Derek Lyons wrote:

The Pentagon 'decided' to obey the President, who ordered that the initial
group of astronauts come from the services. (The DoDs interest in space
comes somewhat later.)

Sorry, the bracketed remark is incorrect. Both the USAF's X-15 and MISS (Main
in Space Soonest) projects pre-date both the formation of NASA and the
selection of the Original 7.

In fact, the first ever U.S. (preliminary) astronaut selection was announced
in a USAF briefing concerning MISS on 25 June 1958. The list included
test pilots Robert Walker, Scott Crossfield, Neil Armstrong, Robert
Rushworth, William Bridgeman, Alvin White, Iven Kincheloe, Robert White, and
Jack McKay.

The project was cancelled on 1 Aug 1958 when NASA was formed.

It's interesting to note that it seems that Armstrong was simply destined to
get into space one way or another. (MISS candidate, X-15 pilot, X-20
candidate, NASA Group II.)

--
Dave Michelson