History: Atomic Bombing Of Hiroshima, Japan

Responsibility for the timing of the second bombing was delegated to Colonel Tibbets as commander of the 509th Composite Group on Tinian. Scheduled for August 11 against Kokura, the raid was moved earlier by two days to avoid a five day period of bad weather forecast to begin on August 10. Three bomb pre-assemblies had been transported to Tinian, labeled F-31, F-32, and F-33 on their exteriors. On August 8, a dress rehearsal was conducted off Tinian by Maj. Charles Sweeney using Bockscar as the drop airplane. Assembly F-33 was expended testing the components and F-31 was designated for the August 9 mission.
Nagasaki
"I realize the tragic significance of the atomic bomb... It is an awful responsibility which has come to us... We thank God that it has come to us, instead of to our enemies; and we pray that He may guide us to use it in His ways and for His purposes." —President Harry S. Truman, August 9, 1945