Charles Sweeney
Poor bombing visibility and an increasingly critical fuel shortage eventually forced "Bockscar" to divert from Kokura and attack the secondary target, Nagasaki. As they approached Nagasaki, the heart of the city's downtown was covered by dense cloud, and Sweeney and the plane's weaponeer, Commander Ashworth, initially decided to bomb Nagasaki using radar. However, a small opening in the clouds allowed "Bockscar's" bombardier to verify the target as Nagasaki. As the crew had been ordered to drop the bomb visually if possible, Sweeney decided to proceed with a visual bomb run. "Bockscar" then dropped "Fat Man", with a blast yield equivalent to 21 kilotons of TNT. It exploded 43 seconds later at above the ground, at least northwest of the planned aim point. The failure to drop "Fat Man" at the precise bomb aim point caused the atomic blast to be confined to the Urakami Valley. As a consequence, a major portion of the city was protected by the intervening hills, and only 60% of Nagasaki was destroyed. The bombing also severed the Mitsubishi arms production extensively and killed an estimated 35,000-40,000 people outright, including 23,200-28,200 Japanese industrial workers, 2,000 Korean slave laborers, and 150 Japanese soldiers.
Hiroshima
On Monday, August 6, 1945, at 8:15 a.m., the nuclear weapon "Little Boy" was dropped on Hiroshima from an American Boeing B-29 Superfortress, the "Enola Gay", flown by Colonel Paul Tibbets, directly killing an estimated 70,000 people, including 20,000 Japanese combatants and 2,000 Korean slave laborers. By the end of the year, injury and radiation brought the total number of deaths to 90,000–166,000. The population before the bombing was around 340,000 to 350,000. About 70% of the city's buildings were destroyed, and another 7% severely damaged.