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.

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