He was training to invade Japan when the first A-bomb was dropped.
He was completely thrilled about the atomic bomb!
My own impression is that US military and political leaders feared that Japan and/or Germany might have built several nuclear weapons and would use them against the USA mainland via submarine or other secret methods.
My uncle was with the Air Force and was some sort of tech guy (radios, radar?) and was on Iwo Jima a couple days after they landed trying to get the runways going.
“Wow? Just two days?”
“Yeah - but the Marines had cleared all the Japs out. Well, sometimes they would snipe at us from the other side of the runway, but they were lousy shots.”
He stayed in that line of work and worked with NASA, etc.