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.
Nagasaki Atomic Bomb Museum
Within the museum is a history of the city before the bomb was dropped. The hypocenter of the explosion was the Urakami district, which was a traditionally rustic and isolated suburb. However, the population soared after the 1920s when the district was chosen as the site for munitions factories. An industrial zone was quickly created. Additionally, the Urakami district was home to the Nagasaki Medical College. When the bomb was dropped at 11:02 A.M. on August 9, 1945, the 20 neighborhoods within a one-kilometer radius of the hypocenter were completely destroyed by the heat flash and blast winds generated by the explosion. They were then reduced to ashes by the fires which followed. Within 2 km of the hypocenter, roughly 80% of the houses collapsed and burned. When the smoke cleared, the area was strewn with corpses.