43 Seconds Over Hiroshima: The First Atomic Strike

At 8:15 a.m. on August 6, 1945, Major Thomas W. Ferebee released an atomic bomb from the B-29 *Enola Gay* over Hiroshima, Japan. Forty-three seconds later, *Little Boy* exploded about 1,900 feet above the city, near Shima Hospital. ^[2][3]

The intended visual aiming point was the T-shaped Aioi Bridge. The bomb detonated nearby and tore through central Hiroshima with blast, heat, and radiation. The United States had used an atomic weapon in war for the first time. ^[2][3]

From Tinian to Hiroshima

The *Enola Gay* left North Field on Tinian Island at 2:45 a.m. Colonel Paul W. Tibbets Jr., commander of the 509th Composite Group, piloted the aircraft. Captain William S. Parsons armed the bomb after takeoff, reducing the danger of carrying a fully armed weapon during departure. ^[2][3]

*Little Boy* was a uranium-235 weapon using a gun-type assembly. Its explosive force was roughly equivalent to 15,000 tons of TNT. Unlike the plutonium-based device tested at Trinity in New Mexico on July 16, the uranium weapon had not been tested in a full-scale detonation before the mission. ^[3][4]

Hiroshima had military headquarters, troop facilities, and industrial activity. It had also avoided the extensive conventional bombing that had damaged many other Japanese cities. Those factors made it a target for U.S. planners. But Hiroshima was a city of soldiers, workers, children, patients, and families. ^[2]

Destruction in a Populated City

Near the center of the blast, buildings were destroyed or severely damaged. Fires spread through the city, and the National Archives describes devastation extending more than a mile from the blast area. ^[2]

The dead included people killed by the initial flash and blast, as well as people trapped in fires or injured amid the wreckage. Damage to hospitals, roads, water systems, and medical personnel made rescue and treatment far more difficult.

No exact death toll can be established. Wartime records were destroyed, many victims were never fully identified, and deaths continued after the attack. Estimates place the immediate death toll at roughly 70,000 to 80,000 people. By the end of 1945, deaths from burns, traumatic injuries, and radiation sickness had brought the estimated total to roughly 90,000 to 140,000 or more. ^[2][3]

Radiation made the attack different from the conventional bombing raids that had already killed large numbers of civilians in Japan. People who survived the flash and the blast could become gravely ill afterward. Hiroshima showed that one aircraft and one weapon could devastate a city and leave consequences that continued long after the explosion.

Hiroshima, Nagasaki, and Japan's Surrender

On July 26, the United States, Britain, and China issued the Potsdam Declaration, demanding Japan's surrender and warning of severe destruction if it refused. The declaration did not disclose that the United States possessed an atomic bomb. ^[1][5]

President Harry S. Truman was returning from the Potsdam Conference aboard the USS *Augusta* when he received confirmation that the Hiroshima mission had succeeded. Later that day, the White House released his statement announcing the attack and warning that further strikes could follow. ^[1]

Japan did not surrender immediately. On August 9, the United States dropped a second atomic bomb on Nagasaki. That day, the Soviet Union invaded Japanese-held Manchuria, opening a new front against Japan. ^[5]

On August 15, Emperor Hirohito broadcast Japan's acceptance of the Potsdam terms. Hiroshima, Nagasaki, and the Soviet entry into the war all belonged to the fast-moving crisis that preceded that decision. Historians continue to debate their relative weight, and Hiroshima alone cannot account for Japan's surrender. ^[1][5]

Why the Argument Has Endured

The decision to use the bomb remains contested because military calculation and civilian suffering cannot be separated from one another. Truman's administration publicly argued that the bomb helped avoid an invasion of Japan that could bring severe casualties. ^[1]

Other interpretations place greater emphasis on diplomacy and on the Soviet Union's entry into the war. Declassified records and later scholarship have kept the debate open rather than resolving it into a single explanation. ^[5]

What is not in dispute is the scale of the event. The bomb destroyed much of Hiroshima, killed civilians on a massive scale, and introduced a weapon whose implications reached far beyond the end of World War II. The nuclear age began with the destruction of a city.

Questions Readers Often Ask

Why was Hiroshima selected?

U.S. planners identified Hiroshima as a military headquarters, troop staging area, and industrial center. Its relative lack of earlier conventional bomb damage also made the effects of the atomic weapon easier to observe. The target area nevertheless contained a large civilian population. ^[2]

Was *Little Boy* tested before it was dropped?

No. The Trinity test examined a plutonium implosion device, not the uranium gun-type weapon used at Hiroshima. *Little Boy* was used without a prior full-scale test. ^[3][4]

How many people died in the Hiroshima bombing?

No exact total is possible. Estimates place immediate deaths at about 70,000 to 80,000, with the total by the end of 1945 estimated at roughly 90,000 to 140,000 or more. ^[2][3]

TIMELINE

Key moments

Sources

1. The Decision to Drop the Atomic Bomb — Harry S. Truman Presidential Library and Museum
2. The Atomic Bombing of Hiroshima and Nagasaki — National Archives Museum
3. Manhattan Project: The Atomic Bombing of Hiroshima, August 6, 1945 — U.S. Department of Energy Office of Scientific and Technical Information
4. Little Boy - Hiroshima - August 6, 1945 — Naval History and Heritage Command
5. The Atomic Bomb and the End of World War II — National Security Archive (George Washington University)

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