Pentagon, Washington, D.C. May 31, 1945

On this date in 1945 a special group met in the Pen­ta­gon to search for an alter­na­tive to dropping the atomic bomb on Japan. The group had been called into exis­tence by the new Ameri­can presi­dent, Harry S. Tru­man. Neither Truman nor any­one else in the room knew what kind of damage the still-untested weapon might do.

What the planners thought they knew, how­ever, espe­cially as the fero­city of Japa­nese resis­tance on Oki­nawa became clear, was this: the tally of U.S. and Japa­nese war dead would boggle the mind. As it turned out, at the end of the Oki­nawa cam­paign (April 1 to June 21, 1945) the dead numbered 12,500 Amer­i­cans and 110,000 Japa­nese; the loss in tanks, ships (36 sunk and 368 damaged), air­craft, and other materiel was so severe three-quarters of the way through the cam­paign that poli­tical and mili­tary leaders alike were increas­ingly wary of the end­game costs. The inva­sion of the Japa­nese main islands, or Home Islands, set to begin in November 1945 and end the next April, was pre­dicted to cost as many as one million Allied lives, to say nothing of other losses on both sides. (Though the pre­dic­tion came out after the war had ended, some analysts believed it was too low.)

Six weeks later, on July 16, a huge pre­dawn explo­sion in the New Mexico desert settled the issue. “We have dis­covered the most terri­ble bomb in the his­tory of the world,” Truman wrote in his diary on July 25 while attending the victors’ Potsdam Con­fer­ence out­side the former Nazi capital of Berlin. Three days later, the Japa­nese cabi­net under 77‑year-old Adm. Kantarō Suzuki, having failed to over­come the resis­tance of the over­whelming major­ity of Japa­nese mili­tary offi­cers to the Allies’ final demand for their coun­try’s uncon­di­tional sur­render—the July 26 Pots­dam Dec­la­ra­tion—ignored the ulti­ma­tum, despite its expli­cit warning that the only alter­na­tive would be “prompt and utter destruc­tion.” (The word used in the Japa­nese press for the cabi­net’s non-response, moku­satsu, means “to kill it with silence” (as in silent con­tempt), though one Japa­nese-run news­paper, the Hong Kong News, broke press ranks to blast the Pots­dam Dec­la­ra­tion as a piece of unqual­i­fied impu­dence.) Days before, Truman had con­fided to Soviet dicta­tor Joseph Stalin, who was not offic­i­ally a party to the Pots­dam Declara­tion because his country had not yet declared war on Japan, that the U.S. was pre­pared to use its dooms­day weapon “very soon unless Japan surrenders.”

But the president was concerned about where to use it. Neither Tokyo, or what was left of it, nor the ancient Japa­nese capital of Kyoto was an appro­pri­ate tar­get for nuclear destruc­tion. Truman ordered the Sec­re­tary of War was to find tar­gets with heavy con­cen­tra­tions of mili­tary person­nel and to issue warning state­ments asking the Japa­nese to sur­render to save lives. “I’m sure they will not do that,” he wrote in his private papers, “but we will have given them the chance.”

A short list of suitable targets was devised. Within two weeks Hiro­shima and Naga­saki lay in ruins, not to be the last devas­tated Japa­nese city if the coun­try didn’t surrender, Truman pro­mised its leaders. The most destruc­tive bomb in his­tory killed 120,000 people, brought World War II to an end, and marked the beginning of the atomic age.

Hiroshima, August 1945

U.S. Army poster 1945 Atomic bombing of Hiroshima and Nagasaki: Mission map for the atomic bombings, August 1945

Left: U.S. Army poster prepares the Amer­i­can pub­lic for the in­va­sion of Japan after ending war with Germany and Italy. Presi­dent Truman’s mili­tary chief of staff, Army Gen. George Marshall, esti­mated that the U.S. armed forces would suffer up to one million casual­ties over the next two years trying to take the Japa­nese Home Islands by conven­tional force. Truman was unwilling to sell terms like these to the Amer­i­can public, in spite of likely becoming the object of condem­na­tion in some quarters for ordering the atomic destruction of Japan.

Right: Mission map for the atomic bombings of Hiro­shima and Naga­saki, August 6 (Enola Gay) and August 9, 1945 (Bocks­car). Kokura, on the north­ern tip of the south­ern island of Kyūshū, appears on this map because it was the origi­nal tar­get for August 9. Weather obscured visi­bility over Kokura, so Nagasaki, also on Kyūshū, was chosen instead.

Atomic bombing of Hiroshima and Nagasaki: Warning leaflet dropped over Japanese cities, August 1945 Atomic bombing of Hiroshima and Nagasaki: Atomic cloud over Hiroshima, August 6, 1945

Left: Front and back of leaf­lets urging Japan’s quick sur­render were dropped over the coun­try by the 509th Com­po­site Group, a group that com­prised B‑29 bombers and trans­port air­craft. The 509th was a component of the U.S. Man­hat­tan Pro­ject under the com­mand of Lt. Col. Paul W. Tibbets, Jr. At 2:45 a.m. on August 6, 1945, the Enola Gay departed Tinian in the Mari­ana Islands for Hiro­shima with Tibbets at the con­trols. Flight distance from Tinian to Hiro­shima was just under 1,600 miles, so it took the Enola Gay six hours to reach its desti­nation. The atomic bomb, code­named “Little Boy,” was dropped over the city at 8:15 local time. Tibbets reported that Hiro­shima was covered with a tall mushroom cloud after the bomb was dropped.

Right: Atomic cloud over Hiroshima, August 6, 1945, 8:45 a.m. This photo­graph was found in 2013 at Hon­kawa Ele­men­tary School (now a peace museum) and is believed to have been taken 6 miles east of ground zero (aka hypo­center) about 30 minutes after deto­na­tion. Samples of beach sand four miles and more from Hiro­shima’s hypo­center reveal round, fine glassy shards that were once buildings and other urban-built struc­tures that were swept up in the nuclear blast and fused in incred­i­ble heat before cooling and raining down to earth. Esti­mated to weigh in aggre­gate thou­sands of tons, these tiny spher­u­lar par­ti­cles of the vanished city of Hiro­shima, nick­named “Hiro­shi­maites,” consti­tute up to 2.5 per­cent of the regular sand along the beaches of Hiroshima Bay.

Atomic bombing of Hiroshima and Nagasaki: Hiroshima, September 1945. Genbaku (A-Bomb) Dome in background Atomic bombing of Hiroshima and Nagasaki: Hiroshima, September 1945

Left: Hiroshima, September 1945. In the background the Genba­ku (A-Bomb) Dome, the only struc­ture left standing near ground zero. The building, at the time serving as the Hiro­shima Prefec­tural Indus­trial Pro­mo­tion Hall, later became a part of the Hiro­shima Peace Memo­rial Park, which was desig­nated a UNESCO World Heritage Site in 1996.

Right: Hiroshima, September 1945. Japa­nese off­icials deter­mined that 69 per­cent of Hiro­shima’s buildings were de­stroyed and another 6–7 per­cent were damaged. Out of some 70,000–80,000 peo­ple killed imme­di­ately in the blast and ensuing fire­storm (a conser­va­tive figure), 20,000 were sol­diers, a ratio of mili­tary to civil­ian dead Pre­si­dent Truman had urged (the higher the better) in his directive to Secretary of War Henry L. Simpson. Need­less to say the final tally of Hiro­shima’s dead must include the tens of thou­sands who later succumbed to their horrific injuries and those who perished months and years later from radiation-related sicknesses.

Hiroshima: The Day and the Day After That Day