At 3 PM, on August 4, 1945, Colonel Paul Tibbets began briefing the crew of the B-29 named Enola Gay. In the early morning hours of August 5, the crew made its final preparations. At midnight there was a final briefing. The call sign decided upon was, innocuously, "Dimples." Tibbets finished his talk: "Do your jobs. Follow your orders. Don't cut corners and don't take chances." Then the weather officer passed along last-minute information and the chaplain offered a prayer.

At 2:27 AM on August 6, the engines were started. At 2:45, the Enola Gay took off. She was followed by the Great Artiste, carrying scientific instruments, and No. 91, carrying photographic equipment. At 5:30 AM, just before dawn, Enola Gay circled above Iwo Jima. At 8:15:17 AM, the bomb-bay doors opened and the first atomic bomb fell toward Hiroshima. Sixteen hours later, President Harry S. Truman once again called upon the Japanese to surrender.