When john boy signed up for swift boat duty the swift boats were doing recon and described as non-combat, but then shazam! shazam! suprise suprise they're mission had changed and it was too late for him to get out.

One guy can fly a jet fighter while the other guy can beach a tollycraft.
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"Hunting is the only sport that I know of, in which one of the participants doesn't know that he is in the game." John Madden