The Hiroshima Peace Memorial marks the place where the first atomic bomb was dropped on Japan in 1945.

World War II came to an end in August 1945 in the wake of the atomic bombing of two Japanese cities by the United States. Hiroshima was the first city to have an atomic bomb dropped on it, on August 6, 1945. A second bomb was dropped on Nagasaki three days later. The following week, on August 15, 1945, the Japanese emperor announced Japan's intention to surrender to the United States.

The Atomic Bomb

Based on the principle of nuclear fission, the atomic bomb was developed amid high security by the Manhattan Project. The first test, codenamed Trinity, took place in the New Mexico desert on July 16, 1945. It produced an explosive blast equivalent to 21,000 tons of TNT. Less than two weeks after this test, U.S. President Harry S. Truman made the final decision to use the bomb against Japan. A special unit of the U.S Army Air Force, the 509th Composite Group, was already deployed to the Pacific theater in readiness for the atomic mission.

The Target Cities

A number of Japanese cities were selected as suitable targets for atomic bombs. One main criterion was that the city, despite its strategic importance, should not have been previously targeted by conventional bombing raids. The top three cities on the final list were Hiroshima, Kokura and Nagasaki, all in the south of Japan. Hiroshima is close to the southern tip of Honshu, the largest island of the Japanese archipelago. The other two cities are on the smaller island of Kyushu to the south of Honshu.

Dropping the Bomb

The 509th Composite Group's first mission, led by Colonel Paul Tibbets, was flown on August 6, 1945. The bomb was carried by a modified B-29 aircraft that Tibbets had named Enola Gay after his mother. The primary target was Hiroshima because of its military importance, with Kokura as a secondary target if conditions, such as low visibility due to inclement weather, at the first site were unsuitable. The conditions were perfect, however, and the atomic bomb was dropped on Hiroshima at 8.15 a.m. local time.

The primary target for the second mission on August 9 was Kokura, but the visibility there was poor so the bomb was dropped on the secondary target, Nagasaki, instead. Air Force pilot Charles W. Sweeney climbed aboard a B-29 plane for his mission to bomb Nagasaki. Sweeney dropped what was dubbed the Fat Man atomic bomb at noon August 9, 1945. The New York Times, August 8, 1945, ran a front-page story declaring "First Atomic Bomb Dropped on Japan." It also held President Trump's warning of "Rain and Ruin" for foes of the United States. That second bomb that Sweeney dropped culminated in Japan's unconditional surrender.

Hiroshima After the Bomb

The two atomic bombs, first at Hiroshima and Nagasaki three days later, caused enormous devastation, with the instantaneous deaths of tens of thousands of people. Many more died in the ensuing months and years, either from injuries sustained or from the after-effects of radiation. In Hiroshima, the only building left standing near the center of the explosion at the time was the Prefectural Industrial Promotion Hall, which was renamed the Hiroshima Peace Memorial and is now a UNESCO World Heritage Site. In the years since the war, however, both Hiroshima and Nagasaki have been rebuilt from the ground up and are once more large, thriving cities.