On This Day: US Drops Atomic Bomb on Hiroshima

The United States and Japan had been at war since 1941. By 1945, U.S. forces were closing in on the Japanese mainland and launching bombing attacks on Japanese cities.

On July 16, 1945, in the Trinity Test in New Mexico, the U.S. successfully detonated the world’s first atomic bomb. Maj. Gen. Leslie Groves, leader of the Manhattan Project, wrote to the secretary of war that the U.S. “now had the means to insure [the war’s] speedy conclusion and save thousands of American lives.”

Nine days later, on July 25, President Harry S. Truman and fellow Allied leaders, Josef Stalin and Clement Attlee, issued the Potsdam Declaration, an ultimatum for Japan to surrender unconditionally or face “prompt and utter destruction.”

When Japan refused to accept the terms on July 29, Truman authorized the use of the atomic bomb “as soon after August 3 as weather permitted,” which meant that “targeting now simply depended on which city was not obscured by clouds on the day of attack,” according to the U.S. Department of Energy.

The 8,900-pound bomb, called “Little Boy,” was to be carried in a B-29 Superfortress piloted by Col. Paul W. Tibbets, commander of the 509th Operations Group. On Aug. 6, Tibbets and 11 crewmembers took off on the B-29—which the night before had been given the nickname “Enola Gay,” after Tibbets’ mother—from the island of Tinian toward Hiroshima, an industrial city and important military center.

At 8:15 a.m. local time, the Enola Gay dropped Little Boy onto Hiroshima. Just 43 seconds later it exploded 1,900 feet above the city. “Then the brilliant morning sunlight was slashed by a more brilliant white flash. … From the men who had rung up the curtain on a new era in history burst nothing more original than an awed ‘My God!,’” wrote Time.

Nearly five square miles, over 60 percent of the developed city, was destroyed. “All around, I found dead and wounded,” described one Japanese official. “Some were bloated and scorched—such an awesome sight, their legs and bodies stripped of clothes and burned with a huge blister. All green vegetation, from grasses to trees, perished in that period.”

It has been difficult to determine a definitive death toll. Between 70,000 and 80,000 of the more than 340,000 people in the city are believed to have been killed by the initial blast, and many more died in the following weeks and years from injuries and radiation. The official Japanese death toll, calculated a year after the explosion, is 118,661. Other estimates put the number of deaths at more than 140,000, while thousands of other victims have suffered from radiation sickness, cancer and other long-term effects.

The White House put out a press release 16 hours after the blast. In it, Truman demanded that the Japanese leaders accept the terms of the Potsdam Declaration. “If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth,” he said.

The U.S. also dropped leaflets on Japanese cities warning civilians to evacuate. “Act at once or we shall resolutely employ this bomb and all our other superior weapons to promptly and forcefully end the war,” one leaflet stated.

Japan did not immediately accept surrender. On Aug. 9, the U.S. dropped a second atomic bomb, this time on the city of Nagasaki. The B-29 “Bockscar” dropped the bomb “Fat Man,” killing 70,000 to 80,000 people.

That same day, the Soviet Union declared war on the severely weakened Japan. Japanese leaders had no choice but to surrender.

“I cannot bear to see my innocent people suffer any longer,” declared Emperor Hirohito before the Japanese Supreme Council. “Ending the war is the only way to restore world peace and to relieve the nation from the terrible distress with which it is burdened.”

Japan accepted the Potsdam terms and unconditionally surrendered to the United States on Aug. 14, a day known as Victory in Japan, or V-J, Day. It marked the end of World War II.

Japan had allied itself with Nazi Germany and Italy to form the Axis Powers. On Dec. 7, 1941, it bombed a U.S. military base at Pearl Harbor, drawing the U.S. into World War II.

For four years, the U.S. and Japan waged war in the Pacific. By 1945, Japan had begun suffering heavy losses. It lost battles on home islands of Iwo Jima and Okinawa, and American B-29s dropped incendiary bombs on Tokyo, Nagoya, Osaka and Kobe, ravaging the cities.

Reactions to Truman's decision to use the atomic bomb are split. Many consider the bombing cruel and inhumane while others argue that the U.S. government was left with no alternative to end the war.

A feature in The Atlantic analyzes both sides of the story. It highlights Karl T. Compton’s “If the Atomic Bomb Had Not Been Used,” in which he notes “the nuclear explosions killed far fewer people than the firebombings.

Moreover, without the nuclear attacks, the Japanese would not have surrendered, even though they were militarily beaten: ‘I cannot believe,’ he wrote, ‘that, without the atomic bomb, the surrender would have come without a great deal more of costly struggle and bloodshed.’”

Thomas Powers offers a contrasting perspective in “Was It Right?” asking "how could the killing of 100,000 civilians in a day for political purposes ever be considered anything but a crime?" He does admit, however, that "the bombing was cruel … but it ended a greater, longer cruelty.”