In April-July 1945 Japanese forces inflicted Allied casualties totaling nearly half those suffered in three full years of war in the Pacific.  In late July, Japan’s militarist government rejected the Potsdam Declaration demanding unconditional surrender or total destruction. For the new U.S. president Harry S. Truman, the Empire of Japan appeared ever more deadly when faced with defeat.

General Douglas MacArthur, along with General Dwight Eisenhower, some Manhattan Project scientists and senior U.S. military commanders recommended a continuation of conventional bombing followed by a massive invasion of mainland Japan. Informed that the invasion would cost up to a million U.S. Casualties, President Truman opted to use the atomic bomb, hoping to conclude the war swiftly.

Hiroshima, a manufacturing center of some 350,000 people located about 500 miles west of Tokyo, was selected as the first target.

Hiroshima before the atomic bombing

On Tinian island, a ~ 9,000-pound uranium-235 bomb was loaded aboard a modified B-29 bomber named Enola Gay (named after the mother of its pilot, USAAF Colonel Paul Tibbets.

At 08:45 in the morning on August 6, 1945, the Enola Gay dropped “Little Boy,” the world’s first deployed atomic bomb over the city of Hiroshima.

Parachuting down, the bomb exploded 2,000 feet above the city with a blast equal to 12-15,000 tons of TNT. 90% of the city (five square miles) was destroyed and 80,000 people were killed instantly; tens of thousands died later from radiation exposure.

A Reporter at Large  New Yorker Magazine ~ August 31, 1946 Issue

Hiroshima  – Open link to read the entire story
By John Hersey

source: history.com