[colorado tanker]

That's a good question I've wondered about for a while. There are a lot of apocryphal quotes on the Internet by military leaders after the bombs dropped, but very little authoritative about who knew before. According to this article on the Army history website, the Joint Chiefs knew about the bomb, but were not consulted by Truman about whether to drop it. The service secretaries knew and Stimson argued strenuously to use to bomb in hopes of rendering the planned invasion unnecessary.

http://www.history.army.mil/books/70-7_23.htm

[Hebrews 11:6]

Sounds about right. Obviously it was on a need-to-know basis, and the field commanders didn’t make that cut.

[henkster]

LeMay knew well in advance, as early as March 30. Nimitz was briefed at the same time. They had to be briefed about the purpose of the 509th Composite Group. And having been briefed, LeMay was forbidden from flying combat missions.