Chicago, Illinois · July 3, 1945

On this date in 1945 Hungarian-born physicist and inven­tor Leó Szilárd drafted the first of two ver­sions of a peti­tion to Presi­dent Harry S. Tru­man, urging him not to use the atomic bomb on Japan before that nation had been given a chance to sur­render. It was Szilárd who, in 1933, had con­ceived the nuclear chain reaction and patented the idea of a nuclear reactor with Italian-born Enrico Fermi. And it was Szilárd who, in July 1939, wrote the letter for Albert Ein­stein’s signa­ture that resulted in the Manhattan Project, which built the atomic bomb.

By 1945, how­ever, Szilárd was firmly con­vinced that using a nuclear wea­pon on Japan would carry the world further down a path of ruth­less­ness that began with Ger­many raining bombs on Polish and British cities in the early days of the war. In reaction to the final ver­sion of the peti­tion, signed and dated July 17, 1945, by 70 leading scien­tists who were in­volved in the atomic bomb research pro­ject, Brig. Gen. Leslie Groves, the director of the $2 billion-plus Man­hat­tan Pro­ject, unsuc­cess­fully sought evi­dence of Szilárd vio­lating the U.S. Espi­o­nage Act. Most of the signers were punished by losing their jobs in weapons work.

In the mean­time, on August 6, 1945, a specially modi­fied B‑29 Super­for­tress named Enola Gay dropped the first of two atomic bombs on Japan, “Little Boy,” a five‑ton bomb of which less than a kilo­gram under­went nuclear fis­sion. Yet “Little Boy” pro­duced enough energy to kill more than 90,000 cit­i­zens of Hiro­shima out­right and in­jure over 37,000, many of whom would die later from the effects of radi­a­tion poisoning. Three days later Bocks­car, another modified B‑29, exploded a second atomic bomb, “Fat Man,” over Na­ga­saki, 260 miles to the south, killing 40,000–75,000 peo­ple. By the end of 1945 total deaths in Na­ga­saki may have reached 80,000. Both atomic bombs de­stroyed 50 per­cent of each city. In­deed, an esti­mated 40 per­cent of Japan’s built-up cities were devas­tated in U.S. air attacks in 1944–1945.

On August 14, 1945, when Emperor Hiro­hito (post­humously referred to as Emperor Shōwa) announced to the Imperial Council his per­sonal deci­sion to accept the Allies’ terms for Japan’s uncon­di­tional sur­render, World War II was suddenly over—a war that had engaged the U.S. for three years and eight months and had killed 405,399 Americans and wounded 670,846.

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Dawn of the Atomic Age: Hiroshima and Nagasaki, August 6 and 9, 1945

Mushroom clouds over Hiroshima and Nagasaki, August 1945

Left: At the time this photo was made, August 6, 1945, a column of radio­active smoke billowed 20,000 feet above Hiro­shima while smoke from the burst spread over 10,000 feet from the base of the rising column. Bad weather dis­quali­fied a tar­get because scientists insisted on a visual delivery of the atomic bomb. The pri­mary bombing tar­get on August 6 was Hiro­shima. Secondary and ter­tiary targets were Ko­kura and Naga­saki, respectively.

Right: Atomic bombing of secondary target Naga­saki, August 9, 1945. Cloud cover over Kokura, the pri­mary target that day, inhibited a visual attack. A last-minute break in the clouds over Naga­saki doomed that city. The next day, August 10, Tokyo pro­tested the cata­clys­mic bombings in a letter to the U.S. govern­ment via the Swiss embassy.

Hiroshima before August 6, 1945, bombingHiroshima after August 6, 1945, bombing

Left: Hiroshima, a metropolis of 300,000 people before the August 6, 1945, bombing. Area around ground zero. 1,000 ft circles.

Right: Hiroshima after its devastation. Area around ground zero. 1,000 ft circles.

“A Tale of Two Cities”: 1946 U.S. War Department Film Documents Hiro­shima’s and Naga­saki’s Destruction