On August 6, 1945, a B-29 Superfortress bomber, the “Enola Gay,” dropped an atomic bomb on Hiroshima, Japan. There days later, Nagasaki was the target of a second atomic bomb. On August 15, after years of war and following the recent withdrawal of the Soviet Union from a Japan-Soviet non-aggression pact, Japan agreed to surrender unconditionally. During the war, Lieutenant General Leslie R. Groves served as the military commander of the Manhattan Project, the massive $2 billion “top secret” project to develop the atomic bomb. The paper examines the bombing of Hiroshima and Nagasaki through declassified archival report by Prof. Bunsaku Arakatsu.