The single A-bomb dropped on Hiroshima on 6th August did an enormous amount of damage and instantly killed about 70,000 to 80,000 people (mostly civilians). The main purpose of the Hiroshima A-bomb was to force Japan to surrender, by acceding to the Potsdam Declaration issued by Britain, China and the USA on 26th July 1945 and which Japan had rejected on 29th July (see full Potsdam Declaration text via a link in the Further Readings below). But no surrender was forthcoming after the Hiroshima bomb and a second bomb (using plutonium as its fissile material and code name “Fat Man”) had been assembled and was ready to be used around 11th August on a second Japanese city. The date for dropping Fat Man was moved up to August 10, then to August 9, to avoid a projected 5 days of bad weather, by General Leslie Groves.  He was overall in charge of the Manhattan Project and could decide on when to drop another A-bomb without consulting further with the President or the Interim Committee (see 30 May entry regarding who was on the Interim Committee and its purposes).

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The B29 bomber carrying Fat Man took off from Tinian Island at 03:47 with Kokura Arsenal as the target, but Kokura was covered in haze so the plane flew to nearby Nagasaki instead. Nagasaki was covered with clouds, but one gap allowed a drop several miles from the intended aim point. At 11:02 (Nagasaki time): Fat Man exploded at 1950 feet near the perimeter of the city, scoring a direct hit on the Mitsubishi Steel and Arms Works. Yield was 19-23 Kton equivalent in TNT. (best estimate was 21 Kt)

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Here is how the “Life” magazine described what the men in other planes saw when the A-bomb exploded over Nagasaki and some hours later:

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“When the [Nagasaki] bomb went off, a flier on another mission 250 miles away saw a huge ball of fiery yellow erupt. Others, nearer at hand, saw a big mushroom of dust and smoke billow darkly up to 20,000 feet, and then the same detached floating head as at Hiroshima. Twelve hours later Nagasaki was a mass of flame, palled by acrid smoke, its pyre still visible to pilots 200 miles away. The bombers reported that black smoke had shot up like a tremendous, ugly waterspout. With grim satisfaction, [physicists] declared that the ‘improved’ second atomic bomb had already made the first one obsolete.” From the article, “War’s Ending,” LIFE magazine, 8/20/1945

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The first American photographer to take photos in post-bombed Hiroshima and Nagasaki was Bernard Hoffman of “Life” magazine, in early September 1945; one of his photos is shown at the top of this entry. A series of his photos and some reports that appeared in “Life” Magazine, are recommended to the reader so you might understand the full horror of the two bombs and can be found in this website: https://www.life.com/history/hiroshima-and-nagasaki-photos-from-the-ruins/

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In the first few weeks after these bombings the only readily available information had been prepared under the auspices of the War Department and under the watchful eye of General Groves. Early reports that the A-bomb would keep killing people long after its blast was over were dismissed by the US military as propaganda. The Allied occupation of Japan, from the end of the war through April 1952, made it easier to censor news reports. For this reason, both the Japanese and the American public were slow to learn of the longer-lasting consequences of this horrible new weapon.

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On the day the bomb was dropped on Hiroshima Truman has been on the U.S.S. Augusta in the north Atlantic, returning from the Potsdam Conference in Germany, and he heard about it from a land-to-sea telegram. Did he have any direct say in the dropping of the 2nd bomb on Nagasaki? Historians Barton J. Bernstein and Martin Sherwin say no, they have argued that if top Washington policymakers had kept tight control of the delivery of the bomb instead of delegating it to General Leslie Groves the attack on Nagasaki could have been avoided. They argue that the combination of the first bomb and the Soviet declaration of war would have been enough to induce Tokyo’s surrender (see 6th August entry too). By contrast, another historian, James Maddox, argues that Nagasaki was necessary so that Japanese “hardliners” could not “minimize the first explosion” or otherwise explain it away. The controversy amongst historians, social scientists and journalists as to whether either bomb was necessary to force Japan to surrender continues to this day. Some more recent analyses can be found in “Further readings” below.

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On 10th August Truman met with various advisers, and members of his cabinet. It is surmised that at some point during the day someone explained to Truman that the bombs had caused mass casualties and the targets had not been purely military ones. We do know that Truman asserted Presidential control and ordered a halt to further atomic bombings. In Secretary of Commerce, Henry Wallace’s notes about the 10th August cabinet meeting he wrote: Truman said he had given orders to stop atomic bombing. He said the thought of wiping out another 100,000 people was too horrible. He didn’t like the idea of killing, as he said, “all those kids”.

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So there was never any other A-bomb dropped on Japan, but many more were made by the Manhattan Project and its succeeding government agencies. Nor have we seen any other nuclear weapons used in war. But these 2 bombs usher in what was to become a Cold War military build-up and eventually the age of weapons of mass destruction.

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Further readings:

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https://www.life.com/history/hiroshima-and-nagasaki-photos-from-the-ruins/

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https://nsarchive2.gwu.edu/nukevault/ebb525-The-Atomic-Bomb-and-the-End-of-World-War-II A Collection of Primary Sources

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https://www.newyorker.com/tech/elements/nagasaki-the-last-bomb   by Alex Wellerstein

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https://historynewsnetwork.org/article/13531 by Barton Bernstein

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J. Samuel Walker, “Prompt and Utter Destruction: Truman and the Use of Atomic Bombs against Japan”, Third Edition (Chapel Hill: University of North Carolina Press, 2016)

Gar Alperovitz, “The Decision to Use the Bomb and the Architecture of an American Myth” (New York: Alfred E. Knopf, 1995)