their comprehension. They thought it was just a really big bomb, and ordinary concrete shelters could provide protection. (I wonder if they also thought they could “duck and cover?”)

Anyway, Field Marshal Sugiyama, whose HQ for the Southern Command was in Hiroshima, was the first among the leadership to grasp the significance of atomic warfare. He had been as ardent a hawk as any in the Japanese leadership; a hardliner for continuing the war. After Hiroshima, he didn't have the stomach for it. He knew there was no defense and the bomb was indeed a “new thing,” a game changer in war. He expressed his opinion at a meeting of the High Command, and I believe his change of heart shocked many of his colleagues, and was instrumental in bringing about the change of attitude among the military such that they could accept the Emperor's command to surrender.