This oral history is adapted from Garrett M. Graff’s book “The Devil Reached Toward the Sky: An Oral History of the Making and Unleashing of the Atomic Bomb,” which published on Tuesday.

Eighty years ago today, on Aug. 6, 1945, a B-29 bomber named the Enola Gay took off from Tinian Island, in the Northern Mariana Islands, for a mission that its flight crew knew would make history. It belonged to the 509th Composite Group, a unit that had been created and trained in secret for some nine months for the sole purpose of dropping the world’s first atomic bomb. In addition to the Enola Gay, which carried the bomb itself, the mission involved several other B-29s, including the weather reconnaissance plane Straight Flush, the camera plane Necessary Evil and the Great Artiste, which carried scientific observers from Project Alberta, the forward-deployed science component of the Manhattan Project. The Enola Gay’s commander and lead pilot for the mission, Col. Paul W. Tibbets, was barely 30 years old. Though Tibbets had known the secret of the Manhattan Project since its start, many of the Enola Gay crew learned the phrase “atomic bomb” only when they gathered for the August mission itself.